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MANAGING SOIL ORGANIC MATTER FOR SUSTAINABLE AGRICULTURE

MANAGING SOIL ORGANIC MATTER FOR SUSTAINABLE AGRICULTURE AND MITIGATION OF THE EFFECTS OF CLIMATE CHANGE. Peter Motavalli Dept. of Soil, Environmental and Atmospheric Sciences University of Missouri.

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MANAGING SOIL ORGANIC MATTER FOR SUSTAINABLE AGRICULTURE

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  1. MANAGING SOIL ORGANIC MATTER FOR SUSTAINABLE AGRICULTURE AND MITIGATION OF THE EFFECTS OF CLIMATE CHANGE Peter Motavalli Dept. of Soil, Environmental and Atmospheric Sciences University of Missouri 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. THE VALUE OF SOIL ORGANIC MATTER A. B. Which soil would you pick to grow plants in your garden or field?

  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 Organic residues CO2 (60-80%) Soil Soil organisms (3-8%) Organic residues in soil Nonhumic substances (3-8%) Complex humic substances (10-30%) Soil humus (15-35%) • What are the major forms of C in soil? 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 DescriptionMean Residence Time --- years --- Grassland soil (North Dakota) Virgin soil 1,175 ± 100 Manured orchard 880 ± 74 Bridgeport loam, WyomingSurface sod layer 3,280 Clay fraction from virgin soil 6,690Continuous wheat plot 1,815 Mollisol, SaskatchewaSurface soil 545 to presentB horizons 700 to 4,000 Buried horizons 5,900 and 8,410

  7. THE GLOBAL CARBON CYCLE In Gt or Gt/year 1 Gt =1 Pg = 1015g Historic net loss of 66 – 90 Gt C from soil

  8. CARBON SEQUESTRATION: DEFINITION • Carbon sequestration is: • “the long-term storage of carbon in oceans, soils, vegetation, and geologic formations” (ESA, 2000) • Process of removing CO2 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 technologies CO2

  9. FUNCTIONS OF SOIL ORGANIC MATTER

  10. SOIL ORGANIC MATTER AND SUSTAINABILITY • Provides soil nutrients and enhances soil nutrient availability over several growing seasons. • 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). • 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.

  11. RESERVOIR OF PLANT NUTRIENTS • 95% 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 layer = 3800 kg organic N/hectare plow layer

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

  13. MANAGEMENT PRACTICES THAT DECREASE SOIL ORGANIC CARBON • Frequent tillage • Burning for clearing • Removal of cropresidues • Inadequatefertilization • Soil erosion

  14. EFFECTS OF TILLAGE ON SOIL OM

  15. Sanborn Field LOSS OF SOIL ORGANIC C WITH TILLAGE

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

  17. MANAGEMENT PRACTICES THAT DECREASE SOIL ORGANIC C 1. 2. 3. 4. Deforestation leading to erosion in the Brazilian Amazon

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

  19. 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: • Improved use of organic soil amendments and chemical fertilizers • Better management of crop residues • Use of green manures • Development of managed fallow systems with multipurpose plants (i.e., for forage, soil fertility and erosion control) • Reduced tillage practices

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

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

  22. CONSERVATION TILLAGE Tillage No-Till

  23. Landscape TOC POM C DOC position GR AF CR GR AF CR GR AF CR--------------------------- g kg-1 soil -------------------------- -------- mg kg-1 soil ------ Upper 19.5 24.5 19.5 3.54 6.60 3.03 106.8 123.3 80.1 Middle 22.5 23.5 22.0 5.42 5.76 4.52 105.7 147.2 75.0 Lower 25.5 24.0 18.5 7.12 7.38 3.28 133.5 124.6 72.4 LSD(0.10) ------------- 2.4 ------------ ----------- 2.68 ------------ ------------ 22.2 ------------ Greenley Agroforestry Watershed Research in Northeastern Missouri SOIL C DISTRIBUTION WITH DIFFERENT LAND MANAGEMENT PRACTICES

  24. REASONSFOR CONSERVINGSOIL ORGANIC C

  25. 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

  26. ANY QUESTIONS OR COMMENTS?

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