Organic Matter

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Organic Matter

• What is organic matter

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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,
• Prairiesgrass roots and tops
• Farmland crop residue

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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

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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

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Chemical Makeup of O.M

• C. Protein
• Amino acid chains
• Supplies N when broken down

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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

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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

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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

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Factors affecting O.M.

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

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Factors affecting O.M.

• 3. Texture
• Fine textured soils hold more organic material
  because clay protects hums from decay

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Factors affecting O.M

• 4. Tillage
• Prairie will return more than cropping

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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

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Functions of O.M.

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

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Functions of O.M.

• B. Nutrient Availability
• Makes several nutrients more available for plant
  use

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Functions of O.M

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

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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

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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

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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

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Maintaining Soil O.M.

• B. Adding fresh organic matter will improve soil
  the best

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Maintaining Soil O.M.

• C. Crop Residues
• Leave all crop materials possible. Dont burn
  residues, harvest some
• Use good fertilizer, healthy plants make more
  residue

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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

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Maintaining Soil O.M.

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

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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.

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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

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Maintaining Soil O.M.

• 4. Horticulture crops are mulched

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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

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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

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Nitrogen Tie-up and Composting

• 2. They compete with plants for N and can cause
  slow plant growth

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Nitrogen Tie-up and Composting

• B. Carbon-Nitrogen Ratio (CN ratio)
• 1. The measure of carbon amounts compared to N
  amounts
• 2. Plants with high cn ratios are of greatest
  concern

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Nitrogen Tie-up and Composting

• 3. Matter with a low cn ratio N rich
• A high cn ratio is N poor

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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