1 / 26

Decomposition

Decomposition. Decomposition. Breakdown of organic matter, recycles nutrients . I mportant for recycling of C and energy, as well as all nutrient elements (N, P, K, etc.). Determines productivity and health of plants. Biotic Decomposition.

fadhila
Download Presentation

Decomposition

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Decomposition

  2. Decomposition • Breakdown of organic matter, recycles nutrients. • Important for recycling of C and energy, as well as all nutrient elements (N, P, K, etc.). • Determines productivity and health of plants.

  3. Biotic Decomposition • Organisms most directly responsible for decomposition are bacteria and fungi. • Biotic processes: • Aerobic respiration • OM + O2 CO2, organic products. • Anaerobic respiration • Use of acceptors other thanoxygen. • Facultative or obligate anaerobes • OM + CO2 CH4 + organic products.

  4. Sequence – Biotic Decomposition Inorganiccompounds Humus Living organisms Deadorganisms Litter OM Detritus

  5. Biotic decomposition • Many organisms are very beneficial in ecosystems, participate in biotic decomposition.

  6. Sequence – Biotic Decomposition Inorganiccompounds Humus Living organisms Deadorganisms Litter OM Detritus Bacteria, fungi Soil chemistry, mineralization Soil Animals

  7. Sequence of Events in Decomposition • Animals speed decomposition: • Break litter into small pieces. • Add products (excretion) to stimulate microbial growth. • Feeding on fungi and bacteria often increases growth rate of these decomposers, since new surface area is exposed to decomposition. • Predators regulate densities of animals that consume bacteria and fungi. • Move decomposers (bacteria, fungi) to new locations.

  8. Measuring Decomposition • Litter bag method.

  9. Decomposition Rates • Decomposition rates vary depending on: • Climate and temperature • Soil organisms present • Aeration of the soil • Composition of the material (C:N ratio) • Etc.– season, tillage

  10. Decomposition Rates • Decomposition rates vary depending on: • Climate and temperature • Soil organisms present • Aeration of the soil • Composition of the material (C:N ratio) • Etc.– season, tillage • Temperature affects decomposition rates (heat units). • Less Organic Matter in warm climates.

  11. Decomposition Rates • Decomposition rates vary depending on: • Climate and temperature • Soil organisms present • Aeration of the soil • Composition of the material (C:N ratio) • Etc.– season, tillage

  12. Decomposition Rates • Decomposition rates vary depending on: • Climate and temperature • Soil organisms present • Aeration of the soil • Composition of the material (C:N ratio) • Etc.– season, tillage • Season: spring = fresh green material; fall = tough residues. • Tillage: aerates soil.

  13. Decomposition Rates • Decomposition rates vary depending on: • Climate and temperature • Soil organisms present • Aeration of the soil • Composition of the material (C:N ratio) • Etc.– season, tillage

  14. C:N ratio • Most important factor influencing the rate of decomposition of OM. • Ratio of amount of carbon to the amount of nitrogen in a substance. • Slower decomposition if C:N ratio is high. • Examples of C:N ratios…..

  15. C:N Ratios of Selected Materials 20:1 for crops

  16. Importance of C:N ratio • With residues with a C:N ratio that is high, there is competition for the limited N available. • If C:N ratio is high: • Only some organisms can decompose (some types of bacteria and fungi, protozoan symbionts of termites). • They use up N quickly, so N becomes tied up and unavailable (immobilized).

  17. Adding organic N to soil Organic N materials decompose, release nitrate. Uptake, leaching,denitrification

  18. Adding organic N to soil Organic N materials decompose, release nitrate. Nitrate used in decomposition process by bacteria, etc.

  19. Adding organic N to soilLow C:N ratio material Decomposition and release of nitrate is fast, levels recover quickly.

  20. Adding organic N to soilHigh C:N ratio material Nitrate release difficult, tied up for a long time. N rob = immobility of N in presence of residues with high C:N ratios.

  21. Importance of C:N Ratio Bacteria free up N Organic N Inorganic N Mineralization Immobilization Bacteria take scarce N for themselves !Nrob

  22. Risky Mix of High and Low C:N • High C:N residue + Inorganic N fertilizer = • N from fertilizer immobilized by bacteria.

  23. Importance of C:N ratio • As C:N ratio goes lower (as it does during decomposition), more organisms (especially fungi, different bacteria types, even some insects) can join in, so decomposition proceeds much faster. • Most insects and other animals join later in the process, as the C:N ratio of their food is low: • E.g., fungi 10:1, decomposed animals 6:1, nematodes 10:1.

  24. Composting • Accelerates decomposition process. • Reduces C:N ratio. • High temperatures – 60-80oC (140-175oF). • Thermophilic bacteria. • Many recipes available.

  25. Practical Application • Farmer incorporates 2560 kg of OM to soil.55% Carbon, C:N ratio = 20:1. • Will there be any available for crop or all immobilized? • 2560 X 0.55 = 1408 kg C1408 / 20 = 70 kg N • Microbes use 75% of C and incorporate 25% in new tissue.C:N ratio of microbe is 8:1, so they require 1 kg N to incorporate 8 kg C in new tissue. • 1408 / 0.25 = 352 kg C used in new tissue. • 352 / 8 = 44 kg N used in new tissue. • 70 – 44 = 26 kg N leftover for uptake by plants.

  26. References • Text, pp. 68-73. • Brady and Weil, 1996. The Nature and Properties of Soils. Prentice Hall, Upper Saddle River, NJ. • Odum, 1983.

More Related