guide to soils and plant growth in northern nimba county, liberia · 2014-03-20 · 3....

Nimba Western Range Iron Ore Project, Liberia Environmental and Social Studies, 2008-2015

Guide to Soils and Plant Growth

in Northern Nimba County, Liberia

Harvesting beans at an improved agricultural plot run by RICCE at Zortapa, Nimba, in July 2013

VERSION DATE: 8 FEBRUARY 2014

ArcelorMittal Liberia Limited

P.O. Box 1275 Tubman Boulevard at 15

th Street

Sinkor, Monrovia Liberia

T +231 77 018 056

www.arcelormittal.com

Nimba Western Range Iron Ore Project, Liberia

Environmental and Social Studies, 2008-2015: Project Phase 2 – Concentrator Guide to Soils and Plant Growth in Northern Nimba County

Version: 8 February 2014 of 68

Contents

1. INTRODUCTION ...................................................................................................................... 4 1.1 Why We Need to Understand Soils and Plant Growth ............................................................................ 4 1.2 The Way Forward .................................................................................................................................. 4

2. SUMMARY OF NORTHERN NIMBA SOIL CHARACTERISTICS ........................................... 5 2.1 The Setting of Soils in Northern Nimba County ...................................................................................... 5 2.2 Findings of the Soil Surveys .................................................................................................................. 7 2.3 Physical Integrity ................................................................................................................................. 13 2.4 Soil Chemistry ..................................................................................................................................... 14 2.5 Land Capability ................................................................................................................................... 15

3. CHARACTERISTICS OF WEST AFRICAN SOILS ................................................................ 18 3.1 Overview of Soil Characteristics in Liberia ........................................................................................... 18 3.2 Review of Soils under West African Shifting Cultivation Regimes ......................................................... 18 3.3 Soil-forest Nutrient Cycles ................................................................................................................... 19 3.4 Soil Nutrient Storage ........................................................................................................................... 20 3.5 Changes in Soil Properties in Shifting Cultivation ................................................................................. 21 3.6 Crop Performance under Shifting Cultivation........................................................................................ 24 3.7 Conclusions on Soils under Shifting Cultivation .................................................................................... 25

4. SOIL FERTILITY MANAGEMENT ......................................................................................... 27

5. CURRENT LAND USE AND SOIL MANAGEMENT PRACTICES ......................................... 29 5.1 Present Farming System ..................................................................................................................... 29 5.2 Shifting Cultivation............................................................................................................................... 30 5.3 Optimum Fallow Period and impact on Fertility .................................................................................... 31 5.4 Impact of Tree Crops on Long Term Fertility ........................................................................................ 31

6. MAINTAINING SOIL FERTILITY IN AN INTENSIVE FARMING SYSTEM ............................ 33 6.1 Agriculture and Soils ........................................................................................................................... 33 6.2 Potential Use of Fertilisers ................................................................................................................... 33 6.3 The Importance of the Farmer ............................................................................................................. 34 6.4 Simple Soil Fertility Improvement Methods .......................................................................................... 34 6.5 Land Rehabilitation and Improvement Methods ................................................................................... 35

7. VEGETATION MANAGEMENT FOR SOIL CONSERVATION .............................................. 37 7.1 Summary of Soil Conservation Methods using Vegetation.................................................................... 37 7.2 General Principles of Vegetation Management for Soil Conservation ................................................... 38

ANNEX A: TYPICAL SOIL CHEMICAL AND PHYSICAL CHARACTERISTICS ............................. 39 A.1 Ferralic Cambisols............................................................................................................................... 39 A.2 Ferralsols ............................................................................................................................................ 42 A.3 Fluvisols .............................................................................................................................................. 45 A.4 Gleysols .............................................................................................................................................. 46 A.5 General Character of Soil Samples Reported In 2008 Soil Survey........................................................ 47

ANNEX B: SOIL ASSESSMENT IN THE FIELD ............................................................................. 49 B.1 Signs of soil condition .......................................................................................................................... 49 B.2 Assessment of Soil Texture, Consistence and Structure ...................................................................... 51

ANNEX C: NOTES ON INTEGRATED PEST MANAGEMENT ....................................................... 53

ANNEX D: TREE CROP GROWTH REQUIREMENTS................................................................... 56 D.1 Coffee ................................................................................................................................................. 56 D.2 Cocoa ................................................................................................................................................. 57 D.3 Oil Palm .............................................................................................................................................. 59 D.4 Rubber ................................................................................................................................................ 61

ANNEX E: DEFINITIONS OF COMMON TERMS ........................................................................... 63

REFERENCES ................................................................................................................................... 65




List of Abbreviations AML ArcelorMittal Liberia

BCP Biodiversity Conservation Programme

CA Conservation Agriculture

CEC Cation exchange capacity

CF Community Forest

CFG Community Forest Guard

CFMA Community Forest Management Agreement

CFMB Community Forest Management Body

CMC Co-Management Committee

DSO Direct Shipping Ore

EC Electrical conductivity

ENNR East Nimba Nature Reserve

EPA Environmental Protection Agency

ESIA Environmental and Social Impact Assessment

FDA Forestry Development Authority

GoL Government of Liberia

GPS Global Positioning System

NGO Non-governmental Organisation

NMCDA Nimba Mountains Conservation and Development Area

NTFP Non-timber Forest Product

Acknowledgements This guide was adapted from a report produced by URS for ArcelorMittal Liberia Limited. Much of the original text was written by Wayne Borden, with contributions from Geoff Pettifer, Tanya Romanenko and Gareth Hearn. The classic soil survey that underpins our knowledge of the soils of Nimba was directed by John Aitken and undertaken by Teshome Afrassa, Wondwesen Haile, Behailu Kasahun, Aman Redi and Zewdu Shegana under contract to W. S. Atkins for ArcelorMittal.




1. INTRODUCTION

1.1 Why We Need to Understand Soils and Plant Growth For most of the year, the landscape of Liberia is a lush green, dominated by a stunning growth of vegetation. This gives the impression that it is a place of rich fertility. Certainly many crops do grow well here – rubber trees, for example – but the situation is more complex than it first appears. This is an ancient landscape that has been subject to intense weathering over hundreds of millions of years. The soils are weathered to the extent that the minerals are either very inert or are incapable of retaining large amounts of the elements needed as plant nutrients. Heavy rainfall leaches what nutrients are formed, and with the tropical heat causes rapid decomposition of organic material. These factors also lead to acidity and high iron concentrations, which further inhibit nutrient availability. While trees grow well because their deeper roots find what available nutrients there are, shallow-rooted plants are limited to herbaceous vegetation tolerant of infertile soils and despite a lot of leaf growth are not very productive. Sustaining agricultural crop yields for more than a few years is very difficult.

1.2 The Way Forward This version of ArcelorMittal‟s Guide to Soils and Plant Growth in Northern Nimba County is produced at the point between research of the underlying problems, and the development of proven solutions. It explains what we know and understand about the soils, and how plants grow in them, but it is not a fully comprehensive manual to soil and plant management. Through the company‟s Biodiversity Conservation Programme and the livelihoods component of its Resettlement Programme, ways are being sought to improve smallholder agricultural production in the long term, in ways that require less land per family, and produce greater and more reliable returns, than does traditional shifting cultivation. The company is funding work to this end by a number of specialist non-governmental organisations in partnership with farmers and community groups. It is intended that these will be supported by in-depth scientific research to validate the findings. But as of the date of producing this version of the guide, we do not have the confidence to state that certain approaches really work. It is intended that future versions of the guide will contain both an updated and improved understanding of the issues discussed above, and recommended options for practical agricultural management systems appropriate to the soils and farmers of northern Nimba. To achieve that, trials like the one shown in the cover photograph need to be fully tested and proven effective.




2. SUMMARY OF NORTHERN NIMBA SOIL CHARACTERISTICS

2.1 The Setting of Soils in Northern Nimba County The landscape of northern Nimba is the product of weathering, erosion and deposition over millions of years under tropical climates in a stable tectonic environment. Steep upper slopes below ridgelines at about 1000 metres above sea level formed on iron formation or other more resistant rocks. These pass down into lower, flatter slopes and then into undulating plains with a network of poorly drained valley floors at 420 to 480 metres, bounded by better-drained terraces. Weathering products comprise decomposed bedrock with recognisable relict structure (saprolite), passing up into residual soil with no relict structure (laterite). Colluvium (material that has moved down a slope) derived from these materials together with particles of more resistant rock types, has accumulated towards the foot of steep hillsides. Soils tend to be dominated by terrain characteristics in this area. Those on the upper slopes are generally shallow leptosols (very shallow soils over continuous rock or soils that are extremely gravelly or stony). Deeper ferralic cambisols (iron-rich, well-drained brown soils) have developed on the lower slopes, particularly where colluvium has accumulated. Low hills on the undulating plains typically have deep ferralsols (deeply weathered, red or yellow soils of the humid tropics) developed over very long periods of time in residual soils derived from decomposed gneiss. Suitable soils are cultivated using „slash and burn‟ rotations. Younger fluvisols (soils derived from river deposits) and gleysols (stagnant, waterlogged grey soils) developed in alluvial materials on terraces and valley floors are cultivated separately from the rotation practices on higher ground. The ferralsols and ferralic cambisols are typically sandy clay loams or clay loams and have a clay mineralogy dominated by low activity kaolinite (i.e. very highly weathered minerals). Vertisols (deep and usually more fertile clay rich tropical soils), characterised by smectite or montmorillonite clay, are not found here. Figures 1 and 2 give a summary and illustrations of the main soils found in northern Nimba. Figure 1. Summary of the main soils found in northern Nimba

Upland soils (ferralsols/ferralic cambisols) Strong brown to dark red, well drained soils developed in-situ from deeply weathered gneiss or ironstone (iron-ore bearing) bedrock, occurring on undulating to steeply sloping dissected plains and major hill slopes. The soils are mainly deep (>2.0m), fine-gravelly clays and sandy clays with weakly developed subangular blocky structures. Many soils are also gravelly. Sandy soils occur, as do shallow soils overlying very stony and bouldery ironstone. Leptosols are very shallow soils over continuous rock and soils that are extremely gravelly or stony, or both. In

Nimba they are mainly found on hill tops, on hard iron formations or on hard granite domes (see Figure 5).

Valley margin soils (gleysols)

Yellowish brown to brown soils occurring at the margins of the dissected plains and valley bottoms on gently sloping to undulating old alluvial or colluvial terraces and in-situ on weathered gneiss or colluvial toe slopes. Soils are clayey or loamy textured, weakly structured, well to imperfectly drained and usually affected by groundwater: this is shown by mottling in the subsoil.

Valley bottom soils (gleysols)

Mainly deep, very poorly drained, gleyed alluvial soils of varying texture, occurring in the small and usually swampy valley floors within the uplands. The soils are grey, mottled, gleyed and affected by shallow groundwater. Some soils are peaty.

Floodplain soils (fluvisols) Dark brown to yellowish brown deep alluvial soils bordering the main rivers and flooded annually. Soil textures are variable and frequently stratified. Soils are well to moderately well drained.

Contaminated soils (ferralsols/ferralic cambisols)

Undifferentiated soils affected by mining




Figure 2: Illustrations of typical soil profiles

2(a) Cambisol under cultivation 2(b) Cambisol under forest

2(c) Ferralsol under cultivation 2(d) Ferralsol under forest

2(d) Gleysol (courtesy of www.ulrichschuler.net) 2(e) Fluvisol




2.2 Findings of the Soil Surveys The soil survey carried out in 2008 identified four major soils: fluvisols, gleysols, ferralsols and ferralic cambisols. The first two are developed on relatively recent alluvial parent material while the latter two are on older, highly weathered ironstone, gneiss or older alluvium. A map showing the distribution of the main soils is given in Figure 3, and a typology description given in Figure 4. Fluvisols are well drained alluvial soils found on the narrow floodplains adjacent to the main rivers. Of the soils identified in northern Nimba, the fluvisols have the most agriculturally suitable physical and chemical characteristics (soil profile 30). They are generally deep profiles of medium texture and moderate to high fertility, and thus should require a shorter fallow period than the rest of the soils found in the valley and on the uplands. The majority of these are found on the narrow floodplains adjacent to the main rivers. Like the fluvisols, gleysols are formed on the narrow flood plains along the water courses and are most often found on the narrow valley floor of the smaller streams where conditions restrict drainage. They vary from the fluvisols in that they are formed under poorly drained or waterlogged conditions. These areas are also frequently flooded during the rainy season. The ferralsols and ferralic cambisols have formed under conditions of good drainage and aeration. They tend to have good physical properties but their chemical properties tend to be poor. They are mainly deep, friable and permeable, with a very variable gravel and stone content. The good permeability and stable microstructure, along with their cohesion, make them less susceptible to erosion. They are well drained but may dry out quickly because of their permeability and low porosity. Soil depth is good. Ferralsols and ferralic cambisols often grow rainforest vegetation, and examples of this can be found on untouched parts of the northern Nimba mountains. Owing to the residual metal oxides and the leaching of mineral nutrients, these soils generally have low fertility and often require additions of lime and fertiliser if they are to be used for agriculture. However, as described below in the paragraphs on land capability, the suitability of such land for agriculture is also dependant on other factors such as slope and soil depth. All soils are very acid (generally pH 4.2 to 5.5, but mostly 5.3 or less) and are characterised by low cation exchange capacity (due to their kaolinite clay fraction) and absence of weatherable minerals (resulting in low reserves of exchangeable bases) and thus low fertility. Organic matter content is very low, except for the topsoils. Topsoil organic carbon varies mainly from 1 to 6 percent but there are some higher values up to 13 percent. Subsoil organic carbon levels are mostly less than 1 percent. Away from the main Dayea River valley, most valleys in the area are narrow and contain an association of soil types comprising a mixture of fluvisols and gleysols. Valleys containing larger streams and rivers have fluvisols on their floodplains, and often have ponds and swampy clay soils in swamps at the back of the floodplain. Higher ground at the valley floor margins contains marginal gleysols and some upland soils. Smaller valleys contain the very poorly drained gleysols in the valley bottom. All the upland and valley-margin soils which make up the majority of the soils within the areas studied in and around the ArcelorMittal mine sites in the western part of northern Nimba are ferralsols or ferralic cambisols. These typically comprise a fine-textured subsurface layer of low silt-to-clay ratio, high contents of kaolinitic clay, and iron and aluminium oxides, and low amounts of available calcium or magnesium ions. They are often deeply weathered, acidic, and red or yellow in colour resulting from an accumulation of metal oxides, often iron or aluminium, or both (from which the name of the soil group is derived).




Figure 3: Soils map of the study area (for key see Figure 4)

Notes: Suffix s = very stony, bouldery below 0.5m; suffix g = very gravelly (>15% volume gravel) within 1.0m

*Soil types are included within VX1 and VX2, as soil types occur together and cannot be individually delineated.




Figure 4: Soil types

Soil Description Profile Pits No.

Upland soils (ferralsols/ferralic cambisols)

Strong brown to dark red, well drained soils developed in-situ from deeply weathered gneiss or ironstone (iron-ore bearing) bedrock, occurring on undulating to steeply sloping dissected plains and major hill slopes. The soils are mainly deep (>2.0m), fine-gravelly clays and sandy clays with weakly developed subangular blocky structures. Many soils are also gravelly. Sandy soils occur, as do shallow soils overlying very stony and bouldery ironstone.

U1 Deep, yellowish red clay and/or sandy clay 2, 4, 15

U2 Deep, yellowish red to strong brown over dark red and/or red clay and/or sandy clay 1

U3 Deep, dark reddish brown, red or dark red clay and/or sandy clay 7, 11, 14, 16, 26, 28

U4 Deep, dark reddish brown, red or dark red sandy loam to loamy sand 17, 18

U5 Deep, strong brown to brown over yellowish red clay and/or sandy clay 6, 9, 19, 23, 25

U6 Deep, strong brown to (dark) yellowish brown clay and/or sandy clay 22

US Shallow, clayey or loamy over ironstone boulders and stones within 0.5m 31

Valley margin soils (gleysols)

Yellowish brown to brown soils occurring at the margins of the dissected plains and valley bottoms on gently sloping to undulating old alluvial or colluvial terraces and in-situ on weathered gneiss or colluvial toe slopes. Soils are clayey or loamy textured, weakly structured, well to imperfectly drained and usually affected by groundwater.

T1 Deep, (light) yellowish / olive brown clay and/or sandy clay, mottled (plinthite?) below 0.5m. May be groundwater below 1.0m. Imperfectly drained

3, 13, 29

T2 Deep, strong brown to brownish yellow clay and/or sandy clay. May be groundwater below 1.0m. Well drained

8, 10, 20, 24

T3 As T2 but clay loam and sandy clay loam textures 21, 27

Valley bottom soils (gleysols)

Mainly deep, very poorly drained, gleyed alluvial soils of varying texture, occurring in the small and usually swampy valley floors within the uplands. The soils are grey, mottled, gleyed and affected by shallow groundwater. Some soils are peaty.

V1 Deep, greyish mottled over gleyed clay and/or sandy clay. Groundwater below about 0.5m. Very poorly drained. May be sandy loam below 0.6m

V2 As V1 but sandy clay loam or sandy loam textures. May be loamy sand below 0.6m 5

Floodplain soils (fluvisols)

Dark brown to yellowish brown deep alluvial soils bordering the main rivers and flooded annually. Soil textures are variable and frequently stratified. Soils are well to moderately well drained.

F1 Dark brown to strong brown clay loam, silty clay loam and/or light clay; may be sandy below 0.6m. May be some mottling. Moderately well drained

30

F2 Yellowish brown over reddish yellow sandy loam to loamy sand. Well drained

Contaminated soils (ferralsols/ferralic cambisols)

C Undifferentiated soils affected by mining 12

SOIL ASSOCIATIONS

Gleysols and fluvisols

VX1 Valley: V1, V2 and ponds in wet valley floors; T1, T2 and T3 and some upland soils on slightly higher land at valley margins. Shown in Maps

VX2 Valley F1, F2 on floodplains; ponds, swampy clay soils back of floodplain; T1, T2, T3 and some upland soils on slightly higher land at valley margins. Shown in Maps

Notes:

1. In databases and on the soil map: suffix s = very stony, bouldery below 0.5m; suffix g = very gravelly (>15% volume gravel) within 1.0m. 2. Ironstone is a fine grained compact sedimentary rock comprising carbonated or oxides of iron, clay and/or sand, typically containing less than 50% iron. 3. Full descriptions of all soil pits are given in ArcelorMittal Liberia (2010), which is available on the internet at www.arcelormittal.com/liberia/documents




Currently all soils except for the gleysols are used for upland rice farming, though they are better suited to tree crops than annual crops unless supported by high inputs of agro-chemicals: Figure 17 shows a farm in a typical ferralic cambisol. The gleysols and some of the fluvisols are frequently planted to lowland (paddy) rice, but also provide a range of wetland flora and fauna that supplement the farm family diet or are used for other purposes. Where the flow in the streams and rivers is adequate, irrigation can be developed to supply water to the rice crop during dry spells of the rainy season, and support early dry season vegetables. The soils over the upland areas are shallow, generally less than 400 mm and rocky, although in valleys deeper soils are found as a result of colluvial deposition. High rainfall, hilly topography (i.e. steepness of slope) and nature of substrata are responsible for the thinness of the topsoil layer in the mountainous regions. On the iron formations, soils can be less than 200 mm in depth over extensive areas, and are underlain by a hard substrate (e.g. Figure 5). Maps of topsoil depth and overall soil depth are given in Figures 6 and 7 respectively. Figure 5. The very shallow root plate of a tree blown over in a shallow leptosol on a hard iron formation on the northern ridge of Mount Tokadeh. Lines of deeper roots were exploiting fractures in the rock.




Figure 6. Topsoil thickness in the study area




Figure 7. Overall soil depth in the study area




2.3 Physical Integrity The potential soil loss from erosion was calculated using the Revised Universal Soil Loss Equation (RUSLE), an empirical model that relates management and environmental factors directly to soil loss through a statistical relationship. The RUSLE (Galetovic, 1998) is composed of six factors to predict the long-term average annual soil loss (A). The basic equation is

A = R x K x LS x C x P Where:

A = soil loss in t/ha R = rainfall erosivity based on the 30 minute intensity K = soil erodibility LS = slope length and steepness C = crop factor P = conservation factor

The rainfall erosivity index (R) is obtained from the report „D‟apres les donnees pluviometriques rassemplees par le Service Hydrologique de l‟ORSTOM et arretees en 1975‟, which shows the R value for Western Africa. Soil erodibility (K) was derived from a method devised by Wischmeier et al (1971). The soil erodibility factor K can be approximated from a nomograph using the particle size of the soil, organic matter content, soil structure and profile permeability, factors obtained from the results of the soil survey and laboratory analysis. Also relevant to the RUSLE is the slope factor (LS), which is derived from an equation relating slope angle and length. The crop factors (C) used are as follows:

Land cover types of RUSLE C factor Dense closed forest 0.001 Mature open forest 0.01 Young Forest 0.01 Scrub 0.1 Grassland 0.08 Agriculture/sparse vegetation 0.25 Grassland / low scrubs 0.2 Marsh / wetland 0.05 Bare ground – Disturbed 0.35 Bare ground – Urban and Roads 0.1

There are no known conservation practices in the project area, and therefore the conservation factor (P) has been taken as 1. Results from the calculations are shown below. The current “average soil loss” as estimated using the RUSLE by land class is summarised in Figure 8. These values give a relative estimate of soil loss for different land cover classes, and they cannot be taken as absolute values. At Mount Tokadeh losses are largely attributable to areas of bare ground, which are a legacy from the LAMCO mining period between 1974 and 1989. It should be noted that this did not account for the very large landslide feature that then existed at Tokadeh as a result of previous mining activity, which would have significantly increased the actual load of residual soils that were being removed from the mountain (the landslide was subsequently mined out in 2013). Although not subject to previous mining activity, a higher rate of soil loss of non-disturbed ground occurs from Mounts Gangra and Yuelliton. This is explained by the steep slopes and the high erodibility value attributed to the soil types.




Figure 8. Relative estimate of soil loss from Mount Tokadeh

Land Cover Classes Area

Total soil loss from area

Ha % t/ha/year %

Mount Tokadeh

Dense closed forest 56.1 6.8 0.6 0.0

Mature open forest 268.6 32.5 5.8 0.4

Young Forest 159.7 19.3 5.8 0.3

Scrub 94.6 11.5 320.1 8.5

Grassland 84.5 10.2 256.1 6.1

Agriculture/sparse vegetation 14.5 1.8 800.2 3.3

Grassland/low scrubs 31.9 3.9 640.1 5.8

Marsh/wetland 27.2 3.3 160.0 1.2

Bare ground – Disturbed (Legacy area) 61.1 7.4 3869.9 66.6

Bare ground – Urban and Roads 25.1 3.0 1105.7 7.8

Water Bodies 2.4 0.3 0.4 0.0

Total area (Mount Tokadeh) 825.7 100.0

Mounts Gangra and Yuelliton

Dense closed forest 2.8 0.7 4.4 0.0

Mature open forest 188.3 48.9 43.8 4.8

Young Forest 69.0 17.9 125.0 5.0

Scrub 66.4 17.3 1249.6 48.0

Grassland 23.9 6.2 999.7 13.8

Agriculture/sparse vegetation 14.9 3.9 1636.4 14.0

Grassland/low scrubs 12.9 3.3 1309.1 9.7

Marsh/wetland 4.6 1.2 327.3 0.9

Bare ground – Disturbed (Legacy area) 1.6 0.4 3957.2 3.6

Bare ground – Urban and Roads 0.8 0.2 565.3 0.2

Water Bodies 0.0 0.0 0.4 0.0

Total area (Mounts Gangra and Yuelliton) 385.2 100.0

2.4 Soil Chemistry Values determined during ArcelorMittal‟s later soil studies for pH are higher than the optimal minimum value of 5.0, while those determined by Reed (1951) and Atkins (URS/SW, 2010) tend to be close to this value, particularly for uncultivated ferralsols and leptosols. Levels of magnesium and total nitrogen are generally acceptable, but potassium and available phosphorus are likely to be deficient in ferralsols and ferralic cambisols, and in some fluvisols. Cultivated ferralsols and some ferralic cambisols tend to have a low calcium:magnesium ratio, and soils of all types are likely to have a cation exchange capacity below 15 cmol/kg. Three samples were subjected to X-ray fluorescence spectrometry (XRF) analysis in one study, for calcium, magnesium, potassium, phosphorus and iron. Values for total calcium, magnesium and potassium were close to those determined for exchangeable cations in the earlier studies; total phosphorus values were much higher because most is unavailable to plants. One sample contained high levels of calcium (500 ppm), phosphate (i.e. P2O5) (1800ppm) and iron (43%). The electrical conductivity (EC) of soil extracts was determined for nine samples in the study, after 30 minutes, 17 hours and 3 days. The intention was to investigate any progressive extraction of soil constituents. EC values after 3 days for the two ferralsol samples remained very low (13 and 15 μS/cm), whilst values for fluvisols, leptosols and ferralic cambisols were higher (generally 41 to 145 μS/cm). For sample SP7, EC increased from 158 (after 30 minutes) to 388 μS/cm (after 3 days). These very high values may be related to progressive extraction of hydrated calcium or iron phosphates. Figure 9 compares some of the chemical properties derived for soil types found in the project area.




Figure 9. Comparison of chemical properties by different studies for soils in northern Nimba. In the references, “this study” refers to the ESIA for ArcelorMittal’s Project Phase 2.

2.5 Land Capability Land capability was mapped in the environmental studies on an eight-class system (see Figure 10). Owing to the very acid soils and low fertility, the most fertile classes, I to III, do not occur and the surveyed land is no better than class IV: see map in Figure 11. The calculated areas for the mountains in Figure 10 were derived as part of the environmental impact assessment process, but they serve here to demonstrate the effects of limited soil depth and extreme weathering on the productive capability of the mountain soils. Figure 10. Land capability classes and area

Land Capability Class

Study Area (% of total Area)

Mt. Tokadeh (% of footprint)

Mt. Gangra and Yuelliton (% of footprint)

IV 40.70 3.85 0.00

V + VI 12.67 0.00 0.00

VI 3.06 0.00 0.00

VII 22.94 13.44 67.13

VIII 20.64 82.71 32.87

Total 100% (6667 ha) 100% (826ha) 100% (387ha)

The better drained fluvisols of the larger valleys are classified as an association of Land Class IV and V in the small, wet valley bottoms with high groundwater. Here they are strongly associated with the gleysols. The ferralsols and ferralic cambisols are mainly found on the higher land away from the valley floor. These are generally classes VI to VIII, more because of the slopes on which they developed, but also their physical and chemical properties. Where land slopes are below 25% these soils are mainly class VI. Where slopes exceed 25% they are Classes VII and VIII. However, despite the indicative agricultural quality provided by this land capability classification, significant farming is occurring, not just in Class IV, but in higher classifications including those on the mountains where Classes VI and VII occur.




Figure 11: Land capability classification in the study area




In general, where slopes are less than 25%, class IV land is better suited to long-fallow shifting cultivation or tree crops such as rubber or coffee, and would usually require liming and fertilising to sustain permanent cropping due to the characteristics of the ferralsols and ferralic cambisols present in the area. In this case it is probably uneconomic and undesirable to provide adequate lime and fertiliser to sustain permanent farming. Where slopes of such acidic soils exceed 25%, the land is best suited to tree cropping or left as natural forest. For classes VI to VIII the addition of organic-rich topsoil (e.g. from land stripped for mining operations) could boost productivity but would be of short-term benefit because it would eventually mineralise (i.e. burn up through chemical change). In the wet valley bottom soils with high groundwater, normal tillage of a range of crops is impossible, and here paddy rice is the most appropriate agricultural use.




3. CHARACTERISTICS OF WEST AFRICAN SOILS

3.1 Overview of Soil Characteristics in Liberia Reed (1951) noted that Liberian agriculture (with the exception of rubber plantations) was centred around rice and cassava production for local consumption, and that remains true today. Local deep ferralsols and moderately deep ferralic cambisols generally have good physical properties for plant growth but poor chemical fertility. Some shallower soils appear to contain reserves of primary minerals such as feldspars, amphiboles and pyroxenes that gradually decompose and replenish levels of available calcium, magnesium and potassium. There has been little, if any, published work on the characteristics of Liberian soils since the study by Reed (1951), but broad soil classes extend across West Africa as shown on the Soil Map of the World (FAO-UNESCO, 1995). FAO (2000a) proposed critical minimum soil test values for nutrients which are commonly deficient in Nigerian soils. Concentrations below the critical values are considered insufficient for optimum crop growth and yield in Nigeria, and can be used as an approximate guide in other tropical countries where such values have not been established. FAO (2000b) recognised particular constraints for tropical soils in terms of fertility. These included low cation exchange capacity (CEC, generally the degree to which nutrients in cationic form can be held in the matrices of clay minerals), and hence low inherent fertility; aluminium toxicity for sandy, non-humic ferralsols, and high phosphorus fixation for clayey ferralsols. Soils are now described using FAO (2006a) and classified according to FAO (2006b). Under „slash and burn‟ cultivation, plant nutrients, in particular nitrogen and potassium, accumulate in the bush cover and upper layer of fallow soils. Ferralsols typically contain 1100 to 1700 ppm total phosphorus but only 8 to 10 ppm as plant-available phosphorus (Reed, 1951). Available phosphorus content in all soil types is lower than that of any other nutrient and is replenished, together with potassium, by ash from cut bush that has been allowed to dry and then burnt in-situ. The calcium:magnesium ratio has been found to be an important factor in controlling phosphorus uptake by crops in Nigeria (FAO, 2000a). The optimum calcium:magnesium value for most crops is between 3:1 and 4:1, and 1:1 is considered to be the lowest acceptable limit. Soils with a clay mineralogy dominated by kaolinite have a low CEC: at a CEC below 15 cmol/kg calcium, magnesium and potassium ions either remain available in the soil solution for a longer period or are leached out. At pH values below 5.0, aluminium, iron and some micronutrients may be at toxic levels and reduced microbial activity may cause nitrogen to become unavailable to plants (FAO, 2000a). Crops such as cassava and pineapple are tolerant of aluminium toxicity but others (e.g. tomatoes and maize) are not. In upland soils, for example, acidic aluminium and iron oxides react with phosphorus so that it is unavailable for plants (WARDA, 1999). In flooded lowland acid soils, high levels of reduced iron typically result in iron toxicity, and zinc and potassium deficiencies in rice (Becker and Asch, 2005). Aluminium toxicity is cited by FAO (2000b) as one reason why subsistence agriculture is based on root crops, such as cassava and yams, rather than cereals. Traditional criteria for assessing soil fertility are discussed below.

3.2 Review of Soils under West African Shifting Cultivation Regimes Nye and Greenland (1960) provided the seminal understanding of soil behaviour under shifting cultivation, though they were not the only scientists researching the subject at the time. Much of the very early work was only published in Country Government Reports, but occasionally some of the work appeared in scientific journals. Since the 1960s, even though a range of scientists in various parts of the world have been adopting and adapting this work in their own environment, most of the published research has been carried out by International Institute for Tropical Agriculture (IITA, at Ibadan, Nigeria) and International Council for Research in Agro-forestry (ICRAF, at Nairobi, Kenya) and the Food and Agriculture Organisation (FAO, in Rome, Italy). Sanchez (1973), with colleagues at South Carolina State University, has brought together a wide range of other work in all parts of the world in his Review of Soils Research in Tropical Latin America. Other sources of research are the proceedings of various conferences and workshops, but few of these are widely published. Since the




late 1980s there has been very little published research related to shifting cultivation and none has been undertaken in Liberia due to the civil war. A schematic diagram of Nye and Greenland‟s (1960) model of soil changes in the cycle of shifting cultivation is shown in Figure 12. In the following paragraphs, unless noted otherwise, the primary information is from either or both of the works of Nye and Greenland (1960) and Sanchez (1973). Figure 12: Soil changes in the shifting cultivation cycle.

Courtesy of Katharine Howell

3.3 Soil-forest Nutrient Cycles One of the reasons that shifting – or slash and burn cultivation – is practiced so widely is that there exists a nearly closed nutrient cycle between a mature tropical forest and the soil (Hardy, 1936). This cycle has two main nutrient storages: the biomass and the topsoil, which are connected by several




pathways. Biomass production in mature forests has been found to provide the nutrient ranges shown in Figure 13. Figure 13. Ranges of nutrients in biomass production in mature forests.

Nutrient Kg/ha Nutrient Kg/ha Nutrient Kg/ha

N 700-2044 Mg 381-3890 Zn* 13

P 33-137 S 196 * Mn* 5

K 600-1017 Fe 43* Cu* 3

Ca 653-2700

* One observation Long term studies in Nigeria showed that a secondary forest could produce 40 t/ha after six years, while Stargrass (Cynodon nlemfuensi) pasture established at the same time produced 17 t/ha (Jaiyebo and Moore, 1964).

3.4 Soil Nutrient Storage The top 30 cm of a Latosol

1 soil (similar to those in Nimba: see Figure 14) under forest has been

found to contain:

2.6 times as much nitrogen as the biomass (the vegetation above ground) and about the same amount of exchangeable calcium and magnesium as the total plant content of these two elements;

75 percent of the biomass potassium as exchangeable potassium; and

nine percent of the biomass phosphorous as available phosphorous (Greenland and Kowal, 1960).

Figure 14. A typical ferralic cambisol formed in a deep residual soil on a spur of Mount Tokadeh, Nimba.

1 Latosol is a general term for a range of highly weathered, reddish or yellowish tropical residual soils, low fertility,

of which the Ferralsols and Ferric Cambisols of Nimba are representative.




The top 15 to 30 cm of the soil profile has been shown to contain 68 to 85 percent of a mature forest root system (Greenland and Kowal, 1960), and the subsoil, containing the remaining 15 to 32 percent is estimated to account for 20 percent of the total nutrient uptake. The ranges of nutrient composition in the litter layers are shown in Figure 15. The nutrient additions from the vegetation to the soil are balanced with the nutrient uptake of vegetation from the topsoil. Figure 15. Ranges of nutrients in the litter layers of forest soils.

Nutrient Kg/ha Nutrient Kg/ha Nutrient Kg/ha

N 74-199 K 8-81 Mg 10-94

P 1-7 Ca 45-220 S* 9-10

* One observation According to Sanchez (quoting various sources) the nitrogen cycle consists of an annual flow of 102 kg N/ha per year, and it is held tightly in the cycle. The phosphorous cycle is restricted to the superficial soil layer (almost entirely held by the surface roots in the top 5 cm of soil) and is strongly held in the cycle. Potassium is loosely held and cycles at very high rates. The micro-nutrients (Ca, Mg, Mn, Fe, and Cu) are cycled slowly and are bound very tightly.

3.5 Changes in Soil Properties in Shifting Cultivation When the balanced nutrient cycle established under a mature fallow is disrupted by clearing, burning and cropping, the soil undergoes a series of physical and chemical changes. Soil Physical Changes Agents of soil physical changes include soil temperature, soil moisture content, rain drop impact and erosion. Soil temperature. Clearing exposes the soil surface to direct sunlight which increases the

temperature in the topsoil to that resembling air temperature. During the burning process, the soil surface layer can experience temperatures of several hundred degrees centigrade (see Figure 16). This raising of soil temperature significantly stimulates the biological processes in the soil, resulting in rapid breakdown of remaining fragments of litter and the soil humus component, though this process slows down again with increasing vegetation regeneration, either crop or fallow. Soil moisture. A mature 40-year old forest canopy intercepts and evaporates about 16 percent of total rainfall; or stated another way, the leaching potential of rainfall increases by 16 percent when the vegetation cover is removed. Forest soils tend to have a uniform soil moisture profile with deep water tables (if present) due to high transpiration rates from different layers within the soil profile. Removal of the forest cover breaks the cycle below the soil surface, allowing direct evapotranspiration from the top horizons: this depletes the moisture in these but leaves residual moisture in the lower horizons, resulting in a non-uniform moisture profile. Mulching the soil surface reduces run-off and soil erosion as well as reducing soil temperature (Kamara, 1986). Soil structure. Clearing and burning have been observed to increase infiltration rate, soil

aggregation, bulk density, and compaction. The latter results in decreased total porosity and water stable aggregates. Apparently the impact is not as great on latosols (a general term for soils such as the ferralsols and ferralic cambisols of North Nimba) as on soils with less desirable physical properties. Runoff and erosion. The extent of this is dependent on rainfall, soil physical properties, degree of

land slope and density of ground cover, and thus may be severe or negligible depending on location and farming practice. Under mixed plantings on small plots (as is common practice) and with slopes less than 50 percent, erosion on Latosols has seldom been found to be serious due to the usual high cohesion of these soils.




Erosion. In a forest soil under crop the greatest concentration of nutrients is in the top 7 cm or so,

provided the surface is not significantly disturbed by cultivation. Under normal native practice, on slopes less than 10 percent, loss by erosion during three years of cropping should not exceed 125 t/ha (50 tons per acre) and will usually be much less than this. Thus, the loss is at most about one tenth of the fertile top 7 cm layer. Figure 16. High temperatures are reached during the clearing of new farms.

Soil Chemical Changes Soil acidity. The ash resulting from burning fallow vegetation contains large amounts of bases which increase the pH of most soils. Ash has been estimated to contain about 5.3 t/ha of calcium, 0.7 t/ha of magnesium and 1.6 t/ha of potassium. These base levels were found to increase soil pH from 5.2 to 8.1 in the top 5 cm, and from 4.9 to 6.2 in the 5 to 15 cm layer following burning. After two years, the pH in the two horizons had decreased to 7.0 and 5.0 respectively due to leaching of the base cations during cultivation. This and other studies indicate that ash-derived base ions tend to move down the profile and increase pH at substantial depth. This mobility tends to cause short lived pH changes, though apparently sufficient to be of benefit to the crops grown and the initial stages of forest regrowth. In contrast, commercial lime is less mobile and thus has a longer impact in the surface horizon. Organic matter and nitrogen. While burning volatilises most of the nitrogen, carbon and sulphur present in the vegetation, it tends to increase the amount of organic carbon and total nitrogen content in the topsoil. Organic matter contents decreased rather sharply in the top 5 cm of the soil, possibly due to increased soil temperatures. Carbon/nitrogen (C/N) ratios vary, decreasing in some cases and remaining stable in others. Generally changes in carbon, nitrogen and C/N ratios below the first few centimetres are negligible, and where changes occur they reach equilibrium relatively quickly. The




average decomposition rate of organic carbon is about three percent. Regrowth of secondary forests reverses the above trend with annual increases in the order of 700 kg/ha of nitrogen per year during the first three years of forest regrowth (Jaiyebo and Moore, 1963). Losses of organic material. Very little of fresh organic matter added to the soil becomes humus due

to the high rate of loss due to oxidation, leaching and erosion. It is estimated that the proportion of fresh material converted to soil humus will probably lie between 10 and 20 percent of the total, the actual proportion depending on a variety of factors and conditions. Increase of soil humus and nitrogen. The rate of humus increase is primarily dependent on the balance between the rate organic matter is added and the losses of organic matter from a soil. Other factors are the type of vegetation and its growth rate. In the forest zone where fallow regenerates from seedlings and stumps and roots left in the ground, and where rainfall is usually plentiful, rapid establishment will take place when the cropping period is complete. Research on fallow regrowth has shown that a significant part of the regrowth vegetation is as great after five years as after 18 years (Bartholomew et al, 1953), indicating that the incremental value of fallow declines with time. A portion of the humus in a soil is also lost through oxidation, the degree of reduction apparently dependent on the intensity and length of cultivation. Analyses of soils in Liberia showed that the level of organic matter under secondary forest was 75 percent of the level under virgin forest. The soils under secondary forest were cropped for 2 years and fallowed for about 10 years (Reed, 1951, quoted in Nye and Greenland, 1960). Rate of increase in nitrogen. The rate of increase in humus carbon in the soil under fallow and the

C/N ratio are used to calculate the increase in nitrogen. For the Liberia analysis (see paragraph above), the C/N ratio for cropped land was reported as 17-1; for forest fallow 16-3 and virgin forest 18-0. On this basis the average soil nitrogen rate of increase would be about 39 kg/ha (35 lb. per acre) per annum. Thus a 10-year fallow period will lead to the accumulation of about 390 kg of nitrogen per hectare (350 lb. per acre) during the fallow period. However, this amount does not represent the total nitrogen gain of the soil-fallow during the fallow period. A 10-year old forest fallow has been shown to contain about twice that much nitrogen. Taking account of losses, the net annual fixation rate in forest must be of the order of 106 kg/ha (95 lb. per acre). However, because all nitrogen stored in the fallow is lost in the burn following clearing, it is only the soil increment that can be used by crops in the succeeding cropping period. Phosphorus. Though present in relatively low amounts, the tightness of the phosphorus (P) cycle

seems to prevent P deficiency under natural conditions. This restricted mobility appears to favour its conservation in the soil. Following burning, extractable P in the top 5 cm layer of a Guatemalan soil increased by about four times, remained so for about six months and a year later was still twice the original value. No changes in available P were observed below that layer. Increase in organic phosphorus. Fallow appears to play a useful function in the quantity of organic

phosphorous in a soil. The ratio of organic P to carbon in these generally phosphorus deficient soils has been calculated at about 1:200. Thus the increase under a 10-year fallow in forest areas at the 75 percent equilibrium level should be of the order of 13 to 33 kg/ha (12 to 30 lb. per acre), the higher amount comparing favourably with the amount of 33 to 45 kg (30 to 40 lb.) accumulated in the vegetation. Exchangeable bases. The amount of potassium, calcium and magnesium in the vegetation appears to mirror the increase in exchangeable K, Ca and Mg in the topsoil after burning. Though there are large K and Mg leaching losses during the first year, Ca losses tend to be small. Exchangeable K content in the top 0 to 5 cm layer has been measured at three times the original after burning, and then found to decrease to two times within three months and to the original value within a year. The potassium content in the 5 to 40 cm layer remained unchanged. Exchangeable Ca in the top 5 cm increased by 50 percent and exchangeable Mg by 75 percent with burning, but both elements reverted to the original value in less than a year. Calcium and magnesium have been observed to move down to the 20 to 40 cm layers, where they would still be recovered by crop roots (Popenoe, 1957, quoted in Sanchez, 1973). After two years, leaching, erosion and crop removal of Ca and K from the soils accounted for only 50 percent of that added after burning in Ghana, implying that the beneficial effects of the ash may extend beyond the usual cropping period.




Increase of cation exchange capacity. The storage of cations in the exchangeable pool is generally limited by the level of the exchange capacity. Due to the kaolinite dominance of the clay fraction in the north Nimba soils, the exchange capacity of the surface horizons depends on their organic matter content. Thus the greater the CEC, the greater is the cation release during the clearing and burning of the fallow vegetation, and the greater will be the quantity of base cations retained. Indirectly, the level of pH and overall soil fertility will also be higher. Soil microbiology. There appears to be varying opinions on the fate of soil micro-flora during

burning, with a study in Kenya reporting that burning destroyed the aerobic nitrogen fixers and other microflora in the soil, but not anaerobic nitrogen fixers (Miekeljohn, 1955, quoted in Sanchez, 1973). A study in Columbia (Suarez de Castro, 1957, quoted in Sanchez, 1973) found no changes in the fungi Actinomycete and bacterial flora within one week after burning in the 0 to 10 and 10 to 20 cm layers.

3.6 Crop Performance under Shifting Cultivation The high supply of organic nitrogen (and probably sulphur) left in the topsoil after burning, plus the large quantities of phosphorus, potassium, calcium, magnesium and probably other micronutrients added in the ash, almost ensures no fertility limitations to the first crop grown in most tropical soils (see Figure 17, for example). Research in West Africa and elsewhere indicates that farmers abandon their fields when crop yield reduces to half of that obtained in the first year. If fertility can be maintained at a slow decline, it should then be possible to crop a field for more than one season. Figure 17. A shifting farm of maize, cassava and upland rice in northern Nimba, in October 2013.




Despite the fact that this research suggests that the levels of soil fertility in soils following clearing and burning of a mature fallow should decline at a rate that would allow three or more crops without recourse to use of fertiliser, and to continue to plant these same fields with limited amounts of fertiliser for even longer periods, farmers in northern Nimba abandon their fields after one year. As the soils of this area are found widely throughout West Africa, this suggests that there is another reason – possibly that they cannot cope with the weed growth which competes with their crops, or with crop diseases or other pests – and find it easier to clear new land to maintain their food supply. Crop yields. Sanchez (1973) reports that in Latin America, upland rice yields have been observed to

be more dependent on rainfall than on fertility decline, and that weed control was a key factor in limiting cropping for more than one year. Fertiliser responses. Sanchez (1973) also observed that the limited agronomic experiments on

shifting cultivation systems in Latin America indicate that the high nutrient supplying capacity of the soils following forest clearing prevents fertiliser responses in the first crop of upland rice or maize, but that responses to nitrogen but not phosphorus or potassium fertilisers are commonly observed after the second crop. This suggests that fertility decline is relatively slow.

3.7 Conclusions on Soils under Shifting Cultivation The processes at work during the rise in the soil fertility under a natural fallow and those related to the subsequent reversal during cropping under the present farming system practiced in northern Nimba are broadly understood. In summary, these are as follows.

Following a cropping period, the forest quickly re-establishes itself from new seeds, seedlings and the root system of the former fallow period.

As the forest re-establishes itself, some of the vegetative material returns to the soil surface as litter (leaves, twigs), adding organic matter to the soil surface. Also, elemental plant nutrients are added to the soil as a result of rain wash on leaf surfaces.

The change in environment (as a result of increased ground cover) stimulates increased biotic activity in the litter layer, breaking it down to its various components. As well as plant nutrient release, the content of humus (which helps hold the exchangeable cations and nitrogen released) is also increased during this process as not all the carbon in the litter is lost as carbon dioxide.

Rainfall washes the plant nutrients into and down the soil profile, though the volume and intensity of the rain is restricted by vegetation cover, thus slowing this leaching process down and perhaps assisting in nutrient re-absorption.

Physical changes occur in parallel with chemical changes in the soil. The interaction of the various living organisms (termites, worms, bacteria, fungi, finer plant roots, etc.) result in the aggregation of soil particles, creating a more stable porous soil structure which improves infiltration and aeration, and reduces susceptibility to soil erosion.

The vegetation cover and litter layer significantly reduce soil erosion by absorbing the impact of rain drops. The decomposition of the litter layer assists in strengthening the physical structure of the soil particles, further reducing susceptibility to erosional forces.

These processes continue until the forest reaches a state of maturity where a nearly closed cycle of nutrients occurs between subsoil and vegetation, and then the topsoil.

This process is reversed when the forest is cleared. Removal of the surface vegetation by burning deposits all the nutrient elements (except nitrogen and sulphur, which along with carbon are lost as gas) on the soil surface as ash where they are washed into the soil (or off the field) by the early rains. Much of the litter layer is also destroyed and the soil surface is exposed to the sun and rain, and open to wind and water erosion. However, the resulting ash acts as a buffering agent, raising the pH level of the topsoil (i.e. reducing soil acidity thus making more of the nutrient capital available to the planted crop).

The amount of rainfall intercepted or transpired by the vegetation is considerably reduced, increasing the amount of water available for leaching and consequently aiding the movement of plant nutrients down the profile and out of the shallow rooting zone (even out of the entire rooting zone). At the same time, any part of the litter layer not consumed in the burning




rapidly decomposes. With the impact of the rain, this results in a breakdown of surface soil structure which aids erosion and further loss of fertility.

Once the first crop has established a full ground cover, the deterioration processes diminish, though now the nutrient demands of the crop add to the loss through downward leaching. In Liberia it is normal to have an intercrop following the first crop so that there is limited opportunity for the soil surface to be exposed a second time by the harvesting of the first crop, thus reducing the decline in fertility due to oxidation, leaching and erosion.

Mulching the soil surface reduces run-off and soil erosion, as well as reducing soil temperature.

There are various methods of maintaining soil fertility under shifting cultivation (slash and burn agriculture) in West Africa as well as other parts of the world where this farming system is practised.

All of these effects in the characteristics of soils have implications to society. Their impacts are summarised in Figure 18. Increasing land scarcity results from population growth and other pressures on land, and leads in turn to shorter fallows; soil fertility declines and shifting cultivation becomes increasingly untenable. There are then two choices: either remain in a cycle of increasing land scarcity, and declining soil fertility and crop yields, or find a way to break out of the cycle by adaptation and improvement of some part of the system. The residual soils of Liberia are essentially the same as those found in many locations where shifting cultivation is practised in West Africa and most other parts of the tropics, and thus research elsewhere gives a good indication of the type of management that should be beneficial to intensification of agriculture in northern Nimba. However, subtle (micro) differences in soil characteristics require that each potential solution is tested, and adapted as necessary, before it is put into full practice. Figure 18. The implications of increasing population, shifting cultivation and soil fertility.

Courtesy of Katharine Howell




4. SOIL FERTILITY MANAGEMENT The soil survey of the Dayea Valley and the western mountains (section 2 above) identified four types of soils, distinguished first by their physical attributes and confirmed at a finer level by their chemical characteristics. There are clear physical differences between the four soils which to some extent will guide land use. Analysis of samples taken from the 30 representative soil pits show that in terms of fertility management, these soils are not sufficiently different in their chemical characteristics to require different management. This could be because 28 of the samples were from the cambisols (13) and ferralsols (15) which are the predominant soils of the mapped area. The other two soils identified are the fluvisols and gleysols, found in smaller, less contiguous areas along the river and its tributaries. With the exception of the gleysols, the key to maintaining fertility of these soils will be:

building and maintaining the organic content since this provides the bulk of the cation exchange capacity (CEC) given that the dominant clay fraction in all these soils (kaolinite) has an inherently low CEC; and

having enough deep-rooted plants in the mix to recycle plant nutrients washed deeper down the soil profile.

Simply stated, the land should be managed in such a manner that an adequate amount of biomass is produced and incorporated into the topsoil to maintain high levels of organic matter, and the crops grown should be a mix of deep and shallow root species to maintain a healthy nutrient cycle. The gleysols are a slight exception in that while the methods required to maintain soil fertility will be essentially the same as for the other soils, maintaining a high level of organic matter should be easier as under conditions of poor drainage the organic matter content will degrade more slowly. However, for this reason recycling leached plant nutrients via deep-rooted plants will be more problematic. Methods of building and maintaining fertility will thus be discussed in the following sections. A review of research literature (see section 2) indicates that, from a fertility standpoint at least, it should be possible to obtain a second or third (or more) crop from a given field. For example, a summary of research findings in Nigeria (Vine, 1953 and 1954) concluded that crop yields can be maintained satisfactorily for long periods of time with small amounts of green manures or fertiliser. Similar results have been reported in other parts of West Africa and the world (various references: see list). In the Nigeria research cited, maize yields fluctuated from 1.3 to 1.6 t/ha during 17 years when a velvet-bean (Mucuna pruriens) crop was planted, burned and incorporated every year. Response to nitrogen fertiliser was not observed in the first 8 to 10 years, after which short term green manure crops alone were not sufficient (i.e. the soil nitrogen had become too depleted to support the crop). While not all of these trials were done under strict research conditions, they were closely supervised by scientists, and thus it would be unrealistic to expect the same results to occur under smallholder management in northern Nimba. Nevertheless, intercropping rice or maize with a legume crop that will provide ground cover to protect the soil surface and assist in suppressing weed growth should allow two or more years of cropping under Nimba conditions. Burning the legume ground cover at the end of each dry season will top up the plant nutrient supply to the topsoil and add ash to counter natural soil acidity, further assisting nutrient availability. Research in Ghana (Nye and Greenland, 1960) found that under forest soils responses to nitrogen fertiliser were very small where the fallow has been long (say 10 years or more), but in land more intensively cropped with only short fallow the responses become large. Responses to phosphorus appeared to depend as much on inherent properties of the soil as on its cropping history. Large responses were obtained following a long fallow, and negligible responses following a short fallow. When responses were obtained they were smaller in the first year of cropping than in later years. Small or moderate responses to potash frequently occurred on short fallow land or land that had been cropped for a number of years. Responses to lime were usually small except in soils with pH < 5.0. While the literature review suggests that it should be relatively easy to extend the cropping period and shorten the fallow period from a soil fertility standpoint, it would be necessary also to adopt methods that will handle the pest and disease problems which, in fact, may be the main reason that farmers shift fields so quickly. In this regard it is important to note that while crop residues are one means of adding organic matter and attendant fertility to a soil, they can also harbour pests and diseases and thus, if not burned at the end of each dry season, should preferably be removed from the field.




Another aspect to bear in mind is that crop residues are also sources of fodder for any livestock that the farmers include in their farming system, and this will divert that resource from the field. As a general rule, 5 to 10 t/ha/yr. of farmyard manure will sustain soil fertility, but anything less is not likely to be sufficient. As noted in the Nigeria research above, at some point in the cropping sequence, a green manure intercrop alone will not supply adequate plant nutrition. At this point there was a response to fertiliser applications. Where only one or two of the plant nutrients are required (e.g. nitrogen, phosphorus, sulphur), applications of small amounts of fertiliser could allow the cropping to continue. However, this will require access to a laboratory that can undertake soil fertility analysis, which is difficult in rural Liberia. Thus the option for the foreseeable future will be to revert to a fallow period to allow nature to restore the nutrient cycle and build up the soil fertility capital to a level where cropping can commence again. Re-establishing the bush fallow is unlikely to be as natural and easy as at present because as each year passes the former forest seed bank and root system will be consumed by biotic activity in the soil. The necessary fallow should be a planted fallow containing a high proportion of legume species and high biomass-producing vegetation. Such a fallow should be significantly shorter than the traditional fallow periods noted in Nimba. This managed fallow could be part of a rotation – one portion of the farm in fallow and another in crop. It is also possible that the fallow crop could be an economic crop with some of the tree species harvested for sale at the end of the fallow period, though this would reduce the amount of ash and nutrients deposited during the burning of the fallow.




5. CURRENT LAND USE AND SOIL MANAGEMENT PRACTICES

5.1 Present Farming System Farmland is traditionally allocated on a kinship basis (quarters) within communities, but this practice has been under increasing pressure in recent decades. Current land tenure is complicated by the co-existence of customary tenure (Tribal Land Certificates) and formal land ownership (Title Deeds), including parcels of land purchased directly from the government. Farm size, crop mix and the length of the fallow period depend on several factors, including soil type, bush growth, water supply, available labour and expertise. The vegetation and soil characteristics of a site determine whether it is suitable for farming. For example, dark-coloured soils with a thick vegetation cover and an upper layer of decomposed leaf litter are generally considered to be fertile and can be cleared to grow a range of crops. Soils on the lower slopes at Tokadeh were thought to be particularly fertile because plants such as bitterballs, peppers and palava sauce occurred naturally and did not need to be sown (URS/SW, 2010). Root crops such as cassava grow best in deep, well-drained loamy soils with little gravel and are not suited to poorly drained valley bottom soils. No crops can be grown successfully on shallow sandy soils with savannah (grassland) cover. Figure 19 illustrates the range of traditional subsistence practices in northern Nimba. Steep upper slopes with thin leptosols below major iron formation ridges are forested, including some areas of primary forest. Hunting, gathering, craft industries and cultural activities are carried out in these areas. Flatter lower slopes tend to have thicker ferralic cambisols and some forest remnants. Tree crops such as coffee, cocoa, oil palms, bananas and plantains are grown mainly by men, and may be sold for cash. Shifting „slash and burn‟ agricultural areas extend from these slopes on to undulating plains where thick ferralsols typically have good physical properties but poor nutrient levels. Upland rice, maize, cassava and other crops are grown in cleared fields of about 1 to 3 ha for 1 or 2 years. The fields are then left fallow to regain fertility for between 6 and 15 years, with an average of about 8 years. The length of the fallow period tends to increase with distance from permanent settlements but is also determined by factors such as labour availability. Figure 19. Schematic cross-section illustrating traditional subsistence practices in northern Nimba.

Homesteads are surrounded by permanent vegetable gardens, worked mainly by women, with coffee and some other crops. Swamp rice is grown on fluvisols and gleysols on low terraces and valley bottoms. Clear streams on higher ground traditionally supply drinking water while rivers on lower ground are used for washing and to supply fish. Some families own small numbers of goats, sheep, pigs, chickens and ducks. Soils in fields close to homestead gardens tend to be impoverished by frequent cropping, while more distant fields are more fertile because they are left fallow for longer periods.




Plantain stands are replanted every 2 years while rubber trees, grown mainly on the slopes of Mount Yuelliton and south Tokadeh, take 7 years to mature but can then be tapped for at least 25 years. Cassava produces a crop for two consecutive years and swamp rice can be planted twice a year on the same plot. Traditional uses of forest land include timber, charcoal, pottery and gunpowder production. Iron farming tools have been manufactured at Tokadeh (URS/SW, 2010). A small number of inhabitants of Gbapa are involved in artisanal mining for diamonds (also alluvial gold east of Gbapa Town) and a local stakeholder has remarked that farmland around the town has been destroyed by these activities. Current agricultural practices are sustainable until population density rises above a threshold level, at which point the amount of available farmland is insufficient and fields are either cropped for successive years or fallow periods are reduced. Increasing numbers of farmers are believed to be suffering land shortage and are cultivating land far from their traditional communities, thereby contributing to land conflicts. Added to this, a high proportion of crop is lost during harvesting and storage. The evidence suggests that northern Nimba communities are close to the threshold level.

5.2 Shifting Cultivation Shifting cultivation – or perhaps more appropriately (as locally practiced) slash and burn – is the standard farming system in northern Nimba. This is a low input farming system whereby each cropping period is followed by a long fallow which naturally replenishes soil fertility and at the same time prevents any weed growth and changes any congenial habitat for other pests and diseases. The only input from the farmer is his or her and other family members‟ labour, though extra labour is sometimes employed. Scarce cash resources are not spent on other inputs (i.e. fertiliser, pesticides or farm implements). Such a farming system results in large areas within the community with a highly mixed biodiversity. This is a very sustainable farming system as long as the population density is relatively low, as large areas of land are required to sustain each farming family: Nye and Greenland (1960) believed that “Under normal conditions of bush fallow, when the population density exceeds 25 person per km

2, irreversible processes of soil and vegetation degradation are likely to occur”. During

the ArcelorMittal environmental studies (ArcelorMittal, 2010), upland farm sizes in the area were found to range between 0.1 and 10 acres with the average being 3.0 acres (1.2 ha), and the fallow period following each cropping ranging from 3 to over 30 years with the majority of fallow being between 6 and 10 years. Assuming that there is no land pressure in the Dayea valley, a sustainable land holding would require a period of three times the number of fallow years required to restore soil fertility to a level that will produce an average crop yield. Thus given an average of 3 acres cleared and planted each year, and (say) an average of 10 years fallow, each farmer would require a minimum of 30 acres (12 ha). To the casual observer, there would appear to be large areas of land available for farming, but in fact it is all allocated. New land is normally planted to upland rice with small areas containing a mix of other crops (e.g. maize, chilli peppers, bitterball, okra, squashes etc.). Cassava is inter-planted with these crops and produces in the second and subsequent years until the natural vegetation becomes too prolific. Since the farmer lacks machinery to till the soils there is little disturbance of the soil or the root system of the previous fallow, thus the natural vegetation re-establishes itself quickly and within two to three years will have overgrown the cassava and be well on the way to returning to forest. Even though the farming operation does not significantly disturb the soil surface, where clearing is done on steep slopes significant soil erosion can occur, removing some of the natural soil nutrients and thus partly accounting for the length of fallow required to replenish soil fertility. Even though the norm, this farming system is not particularly suitable at the present time, nor into the future, due to other pressures on land as well as the increasing population. This will soon, if it hasn‟t already, force the normal fallow period to be reduced and thus start a downward spiral of shorter fallow periods and consequent reduction in soil fertility (i.e. at a given point the fallow will be too short to replenish the fertility of the soil). For this reason, a new approach to agriculture in the area is, or may soon be, needed.




5.3 Optimum Fallow Period and impact on Fertility The minimum length of the fallow period is, to a large degree, dependent on the latent fertility of the soil, which is generally low in Northern Nimba. Other factors influencing crop production are pests and diseases. No research appears to have been done as to the optimum length of the fallow period in the area (nor anywhere else in Liberia), but Richards (1986) reported that farmers in one village in Sierra Leone believed that an 8 to 15 year fallow interval was optimum, and that leaving the land fallow for longer than the period judged necessary to ensure a good harvest only compounds the problems of clearing. From his research, Richards found that finer textured soils generally required a fallow period of 8 to 10 years while coarser textured soils needed 12 to 15 years, depending on location, profile characteristics and topographic position. Even so, the community apparently had a number of areas which had not been cultivated for over 30 years. The average fallow period for 90 farms was 11.9 years. Richards‟ findings in Sierra Leone correlate well with that stated in the section above for northern Nimba, where the majority of the farmers surveyed fallowed their fields for between six and ten years, though there were fields that required more years. The two farmers who said that they had cleared their fallow after three years had done so with the intent to plant perennial crops because the soil looked good for these crops, and both found that their rice yields were satisfactory. This could confirm that, despite the above, a short fallow period is all that is needed in some circumstances to replenish soil fertility in the area (or at least on the soils of the cleared areas) or the short fallow could have been long enough to control the arable weeds. Alternatively, if these two farms were located on alluvial soils (fluvisols), a shorter fallow period might be required than that necessary for the ferralsols and cambisols, especially if soil moisture was not limiting. Provided the required fallow period is maintained, therefore, shifting cultivation is very efficient in maintaining soil fertility. It has been suggested that the quantities of nutrients returned annually to the soil from the forest are greater than when applied economically as fertiliser and lime. The deeper rooting system of the mature trees in the fallow recycle plant nutrients that have been washed down the profile through leaching, bringing these up above ground into their biomass and then returning them to the soil surface via litter (leaves, twigs, etc.) and rain wash from leaf surfaces. This all happens in a very efficient nutrient cycle – a near closed system – that is interrupted when a patch of fallow is cleared for farming. As with all living organisms, the length of fallow period has to be sufficient for it to reach maturity or at least to that point in time when the nutrient cycle has replenished the soil fertility sufficiently to produce another rice crop. Depending on a number of factors (e.g. soil characteristics, rainfall, and type of vegetation), the time to maturity can be as short as 3 or 4 years or a long as 30 years. While most farmers in northern Nimba fallow their fields for between 6 and 10 years, it is not known if this is the optimum length of time for the fallow to reach maturity or is forced upon farmers due to scarcity of land.

5.4 Impact of Tree Crops on Long Term Fertility The impact of a given tree crop on long term fertility will depend to some extent on the type of tree crop, its characteristics (e.g. shallow or deep-rooted), how well it is managed and how well it is suited to the local climate (macro or micro, or both). Whether it is a „plantation‟ or „forest‟ species, the deeper rooted tree crops will continue to bring plant nutrients from the lower profile back up to the surface, and once established there should be little if no soil erosion to remove the topsoil and its store of nutrients. The major limitation of a plantation species is that it will not return the level of biomass to the soil surface in the way that a forest fallow does because as a mono-crop it does not have the mix of accompanying species. There could be several reasons why there is a trend toward planting tree crops in northern Nimba including land pressure and more reliable income (tree crops such as rubber and oil palm are harvested year around offering a relatively steady source of income). The price data shown in Figure 20 are somewhat out of date, but are still indicative.




In this example, oil palm (of the major tree crops) offers the highest return, because palm oil is a basic food commanding a price not regulated by the international market (in 2010 this was 33 cents per litre compared to an internationally traded price of 20 cents per litre). It also has the highest labour requirement per hectare because of the labour-intensive nature of processing the fresh fruit into oil. Assuming that the farm family performs this value-added process, it benefits directly on sale. Figure 20. Indicative cost data for different tree crops in Liberia.

Crop

Income and Expenditure per kg Return per

ha Income/kg Cost/kg Margin/kg Man days/

ha/year Return/

man day

Rubber

Small Holder $0.13 $0.11 $0.02 124 $1.41 $26.00

Firestone Estate $0.16 $0.13 $0.03 64 $4.51 $31.00

Coffee

Smallholder $0.16 $0.16 -$0.00 32 $0.96 -$1.00

Potential $0.09 $0.07 64 $1.96 $62.00

Cocoa

Smallholder $0.29 $0.15 $0.14 26 $2.34 $34.00

Potential $0.13 $0.16 60 $2.67 $101.00

Oil Palm (oil)

Smallholder $0.33 $0.15 $0.15 144 $2.02 $146.00

Potential $0.18 $0.18 170 $3.19 $354.00

Rice

Upland $0.23 $0.20 $03 82 $1.48 $97.50

Swamp

Normal $0.23 $0.20 $0.03 124 $1.23 $310.00

Improved $0.23 $0.11 $0.12 138 $2.15 $345.00

Banana/Plantain

Per bunch Per bunch Per bunch

Extensive $0.06 $0.39 $0.49 92 $2.88 $165

Intensive $0.35 $0.53 210 $3.09 $430

Kola Nut

Smallholder $0.10 $0.08 £3.14 34 $1.75 $2.00

Increased interest in tree crops in Nimba could also be a result of activities of farmers who have received training at the Agricultural Training Centre in Sanniquellie: some of these have been instrumental in introducing tree crops into their farming operation. At the time of the first baseline surveys in 2007, 29 households had rubber farms ranging in size from 25 to 7000 trees. None were then in production as the oldest planting dated from 2002

2 but by now perhaps half of them are, and

this may be encouraging other farmers to do the same. Another factor might be the Smallholder Tree Crops Revitalising Support Programme launched by the Government of Liberia. While this is focused (initially at least) on existing tree crop farms and will have fairly stringent requirements, the detail is probably not clear to many of the northern Nimba farmers. Interest could also be due to current sale prices. Cocoa prices reached a 32-year high in 2011 and coffee prices reached a 12-year high with global stocks at the lowest level for a decade

3.

Also, a factor not to be discounted is the hope for greater compensation by those who believe that they will be moved from their land by mine activities.

2 Two households, not included here, said that they had cleared their 2007 farms with a view to planting rubber, though

whether they did so or not, was not determined 3 The Observer 9th September 2010 – Business Section (Food).




6. MAINTAINING SOIL FERTILITY IN AN INTENSIVE FARMING SYSTEM

6.1 Agriculture and Soils The level of organic matter in the soils of northern Nimba essentially dictates the level of fertility as organic matter is the main source of plant nutrients – due to the low cation exchange capacity of the dominant kaolinite clay minerals and low amount of weathering minerals. Thus land management needs to focus on maintaining, even enhancing, the level of organic compounds (humus, etc.) in the upper part of the soil profile. Maintaining or enhancing the organic matter content of these soils under a more permanent cropping regime would require developing an alternative farming system that mirrors the bush fallow system – i.e. uses economic crop species that handle all the functions of the bush fallow – deep-rooted plants (trees and large shrubs) intermixed with the shallow-rooted species as green manure and crop rotations. The inclusion of small livestock in the mix would also offer additional soil nutrition. Long term agriculture should, ideally, only be developed on land with slopes less than 25%. Steeper slopes are much more difficult to work (more labour intensive) and the risk of erosion is higher and more difficult to manage. The advantage of leaving the steeper slopes as forest is that the communities would still have access to some of the traditional forest species and production that are of benefit to them, and the forest will provide habitat for much of the fauna that will be dislocated by the more intense cultivation of the lower slopes. Shifting cultivation is the oldest known agro-forestry system, but it relies on nature-controlled fallow periods to restore soil fertility. Modern agro-forestry is a continuous system using a combination of tree and arable crops in a way that simulates crop and fallow regimes at the same time, or in some cases alternating as crop and fallow but with much shorter fallow periods. The tree crops can be any of a wide range of economic species (e.g. oil palm, coffee, kola, fruit trees) or native forest species which have uses beneficial to the farm family and community. For the latter, fast growing legume species might be best as these will add nitrogen to the soil as well as provide income from sales. Shade can be provided for coffee and cocoa by inter-planting these two crops with banana, plantain, oil palm, rubber, various fruit and nut trees or forest tree species. Shade tolerant low-growing legumes can be inter-planted with the tree crops to provide ground cover and green manure, and to suppress weeds. These can also provide grazing for livestock.

6.2 Potential Use of Fertilisers It is possible to modify traditional farming practices so as to reduce the length of fallow periods. This would require field outlines to be permanently defined. Reed (1951) considered that the fertility of Liberian soils could be maintained at suitable levels for vegetable cultivation with the use of fertilisers containing phosphorus and potassium, leguminous green manure cover crops such as velvet bean (Mucuna utilis) to add nitrogen and, in highly acidic soils, addition of lime (from either crushed limestone or gypsum). He cautioned, however, that the use of commercial fertilisers in under-developed areas is likely to be determined more by supply and capital than by actual plant nutrient requirements. For small-scale use, poultry manure has a high NPK content and also contains useful amounts of calcium and magnesium, but it is best composted before use in order to conserve volatile nitrogen (Caplan, 1992). Tree crops would not benefit from these new practices, because their relatively small nutrient requirements are satisfied by present cultivation methods, and are therefore more suited to extensive agricultural production. Additions of lime and fertilisers have to be carefully planned on the basis of plant requirements, soil properties and likely chemical reactions. It is important not to apply fertilisers in quantities greater than those required by crops as this will waste scarce and expensive resources, may retard crop growth, and the surplus will be removed either by surface runoff or downwards percolation and may therefore pollute watercourses or groundwater with nutrients. It is also important to avoid over-liming, as this can lock up most nutrients, and lime must not be applied at the same time as manure or compost as this will cause nitrogen to be lost as ammonia gas (i.e. NH3) (Caplan, 1992). The addition of large amounts of easily decomposable organic matter (e.g. green manure) in seasonally flooded




lowland acid soils will intensify the effects of iron toxicity and zinc and potassium deficiencies in rice (Becker and Asch, 2005). It should be noted that both limestone and gypsum are either very rare or absent in Liberia, but limestone does occur in Ivory Coast. With reference to Read (1962), a potential local source of calcium might be relatively unweathered gneissic rocks rich in oligoclase (soda-lime plagioclase feldspar), hornblende (an amphibole containing calcium, magnesium, sodium, iron and aluminium) or augite (a pyroxene containing calcium, magnesium, iron and aluminium). Of particular importance, crushed or ground animal bones (bone meal) can be used as a slow-acting source of both calcium and phosphorus (Caplan, 1992). All vegetable and bone waste can be re-used in various ways as fertilisers and, using processes that have proved successful in other African countries (e.g. Dagerskog et al, 2010), this could be extended to include human faeces and urine.

6.3 The Importance of the Farmer It is important to appreciate that a technology-led approach to stimulating agricultural change is bound to end in costly failure if it fails to understand the diverse constraints of smallholder farmers at the design stage. Unfortunately the scientific approach to agriculture has over decades led to a technology design process in which the measurable physical variables (soils, water, growth rates etc.) have obscured all social variables in farming. This approach has become economically very powerful since it is able to prescribe neat packages, demonstrable if necessary on research stations, to meet political desires for increased production, food security and the like. People understandably want straightforward answers and reassurances for complex problems. It is necessary to orientate sustainable agriculture development goals away from simple yield maximisation towards a more farmer-focussed approach. Most farmers want to increase their production but can only do so with the means available to them and in the particular setting that they are in. They are also very adept at adjusting their farming to incorporate new technologies, other livelihood opportunities, markets and shifting constraints. A range of opportunities and constraints around crop marketing channels also needs to be examined, and ways found to ameliorate and overcome these are a necessary part of improving local livelihoods which will help stimulate agricultural changes. Farmers will pursue these changes in very different ways and there is certainly a support role to be played in advising on the range of options available, bringing in new ideas from elsewhere and encouraging farmer-to-farmer knowledge exchange. Listening to and understanding farmers constraints and objectives needs to be central to developing this role.

6.4 Simple Soil Fertility Improvement Methods

The use of composts, manures and fertilisers can be very effective in improving growth. The main

effects are as follows.

Composts, manures and fertilisers increase the available plant nutrients in the soil and

improve growth.

Compost and manure also increase the amount of organic material in the soil. Organic matter

improves the soil‟s physical properties and holds more moisture in the soil.

Compost and manure can also be used as a mulch. A mulch is a surface layer of rotted

organic matter that helps to hold moisture in the soil by reducing evaporation, and also

suppresses weeds.

Although composts and manures have additional benefits over chemical fertilisers, they contain

relatively small amounts of the major soil nutrients. The table in Figure 18 lists the chemical

composition and percentage of the major soil nutrients in chemical fertilisers and organic manures

commonly available. The improvement of soil fertility on agricultural land is a specialised business. Cultivated soils vary greatly in their nutrient status, and without conducting soil tests it is not possible to make accurate fertiliser recommendations. The unscientific use of fertilisers can create damaging levels of soil chemicals, for example where certain minor nutrients become chemically bonded and unavailable to




plants. For this reason, in cases of fertiliser recommendation you should refer to a fully equipped laboratory. If this is not available, the quantities in Figure 21 may be used as an approximation. The use of composts and manures, however, is to be strongly recommended in all cases. Unless the material contains industrial waste (unlikely in rural areas) it will not have a toxic effect. Instead, the additional nutrients will almost certainly benefit crops, and the physical benefits of organic matter will also improve the soil. Practical features in composting and manuring are as follows.

Always ensure that the material is well rotted. Under no circumstances allow green plant

material or fresh dung to be applied to the land.

Try to use a mixture of materials: e.g. goat dung, forest litter and household compost.

When making compost, mix together the available materials and allow it to decompose while

aerated. It should be turned regularly (ideally every two weeks) and used only when it is com-

pletely black and amorphous.

Keep the composting material in pits or heaps. If in a pit, make sure that the pit is freely

drained and does not get waterlogged.

When the compost or manure is put on the land, spread it out within one day. Do not allow it

to be left in heaps, as this reduces its effects on the soil. It must be ploughed or dug into the

soil well before seed sowing time.

Figure 21. Composition of commonly available fertilisers and manures

Commercial name Chemical formula Percentage by weight

N : P : K

Manures

Cow manure Variable 0.7 : 0.1 : 0.5

Goat manure Variable 2.8 : 0.6 : 2.4

Pig manure Variable 1.0 : 0.3 : 0.7

Poultry manure Variable 1.6 : 0.5 : 0.8

Sheep manure Variable 2.0 : 0.4 : 2.1

Mixed FYM, mean Variable 0.6 : 0.1 : 0.5

Digested sewage sludge Variable 2.0 : 0.5 : 0.3

Fertilisers

Sulphate of ammonia (NH4)2SO4 21 : 0 : 0

Urea CO(NH2)2 46 : 0 : 0

Triple superphosphate CaH(PO4) 0 : 21 : 0

Muriate of potash KCl 0 : 0 : 49

Complexol Unknown 20 : 9 : 0

Diammonium phosphate (NH4)2HPO4 18 : 20 : 0

6.5 Land Rehabilitation and Improvement Methods This section provides a checklist of the most common and practical methods for land and soil improvement. In any particular situation, only a few might be possible. You should consider how many can be applied to each site where improvement is required, since a combination of approaches is always better than one method alone. Soil working/cultivation. The soil is loosened by hand working or cultivation. This improves physical conditions so that plants can root more easily, and more water can infiltrate and be stored in the soil. Tree planting/re-afforestation. This is a simple method of establishing a vegetation canopy so that

there is a better vegetation cover and improved soil physical conditions. The trees also have chemical functions, particularly in recycling plant nutrients from deep in the soil. Agroforestry. Trees are grown among the crops on farm land. The crops may be annual (e.g. maize

or upland rice) or more perennial (e.g. cassava). The trees are usually fruit or other productive trees (e.g. plantain, coffee or rubber).




Fertilising, manuring, composting and mulching. These practices increase both the amount of

organic material and nutrients in the soil. They are common methods of soil improvement, with both physical and chemical benefits. Organic matter holds moisture in the soil, and improves the biological activity and physical condition. Under-planting of crops (relay planting or multiple cropping). When one crop is almost ripe, another crop is planted in between. A common example is the under-planting of maize with rice. This ensures a continuous cover of vegetation and shading of the soil surface; these in turn mean that the soil is stable and maintained in a good physical condition. Cover cropping. Low, shallow-rooting plants are sown between a main crop to protect the surface

against erosion. An example is sowing small leguminous pulse crops (such as beans) or “green manurer” under maize. Successful use of cover crops depends on getting a beneficial, non-competitive combination of plants, so that the main crop is not adversely affected. Use of legumes. Legumes are part of a large family of herbs, shrubs and trees that have special bacteria living in their roots. These bacteria mineralise atmospheric nitrogen, making it into a form available to plants. Since nitrogen is the most volatile and easily leached (washed out) of the major nutrients, this is usually beneficial to other plants. However, legumes use soil water and supplies of all the other nutrients, and so may compete with the other plants. Legumes can be used either in combination with other crops, or can be sown when an area of land is left fallow for a year or more. If used in fallowing, they are usually burnt or cultivated back into the soil at the end of the fallow period. Rotation cropping. Different crops are planted in successive years, An example might be a farm planted with upland rice, maize and beans on a three-year rotation. Fallowing. The land is left uncultivated for one or more years. This allows the soil to recover some

of its fertility naturally, since mineral weathering and biological activity continue without nutrients being removed in crops. Planting with a legume that is then burnt or cultivated back in, can help improve the nutrient status. Reduced tillage. The amount of cultivation is reduced to a minimum. This helps the soil to develop a stronger structure, that is more resistant to erosion. In some cases complete cultivation is essential, but in other instances it may be possible to plant or sow the next crop between the dead stems of the last crop, without cultivation. However, weeding may be more difficult in this situation. Contour bunds. On sloping land, earth bunds can be constructed along the contours to interrupt

runoff and increase infiltration. Contour hedges. Also on sloping land, hedges of grasses (particularly productive thatch grasses) can be planted in hedge lines along the contour. The hedges should be at least three rows of grass plants thick, with the rows planted 50-cm apart and the initial spacing of grasses within the rows at 10-cm. Cultivation should stop a little way back from the hedge so that it is not damaged, but forms a strong barrier to erosion and soil loss. Careful management of the hedge can make it highly productive. Other herbs and shrubs can also be used for hedges. Strip cropping. On long sloping sections of cultivated land, wide contour bands of different crops

can sometimes be grown. The intention is that alternate strips are under a dense crop while the in-between strips are freshly cultivated. Strips should not be wider than 15-metres. Perennial grass planting. This is a common form of protecting slopes against erosion that are too

marginal for cultivation but still hold useful potential. Large thatch grasses reinforce the surface soil and resist erosion. Forest plot management. This is normally done to ensure a sustained yield of forest products, and

therefore means that it keeps plots of forest close to farms in good condition. In turn, the forest cover keeps the soil stable and in good condition, well protected and undisturbed by erosion.




7. VEGETATION MANAGEMENT FOR SOIL CONSERVATION

7.1 Summary of Soil Conservation Methods using Vegetation The techniques given below are the most common methods of using vegetation for soil conservation. Details of how to implement them are given in the ArcelorMittal Liberia Environmental Standards Manual. Planted lines of grass protect and reinforce the slope with their roots and, by providing a surface cover, reduce the speed of runoff and catch debris, thereby armouring it against erosion.

Shrub and tree planting: shrubs or trees are planted at regular intervals on a slope. As they grow, they create a dense network of roots in the soil. The main engineering functions are to reinforce the soil and, later, to anchor deeply into the subsoil.

Large bamboo planting can reduce movement of soil and stabilise slopes. Large bamboos are usually planted by one of two methods: (1) by digging out a section of rooted rhizome and culm, and replanting it in a new location; or (2) by taking culm cuttings from a mother plant, rooting them in a nursery and then planting them on site. Large clumps of the big bamboos are one of the most substantial vegetation structures available to reinforce and support a slope. However, they do not have deeply penetrating roots and so do not anchor deeply into the subsoil.

Grass seeding is where grass is sown direct on to the soil surface. It allows easy vegetation coverage of large areas. The main functions are to protect the surface against erosion, and later also to reinforce the soil through root strengthening.

Brush layering: woody (or hardwood) cuttings are laid in lines across the slope, usually following the contour. These form a strong barrier, preventing the development of rills, and trap material moving down the slope. In the long term, a small terrace will develop. The main functions are to catch debris, and to protect the slope against erosion. In certain locations, brush layers can be angled to provide a drainage function.

Palisades: woody (or hardwood) cuttings are planted in lines across the slope, usually following the contour. These form a strong barrier and trap material moving downwards. In the long term, a small terrace will develop. The main functions are to catch debris, and to slow erosion on a slope. In certain locations, palisades can be angled to give a drainage function.

Live check dams: large woody (or hardwood) cuttings are planted across an erosion gully. These form a strong barrier and trap material moving downwards. In the longer term, a small step will develop in the floor of the gully. The main purposes are to catch debris, reinforce the gully floor and stop heavy erosion.




7.2 General Principles of Vegetation Management for Soil Conservation In soil conservation, the aim is to stop all forms of erosion and shallow mass movement from agricultural and bare slopes in degraded land. It is usually necessary to manage vegetation in order to achieve this since a semi-natural (or unmanaged) community of vegetation does not always provide the functions required for complete slope stabilisation and soil conservation. Mixed structure. You should aim to manage the vegetation to produce a mixed vegetation community with a variety of trees, shrubs and grasses on a single site. Single species, or vegetation communities dominated by one or a few species, are unlikely to have either an irregular structure or a variety of ages. Mixed age. Try to achieve a collection of plants of mixed ages for each site (an uneven-aged

structure). This means that all plants do not need to be replaced at the same time and there will always be some strong, healthy plants protecting the soil. Low maintenance. Aim to establish a vegetation community that does not need too much

intervention from outside to maintain it. For example, choose species that can regenerate naturally (without planting); species that do not grow too fast or too tall (less need for frequent cutting and removal); species that live longer, etc. Managed progression. In soil conservation it is often necessary to start with pioneer species and move towards a climax community.

Pioneer or colonising species are the first plants to appear on bare ground and are naturally adapted to living on sites with harsh conditions.

Climax community species are plants that form permanent natural forest. They tend to require better sites to grow and need the partial shade from other plants, and grow more slowly.

An ideal vegetation community for soil conservation might have the features shown in Figure 2. This has large trees which root deeply, giving the maximum soil anchoring effects. Shrubs form an intermediate level, with strong, woody roots more shallow than the trees, providing good reinforcement of the soil, and many stems to catch debris. Large clumping grasses catch small debris and provide a thick surface cover to protect against erosion, with a dense network of fibrous roots. Figure 22. Ideal plant community arrangement for soil conservation

Drawing © Jaquelien Chapman




ANNEX A: TYPICAL SOIL CHEMICAL AND PHYSICAL CHARACTERISTICS

A.1 Ferralic Cambisols Cambisols are soils with at least the beginnings of horizon differentiation in the subsoil, evident from changes in structure, colour, clay content or carbonate content. They are characterised by slight or moderate weathering of parent material and by absence of appreciable quantities of illuviated (i.e. washed down the profile) clay, organic matter, aluminium or iron compounds. They are found in level to mountainous terrain in all climates, and with a wide range of vegetation types. Ferralic Cambisols under Cultivation Soil Profile Description (Profiles 23 & 26) SOIL UNIT: U5g U3g Hypoplinthic Ferralic Cambisol Landform Undulating plain Undulating plain Crop(s) Maize, Avocado Cassava, coffee, cacao, Avocado, Banana Vegetation Clearing, secondary forest Cleared Soil drainage class Well drained Well drained Soil parent material Weathered gneiss Weathered gneiss

Horizon Depth

cm Lab.

texture

Sum of exchangeable

cations, cmolc kg-1

CEC cmolc kg-1

OC %

pH, water 1:2.5

C:N Av. P mg/kg

Total N %

K - cmolc kg-1

23/1 0-14 SL 4.9 25-M 3-L 5.1-L 16-M 5.9-L 0.17-L 0.2-L

23/2 14-45 SCL 5.7 31-H 1-L 4.9-L 9-N 1.4-L 0.14-L 0.1-L

23/3 45-100 SCL 19.0 54-vH 0-L 5.0-L 7-L 1.4-L 0.06-VL 0.3-L

26/1 0-30 SL 25.4 9–L 4-M 5.7-M 22-H 16.7-M 0.17-L 0.1-L

26/2 30-107 SCL 19.2 6–L 1-L 5.9-M 11-N 5.6-L 0.05-VL 0.1-L

Notes. Ferralic properties refer to mineral soil material that has a relatively low CEC, or that has a subsurface horizon resulting from long and intense weathering in which the clay fraction is dominated by low-activity clays and the silt and sand fractions by highly resistant minerals, such as (hydr)oxides of Fe or Al. A plinthic horizon is a subsurface horizon that consists of an Fe-rich, humus-poor mixture of kaolinitic clay (and other products of strong weathering, such as gibbsite) with quartz and other constituents, and which changes irreversibly to a layer with hard nodules, a hardpan or irregular aggregates on exposure to repeated wetting and drying with free access of oxygen. Hypo denotes that these features are weak.




Ferralic Cambisols under Perennial Cultivation Soil units (see Figures 8 and 9): U1g, U3g, U3s, U4, U4g, U5g, U6g, Us, T1, T2, T3. Soil Profile Description (Profiles 21 & 22)

SOIL UNIT: T3 U6g Ferralic Cambisol Landform Valley floor / terrace Rolling plain Cultivation Shifting Perennial cropping Tree crop(s) Mango, grapefruit, papaya Coffee Vegetation Secondary forest Secondary forest Soil drainage class Well drained Well drained Soil parent material Weathered gneiss, ironstone Weathered gneiss

Horizon Depth

cm Lab.

texture

Sum of exchangeable

cations, cmolc kg-1

CEC cmolc kg-1

OC %

pH, water 1:2.5

C:N Av. P mg/kg

Total N %

K - cmolc kg-1

21/1 0-20 SL 4.3 24-M 3-L 4.7-L 15-M 8.5-L 0.22-M 0.1-L

21/2 20-90 SL 9.5 41-vH 1-L 5.1-L 11-N 4.6-L 0.08-VL 0.0-L

22/1 0-20 SL 7.9 33-H 3-L 5.1-L 17-M 5.2-L 0.20-L 0.1-L

22/2 20-50 SCL 5.2 35-H 1-L 4.9-L 16-M 25.5-H 0.08-VL 0.1-L

22/3 50-130 SCL 6.1 52-vH 0-L 11-N 2.9-L 0.04-VL 0.1-L

Notes. Ferralic properties refer to mineral soil material that has a relatively low CEC, or that has a subsurface horizon resulting from long and intense weathering in which the clay fraction is dominated by low-activity clays and the silt and sand fractions by highly resistant minerals, such as (hydr)oxides of Fe or Al. Both of these profiles have relatively good CEC and C:N ratios however, even though organic carbon levels are low.




Ferralic Cambisols under Forest

Soil units (see Figures 8 and 9): U1g, U3g, U3s, U4, U4g, U5g, U6g, Us, T1, T2, T3. Soil Profile Description [Profiles 17 & 18]

SOIL UNIT: U4 U4g Hypoplinthic Ferralic Cambisol Landform Steep hillside Steep hillside Vegetation Secondary forest Secondary forest Soil drainage class Well drained Well drained Soil parent material Weathered ironstone Weathered ironstone

Horizon Depth

cm Lab.

texture

Sum of exchangeable

cations, cmolc kg-1

CEC cmolc kg-1

OC %

pH, water 1:2.5

C:N Av. P mg/kg

Total N %

K - cmolc kg-1

17/1 0-9 LS 12.7 71-vH 10-H 4.5-L 21-H 2.9-L 0.46-M 0.3-M

17/2 9-30 SCL 4.1 16-M 3-L 4.7-L 21-H 5.5-L 0.12-L 0.1-L

17/3 30-115 SL 3.0 28-H 1-L 5.0-L 18-M 4.0-L 0.08-VL 0.0-L

18/1 0-15 SL 6.0 16-M 6-M 5.2-L 21-H 6.7-L 0.29-M 0.1-L

18/2 15-70 S 3.3 19-M 2-L 5.1-L 21-H 2.9-L 0.09-VL 0.1-L

18/3 70-120 SL 3.2 15-M 1-L 5.2-L 19-M 4.7-L 0.06-VL 0.1-L

Notes. Ferralic properties refer to mineral soil material that has a relatively low CEC, or that has a subsurface horizon resulting from long and intense weathering in which the clay fraction is dominated by low-activity clays and the silt and sand fractions by highly resistant minerals, such as (hydr)oxides of Fe or Al. A plinthic horizon is a subsurface horizon that consists of an Fe-rich, humus-poor mixture of kaolinitic clay (and other products of strong weathering, such as gibbsite) with quartz and other constituents, and which changes irreversibly to a layer with hard nodules, a hardpan or irregular aggregates on exposure to repeated wetting and drying with free access of oxygen. Hypo denotes that these features are weak.




A.2 Ferralsols Ferralsols are red and yellow tropical soils with a high content of sesquioxides. Parent material is strongly weathered material on old, stable geomorphic surfaces. They are mostly found in (or were previously formed in) the humid tropics. Deep and intensive weathering has resulted in a residual concentration of resistant primary minerals (e.g. quartz) alongside sesquioxides and kaolinite. This mineralogy and the relatively low pH explain the stable microstructure (pseudo-sand) and yellowish (goethite) or reddish (haematite) soil colours Ferralsols under Cultivation Soil Profile Description [Profiles 1 & 3] SOIL UNIT: U2g T1 Hypoplinthic Ferralsol Landform Undulating plain Undulating plain Cultivation Shifting Shifting Crop(s) Rice Rice, cassava Tree crop(s) Young rubber None Vegetation Cleared Secondary forest Soil drainage class Well drained Moderately well drained Soil parent material Weathered gneiss Weathered gneiss

Horizon Depth

cm Lab.

texture

Sum of exchangeable

cations, cmolc kg-1

CEC cmolc kg-1

OC %

pH, water 1:2.5

C:N Av. P mg/kg

Total N %

K - cmolc kg-1

1/1 0-18 SL 4.9 14–L 3-L 4.8-L 18-M 9.4-M 0.18-L 0.1-L

1/2 18-47 SCL 1.3 13–L 1-L 5.0-L 15-M 6.8-L 0.06-VL 0.1-L

1/3 47-90 SCL 6.0 11–L 1-L 5.0-L 15-M 3.3-L 0.05-VL 0.1-L

1/4 90-137 CL 2.1 28–H 0-L 5.1-L 9-N Trace 0.05-VL 0.1-L

3/1 0-14 LS 4.7 23-M 3-L 4.8-L 21-H 62.8-H 0.13-L 0.2-L

3/2 14-32 SL 4.8 18-M 2-L 4.7-L 18-M 2.3-L 0.11-L 0.1-L

3/3 32-80 SCL 3.1 43-vH 1-L 4.7-L 14-M Trace 0.06-VL 0.1-L

3/4 80-130 SCL 3.0 27-H 1-L 4.9-L 13-M 0.2-L 0.05-VL 0.1

Notes. A plinthic horizon is a subsurface horizon that consists of an Fe-rich, humus-poor mixture of kaolinitic clay (and other products of strong weathering, such as gibbsite) with quartz and other constituents, and which changes irreversibly to a layer with hard nodules, a hardpan or irregular aggregates on exposure to repeated wetting and drying with free access of oxygen. Hypo denotes that these features are weak.




Ferralsols under Forest Soil Profile Description [Profiles 10 & 27]

SOIL UNIT: T2g T3 Hypoplinthic Ferralsol Landform Valley floor / terrace Valley bottom / terrace Vegetation Secondary forest Bush Soil drainage class Well drained Well drained Soil parent material Weathered gneiss Alluvium

Horizon Depth

cm Lab.

texture

Sum of exchangeable

cations, cmolc kg-1

CEC cmolc kg-1

OC %

pH, water 1:2.5

C:N Av. P mg/k

g

Total N %

K - cmolc kg-1

10/1 0-10 SCL 4.1 25-M 5-M 4.5-L 15-M 3.1-L 0.37-M 0.2-L

2 10-25 SC 4.0 17-M 3-L 4.5-L 9-N 1.7-L 0.35-M 0.1-L

3 25-65 SCL 3.0 19-M 2-L 4.7-L 7-L 3.1-L 0.22-M 0.1-L

4 65-90 SL 4.1 26-H 1-L 4.8-L 6-L 4.2-L 0.15-L 0.1-L

5 90-200 C 5.9 15-L 1-L 4.8-L 9-N 0.3-L 0.07-VL 0.1-L

1 0-23 SL 9.3 29-H 3-L 5.1-L 17-M 5.4-L 0.17-L 0.2-L

2 23-80 SCL 1.2 34-H 1-L 5.0-L 18-M 2.0-L 0.04-VL 0.1-L

3 80-133 SCL 3.3 40-H 0-L 5.1-L 16-M 1.3-L 0.02-VL 0.1-L

Notes. A plinthic horizon is a subsurface horizon that consists of an Fe-rich, humus-poor mixture of kaolinitic clay (and other products of strong weathering, such as gibbsite) with quartz and other constituents, and which changes irreversibly to a layer with hard nodules, a hardpan or irregular aggregates on exposure to repeated wetting and drying with free access of oxygen. Hypo denotes that these features are weak.




Ferralsols under Forest Soil Profile Description [Profiles 13 & 20]

SOIL UNIT: T1 T2 Haplic Ferralsol Landform Valley bottom / terrace Undulating terrace Vegetation Secondary forest Secondary forest Soil drainage class Imperfectly drained Well drained Soil parent material Weathered gneiss/old alluvium Alluvium

Horizon Depth

cm Lab.

texture

Sum of exchangeable

cations, cmolc kg-1

CEC cmolc kg-1

OC %

pH, water 1:2.5

C:N Av. P mg/kg

Total N %

K - cmolc kg-1

13/1 0-20 SCL 2.8 37-H 1-L 4.7-L 12-M 0.8-L 0.12-L 0.3-L

13/2 20-60 C 9.7 22-M 1-L 4.8-L 19-M Trace 0.05-VL 0.1-L

13/3 60-90 C 12.6 35-H 1-L 5.0-L 15-M Trace 0.05-VL 0.1-L

20/1 0-24 SL 1.4 29-H 3-L 4.8-L 22-H 4.7-L 0.12-L 0.0-L

20/2 24-68 SCL 18.4 23-M 1-L 4.9-L 16-M 2.9-L 0.05-VL 0.1-L

20/3 68-100 SL 12.9 30-H 1-L 5.0-L 21-H 2.9-L 0.03-VL 0.1-L

Notes. Haplic describes a soil having a typical expression of certain features (typical in the sense that there is no further or meaningful characterisation) and is only used if none of the other type qualifiers applies. These examples are therefore “typical” ferralsols with no other significant features.




A.3 Fluvisols Fluvisols are soils developed in river-borne alluvial deposits. they are found in alluvial plains, river fans, valleys and tidal marshes on all continents and in all climate zones; many fluvisols are flooded periodically under natural conditions. Profiles have evidence of stratification but weak horizon differentiation, although a distinct topsoil horizon may be present. Signs of mixed iron reduction and oxidation are common (usually with mottled colouring), particularly in the lower part of the profile. Fluvisol under Cultivation

Soil Profile Description [Profile 30]

SOIL UNIT: F1 Hypoendostagnic Fluvisol Landform Floodplain Vegetation Cleared Soil drainage class Moderately drained Soil parent material Alluvium

Horizon Depth

cm Lab.

texture

Sum of exchangeable

cations, cmolc kg-1

CEC cmolc kg-1

OC %

pH, water 1:2.5

C:N Av. P mg/kg

Total N %

K - cmolc kg-1

1 0-20 L 33 36-H 0.12 4.8-L 6.3-L 4.5-L 18-VH 12.0-H

2 20-70 SCL 37 32-H 0.05 5.0-L 3.6-L 3.6-L 14-VH 11.7-H

3 70-120 CL 41 14–L 0.02 5.0-L 2.0-L 4.5-L 19-VH 5.9-H

Notes. Endostagnic soils have reducing conditions for some time during the year in some parts of the profile between 50 and 100 cm from the mineral soil surface. In 25 percent or more of the soil volume, single or in combination, they also have a mottled colour pattern with lighter and paler areas; or a light-coloured subsurface horizon from which clay and free iron oxides have been removed, or in which the oxides have been segregated to the extent that the colour of the horizon is determined by the colour of the sand and silt particles rather than by coatings on these particles. Hypo denotes that these features are weak.




A.4 Gleysols Gleysols are wetland soils that, unless drained, are saturated with groundwater for long enough periods to develop a characteristic gleyic colour pattern. This pattern is essentially made up of reddish, brownish or yellowish colours at ped surfaces or in the upper soil layer, in combination with greyish or bluish colours inside the peds or deeper in the soil. they are found in depressional areas and low landscape positions with shallow groundwater. Gleysol under Forest

Soil Profile Description [Profile 5]

SOIL UNIT: V2 Haplic Gleysol Landform Valley floor Vegetation Secondary forest Soil drainage class Very poorly drained Soil parent material Alluvium

Horizon Depth

cm Lab.

texture

Sum of exchangeable

cations, cmolc kg-1

CEC cmolc kg-1

OC %

pH, water 1:2.5

C:N Av. P mg/k

g

Total N %

K - cmolc kg-1

1 0-15 SL 5.1 38-H 4-M 5.5-M 20-H 2.5-L 0.20-L 0.1-L

2 15-45 SL 5.5 29-H 3-L 5.2-L 22-H 3.6-L 0.15-L 0.1-L

Notes. Haplic describes a soil having a typical expression of certain features (typical in the sense that there is no further or meaningful characterisation) and is only used if none of the other type qualifiers applies. These examples are therefore “typical” ferralsols with no other significant features. No photograph available.

cm Soil profile description

0-15 Brown (10YR 4/3); wet; slowly permeable; clay loam; few fine distinct gley mottles; slightly sticky slightly plastic wet; massive structure; many fine and common medium roots; clear smooth boundary.

15-45 Very dark greyish brown (10YR3/2); wet; slowly permeable; sandy clay loam; common medium distinct gley mottles; slightly sticky slightly plastic wet; massive structure; common fine and few medium roots.

45+ Water table.




A.5 General Character of Soil Samples Reported In 2008 Soil Survey

Profile Pit No.

UTM Coordinates

Soil Type Altitu

de (m)

Terrain Character Farmland Status

Class Texture

Tokadeh (Zulowi)

P6 539067/824454 Ferralsol (U5g) Sandy clay loam 465 Low hill (120 slope) on undulating plain 2 km from ridgeline Cultivated (rice, cassava etc.)

P11 537239/823622 Ferralsol (U3g) Gravelly clay loam 600 Lower slope (200) 0.5 km below ridgeline Secondary forest

P29 539572/821958 Fluvisol (T1) Sandy clay loam 470 Terrace (30 slope) on undulating plain 1 km from ridgeline Secondary forest with palms

West Gbapa Plain (including TMF and WSR)

P3 541210/825330 Fluvisol (T1) Clayey silty sand 430 Terrace (60 slope) on undulating plain 3 km from ridgeline Cultivated (rice, cassava)

P4 540409/825461 Ferralsol (U1) Clay loam 450 Undulating plain 2 km from ridgeline Secondary forest (fallow?)

P5 539923/824886 Gleysol (V2) Sandy clay loam 460 Valley floor within undulating plain 2 km from ridgeline Secondary forest

P7 538618/828111 Ferr.Cambisol (U3g) Gravelly clay loam 480 Lower slope (140) 0.2 km below ridgeline Secondary forest (fallow?)

P8 541184/827608 Fluvisol (T2g) Sandy clay loam 440 Valley floor terrace (10 slope) 2.5 km from ridgeline Secondary forest (fallow?)

P9 542058/826978 Ferralsol (U5g) Clay loam 450 Undulating plain (30 slope) 3.5 km from ridgeline Uncultivated bush (fallow?)

P27 539945/827310 Fluvisol (T3) Sandy clay loam 440 Valley floor terrace (30 slope) 1.5 km from ridgeline Uncultivated bush (fallow?)

North Gbapa Plain (areas on both sides of Dayea River)

P1 542941/829340 Ferralsol (U2g) Sandy clay loam 440 Low hill (200 slope) on undulating plain 4.5 km from ridgeline Cultivated (rice, young rubber)

P2 542317/829980 Ferralsol (U1g) Gravelly clay loam 420 Low hill (120 slope) on undulating plain 4.5 km from ridgeline Secondary forest (fallow?)

P23 542468/831172 Ferr.Cambisol (U5g) Sandy clay loam 460 Low hill (80 slope) on undulating plain 4.5 km from ridgeline Cultivated (maize, avocado)

P30 541094/830400 Stagnic fluvisol (F1) Sandy clay loam 440 Dayea River floodplain terrace (10 slope) 3.5 km from ridge ridgeline Cultivated (rice, plantain)

Gangra (including lower slopes in North Gbapa and Bolo)

P14 540878/835319 Ferr.Cambisol (U3g) Gravelly clay loam 720 Upper slope (250) 0.2 km below ridgeline Secondary forest

P21 541647/832992 Fluviisol (T3) Sandy clay loam 480 Valley floor terrace (30 slope) 1.5 km from ridgeline Cultivated (mango, grapefruit) etc.)

P22 542097/832529 Ferr.Cambisol (U6g) Sandy clay loam 480 Low hill (120 slope) on undulating plain 2.5 km from ridgeline Coffee within secondary forest

P25 542875/834515 Ferr.Cambisol (U5g) Gravelly sandy clay 470 Lower slope (120) 2 km below ridgeline Uncultivated bush (fallow?)

P26 543126/832439 Ferr.Cambisol (U3g) Sandy clay loam 460 Low hill (150 slope) on undulating plain 3.5 km from ridgeline Cultivated (cassava, coffee) etc.)

P31 540965/834703 Leptosol (US) Gravelly sandy clay 730 Gently sloping bench (6

0) on upper slope 0.2 km below ridge

rridgeline Secondary forest

Yuelliton (including lower slopes in Lugbeyee)

P15 541680/836978 Ferr.Cambisol (U1g) Gravelly clay loam 690 Gently sloping bench (70) on lower slope 0.4 km below ridge

rridgeline Secondary forest (fallow?)

P16 541130/835772 Ferr.Cambisol (U3g) Gravelly clay loam 740 Upper slope (220) 0.2 km below ridgeline Degraded primary forest

P20 543542/837076 Fluvisol (T2) Sandy clay loam 500 Terrace (60 slope) on undulating plain 2.5 km from ridgeline Secondary forest (fallow?)




Profile Pit No.

UTM Coordinates

Soil Type (1) Bedrock Sample Depth (cm)

Chemical Analyses (2,3)

Remarks (4) pH

Exchangeable Cations (cmol/kg)

CEC(cmol/kg)

OC (%)

Total N (%)

Avail. P (mg/kg)

Class Texture Ca Mg Na K

Tokadeh (Zulowi)

P6 539067/824454 Ferralsol (U5g) Sandy clay loam Gneiss GL-17 5.2 4.5 4.5 0.3 0.3 19 4 0.34 10.0 Cultivated

P11 537239/823622 Ferralsol (U3g) Gravelly clay loam Gneiss/iron fm GL-30 4.4 1.8 0.9 0.3 0.2 32 6 0.35 6.6 -

P29 539572/821958 Fluvisol (T1) Sandy clay loam Alluvium GL-25 4.6 4.6 2.7 0.2 0.1 13 3 0.39 4.7 Gwe 1.25m

West Gbapa Plain (including Water Supply Reservoir and Tailings Management Facility)

P3 541210/825330 Fluvisol (T1) Clayey silty sand Alluvium GL-14 4.8 1.8 0.9 1.8 0.2 23 3 0.13 62.8 Cultivated

P4 540409/825461 Ferralsol (U1) Clay loam Gneiss GL-9 4.6 2.7 1.8 1.4 0 50 4 0.20 2.7 -

P5 539923/824886 Gleysol (V2) Sandy clay loam Alluvium GL-15 5.5 2.7 0.9 1.4 0.1 38 4 0.20 2.5 -

P7 538618/828111 Ferr.Cambisol (U3g) Gravelly clay loam Iron fm/gneiss GL-14 3.8 2.7 2.7 1.8 0.1 32 10 0.57 58.5 -

P8 541184/827608 Fluvisol (T2g) Sandy clay loam Alluvium GL-22 4.6 3.6 1.8 1.7 0.1 17 5 0.22 3.3 -

P9 542058/826978 Ferralsol (U5g) Clay loam Gneiss GL-15 4.5 1.8 0.9 0.3 0.2 35 4 0.25 3.9 -

P27 539945/827310 Fluvisol (T3) Sandy clay loam Alluvium GL-23 5.1 5.4 3.6 0.2 0.2 29 3 0.17 5.4 -

North Gbapa Plain (areas on both sides of Dayea River)

P1 542941/829340 Ferralsol (U2g) Sandy clay loam Gneiss GL-18 4.8 2.7 1.8 0.3 0.1 14 3 0.18 9.4 Cultivated

P2 542317/829980 Ferralsol (U1g) Gravelly clay loam Gneiss GL-15 4.2 1.8 0.9 0.5 0.1 24 4 0.25 4.6 -

P23 542468/831172 Ferr.Cambisol (U5g) Sandy clay loam Gneiss GL-14 5.1 3.6 0.9 0.3 0.2 25 3 0.17 5.9 Cultivated

P30 541094/830400 Stagnic fluvisol (F1) Sandy clay loam Alluvium GL-20 4.8 4.5 2.7 0.3 12.0 36 113 18.00 4.5 Cult; Gwe 2.0m

Gangra (including lower slopes in North Gbapa and Bolo)

P14 540878/835319 Ferr.Cambisol (U3g) Gravelly clay loam Iron formation GL-12 4.4 4.5 2.7 2.3 0.3 23 13 0.72 142.3 Rock at 1.7m

P21 541647/832992 Fluviisol (T3) Sandy clay loam Alluvium GL-20 4.7 1.8 1.8 0.7 0.1 24 3 0.22 8.5 Cult; Gwe 1.05m

P22 542097/832529 Ferr.Cambisol (U6g) Sandy clay loam Gneiss GL-20 5.1 4.5 2.7 0.6 0.1 33 3 0.20 5.2 Coffee in forest

P25 542875/834515 Ferr.Cambisol (U5g) Gravelly sandy clay Gneiss GL-17 5.3 9.9 1.8 0.3 0.3 15 5 0.22 6.1 -

P26 543126/832439 Ferr.Cambisol (U3g) Sandy clay loam Gneiss GL-30 5.7 12.5 12.5 0.2 0.1 9 4 0.17 16.7 Cultivated

P31 540965/834703 Leptosol (US) Gravelly sandy clay Iron formation GL-10 4.4 1.8 0.9 2.9 0.1 46 9 0.47 13.9 Rock at 0.36m

Yuelliton (including lower slopes in Lugbeyee)



P20 543542/837076 Fluvisol (T2) Sandy clay loam Alluvium GL-24 4.8 0.4 0.4 0.5 0 29 3 0.12 4.7 -

Notes: CEC, cation exchange capacity (1 cmol/kg = 1 meq/100g); OC, organic carbon; Avail. P, available phosphorous (1 mg/kg = 1 ppm); cult., cultivated. (1) Some soils have been reclassified after inspection of field descriptions, photographs and particle size determinations. Most soils were uncultivated at the time of

survey. (2) The electrical conductivity of soil extracts was generally either 0.1 or 0.2 dS/m. The exceptions were 0.3 dS/m in P7 and 0 in P20 (1 dS/m = 1000 μS/cm). (3) C:N values ranged between 6.3 (P30) and 22 (P25), with a mean value of 17. The reported OC value of 0.12% for P30 appeared to be incorrect, and has been

recalculated using the reported C:N and total N values. Unusually high values for C and N in this soil may reflect seasonal flooding by the Dayea River.

(4) Groundwater was only encountered in the pits noted (Gwe).




ANNEX B: SOIL ASSESSMENT IN THE FIELD Understanding soil quality is complex, but with experience it is often possible to obtain a reasonable idea just from careful observation in the field. This section gives some basic guidelines on how to do this.

B.1 Signs of soil condition Look closely at the freshly dug vertical face of a soil profile. This will show signs of the soil‟s characteristics that help to give a better understanding of the quality of the landscape. Typical signs are as follows. Surface

Presence of leaf litter. The presence of organic litter from leaves and twigs is a strong indicator of

the fertility of forest soils. In the humid tropics, leaves decompose quickly, and so soils often have limited organic matter. Surface compaction or capping. Excessive walking by people, movement of vehicles or machines,

or removal of vegetation cover can lead to the compaction of the surface. An impermeable cap is formed which reduces infiltration. In turn, this leads to excessive runoff and erosion; and through the reduced moisture regime in the soil, to a degraded soil profile. It is therefore an indicator of both bad management and poor soil. Topsoil

An organic-rich topsoil horizon. This is an indicator of good soil development. The rate of organic

matter decomposition is so fast in the humid tropics that most soils in Nimba do not show a very dark, organic topsoil even when they are in good condition. Therefore evidence of organic matter in a soil is always a good sign of soil stability and condition. Swamp soils are usually the most organic rich. Evidence of a cultivated layer. This is usually about 15 cm in thickness and will only be found on land that has been cultivated. If it is present, it will give better rooting conditions for plant establishment. Physical conditions Degree of stoniness. If the soil is very stony, it means that there is less fine fraction to hold moisture and nutrients, and certain stone types can impede root development. Visual estimates of stone content by volume usually give a higher proportion of the soil volume occupied by stones than is found by sieve analysis. Root penetration. This shows whether plants are able to exploit the profile. Look to see if roots

penetrate throughout the profile, or are confined to certain horizons of soil, and try to work out why this should be so. Look even for the smallest fibrous roots, as these are often adventitous roots, put out to find soil nutrients; in a good forest soil these are sometimes the only roots found in the most organic rich surface horizon. A grey colour or grey and brown mottling. Grey soil usually indicates water-logging and reduction

of iron in anaerobic conditions. Often it is accompanied by a bad, almost sulphurous smell. This is found in swamp soils, and swamp rice strains require these conditions. The majority of other plants do not, and so mottling and reduction are evidence of poor growing conditions in most cases. It may be through a seasonal rise of the groundwater table or slow percolation during the wet season due to a heavy texture (i.e. a lot of clay).




Soil fertility

Signs of soil fertility. The table in Figure B.1 gives general visible indications of soil fertility.

Figure B.1. General visible conditions affecting soil fertility.

Soil property Conditions favouring high soil fertility

Conditions unfavourable to high soil fertility

Depth to limiting horizon > 150-cm < 100-cm

Texture (see Annex B) Loam, sandy clay loam, sandy clay; clay (only if structure and consistence are favourable)

Sand, loamy sand; heavy clay

Structure and consistence (see Annex E)

Moderate or strong, fine or medium structure; friable consistence

Massive, or coarse structure, with very firm consistence

Moisture conditions Free drainage with good moisture retention

Substantial drainage impedance; low moisture retention and rapid permeability

Organic matter Adequate in relation to levels under natural vegetation

Low levels

Origin of soil Soil origin. The origin of the soil can also reveal further information about the site. Figure B.2 summarises the characteristics relating to origin that are most commonly found in Nimba hill and valley soils. Deep, clay-rich soils. These are fine textured (i.e. high clay content) soils with a distinctively red or yellow colour. A deep clay-rich soil has probably been developing in situ for at least 100,000 years, giving it lateritic characteristics. The red colouring comes from the oxidisation of iron among the clays. The presence of a deep, in situ clay soil indicates a stable landform. However, once the vegetation cover has been degraded, these soils can be prone to very high rates of erosion and may be difficult to rehabilitate. Evidence of deposition by layers. Many soils have been formed by deposition from up valley or

upslope. Most layered soils are alluvial, but sometimes a colluvial soil may be found with distinct layers. In alluvial soils, the layers are usually distinguished by dramatic changes in soil texture. These indicate depositions of materials from different sources. Distinct stony layers are also common. Types of stones. Angular stones have not been transported far and usually indicate colluvium;

rounded stones have been transported a long way and indicate alluvium. Evidence of alluvium and colluvium can help to develop an understanding of the geomorphological dynamics of a site. It may be possible to establish when the last deposition was, and therefore what is the likelihood of a similar event in the future.




Figure B.2. Comparison of the main hill and valley soil type origins in Nimba

Soil origin In situ soils (most soils)

Colluvium (steep mountain sides and foot slopes)

Alluvium (along valley bottoms)

General description

Soils formed from the weathering of minerals and the inter-mixing of organic material over a long period, in the position in which they are still located.

Angular debris, usually loose and unconsolidated, found on slopes below rock outcrops having been transported downslope by gravity and water. Other names are scree and talus, although these are normally of pure fragmented rock while colluvium can also contain fine material.

Material, usually fine sand or silt with larger, rounded particles up to boulder size, deposited by a river, having been transported from elsewhere in suspension.

Character-istics

Compact

few weak fragments

few voids

often quite impermeable

usually plastic

mainly fines

Angular fragments

loose

full of voids

very permeable

low plasticity

small amount of clay

silty fines Main fragments:

mixed sizes of angular fragments

silty fines

other particles: quartzite (hard and angular) and phyllite (flaky, platy and irregular)

Loose

round fragments

full of voids

very permeable

not plastic

no fines Main fragments:

sand size quartz and mica

Summary Material has formed into soil in situ (i.e. in the place

where it now is).

Highly weathered fragments.

Angular debris of mixed origin.

Less clay, because weathering not far advanced.

River-borne material.

Rounded fragments.

Mixed with clay and sand.

Implications for agriculture

Generally quite fertile.

Deep rooting conditions.

Easily cultivated.

Relatively high erosion risk.

Generally low fertility.

Often very stony.

Poor moisture holding capacity.

May be a risk of landsliding or debris flow.

Sandy and gravelly horizons have low fertility.

Clayey and silty horizons can be highly fertile.

May be stony and difficult to cultivate.

May be a risk of flooding.

B.2 Assessment of Soil Texture, Consistence and Structure Definitions Texture. In soils, the „feel‟ of moist soil resulting from the mixture of different particle sizes and organic matter. Texture is classified into groups of soils with similar properties on the basis of the mineral component. for example, clay loam contain 27 to 40 percent clay, 15 to 55 percent silt and 20 to 45 percent sand. Sand. Mineral or rock fragments in the diameter range of 2 to 0.02 mm. The word is also applied to a

class of soil texture.

Silt. Mineral particles in the diameter range of 0.02 to 0.002 mm (20 to 2 m). The term is also used loosely to describe any accumulation of fine material, and applied to a class of soil texture.

Clay. Mineral material < 2 m. Also a term applied to a class of soil texture, and used to describe the silicate clay minerals.




Loam. A soil with moderate amounts of sand, silt and clay, and which is therefore intermediate in

texture and best for plant growth. Sandy soils tend to dry out quickly, and to have limited amounts of plant nutrients. Clay soils are often difficult to work, due to being either wet and sticky, or dry and very hard. Field estimation of soil texture Take a small sample of soil in your hand. Moisten it little by little. Knead it between your fingers and follow the questions below.

START

Is the moist soil predominantly rough and gritty?

Yes Does the soil stain the fingers? No Sand

Yes

Is it difficult to roll the soil into a ball? Yes Loamy sand

No

No Sandy loam

No Does the soil feel smooth and silty, as well as gritty?

Yes

Sandy silt loam

Does the soil mould to form an easily deformed ball, and feel smooth and silky (like butter)?

Yes

Silt loam

No

Clay loam

Does the soil mould to form a strong ball which smears, but does not take a polish?

Also rough and gritty Yes Sandy clay loam Yes

Also smooth and silky Yes

Silty clay loam

No

Clay

Soil moulds like putty, polishes and feels very sticky when wet

Yes Also rough and silky Yes Sandy clay

Also smooth and buttery Yes Silty clay

Soil consistence

Consistence is a field test of soil strength, cohesion and resistance to deformation. Dry soil: powdery, soft or hard. Moist soil: loose, friable or firm. Wet soil: Non-sticky, sticky or plastic. Soil structure Structure is the arrangement of primary soil particles into secondary units, which are characterised on the basis of size, shape and degree of development. Common soil structure terms are as follows. Single grain: soil falls loose into primary particles, as in sand. Massive: the entire soil profile is a single, hard mass, as in a dry, heavy clay.

Crumb: the soil holds together in small, moderately firm clods; this is most common in cultivated upland soils.

Prismatic: the soil has formed into distinct aggregates, with cracks or planes of weakness between them; most common in subsoils with a significant clay content.

Puddled: soil puddled together when saturated, as in swamp rice soils.




ANNEX C: NOTES ON INTEGRATED PEST MANAGEMENT Background

Integrated Pest Management (IPM) is an approach which emphasises biological control of crop pests and diseases. IPM is intended to be efficient and economical with limited or no residual problems. The objective of IPM is to reduce the adverse environmental and social impacts that can result from use or overuse of agro-chemicals. This is achieved by promoting the use of biological or environmental control methods and avoiding the use harmful pesticides. For this to be effectively achieved, it should be backed by a Pest Management Plan (PMP) which sets out the best options and guides the management of required control. Pest Problems in the Liberian Agriculture and Tree Crop Sectors Plant pests and diseases, on visual evidence result in a significant reduction in crop yields throughout Liberia. The extent of such crop loss is not documented, nor has there been any significant research into their control. Very few small farmers in Liberia use any form of chemical pest or disease management due to cost, absence of credit and in many cases lack of local availability. Where they use plant protection chemicals, it is frequently indiscriminate due to lack of application knowledge and ignorance of its impacts on the wider environment and human health. The awareness and use of IPM is virtually non-existent in Liberia, though farmers undoubtedly have traditional methods of controlling some of the pests. The fact that most small farmers do not currently use plant protection chemicals and that these are costly inputs should be seen as a potential opportunity to promote the use of IPM techniques, though it must be recognised that where pests and diseases are in epidemic proportions (as Black Pod and Swollen Shoot are in Cocoa) this will be a herculean task requiring extensive and intense eradication. Regardless, a concerted effort should be made to convince the farmers of the economic and environmental benefits of the IPM. Pest Management and Pesticide Use Strategy The general pest control objectives are:

to maintain good surveillance to control or eradicate the major economic pests whose outbreaks are responsible for large-scale damage to agricultural production; and

to provide protection to people and animals against vectors of deadly diseases. Pest management methods should be a mix of the following methods:

Mechanical: hand picking, digging, trapping;

Biological: use of parasites and predators, NPV, Bt, etc.; and

Chemical: use of eco-friendly and bio-friendly insecticides, fungicides and pesticides. Pest Management Plan

The objectives set out in a PMP should be that the type of pest control used should:

have negligible adverse human health effects;

be effective against the target species;

have minimal effects on non-target species and the natural environment; and

take into account the need to prevent the development of resistance in pests. The methods, timing, and frequency of pesticide application should be such as to avoid or minimise damage to natural enemies, as well as for personnel applying them. The objectives of a PMP for northern Nimba should be:

to collaborate with and assist Nimba County to develop its regulatory framework and build capacity within its institutions to promote and support safe, effective, and environmentally sound pest management;




to provide an information basis for stakeholder groups to establish functional mechanisms enabling farmers to identify, understand and manage pest and vector problems in the rehabilitation of their agriculture production, reduce personal and environmental health risks associated with pesticide use, and protect beneficial biodiversity such as pollinators and natural enemies of pests;

to assist farmers to understand and respond to the external IPM environment that affect their livelihoods (for example, stringent minimum pesticide residue levels that limit the potential for farmers to benefit from international trade opportunities);

to promote participatory approaches in IPM for farmers to learn, test, select and implement “best-bet” IPM options to reduce losses due to arthropod pests, diseases and weeds;

to promote biodiversity monitoring to serve as early warning systems on pest status, alien invasive species, beneficial species, and migratory pests; and

to enable the stakeholder community to monitor pests and disease vectors, and mitigate negative environmental and social impacts associated with pest and vector control in the agriculture and tree crop sectors.

Action Plan

1. Diagnose pest problems affecting the agriculture sector in North Nimba as the basis for stakeholders to develop a shared vision on priority needs and IPM opportunities.

2. Develop the capacity of farmers to understand and manage pest problems through farmer participatory learning approaches with complementary participatory research on feedback issues emanating from farmers‟ field experiences.

3. Introduce and promote biological controls as alternatives to chemical control regimes and thereby reduce environmental and personal health risks in agriculture.

4. Establish a biodiversity monitoring programme among the stakeholder communities as an early warning mechanism regarding changes in pest and vector status, pollinators and natural enemy complexes, and detect migratory pests and the introduction of alien invasive species.

5. Establish partnership linkages with national and international organisations that can provide knowledge and assistance in implementing a more efficient IPM programme.

The process for training and demonstrations could involve identification of a small subset of progressive farmers in each community. The farmers selected for training can then in turn train the other farmers in their respective area. This process is critical because the main benefits of IPM depend on all farmers in a contiguous area practicing IPM; otherwise, the benefits are much less likely to materialise. Anticipated outcomes will be:

Improved farmer awareness of the health hazards of misuse and mishandling of agro-chemicals and the advantages of IPM;

Introduction of training in the proper handling, usage and storage of agro-chemicals, and the proper disposal of chemical containers;

Increased awareness about the efficacy and advantages of eco-friendly alternatives of chemical pesticides;

Development of promotional material, dissemination of IPM through field demonstrations, canvassing through extension personnel and NGOs;

Dissemination of information about traditional and IPM techniques and practices used for the control of insects and other pests;

Improving the information and knowledge base on pests, chemical pesticide use, health impacts, IPM use and trends across the country;

Farmers using newly acquired knowledge to choose compatible methods to reduce losses in production and post-harvest storage; and

Ripple effects spreading out from participating communities to other agricultural activities and from participating farmers to other farmers.




Capacity Building

The success of IPM depends largely on developing and sustaining institutional and human capacity to facilitate informed decision making by farmers, and empowering farmers to integrate scientific and traditional knowledge to solve location-specific problems, and respond to market opportunities. This is particularly important in Liberia as much of the infrastructure and knowledge base was destroyed during the civil war. In IPM, there is the need for farmers to identify and diagnose pests and pest problems accurately, understand trophic relationships that underpin biological control opportunities, and use such knowledge to guide pesticide and other kinds of interventions. A foundation element of the capacity building exercise is the diagnosis of pest problems and IPM opportunities to provide baseline information that will enable stakeholders to develop a shared vision on identified needs and IPM strategies. Through informal interviews, field visits, and planning meetings, stakeholders will develop joint understanding of the key issues affecting production and develop a common IPM plan based on agreed concerns. Group learning should be experiential through farmer-led field trials and discussions on practical aspects of crop and livestock production and pest management including indigenous knowledge and technologies.




ANNEX D: TREE CROP GROWTH REQUIREMENTS

D.1 Coffee The two types of coffee grown in Liberia are:

Liberica (Coffea liberica), a product of the tropical lowlands;

Robusta (Coffea canephora/C. robusta Linden) – may be more than one variety. Origin: West and Central Africa. Yields: The first yield is obtained in the third year after planting. Full production is reached at the age of 7 years, and declines after 15 years. The average annual yield/ha is then 1 -2 tonnes of dry beans. Potential yields/ha of Robusta coffee range from below 300 (poor) to above 2000 (excellent) kg of clean coffee per ha. Yields vary according to the species and variety planted and prevailing growing conditions. Climate: Some 1,000-1,500 mm of well-distributed rain are required annually, preferably interrupted by one or two dry periods, to stimulate flower development. For Robusta coffee temperatures should range from 22 to 27°C. Another source says that the desirable rainfall range is 1200 to 2000 mm and that the optimum daily mean temperature is between 18 and 25

oC. High night time humidity appears

to compensate for low daytime humidity during the dry season. Soils: Coffee trees require a deep soil that is rich in organic matter and has excellent internal drainage. Plant material: Robusta and Liberica coffees are obligatorily cross-pollinated. Commercially, they

are usually propagated by using selected seeds, but vegetative propagation is practised as well. Transplanting in the field is preferably done at the beginning of the rainy season; the young plants are to be shaded for at least 2 weeks. Plant population: Depending on the varieties planted, planting density can range from 1000 to 2000 trees per ha, representing spacing between 4m x 2.5m and 2.5m x 2.0 m. A spacing of 3m x 3 m is fairly standard. Irrigation: Irrigation is sometimes applied during dry months. The use of overhead irrigation is practised. Fertiliser requirements: Fertiliser use is limited. Adequate organic matter is of the utmost

importance, however; shade trees or mulch are used to maintain the required levels. Leguminous cover crops are grown as well. The nutrients removed by coffee trees producing 2 tonnes of dried berries/ha are 30 kg of N, 5 kg of P206 and 48 kg of K20. Weed control: Weed control is necessary, especially when root competition causes moisture stress to the coffee tree. Mechanical weeding should be done very carefully because of the superficial root system of the trees. Maintenance: Trees must be pruned regularly to control their height and shape; to provide for a

plentiful supply of healthy, horizontally growing (plagiotropic) branches, which bear the flowers and fruits; and to remove surplus suckers (orthotrope branches) and weak or dead wood. The most widely practised pruning system is the multiple stem system, in which the trees are rejuvenated by removing one of the older stems and allowing a new sucker to take its place. Pests: There are several pests which are encountered when growing coffee: these include nematodes

in the roots, mealy bugs and scales (stem and berries). Pests are, however, less harmful to coffee trees than diseases.




Diseases: The major diseases are:

Coffee berry disease (Colletotrichum coffeanum), a fungus causing a brown or black colouring of the immature berries. The disease develops strongly when air humidity is high.

Damping off (Rhizoctonia so/am), a fungus affecting the stem of the young seedling, which turns brown or black and then dies.

Root rot (Armillaria spp.), the symptoms of which are wilting and yellowing and falling of leaves, coinciding with dieback of the branches and cracking of the base of the stem and roots.

Brown eye spot (Cercospora coffeicola), which causes berry rot. This is considered a symptom of sub-marginal growth conditions.

Harvesting: Coffee berries are ripe 8-9 months after flowering and fruit setting. Only the red berries

are harvested, which is done by hand. Labour requirements: Including the processing of the berries into marketable coffee, the operations involved with each hectare of coffee plantation require 280 man-days. Processing: Robusta coffee is usually processed by a dry method where:

coffee berries are put in heaps or on racks in thick layers and left to ferment for 1-7 days;

the berries are subsequently dried – normally by the sun on flat surfaces or in solar or other powered driers;

once dry the coffee is hulled and graded. Specific data: Picking berries: 40-70 kg/man-day. The ratio of berry:trade coffee is 5:1. Caffeine

content of dried beans: 1 -2%. Weight of one bag of dry coffee: 60 kg. References: ILACO. 1981; Cambrony, H.R. 1992.

D.2 Cocoa There two main groups of cocoa (Theobroma cacao):

Criollo: longish fruits, which are yellow or red when ripe, and have a rough skin and fluted form;

Forastero: roundish fruits which are yellow when ripe and have a smooth skin. Amelonado cocoa, which is extensively grown in West Africa, belongs to this group.

A hybrid of Criollo and Forastero is grown under the name of Trinitario. Origin: Amazon basin. Yields: At present the average yield per year in the main producing countries varies between 300 kg. ha of dry beans in Ghana and Cameroon and 400 kg. ha in the Ivory Coast and Brazil. Under good management farmers can produce 600 kg. ha of dry beans. Climate: Cocoa is a typical crop of the tropical rain-forest. It requires at least 1000 mm but ideally rainfall should be between 1500 and 2000 mm of well-distributed rainfall annually. A dry season where rainfall is less than 100mm per month should not be longer than 3 months. Optimum temperature is about 25°C and the minimum annual average 18-22°C with a maximum daily variation of 9°C. Optimum relative air humidity is between 80 and 85%. It can be grown at altitudes up to 800 m. Soils: Cocoa can grow in a wide range of soils so long as they are well drained and have a depth of at least 1.5m, but ideally chosen soils would have medium texture, high in organic matter content so as to have moderate to high nutrient levels. Growth period: Trees grown from leaf cuttings start to produce cocoa pods after 3-4 years and those from seedlings after 5-6 years. Trees from leaf cuttings are in full production after 5-7 years and those from seedlings after 7-1 2 years. The average economic life of a cocoa tree is about 30 years.




Planting material: Generative and vegetative propagation methods are used:

direct sowing (not recommended);

sowing in shaded nurseries, usually in polythene bags. Seed rate for planting of 1 ha: 5 kg of fresh seed. Seedlings are transplanted in the field at the start of the main rainy season;

producing leaf cuttings in a nursery which are subsequently transplanted;

grafting. Plant population: Varies between 1,000 and 1,500 trees/ha, depending on soil fertility and the type of planting material. By thinning the least productive trees, ultimately 650 trees will remain. Often, a mixture of varieties is planted to reduce the risk of diseases. Shade trees are planted at a wide spacing Fertiliser requirements: The nutrients removed by 1 tonne of cocoa beans/ha are 20 kg of N, 10 kg of P205 and 15 kg of K2O, Weed control: Weed control is necessary as long as the canopy remains unclosed. In the case of

hand weeding this is restricted to weeding circular areas around the trees. Herbicides are also used. Four rounds of (hand) weeding or three sprayings of an herbicide are required. Sometimes cassava, banana or plantain is planted in open spaces to suppress noxious weeds. Maintenance: To protect the crop, shade is required for at least as long as the canopy has not closed (first 5 years). This is possible by:

leaving those trees in newly deforested areas which are not host plants for cocoa pests and diseases;

planting temporary shade crops (bananas), or a root crop like Colocasia spp.; or permanent shade trees; species used, depending on the local ecology, are: Leucaena glauca, Erythrina spp. (West Indies), and Terminalia superbe (DRC).

The removal of shade in the older plantings has led to substantial yield increases when the crop was supplied with adequate fertiliser. Diseases:

Black pod (Phytophthora pa/mivora), a fungus disease resulting in clearly defined black patches on the pods and finally in complete black pods. The disease is prominent during the humid conditions of the rainy season.

Swollen shoot, a virus disease which seriously affects and finally kills the young shoots. Pests: Capsids (Sahlbergella singularis and Distantiella theobroma), a universal pest which affects

shoots and young fruits. Harvesting: Pods are mature 150-200 days after flowering; they are cut from the trees with machetes. Both machetes and wounds should be disinfected. Since over-ripe fruits drop to the ground and immature fruits are difficult to harvest, fairly frequent harvest rounds are necessary (once in 10-14 days). Harvested pods are then transported to a reception centre. Seeds have no dormancy period. Mechanisation: Cocoa does not lend itself very well to mechanisation.

Labour requirements: The total annual labour requirement of an estate in full production is about 78

man-days/ha. This includes weeding, spraying, pruning, harvesting, breaking of pods, and fermenting and drying of beans. A continuous labour requirement of roughly 1 man/4 ha of cocoa estate can be assumed. Processing: At the reception centre, fresh pods are handled as follows:

breaking of pods to release the beans;

fermentation of the beans for about 6 days to eliminate the pulp and develop the correct cocoa taste;

drying - either in the sun (10-15 days: small scale) or artificially, using a forced flow of hot air (36 h at 80°C) -to reduce the moisture content from 45% to 8%;

grading.




Most of the cocoa is made into chocolate, by adding sugar, cocoa butter and flavours, and into cocoa powder for beverages. Specific data: The ratio of fresh beans:pods is 25%. The ratio of dry beans: fresh beans is 40-45%.

1,000 g. of cocoa give 500 g. of powder plus 400 g. of cocoa butter. Average pod weight: 400 g. Bulk density of dry beans: 575 kg.m

3. Weight of one bag of cocoa beans: 65 kg. Maximum moisture content

for long-term storage: 8%. References: ILACO. 1981; Mossu, G. 1992

D.3 Oil Palm The oil palm (Elaeis guineensis) is one of the most important sources of vegetable oil. There are three different varieties, distinguished by the characteristics of their fruits: Dura, Tenera, Pisifera. In this same order, the fruits of these trees contain an increasing percentage of pulp: Dura has a kernel with a thick shell, Tenera one with a thin shell and Pisifera has kernels without any shell at all. In equatorial areas the oil palm is not grown at altitudes exceeding 500 m. Origin: Tropical wet Africa. Yields: Yields of commercial oil palm estates differ from those obtained by smallholders. Good estates yield from 3 to 4 tonnes of palm oil, plus 0-5-1 tonne of kernels (50% oil), annually/ha, whilst smallholders obtain from 300 to 800 kg of oil/ha annually. The oil yield is about 15% by weight of the yield of the fresh fruit (bunches (FFB) for Dura and about 20% for Tenera. Climate: The oil palm is a typical crop of the tropical rain forest. For optimum production it requires

frequent year-round rainfall and abundant sunshine. The oil palm requires at least 1200 mm of well-distributed rainfall [another source says at least 1800 mm], with dry periods of no longer than 3 consecutive months [but even a short dry season can reduce yields]. The optimum average dally temperature is 27°C [range 18 to 34] and the total annual sunshine should be at least 1,500 h. A high relative air humidity (>75%) is also essential. Soils: The oil palm requires deep, permeable soils, otherwise it is not a very demanding crop. Water-logging is harmful: groundwater levels of less than 90 cm below soil surface lasting more than 14 days should be avoided. Growth period: The oil palm starts producing about 3-4 years after planting and is in full production at in age of 8-10 years. The average economic life of an oil palm is about 30 years. Cropping method: Smallholders‟ oil palms are often intercropped to provide food and some cash

return during unproductive years. Soya beans, cassava, maize and pineapple are some of the crops used in inter-planting. Planting material: The oil palm is seed propagated. To obtain enough healthy trees to plant 1 ha 400 seeds are required. Germination in sand beds is very irregular and takes 3-6 months. A much higher rate of germination can be achieved by the dry heat method. With this method, controlled conditions are used to promote germination; after 60-90 days, about 90% of the seeds will have germinated. Germinated seeds are planted in a nursery or in earth-filled polythene bags. After a further 3-4 months the seedlings have about four leaves. At that stage they are transplanted in another nursery at a wider spacing (50 cm). When the seedlings attain their 10-leaf stage, they are finally transplanted in the fields. Plant population: Optimal results are given by a triangular planting pattern using 9 m spacings. This

gives a plant population density of 120-143 trees/ha.




Fertiliser requirements: The fertility of the soil is checked by leaf analysis on frond 17. Oil palms

readily show potassium and magnesium deficiencies, the latter by orange fronds. The nutrients removed by a crop of 1 5 tons/ha of fresh fruit bunches are: 90 kg of N, 20 kg of P2O5,135 kg of K20 and 39 kg of CaO. The effect of fertilisers can be seen in the fruit bunches 12-18 months after application. Weed control: On estates, weeds are suppressed by cover crops such as Pueraria javanica, Centrosema, etc., or a mixture of various leguminous crops. A circular area around the tree base has to be kept clean. This takes six weeding rounds/year during the palm's immature years, and four rounds/year thereafter. Weeding takes 12 man-days/ha. In addition, the inter-rows are mowed 2-3 times/year. This can be done mechanically as soon as the trees are fully grown (25-40 ha/tractor/day). Chemical weed control is also a common practice on the estates. Diseases: Most diseases are secondary, following nutritional deficiencies.

Blast disease of the root (Pythium splendens and Rhizoctonia lamellifera), which particularly affects the seedlings in the nursery.

Vascular wilt caused by Fusarium oxysporium.

Cercospora elacides, a leaf disease in nurseries and in young palms. Pests:

Rhinoceros beetle (Oryctes rhinoceros), which feeds on the tree crown. At the moment it does not appear to be a serious pest in Liberia.

Rhynchophorus spp., of which the larvae tunnel in the stem. Harvesting: Fruit bunches are harvested by hand (machete), usually once every fortnight. The time of harvesting is very critical: premature harvesting results in a reduced weight, whereas delayed harvesting may result in a reduced quality due to elevated free fatty acid (FFA) content. After harvesting, the fruit bunches should be handled carefully and processed as soon as possible in order to keep the FFA level low. When organized on a piece-work basis, the harvest of 1 ton of fresh fruit bunches (FFB) requires 3-5 man-days, depending on the production level on the estate, Mechanisation: Except for clearing, oil palm farming does not lend itself to mechanisation.

Processing: Palm fruits are processed into palm oil by small, local industries and by oil mills. The

former comprises the following operations: (a) boiling or fermentation of fruits; (b) pounding to disintegrate the pulp; (c) skimming of the oily top layer; and (d) heating of the oily mass to expel the water. In the oil mills the fruits are processed along similar lines in the sense that: (a) the fruit bunches are sterilized at the start of the process; (b) recovery of oil is done by pressing or by centrifuging; (c) clarification is achieved by neutralizing and bleaching; and (d) deodorising is done by passing steam. At the end of this process the remaining nuts are cracked locally. The palm kernels are shipped as such. The best grades of palm oil and palm-kernel oil are used in the manufacture of margarine and cooking fat. The lower grades are used in the production of soap. Palm-kernel oil cake is used in cattle concentrates. On smallholders' farms some of the male palm trees are tapped from the flower stalk for palm wine. Specific data: The weight of one FFB is 4-20 kg (depending on age of tree). Oil content of fruit pulp is

50%, or 20-22% of the bunch weight. Oil content of kernels is 48-52% of the kernel weight, or 2-2-5% of the bunch weight. References: ILACO. 1981; Jacquemard, J-C. 1998.




D.4 Rubber About 90% of the total world production of natural rubber is obtained from Hevea brasiliensis trees. The bark of these trees contains a network of interconnected vessels which yield latex when opened. Latex is a suspension of rubber particles, which have to be coagulated to obtain the rubber. In equatorial areas Hevea brasiliensis is grown at altitudes up to 500-600 m. The tree sheds its leaves annually. Origin: Amazon Valley.

Yields: The average annual rubber yield of unselected seedlings is 330 kg/ha in India and 450-550

kg/ha in Malaysia. Estate yields are about 1,500 kg/ha when new planting stock and farming techniques are applied. Climate: Hevea is a crop of the tropical rain-forest. It requires from 1,500 to 2,000 mm [another

source says ideally more than 2000 mm] of well-distributed rainfall, without pronounced dry seasons (with not more than one dry month). Early morning rain interferes with tapping. The optimum daily mean temperature is 25 to 28

oC; big changes in temperature are unfavourable. Hevea can stand an

occasional frost. Strong winds can be very harmful since Hevea is easily damaged by wind. Soils: It is particularly important that the physical condition of the soil is good. Hevea requires deep,

well-aerated, properly drained soils. Shallow and peaty soils should be avoided, and lime is deleterious. In aspects other than these, Hevea is not very demanding. The crop can withstand short periods of water-logging. Cropping method: Hevea trees are usually intercropped with leguminous crops such as Pueraria javanici and Centrosema pubescens in order to suppress weeds. On smallholdings intercropping with food crops is practised for the first 3-5 years after planting. Growth period: Tapping begins when the trees have attained a certain girth; 50-70% of all trees should have a circumference of 50 cm at 1 m above the soil surface or bud union, which is usually the case after 6-7 years. Seedlings start producing 1 year earlier than buddings. The economic life of a plantation is 25-30 years. Planting material: Seeds are always necessary, either for root stocks to be budded or for seedling

plantings. Seeds for commercial plantings should be obtained from polyclonal seed gardens (illegitimate seeds; the male parent is not known) or from monoclonal plantings of self-fertile clones. The parent clone should be known to have exceptional merits as seed parents. Legitimate seeds are seeds for which both parents are known. They are obtained through artificial pollination and are used mainly in breeding programmes. Seedlings are usually raised in nurseries, but sometimes seeds are planted directly in the field. As most new plantings are clonal plantings, most seedlings are budded either in the nursery or in the field. Rearing of seedlings for field planting takes 10-15 months. Budding of the seedlings can be done at an age of 5-6 months (green budding) or after 12-18 months (brown budding). Bud wood II raised in special nurseries, which have to be set up at least 1 year before the root stock material is sown. Plant population: The usual planting density varies from 400 to 800 trees/ha. Three years before the trees start producing, a gradual thinning of weak trees begins, which continues over a period of 6 years until the stand is reduced to 250-300 trees/ha. Planting can be done in various patterns (square, rectangular, triangular or avenue). On steep slopes planting should be done on contour terraces. An optimum planting arrangement should ensure the highest yields per tree as well as per tapper. Fertiliser requirements: Since the volume of product extracted from the trees is small as compared

with other crops, nutrient requirements are low. In coastal alluvial soils in Malaysia, no response has been observed to fertiliser applications. On inland soils, Hevea responds to both nitrogen and phosphorus. The nutrients removed annually by a crop of 1,500 kg/ha of dried rubber are 40 kg of N 10 kg of P205 and 25 kg of K20




Weed control: Only circular areas around the stems and the tapping lanes are kept clean of weeds. This is done by hand or by using herbicides. The inter-row areas, in which leguminous cover crops are grown to check weed growth, are slashed 2-3 times per year, either by hand or mechanically. The growth of Imperata cylindrica should be controlled. Maintenance:

Pruning to obtain a correct formation of the tree;

Treatment or removal of weak or diseased trees. Diseases:

Root diseases, which are caused by various fungi, the most important of these being fungi from the Fomes spp. These diseases can be very damaging to a rubber plantation.

Various diseases caused by the fungus Phytophthora, of which one of the major ones is the black stripe disease, which affects the tapping panel.

South American leaf blight (Dothidella ulei or Microcyclus ulei).

Powdery mildew (Oidium heveae), which causes distortion of the tree and defoliation. Pests:

With the exception of Termites (Coptertemes curvignatus), Hevea is not otherwise affected by pests since the latex serves as a deterrent. Harvesting: Harvesting latex is done by opening a tapping panel. This involves making a spiral cut

with a tapping knife at a height of 1.20-1.50 m. The tapping panel spans either the full circumference or part of it. Most common is a panel across half the girth. A thin strip of bark is regularly cut away to reopen the latex vessels. The latex then flows along the tapping cut into cups or ethylene bags. Tapping proceeds downwards; about 30 cm of bark are removed per year. When the bark on one side of the tree is cut away, a panel on the opposite of the tree is opened. Tapped bark regenerates and can be retapped after 7-8 years. Different tapping frequencies are used (e.g. every day, every other day, etc.). The most common tapping system is the half-spiral, alternate daily system. This system is referred to as a 100% intensity system. Many other systems are in use, including periodic tapping systems, in which the trees are rested for longer periods. The latex flow shows a distinct seasonal variation and is highest in the wet season. The yield of rubber can be increased by 20-80% by applying a stimulant (2,4-D, copper sulphate or ethrel), which prevents 'plugging' of latex vessels, but this will shorten the productive life of the tree. Tapping is done early in the morning. Collection of latex follows 3-4 h later. One tapper can handle about 400 trees/day. Obviously this operation is very labour intensive, and expenditure on tapping is more than 40% of the total production cost. In order to obtain high-quality rubber it is essential to use clean equipment throughout. Mechanisation: Rubber plantations do not lend themselves well to mechanisation.

Labour requirements: For all operations, including processing, a resident labour force of 1 labourer

per 1.5-2 ha is required. Processing: In Liberia, the only part of the processing carried out by smallholder producers is coagulation of the latex. This is them sold to one of the Concession Holders for further processing and export as crumb rubber. References: ILACO. 1981; Delabarre, M. A. and Serier, J.B. 2000.




ANNEX E: DEFINITIONS OF COMMON TERMS Alluvium. Material, usually fine sand or silt with larger, rounded particles up to boulder size, deposited

by a river, having been transported from elsewhere in suspension.

Canopy. The top layer of a forest, consisting of the crowns of trees.

Colluvium. Angular debris, usually loose and unconsolidated, found on slopes below rock outcrops. Other names are scree and talus, although these are normally of pure fragmented rock while colluvium can also contain fine material.

Coppice. A treatment in which the trunk of a tree is cut off about 30 cm above the ground to allow new

shoots to come from the stump.

Culm. The stem of a grass.

Cutting. Any part of a plant (stem, rhizome or root) that is used for vegetative propagation.

Debris creep. Gradual downward movement observed in unconsolidated debris masses on slopes

(such as colluvium). It may range from a few millimetres to a few metres per year.

Erosion. The gradual wearing away of soil (or other material) and its loss, particle by particle.

Fallow. Where land is cultivated but left unplanted to restore its fertility.

Friable. A term applied to soils that when either wet or dry crumble easily between the fingers.

Grass slip. This term is used loosely to describe any parts of grasses used for vegetative propagation, including fibrous roots, rhizomes, and stem or stolon cuttings.

Landslide. The downslope movement of a mass of soil, rock or other material. The movement may occur suddenly or slowly, and may be shallow or deep-seated. Common causes and mechanisms of landslides are shown on the next page.

Loam. A soil with moderate amounts of sand, silt and clay, which is therefore intermediate in texture

and best for plant growth.

Lop. Where the branches of trees are cut to provide fodder or small firewood.

Man-induced land degradation. Damage to land through mis-use and over-use, leading to a decline of its biological productivity.

Natural land degradation. Damage to land through natural events of downwasting, which lead to a reduction of its biological diversity and productivity. Downwasting includes all types of erosion and landsliding as natural a response to mountain uplift.

Plant community. An established group of plants living more-or-less in balance with each other and

their environment; the group can be either natural or managed.

Pollard. A treatment in which the main trunk of a tree is cut off, usually two to three metres above the

ground, to allow new, smaller, shoots to grow.

Prune. To cut branches carefully in order to improve the shape of a plant or allow more light to

penetrate.

Rill. A small gully, up to about one metre deep.

Safe water discharge. The discharge of used or surplus water into a channel that is protected against erosion at the predicted high level of flow.

Scour. The physical removal of soil from the surface by erosion. In some text books it is used to describe erosion in broad, shallow rills which can coalesce to give sheet erosion.

Slumping. A form of saturated flow of soil or debris. It occurs mostly in weak, poorly drained materials, when a point of liquefaction is reached following heavy rain. In effect, the addition of water to the material causes a reduction in cohesion to a point of limited friction. It is usually shallow (less than 500 mm deep).




Subsoil. In a moderately or well developed soil, the layer(s) or horizon(s) below the topsoil. It is

usually made up almost entirely of mineral constituents, and is less fertile than the topsoil. It is distinguished from weathered parent material by the absence of any structural characteristics of the parent material.

Thin. The removal of a proportion of the plants in a given area, to allow the others to grow bigger.

This is a standard nursery and forestry procedure.

Topsoil. In a moderately or well developed soil, the darker, more fertile and organically rich upper

layer or horizon of soil. In a cultivated soil, it is often the plough layer.

Understorey. The part of a forest underneath the canopy, consisting of shrubs, saplings and herbs.

Weathering. The physical and chemical alteration of minerals into other minerals by the action of heat, water and air,




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