practices of agroforestry system

of 17

Practices of agroforestry system

i) Shifting cultivation

The term shifting cultivationrefers to farming or agricultural systems in which land under

natural vegetation is cleared, cropped with agricultural crops for a few years, and then left

untended while the natural vegetation regenerates. The cultivation phase is usually short (2-3

years), but the regeneration phase, known as the fallow or bush fallow phase, is much longer

(traditionally 10-20 years). The clearing is usually accomplished by the slash-and-burn

method hence the name slash-and-burn agriculture by using simple hand tools. Useful trees

and shrubs are left standing, and are sometimes lightly pruned; other trees and shrubs are

pruned down to stumps of varying height to facilitate fast regeneration and support for

climbing species that require staking. The lengths of the cropping and fallow phases vary

considerably, the former being more variable; usually the fallow phase is several times longer

than the cropping phase. The length of the fallow phase is considered critical to the success

and sustainability of the practice. During this period the soil, having been depleted of its

fertility during the cropping period, regains its fertility through the regenerative action of the

woody vegetation.

System overview

Shifting cultivation is the backbone of traditional farming systems over vast areas of the

tropics and subtropics. Shifting cultivation extends over approximately 360 million hectares

or 30 % of the exploitable soils of the world, and supports over 250 million people. The

system is dominant mainly in sparsely populated and lesser developed areas, where

technological inputs for advanced agriculture such as fertilizers and farm machinery are not

available. It is found in most parts of the tropics, especially in the humid and sub-humid

tropics of Africa and Latin America. Even in densely populated Southeast Asia, it is a major

land-use in some parts.

In forest areas of the lowland humid tropics, the practice consists of clearing a patch of forest

during the dry (or lowest rainfall) period, burning the debris in situ shortly before the first

heavy rains, and planting crops, such as maize, rice, beans, cassava, yams, and plantain, in

the burnt and decaying debris. The crops are occasionally weeded manually thus, irregular

patterns of intercropping are the usual practices. After 2 or 3 years of cropping, the field is

abandoned to allow rapid regrowth of the forest. The farmer returns to the same plot after 5 to

20 years, clears the land once again, and the cycle is repeated.

of 17

In an example as practiced in the savannas, especially in West Africa, the vegetation,

consisting primarily of grasses and some scattered trees and bushes, is cleared and burned in

the dry season. The soil is then raised into mounds, about 50 cm high, on which root crops,

usually yams, are planted. Maize, beans, and other crops are planted between the rows. The

mounds are levelled after the first year of yams. A variety of crops including maize, millets,

and peanuts (groundnuts) are planted for the next 2 to 3 years. Thereafter, the land is left

fallow and regrowth of coarse grasses and bushes occurs. This period lasts for up to about ten

years. Compared with shifting cultivation in the forests, this form results in a more systematic

working of the soil for cropping, longer cropping periods, and, ultimately, a more severe

weed infestation. Moreover, soil erosion hazards are also higher when the soil is bare after

the clearing and burning in the dry season.

Despite the remarkable similarity of the shifting cultivation practiced in different parts of the

world, minor differences exist, and are dependent on the environmental and sociocultural

conditions of the locality and the historical features that have influenced the evolution of

land-use systems over the centuries. These variations are reflected in the various names by

which the system is known in different parts of the world.

Table 1. Local terms for shifting cultivation in different parts of the tropics

Term Country or region

Asia Ladang Indonesia, Malaysia

Jumar Java

Ray Vietnam

Tam-ray, rai Thailand

Hay Laos

Hanumo, caingin Philippines

Chena Sri Lanka

Karen Japan, Korea

Taungya Burma (Myanmar)

Bewar, dhya, dippa, erka, jhum, kumri,

penda, pothu, podu

India

Americas Coamile Mexico

Milpa Mexico, Central America

Roca Brazil

Africa Masole Zaire

Tavy Madagascar

of 17

Chitimene, citimene Zaire, Zambia, Zimbabwe,

Tanzania

Proka Ghana

Shifting cultivation was widespread in Europe until a few centuries ago. Under resource-rich

conditions, shifting cultivation has slowly been replaced by more technologically-oriented

and profitable land-use systems that bear no similarity to the original system. In developing

countries with low population densities, where the farmer had enough land and freedom to

cultivate anywhere, the ratio of the length of fallow period to cultivation phase was 10 to 1.

The system was stable and ecologically sound. However, under increasing population

pressure, the fallow periods became drastically reduced and the system degenerated, resulting

in serious soil erosion and a decline in the soil's fertility and productivity.

Figure 1.Schematic presentation of the changes with time in the length of fallow phase,

and consequent patterns of crop yields and soil productivity in shifting cultivation

Various approaches have been suggested as improvements and/or alternatives to shifting

cultivation, and most of them emphasize the importance of retaining or incorporating the

woody vegetation into the fallow phase, and even in the cultivation phase, as the key to the

maintenance of soil productivity. Depending on the ways in which the woody species are

incorporated, the alternate land-use system can be alley cropping, or some other form of

agroforestry, or even other forms of improved, permanent production systems.

Soil management and shifting cultivation

of 17

Large parts of the humid and subhumid tropics currently under shifting cultivation and

related traditional farming systems are covered by the fragile upland soils. These are

predominantly Ultisols, Oxisols, and associated soil types in the humid tropics, and Alfisols

and associated soils in the subhumid tropics. Many of these soils are also grouped as low-

activity clay (LAC) soils because of their limitations, unique management requirements, and

other distinctive features that adversely affect their potential for crop production.

Ultisols and Oxisols have problems associated with acidity and aluminum toxicity, low

nutrient reserves, nutrient imbalance, and multiple nutrient deficiencies. Ultisols are also

prone to erosion, particularly on exposed sloping land. Alfisols and associated soils have

major physical limitations: They are extremely susceptible to crusting, compaction, and

erosion, and their low moisture-retention capacity causes frequent moisture stress for crops.

In addition, they acidify rapidly under continuous cropping, particularly when moderate to

heavy rates of fertilizers are used.

It is generally accepted that traditional shifting cultivation with adequately long fallow

periods is a sound method of soil management, well adapted to the local ecological and social

environment. Before the forest is cleared, a closed nutrient cycle exists in the soil-forest

system. Within this system, most nutrients are stored in the biomass and topsoil, and a

constant cycle of nutrient transfer from one compartment of the system to another operates

through the physical and biological processes of rainwash (i.e., foliage leaching), litterfall,

root decomposition, and plant uptake.

Clearing and burning the vegetation leads to a disruption of this closed nutrient cycle. During

the burning operation the soil temperature increases, and afterwards, more solar radiation

falling on the bare soil-surface results in higher soil and air temperatures. This change in the

temperature regime causes changes in the biological activity in the soil. The addition of ash to

the soil through burning causes important changes in soil chemical properties and organic

matter content. In general, exchangeable bases and available phosphorus increase slightly

after burning; pH values also increase, but usually only temporarily. Burning is also expected

to increase organic matter content, mainly because of the unburnt vegetation left behind.

These changes in the soil after clearing and burning result in a sharp increase of available

nutrients, so that the first crop that is planted benefits considerably. Afterwards, the soil

becomes less and less productive and crop yields decline. Some examples of yield decline

under continuous cropping without fertilization in different shifting cultivation areas

corresponding to various soil, climate, and vegetation types. The main reasons for the decline

in crop yields are soil fertility depletion, increased weed infestation, deterioration of soil

physical properties, and increased insect and disease attacks. Finally, the farmers decide that

of 17

further cultivation of the fields will be difficult and non-remunerative and they abandon the

site and move on to others. The abandoned site re-inhabits by natural vegetation (forest

fallow); during the fallow period the soil regain its fertility and productivity, and the farmers

return to the site after a lapse of a few years.

ii) Taungya system

History of Taungya system:

Taungya system is the local term of shifting cultivation in Myanmar. Like shifting

cultivation, Taungya system is a forerunner to agroforestry. The word Taung means hill and

ya means cultivation. In 1856, when Dietrich Brandis was in Burma, shifting cultivation was

widespread and there were several court cases against the villagers for encroaching on the

reserve forests. Brandis realized the detrimental effect of shifting cultivation on the

management of timber resources. He encouraged the practice of regeneration of teak

(Tectonagrandis) with the assistance of Taungya system on the well-known German

System of Waldfeldbauwhich involved the cultivation of agricultural crops in forests. Two

decades later the system proved so efficient that teak plantations were established at a very

low cost. The villagers who were given the right to cultivate food crops in the early stages of

plantation, no longer had to defend themselves in court cases on charges of forest destruction;

they promoted afforestation on the cleared land by sowing teak seeds. Then Taungya System

was introduced into other parts of British India, and later it spread throughout Asia, Africa,

and Latin America

System Overview

Taungya system consists of growing annual agricultural crops along with the forestry

species during the early years of establishment of the forestry plantation

Land belongs to the forestry departments or their largescale lessees who allow the subsistence

farmers to raise their crops

Farmers are required to tend the forestry seedlings and in return they get a part or all of the

agricultural products

Agreement would last for two to three years. During this period the forestry species grow and

expand its canopy, gradually declines soil fertility, some soil is lost due to erosion, and weeds

infestation, thus making crop production no remunerative to the farmers

Most of the forest plantations in the tropical world, particularly in Asia and Africa have been

established through Taungya System

of 17

Figure 1.First year of establishment of teak with upland rice

Figure 2.Second year of establishment of teak. The decline in soil productivity is evident

from the relatively low vigor of the rice crop in comparison to that of the first-year rice crop

shown in Figure 1

Figure 3. Commercial Eucalyptus Plantations with Taungya system

Taungya system is known by different names:

Tumpangsariin Indonesia

Kainginingin the Philippines

Ladangin Malaysia

Chenain Sri Lanka

Kumri, Jhooming, Ponam, Taila, and Tucklein different parts of India

Shambain East Africa

Parceleroin Puerto Rico

of 17

Consorciarcaoin Brazil

Advantages:

o Helps the initial establishment and growth of forest species

o Minimizes the cost of maintenance of the trees

o Earns revenue for the forest department

o Provides employment to the rural people

o Full utilization of available land for the utilization of agricultural crops

o Weeds and climbers growth are suppressed

Disadvantages:

o It is labour intensive. It capitalizes on the poor farmer's need for food to offer labor

for plantation establishment free of cost

o Exposure of land leads to erosion and loss of soil fertility

o Taungya lands were converted to agricultural settlements in different parts of the

world. Therefore, forestry departments have become hesitant to lease lands to

Taungya farmers

o In some countries, political or policy decisions have been made to grant ownership

rights of the land to Taungya farmers

o Trees are not properly cared by the farmers once they are settled

o Sometimes the farmers cause damage to the growing trees and adjacent forest areas

Taungya system is considered as another step in the process of transformation from shifting

cultivation to agroforestry

Shifting cultivation Taungya system

Shifting cultivation is a sequential system of

growing woody species and agricultural crops

Taungya system consists of the simultaneous

combination of two components during the early

stages of forest plantation establishment

Ultimate objective is food production Ultimate objective is wood production

Length of agricultural cycle last as long as the

soil sustains reasonable crop yields

Length of agricultural cycle depends on the

physical availability of space and light based on

the planting arrangements of the trees

Agricultural crops are planted to make the best

use of the improved soil fertility built up by the

previous woody plant component

Agricultural crops are planted to make the best

use of the improved soil fertility built up by the

previous woody plant component

of 17

The immediate motivation for practicing

Shifting cultivation

is food production

The immediate motivation for practicing

Taungya system is food production

Fig. Shifting cultivation and Taungya system

List of trees commonly used in Taungya System:

Sl No Common Name Scientific name

1 Teak Techtonagrandis

2 Eucalyptus Eucalyptus spp.

3 Acacia Acacia spp.

4 Sissoo Dalbergiasissoo

5 Gamar Gmelinaarborea

6 Sal Shorearobusta

7 Chandan Santalum album

8 Tetul Tamarindusindica

9 Rubber Heveabrasiliensis

10 Cashewnut Anacardiumoccidentale

11 Shwet Simul Ceibapentandra

Crops commonly grown in Taungya System:

of 17

Rice, Millet, Maize, Gram, Chilli, Mustard, Soybeans, Groundnut Cotton Sugarcane,

Cassava, Cotton, Potatoes Jowar, Bajra, Lentil Gram Arhar, Sunhemp, Potato, Sweet Potato,

Plantain, Til Turmeric, Ginger etc.

iii) Alley Cropping

Viewpoint:

o In traditional system of upland crop production on low activity clay (LAC) soils,

only a small portion of land is used for food-crop production.

o Larger part remains as fallow. This wasteful use of land cannot continue

particularly where population density is high. However, it is impossible to sustain

food production without an adequate fallow period on LAC soils.

o The challenge is to develop production technologies through efficient uses of

resources. The high-input production systems on LAC soils are considered

wasteful, exploitative of natural resources, and environmentally hazardous for

people because of excessive use of chemicals and pesticides.

o Fallow period stops degradation, enhance biological recycling, raise labour use

efficiency, and stabilize favourable environmental conditions for crop production.

o Alley cropping as a low-input regenerative production technology deserves proper

attention and promotion to traditional farmers in the tropics having only limited

input.

o Alley-cropping technology incorporates all the benefits of the fallow period

during food-production period and sustains land productivity for longer periods.

o Alley cropping helps to stop rapid deforestation in tropical and subtropical areas

by providing food, fuel wood and fodder.

Alley Cropping

o Alley Cropping is a promising agroforestry technology for the humid and sub-humid

tropics which has been developed during the past decade. Pioneering work on Alley

cropping was initiated at the International Institute of Tropical Agriculture (IITA), in

Nigeria, by B.T. Kang and co-workers, in the early 1980s.

o Alley cropping includes growing food crops between hedgerows of planted shrubs

and trees preferably leguminous species. The hedges are pruned periodically during

the crop's growth to provide biomass which, when returned to the soil, enhances its

nutrient status and physical properties and to prevent shading of the growing crops.

of 17

o Alley cropping is a form of hedgerow intercropping which combines the regenerative

properties of bush fallow system in association with agricultural crops. Soil-

improving attributes of fast-growing preferably nitrogen fixing trees and shrubs, such

as recycling nutrients, suppressing weeds, and controlling erosion on sloping land,

create soil conditions similar to those in the fallow phase of shifting cultivation.

o Alley-cropping technique can, therefore, be regarded as an improved bush-fallow

system with the following advantages:

o Cropping and fallow phases are combined

o Longer cropping period and increased land-use intensity

o Rapid effective soil fertility regeneration with more efficient plant species

o Reduced requirements for external inputs

o The system is scale-neutral, being flexible enough for use by small-scale farmers and

for large mechanized production.

o By integrating small-ruminant production with alley cropping, the International

Livestock Centre for Africa (ILCA) in Ibadan, Nigeria, has developed the alley

farming concept where pruning from the hedgerows provide high-quality

supplementary fodder.

o So, alley farming can be defined as the planting of arable crops in between hedgerows

of woody species that can be used for producing mulch and green manure to improve

soil fertility and produce high-quality fodder.

Alley-cropping concept is currently, being evaluated in many parts of the tropics

with different names

Country/Institute Name

ICRAF Hedgerow Intercropping

Sri Lanka Avenue Cropping

Indonesia Lamtoronisasi

Potential of alley cropping as a sustainable farming system

o Various field trials were carried out by IITA scientists over the past ten years on

strongly acid soils (Ultisols) and slightly acid soils (Alfisols) in the humid and

sub-humid regions to test the suitability of alley cropping.

of 17

o On Alfisols and associated soils Leucaenaleucocephalaand Gliricidiasepiumwere

the most promising woody species for alley farming.

o Trees can be established by direct seeding in association with a growing crop.

Once established, the hedgerows can be repeatedly pruned to produce large

amounts of biomass that can be used as green manure, mulch or fodder.

Fig. Imperatacylindrical Fig. Gliricidiasepium

Advantages:

o Soils receiving pruning from alley cropping having higher soil organic matter and

nutrient status than soil receiving no pruning.

o Pruning used as mulch substantially increases moisture retention in topsoil.

o Addition of organic matter and partial shading resulting from alley cropping

increase earthworm activity.

o Higher microbial activity is observed by increased biomass carbon under alley

cropping.

o Hedgerows in alley farming suppress weeds, reduce runoff and soil erosion.

o Alley cropping generates short-term income from annual crops and also provide

medium- to long- term products from trees or shrubs

Disadvantages

o Drawback of combining trees with field crop is that they may compete for light,

water, and nutrient, particularly in areas where the available resources are limited

of 17

IV) Scattered trees on cropland or farmland (Parkland agroforestry)

Scattered trees on farms is an agroforestry system whereby perennials are randomly grown in

relatively wider spacing from each other while the surrounding space is used for crops and

marginal grasses. Some of the trees grow naturally from seed dispersed by birds and other

wildlife. Such trees are retained by farmers during land preparation for agriculture and are

often randomly dispersed on the land.

Trees scattered on cropland offer a variety of benefits and these together with the limitations

of this agroforestry practice are listed below:

Fig. Scattered trees on crop land

Benefits of scattered trees on farmland

1. Trees such as Faidherbiaalbida provide shade for livestock during intense heat of the long

dry season

2. Trees diversify ‘farmers’ products and increase crop production and the duration of

cropping the land without fertilizer use

3. Control of wind erosion when tree canopies in farmland intercept wind-blown soil

4. Sale of non-timber products such as charcoal, gum, wine, oil and fruits significantly

increases income

Limitations

1. Scattered trees are often not at the optimum density that would confer maximum benefits

to the environment and crop production

2. Reliance on naturally regenerating trees makes it difficult to improve the system through

use of better germplasm

3. Many species are slow growing, so benefits take long to accrue

4. The trees are often browsed by livestock that are allowed to graze crop residues during the

dry seasons

of 17

5. It may causes of difficulties of ploughing and intercultural operations

6. It may causes of competition with crops for nutrient and water

7. It may causes of insect infestation and bird attack

V) Windbreaks

Windbreaks are narrow strips of trees, shrubs and/or grasses planted to protect fields, homes,

canals and areas from wind and blowing sand. Where wind is a major cause of soil erosion

and moisture loss, windbreaks can make a significant contribution to sustainable production.

Figure. Wind-breaks

VI) Shelterbelt

A shelterbelt is a wide strip of vegetation that slows wind speeds, thereby reducing wind

erosion, evaporation and damage to towns, villages and adjoining farmlands by the wind. It is

sometimes referred to as windbreak, although the latter often implies a single strip of trees

and other vegetation.

of 17

Figure. Shelter belt

A shelterbelt presents a mechanical barrier to the impact of the wind and separates two zones;

the windward and the leeward zones. The windward zone refers to the side from which the

wind blows, whilst the leeward zone relates to the side where the wind passes. As a rule of

the thumb, a belt protects a distance up to its height on the windward side and up to 20 times

its height on the leeward side.

As their main function is to protect agricultural lands against the hazards of wind and wind

speed, shelterbelts are placed on the upwind side of the land to be protected. They are most

effective when the shelterbelt is situated perpendicular (at right angles) to the prevailing wind

direction.

VII) Live fences of fodder trees and shrubs (Living fences)

Live fencing means fencing composed of living plants. Living fences are lines of trees or

shrubs planted on farm boundaries or on the borders of farmyards, pasture plots or animals

enclosures. Sometimes they are also used around agricultural fields. They serve mainly as

field boundaries to keep animals on the farm and off adjacent crop fields or farm areas. They

can be made of single or multiple densely planted rows. Alternatively, one row of living

fence posts can be planted widely spaced with wire, sticks or dead branches between the

trees. Both kinds are made of permanent lines of shrubs or trees that are regularly pollarded

and trimmed. The fences provide shade, protection and privacy for the animals. The trees can

also serve as windbreaks that produce wood and foliage products. The foliage can be eaten by

animals. Legumes are especially valued as they usually have high protein content.

The most important component in the living fence practice is the animal component – the

main reason for establishing living fences and the primary motive in management of the

fences is to control livestock movement. In arid and semi-arid zones, lives fences are often

made of thorny species of the Acacia or Prosopis genera. In the humid and sub-humid tropics,

leguminous species such as Gliricidiasepium and Erythrinaberteroana or species of

multipurpose Hibiscus or Ipomea hedges are used.

of 17

Figure. Living fence

VIII) Sloping Agricultural Land Technology (SALT)

The SALT system

SALT is a package technology of soil conservation and food production, integrating differing

soil conservation measures in just one setting. Basically, SALT is a method of growing field

and permanent crops in 3-5 m wide bands between contoured rows of nitrogen fixing trees.

The nitrogen fixing trees are thickly planted in double rows to make hedgerows. When a

hedge is 1.5-2 m tall, it is cut down to about 75 cm and the cuttings (tops) are placed in the

alleyways to serve as organic fertilizer.

SALT: An Agroforestry Scheme

SALT is a diversified farming system which can be considered agroforestry since rows of

permanent shrubs like coffee, cacao, citrus and other fruit trees are dispersed throughout the

farm plot. The strips not occupied by permanent crops, however, are planted alternately to

cereals (corn, upland rice, sorghum, etc.) or other crops (sweet potato, melon, pineapple,

castor bean, etc.) and legumes (soybean, mung bean, peanut, etc.). This cyclical cropping

provides the farmer some harvest throughout the year. SALT also includes the planting of

trees for timber and firewood on surrounding boundaries. Examples of tree species for

“boundary forest” in SALT are mahogany, Cassuarina, Sesbania, Cashew, etc.

Forms of SALT

There are several forms of SALT and a farmer may wish to use the SALT system in several

variations. Simple Agro-Livestock Technology (SALT 2), Sustainable Agroforestry Land

Technology (SALT 3), and Small Agrofruit Livelihood Technology (SALT 4) are three

variations of SALT that have been developed at the MBRLC based on the original SALT

ideas.

of 17

SALT 2(Simple Agro-Livestock Land Technology) is a small, livestock-based agroforestry

system (preferably with dairy goats) and has a land use of 40% for agriculture, 20% for

forestry and 40% for livestock. As in a conventional SALT project, hedgerows of different

nitrogen fixing trees and shrubs are established on the contour lines. The manure from the

animals is utilized as fertilizer both for food and forage crops.

SALT 3 (Sustainable Agroforestry Land Technology) is a cropping system in which a

farmer can incorporate food production, fruit production and forest trees that can be

marketed. The farmer first develops a conventional SALT project to produce food for his

family and possibly for livestock. On another portion of land, he can plant fruit trees such as

mango, jackfruit and orange tree between the contour lines. The plants in the hedgerows

should be cut and piled around the fruit trees for fertilizer and soil conservation purposes. A

small forest of about 1 ha will be developed in which trees of different species are grown for

short-range production of firewood and charcoal. Other species that would produce wood and

building materials may be grown for medium and long-range production.

SALT 4 (Small Agrofruit Livelihood Technology) is based on a half-hectare piece of

sloping land with two-thirds of it developed in fruit trees and one-third intended for food

crops. Hedgerows of different nitrogen-fixing trees and shrubs are planted along the contours

of the farm.

Advantages of SALT farming

As a proven system of upland farming, SALT has certain good qualities over both the

traditional techniques of slash-andburn and conventional terrace farming.

• The SALT system protects the soil from erosion.

• SALT helps restore soil fertility and structure.

• SALT is efficient in food crop production.

• SALT is applicable to at least 50% of hillside farm.

• SALT is easily replicated by hillside farmers.

• SALT is culturally acceptable because the farming techniques are in harmony with Asian

beliefs and traditional practices.

• SALT is workable in a relatively short time.

• SALT is economically feasible.

• SALT is ecologically sound.

• The SALT farm can easily revert back to forestland if left unfarmed.

Disadvantages of SALT farming

1. Curved rows make it impractical for some farm machinery to be used

2. This practice is impractical on fields with irregular topographic features or very steep

hills.

of 17

Figure: SALT Farming

practices of agroforestry system

Documents