1. 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

2. Which soil would you pick to grow plants in your garden or field? THE VALUE OF SOIL ORGANIC MATTER A. B.

3. What is Soil Organic Matter?  Definition: “The organic fraction of soil including plant, animal, and microbial residues, fresh and at all stages of decomposition… and highly carbonized compounds such as charcoal, graphite and coal” Soil organic matter = (2 x C) + O, H, N, P, S, etc.

4. CARBON IN SOIL What are the major forms of C in soil?What are the major forms of C in soil? Organic residues Soil CO 2 (60-80%) Soil organisms (3-8%) Nonhumic substances (3-8%) Complex humic substances (10-30%) Organic residues in soil Soil humus (15-35%) Soil humus - dark-colored, heterogenous organic compounds resistant to decomposition

5. FORMS OF SOIL ORGANIC MATTER Particulate organic matter and sand particles under magnification

6. AGE OF SOIL ORGANIC CARBON Sample Description Mean Residence Time Sample Description Mean Residence Time --- years --- --- years --- Grassland soil (North Dakota) Virgin soil1,175 ± 100 Manured orchard880 ± 74 Manured orchard880 ± 74 Bridgeport loam, Wyoming Surface sod layer3,280 Clay fraction from virgin soil6,690 Continuous wheat plot1,815 Mollisol, Saskatchewa Surface soil545 to present B horizons700 to 4,000 Buried horizons5,900 and 8,410 Buried horizons5,900 and 8,410

7. In Gt or Gt/year 1 Gt =1 Pg = 10 15 g THE GLOBAL CARBON CYCLE Historic net loss of 66 – 90 Gt C from soil

8. CARBON SEQUESTRATION: DEFINITION Carbon sequestration is:Carbon sequestration is: “the long-term storage of carbon in oceans, soils, vegetation, and geologic formations” (ESA, 2000) “the long-term storage of carbon in oceans, soils, vegetation, and geologic formations” (ESA, 2000) Process of removing CO 2 from the atmosphere or capturing it from emissions and storing it over a long-time somewhere else (a ‘carbon sink’)Process of removing CO 2 from the atmosphere or capturing it from emissions and storing it over a long-time somewhere else (a ‘carbon sink’) Possible sinks: plants and soils, carbonate minerals, geologic formations, ocean, new technologiesPossible sinks: plants and soils, carbonate minerals, geologic formations, ocean, new technologies CO 2

9. FUNCTIONS OF SOIL ORGANIC MATTER

10. SOIL ORGANIC MATTER AND SUSTAINABILITY Provides soil nutrients and enhances soil nutrient availability over several growing seasons.Provides soil nutrients and enhances soil nutrient availability over several growing seasons. Improves soil physical, chemical and biological properties for plant growth.Improves soil physical, chemical and biological properties for plant growth. Buffers changes in soil properties due to disturbance or variation in other environmental factors (e.g. climate).Buffers changes in soil properties due to disturbance or variation in other environmental factors (e.g. climate). Reduces environmental contamination and soil loss.Reduces environmental contamination and soil loss. Possibly reduces need for external inputs and enhances internal recycling when crop residues and/or organic soil amendments are applied.Possibly reduces need for external inputs and enhances internal recycling when crop residues and/or organic soil amendments are applied.

11. RESERVOIR OF PLANT NUTRIENTS 95% or more of total N in soil is organic N95% or more of total N in soil is organic N If soil contains 0.2 % total N then: 0.2 kg N/100 kg soil * 95% * 2,000,000 kg soil/hectare plow layerIf soil contains 0.2 % total N then: 0.2 kg N/100 kg soil * 95% * 2,000,000 kg soil/hectare plow layer = 3800 kg organic N/hectare plow layer

13. LONG-TERM SUSTAINABLE MANAGEMENT AND SOIL CARBON Lowland Taro System in Palau

14. MANAGEMENT PRACTICES THAT DECREASE SOIL ORGANIC CARBON Frequent tillageFrequent tillage Burning for clearingBurning for clearing Removal of crop residuesRemoval of crop residues Inadequate fertilizationInadequate fertilization Soil erosionSoil erosion

15. EFFECTS OF TILLAGE ON SOIL OM EFFECTS OF TILLAGE ON SOIL OM

16. LOSS OF SOIL ORGANIC C WITH TILLAGE Sanborn Field

17. EFFECTS OF LAND-USE ON SOIL OM IN THE TROPICS Research conducted on the Pacific island of Guam

18. 1.2. 3.4. Deforestation leading to erosion in the Brazilian Amazon MANAGEMENT PRACTICES THAT DECREASE SOIL ORGANIC C

19. PRACTICES THAT INCREASE SOIL ORGANIC MATTER Adopt conservation tillage, residue management and mulch farmingAdopt conservation tillage, residue management and mulch farming Apply organic wastes to soilApply organic wastes to soil Use N and other nutrient sources more efficientlyUse N and other nutrient sources more efficiently Convert marginal and degraded lands to restorative land usesConvert marginal and degraded lands to restorative land uses Adopt soil conservation practicesAdopt soil conservation practices Eliminate summer (bare) fallow and incorporate legumes and other appropriate cover crops in rotationsEliminate summer (bare) fallow and incorporate legumes and other appropriate cover crops in rotations Kimble et al., 2002

20. INCREASING SOIL ORGANIC MATTER IN THE ALTIPLANO Focus of SANREM research effort is to develop practices to increase soil organic matter as a means to improve agricultural sustainability and productivity and buffer against the impacts of climate change. Possible strategies for the Altiplano include:Focus of SANREM research effort is to develop practices to increase soil organic matter as a means to improve agricultural sustainability and productivity and buffer against the impacts of climate change. Possible strategies for the Altiplano include: Improved use of organic soil amendments and chemical fertilizers Improved use of organic soil amendments and chemical fertilizers Better management of crop residues Better management of crop residues Use of green manures Use of green manures Development of managed fallow systems with multipurpose plants (i.e., for forage, soil fertility and erosion control) Development of managed fallow systems with multipurpose plants (i.e., for forage, soil fertility and erosion control) Reduced tillage practices Reduced tillage practices

21. FIELD TRIAL RESULTS Soil water content to a 30 cm depth in Cohani Roberto Miranda, Elvio Aruquipa, Mirco Peñaranda, and Edwin Yucra, UMSA

22. MANAGEMENT OF ORGANIC SOIL AMENDMENTS IN THE TROPICS Research conducted in the semi-arid region of India

23. CONSERVATION TILLAGE Tillage No - Till

24. SOIL C DISTRIBUTION WITH DIFFERENT LAND MANAGEMENT PRACTICES LSD (0.10) ------------- 2.4 ------------ ----------- 2.68 ------------------------ 22.2 ------------ Landscape TOC POM C DOC position GR AF CR GR AF CR GR AF CR --------------------------- g kg -1 soil -------------------------- -------- mg kg -1 soil ------ position GR AF CR GR AF CR GR AF CR --------------------------- g kg -1 soil -------------------------- -------- mg kg -1 soil ------ Upper19.524.519.53.546.603.03106.8123.380.1 Upper19.524.519.53.546.603.03106.8123.380.1 Middle22.523.522.05.425.764.52105.7147.275.0 Middle22.523.522.05.425.764.52105.7147.275.0 Lower25.524.018.57.127.383.28133.5124.672.4 Lower25.524.018.57.127.383.28133.5124.672.4 Greenley Agroforestry Watershed Research in Northeastern Missouri

25. REASONS FOR CONSERVING SOIL ORGANIC C

26. GLOBAL 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

27. ANY QUESTIONS OR COMMENTS?