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Organic Matter

Organic Matter. What is organic matter. Nature of O.M. 1. Is the portion of the soil which includes animal and plant remains at stages of decay Forest= leaves, dead trees, Prairies=grass roots and tops Farmland= crop residue. Chemical Makeup of O.M.

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Organic Matter

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  1. Organic Matter What is organic matter

  2. Nature of O.M. • 1. Is the portion of the soil which includes animal and plant remains at stages of decay • Forest= leaves, dead trees, • Prairies=grass roots and tops • Farmland= crop residue

  3. Chemical Makeup of O.M. • 1. Consists of complex carbon-containing compounds • 2. Long chains are formed and other elements use these to make more organic compounds

  4. Chemical Makeup of O.M • 3. The most important compounds are • A. Carbohydrates: simple sugars, starches, and cellulose • B. Lignins: is 10-30% of plant tissue, makes plants rigid, resists decay

  5. Chemical Makeup of O.M • C. Protein • Amino acid chains • Supplies N when broken down

  6. Decomposition • 1. Micro-organisms digest organic matter • 2. Releases CO2 and H2O • 3. Carbohydrates are first to be consumed • 4. Lignin-becomes humus and slowly broke down

  7. Decomposition • 5. Decay Organisms need O2 and microorganisms use O2 to oxidize the different compounds • 6. 1st breakdown is quick and requires weeks or months • 7. Well drained soils will lose 1-3% of humus a year to oxidation

  8. Factors affecting O.M. • 1. Vegetation • 2 times as much o.m. on grassland to woodland • O.M. is deeper in prairie soil and is in soil

  9. Factors affecting O.M. • 2. Climate • Arid conditions soil has less O.M. • High temperatures decay O.M. more rapidly

  10. Factors affecting O.M. • 3. Texture • Fine textured soils hold more organic material because clay protects hums from decay

  11. Factors affecting O.M • 4. Tillage • Prairie will return more than cropping

  12. Functions of O.M. • A. Nutrient and water storage • 1. O.M. stores many of the nutrients used by plants and does it in 2 different ways • Colloids hold water and nutrients • O.M. stores nutrients as part of its own makeup

  13. Functions of O.M. • 2. Both humus and O.M. absorb water like a sponge, humus can store 6 times its own weight

  14. Functions of O.M. • B. Nutrient Availability • Makes several nutrients more available for plant use

  15. Functions of O.M • C. Soil Aggregation • 1. Heavy clay responds best. Breaks down particles, aerates, and makes easier to work with

  16. Functions of O.M • D. Prevents Erosion • 1. Soils kept supplied with O.M. have improved structure that improves water infiltration • 2. Stops excessive water runoff • 3. Increasing O.M. from 1-3% will reduce erosion 1/5-1/3

  17. Functions of O.M. • Undesirable Effects • 1. Nitrogen is immobilized or tied up during the decay process and is unavailable to plants • 2. Certain plant residues are toxic to other plants

  18. Maintaining Soil O.M. • A. It is impractical and not economical to raise O.M. levels significantly but should be a goal to maintain at highest levels

  19. Maintaining Soil O.M. • B. Adding fresh organic matter will improve soil the best

  20. Maintaining Soil O.M. • C. Crop Residues • Leave all crop materials possible. Don’t burn residues, harvest some • Use good fertilizer, healthy plants make more residue

  21. Maintaining Soil O.M. • D. Green Manure • 1. Turn over alfalfa, clover, sudan grass, will increase N levels • 2. Increases O.M. levels and fixes more nutrients

  22. Maintaining Soil O.M. • E. Crop Rotation • 1. A rotation between row crops, small grains, and legumes is better for keeping high O.M.

  23. Maintaining Soil O.M. • F. Organic Matter Additions • 1. Animal Manures, sludge, organic wastes • 2. Industries may provide organic wastes, by products, meat scraps, etc.

  24. Maintaining Soil O.M. • G. Mulches • 1. Not economical in large acres • 2. Reduce tillage leaves some mulch • 3. Limits water evaporation, keeps soil temperature cooler on hot days, and warmer at night

  25. Maintaining Soil O.M. • 4. Horticulture crops are mulched

  26. Maintaining Soil O.M. • H. Conservation Tillage • 1. Conserves topsoil which is high in O.M. • 2. Crop residue decays slower when left on top • 3. No till soils are high in O.M. in the top layer

  27. Nitrogen Tie-up and Composting • A. Soil Microorganisms need both Carbon and N in their diet to grow and multiply • 1. Fresh organic matter will increase number of organisms because higher food supply

  28. Nitrogen Tie-up and Composting • 2. They compete with plants for N and can cause slow plant growth

  29. Nitrogen Tie-up and Composting • B. Carbon-Nitrogen Ratio (C:N ratio) • 1. The measure of carbon amounts compared to N amounts • 2. Plants with high c:n ratio’s are of greatest concern

  30. Nitrogen Tie-up and Composting • 3. Matter with a low c:n ratio N rich • A high c:n ratio is N poor

  31. Nitrogen Tie-up and Composting • Soil Humus 10 Garden Soil 12 • Young Alf 12 compost 15-20 • Rotted manure 20 Clover residue 23 • Corn stalks 60 Straw 60 • Sawdust 400

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