Kefyalew Girma Desta Oklahoma Cooperative Extension Service Plant and Soil Sciences Department

1. Building Soil Organic Matter in Organic Production Kefyalew Girma Desta Oklahoma Cooperative Extension Service Plant and Soil Sciences Department

2. Organic Matter MATTERS! Organic materials are determinants of the health of the soil

3. IT MEANS A LOT! • Improve water infiltration rate/holding capacity • Supply free nutrients • Decrease pests, pollution from pesticides and heavy metals • Soil pH buffer • Improve soil tilth/ structure • Reservoir of nutrients and water • CEC • C sequestration: reduce CO2 and CH4 • Improve microbial mass and species diversity

4. Water holding capacity pH If OM<2.5%, N,P and K leach away Mielniczuk, 1996 NT vs CT Infiltration Prior et al., 2003

5. . . . It means a lot! Effect on microbes, dairy manure Effect on CEC McLaren and Cameron (1996). Gardener et al.,2002; composting and compost proceeding

6. First thing first! • What is the goal? • Short-term nutrient supply • Slow nutrient supply • Highly decomposable material vs slow decomposing materials • Nature of the organic enterprise • Soil type and problem

7. Building Soil OM 3-Strategies • Decrease losses • Add Organic Material/Matter • Consider Sustainability

8. 1. Building Soil OM: decrease losses Reduce tillage Erosion control Corn, Hussain et al., 1999, SSSAJ Schertz et al., 1984, ASAE, proceeding

9. . . . Decrease losses Minimize monocropping * Corn, oats, wheat, clover, timothy, timothy, 100 yrs Gantzer et al. 1991, AJ 83:74-77

10. Building Soil Organic Matter Organic amendment

11. Highly Variable • Decomposition & Contribution • Nutrient content • Availability • Application • Release pattern • Winter & early spring slow • Late spring and summer rapid • Fall release risk of leaching! • Low nutrient content and availability

12. 1. Cover Crops • Spring Annuals • Oats and Triticale. • Summer Annuals • Buckwheat, Cowpea, and Sorghum • Winter Annuals • Austrian Winter Pea, Hairy Vetch and Winter Rye are planted in late summer/early fall, over winter, and resume growing the following spring. • Biennials: • Yellow Blossom Sweet clover and perennials Red Clover can be grown for longer term soil-building.

13. . . . Cover Crops Common C:N ratios of cover crops If we return 2.2 tons/ac/yr of residue to the soil, it will maintain soil OM at constant level in continuously cropped soils.

14. 2. Green manure • Non-legumes: supply OM • Legumes • Both OM and fix N • Legumes add 25-70 lbs N/ac

15. . . . Green Manures “Green manure crops can supply an OM equivalent of 9 to 13 tons per acre of farmyard manure or 1.8 to 2.2 tons dry matter per acre.” However, the benefit from green manure crops’ soil benefits will be gone in a year or less. Biomass and N yields of winter annual GM crops Schmid and Klay, 1984

16. 3. Animal Manure Species, feed, and handling dependent

17. 4. Compost • Low in nutrient • Low availability • More of OM buildup • Very easy procedures available • Any organic material can be composted • Materials vary

18. Compost vs Manure?

19. 5. Uncomposted Yard Debris • Nutrient rich/poor, depends on material • Better than compost • Grass clippings release nutrients quickly; 20 lbs N/wet ton, 5-20% is available • Wood takes for ever! • Leaves and small branches decompose quickly

20. 6. Packaged Organic Fertilizers • Easy to use • Less variable • More concentrated • Expensive! • Blended forms

21. Sustaining Soil Organic Matter

22. Determination Balance Multi-dimensional Courtesy of animation factory

23. Indicators