Segundo Seminario Internacional de Investigación SANREM CRSP: Cambios globales y su efecto sobre los sistemas agropecuarios de la zona andina. La Paz,

28-29 junio, 2007

Which soil would you Which soil would you pick to grow plants in pick to grow plants in your garden or field?your garden or field?

THE VALUE OF SOIL ORGANIC MATTER THE VALUE OF SOIL ORGANIC MATTER

A.A. B.B.

What is Soil Organic Matter?What is Soil Organic Matter?

Definition:Definition:

“The organic fraction of soil including plant, “The organic fraction of soil including plant, animal, and microbial residues, fresh and at animal, and microbial residues, fresh and at all stages of decomposition… and highly all stages of decomposition… and highly carbonized compounds such as charcoal, carbonized compounds such as charcoal, graphite and coal”graphite and coal”

Soil organic matterSoil organic matter = = (2 x C) + O, H, N, P, S, (2 x C) + O, H, N, P, S, etc.etc.

CARBON IN SOILCARBON IN SOIL

• What are the major forms of C in soil?What are the major forms of C in soil?

Organic residuesOrganic residues

SoilSoil

COCO22 (60-80%) (60-80%)

Soil organisms Soil organisms (3-8%)(3-8%)

Nonhumic Nonhumic substances (3-8%)substances (3-8%)

Complex humic Complex humic substances (10-30%)substances (10-30%)

Organic residues in soilOrganic residues in soil

Soil humus (15-35%)Soil humus (15-35%)

Soil humus - dark-colored, heterogenous organicSoil humus - dark-colored, heterogenous organiccompounds resistant to decompositioncompounds resistant to decomposition

FORMS OF SOIL ORGANIC MATTERFORMS OF SOIL ORGANIC MATTER

Particulate organic matter and sand particles under magnificationParticulate organic matter and sand particles under magnification

AGE OF SOIL ORGANIC CARBONAGE OF SOIL ORGANIC CARBON

Sample DescriptionSample Description Mean Residence TimeMean Residence Time --- years ------ years ---

Grassland soil (North Dakota)Grassland soil (North Dakota) Virgin soil Virgin soil 1,175 1,175 ±± 100 100 Manured orchardManured orchard 880 880 ±± 74 74Bridgeport loam, WyomingBridgeport loam, Wyoming Surface sod layerSurface sod layer 3,2803,280 Clay fraction from virgin soil Clay fraction from virgin soil 6,6906,690 Continuous wheat plotContinuous wheat plot 1,8151,815Mollisol, SaskatchewaMollisol, Saskatchewa Surface soilSurface soil 545 to present545 to present B horizonsB horizons 700 to 4,000700 to 4,000 Buried horizonsBuried horizons 5,900 and 8,4105,900 and 8,410

In Gt or Gt/yearIn Gt or Gt/year1 Gt =1 Pg1 Gt =1 Pg= 10= 101515gg

THE GLOBAL CARBON CYCLETHE GLOBAL CARBON CYCLE

Historic net loss of 66 – 90 Gt C from soilHistoric net loss of 66 – 90 Gt C from soil

CARBON SEQUESTRATION: DEFINITIONCARBON SEQUESTRATION: DEFINITION

• Carbon sequestration is:Carbon sequestration is:

“ “the long-term storage of carbon in oceans, the long-term storage of carbon in oceans, soils, vegetation, and geologic formations” soils, vegetation, and geologic formations” (ESA, 2000)(ESA, 2000)

• Process of removing COProcess of removing CO22 from the atmosphere from the atmosphere

or capturing it from emissions and storing it or capturing it from emissions and storing it over a long-time somewhere else (a ‘carbon over a long-time somewhere else (a ‘carbon sink’)sink’)

• Possible sinks: plants and Possible sinks: plants and soilssoils, carbonate , carbonate minerals, geologic formations, ocean, new minerals, geologic formations, ocean, new technologiestechnologies

CO2

FUNCTIONS OF SOIL ORGANIC MATTERFUNCTIONS OF SOIL ORGANIC MATTER

SOIL ORGANIC MATTER AND SUSTAINABILITYSOIL ORGANIC MATTER AND SUSTAINABILITY

• Provides soil nutrients and enhances soil Provides soil nutrients and enhances soil nutrient availability over several growing nutrient availability over several growing seasons.seasons.

• Improves soil physical, chemical and Improves soil physical, chemical and biological properties for plant growth.biological properties for plant growth.

• Buffers changes in soil properties due to Buffers changes in soil properties due to disturbance or variation in other disturbance or variation in other environmental factors (e.g. climate).environmental factors (e.g. climate).

• Reduces environmental contamination and Reduces environmental contamination and soil loss.soil loss.

• Possibly reduces need for external inputs and Possibly reduces need for external inputs and enhances internal recycling when crop enhances internal recycling when crop residues and/or organic soil amendments are residues and/or organic soil amendments are applied. applied.

RESERVOIR OF PLANT NUTRIENTSRESERVOIR OF PLANT NUTRIENTS

• 95% or more of total N in soil is 95% or more of total N in soil is organic N organic N

• If soil contains 0.2 % total N then:If soil contains 0.2 % total N then:

0.2 kg N/100 kg soil * 95% * 2,000,000 0.2 kg N/100 kg soil * 95% * 2,000,000 kg soil/hectare plow layerkg soil/hectare plow layer

= = 3800 kg organic N/hectare plow 3800 kg organic N/hectare plow layer layer

LONG-TERM SUSTAINABLE MANAGEMENT AND LONG-TERM SUSTAINABLE MANAGEMENT AND SOIL CARBONSOIL CARBON

Lowland Taro System in PalauLowland Taro System in Palau

MANAGEMENT PRACTICES THAT MANAGEMENT PRACTICES THAT DECREASE SOIL ORGANIC CARBONDECREASE SOIL ORGANIC CARBON

• Frequent tillageFrequent tillage• Burning for clearingBurning for clearing• Removal of cropRemoval of crop

residuesresidues• InadequateInadequate

fertilizationfertilization

• Soil erosionSoil erosion

EFFECTS OF TILLAGE ON SOIL OMEFFECTS OF TILLAGE ON SOIL OM

LOSS OF SOIL ORGANIC C WITH TILLAGE LOSS OF SOIL ORGANIC C WITH TILLAGE

Sanborn Field

EFFECTS OF LAND-USE ON SOIL OM IN EFFECTS OF LAND-USE ON SOIL OM IN THE TROPICSTHE TROPICS

Research conducted on theResearch conducted on thePacific island of GuamPacific island of Guam

1.1. 2.2.

3.3. 4.4.

Deforestation leading to erosion in the Brazilian AmazonDeforestation leading to erosion in the Brazilian Amazon

MANAGEMENT PRACTICES THAT DECREASEMANAGEMENT PRACTICES THAT DECREASESOIL ORGANIC CSOIL ORGANIC C

PRACTICES THAT INCREASE SOIL PRACTICES THAT INCREASE SOIL ORGANIC MATTERORGANIC MATTER

• Adopt conservation tillage, residue Adopt conservation tillage, residue management and mulch farmingmanagement and mulch farming

• Apply organic wastes to soilApply organic wastes to soil• Use N and other nutrient sources more Use N and other nutrient sources more

efficiently efficiently • Convert marginal and degraded lands to Convert marginal and degraded lands to

restorative land uses restorative land uses • Adopt soil conservation practicesAdopt soil conservation practices• Eliminate summer (bare) fallow and Eliminate summer (bare) fallow and

incorporate legumes and other appropriate incorporate legumes and other appropriate cover crops in rotationscover crops in rotations

Kimble et al., 2002Kimble et al., 2002

INCREASING SOIL ORGANIC MATTER IN THE INCREASING SOIL ORGANIC MATTER IN THE ALTIPLANOALTIPLANO

• Focus of SANREM research effort is to Focus of SANREM research effort is to develop practices to increase soil develop practices to increase soil organic matter as a means to improve organic matter as a means to improve agricultural sustainability and agricultural sustainability and productivity and buffer against the productivity and buffer against the impacts of climate change. impacts of climate change.

Possible strategies for the Altiplano include:Possible strategies for the Altiplano include:

Improved use of organic soil amendments Improved use of organic soil amendments and chemical fertilizersand chemical fertilizers

Better management of crop residuesBetter management of crop residues Use of green manuresUse of green manures Development of managed fallow systems Development of managed fallow systems

with multipurpose plants (i.e., for forage, with multipurpose plants (i.e., for forage, soil fertility and erosion control) soil fertility and erosion control)

Reduced tillage practicesReduced tillage practices

FIELD TRIAL RESULTSFIELD TRIAL RESULTS

0,0

5,0

10,0

15,0

20,0

25,0

30,0

14/02/0,7 02/03/0,7 04/04/0,7 20/04/0,7

Fechas

Hu

med

ad (

%)

Testigo

Urea+FDA

Est. Oveja

Est. Vaca

Turba

Est.ñ Oveja + Fert,

Est, Vaca + Fert,

Soil water content to a 30 cm depth in CohaniSoil water content to a 30 cm depth in Cohani

Roberto Miranda, Elvio Aruquipa,Roberto Miranda, Elvio Aruquipa,Mirco Peñaranda, and Edwin Yucra, UMSAMirco Peñaranda, and Edwin Yucra, UMSA

MANAGEMENT OF ORGANIC SOIL MANAGEMENT OF ORGANIC SOIL AMENDMENTS IN THE TROPICSAMENDMENTS IN THE TROPICS

Research conducted in the semi-arid region of IndiaResearch conducted in the semi-arid region of India

CONSERVATION TILLAGECONSERVATION TILLAGE

Tillage Tillage NoNo--TillTill

SOIL C DISTRIBUTION WITH DIFFERENT SOIL C DISTRIBUTION WITH DIFFERENT LAND MANAGEMENT PRACTICESLAND MANAGEMENT PRACTICES

LSDLSD(0.10)(0.10) ------------- 2.4 ------------------------- 2.4 ------------ ----------- 2.68 ------------ ----------- 2.68 ------------ ------------ 22.2 ------------ ------------ 22.2 ------------

Landscape Landscape TOC TOC POM C POM C DOC DOC position GR AF CR position GR AF CR GR AF CR GR AF CR GR AF CRGR AF CR

--------------------------- g kg--------------------------- g kg-1-1 soil -------------------------- -------- mg kg soil -------------------------- -------- mg kg-1-1 soil ------ soil ------ UpperUpper 19.519.5 24.524.5 19.519.5 3.543.54 6.606.60 3.033.03 106.8106.8 123.3123.3 80.180.1 MiddleMiddle 22.522.5 23.523.5 22.022.0 5.425.42 5.765.76 4.524.52 105.7105.7 147.2147.2 75.075.0 LowerLower 25.525.5 24.024.0 18.518.5 7.127.12 7.387.38 3.283.28 133.5133.5 124.6124.6 72.472.4

Greenley Agroforestry Watershed ResearchGreenley Agroforestry Watershed Researchin Northeastern Missouriin Northeastern Missouri

REASONSREASONSFOR CONSERVINGFOR CONSERVINGSOIL ORGANIC CSOIL ORGANIC C

GLOBAL CARBON EMISSIONS REDUCTIONSGLOBAL CARBON EMISSIONS REDUCTIONS

Potential Global Soil C Sequestration

1-2 Gt C/yr

Would reduce C emissions to

meet targeted levels for

30 to 40 years

ANY QUESTIONS ANY QUESTIONS OR COMMENTS?OR COMMENTS?