Transcript Terms and Definitions

Organic Matter
What is organic matter
Original Power Point Created by Darrin Holle
Modified by Georgia Agricultural Education Curriculum Office
June 2002
August 2008
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
August 2008
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
August 2008
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
August 2008
Chemical Makeup of O.M
– C. Protein
• Amino acid chains
• Supplies N when broken down
August 2008
Decomposition
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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
August 2008
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
August 2008
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
August 2008
Factors affecting O.M.
• 2. Climate
– Arid conditions soil has less O.M.
– High temperatures decay O.M. more rapidly
August 2008
Factors affecting O.M.
• 3. Texture
– Fine textured soils hold more organic material
because clay protects hums from decay
August 2008
Factors affecting O.M
• 4. Tillage
– Prairie will return more than cropping
August 2008
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
August 2008
Functions of O.M.
– 2. Both humus and O.M. absorb water like a
sponge, humus can store 6 times its own
weight
August 2008
Functions of O.M.
• B. Nutrient Availability
– Makes several nutrients more available for
plant use
August 2008
Functions of O.M
• C. Soil Aggregation
– 1. Heavy clay responds best. Breaks down
particles, aerates, and makes easier to work
with
August 2008
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
August 2008
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
August 2008
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
August 2008
Maintaining Soil O.M.
• B. Adding fresh organic matter will
improve soil the best
August 2008
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
August 2008
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
August 2008
Maintaining Soil O.M.
• E. Crop Rotation
– 1. A rotation between row crops, small grains,
and legumes is better for keeping high O.M.
August 2008
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.
August 2008
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
August 2008
Maintaining Soil O.M.
– 4. Horticulture crops are mulched
August 2008
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
August 2008
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
August 2008
Nitrogen Tie-up and
Composting
– 2. They compete with plants for N and can
cause slow plant growth
August 2008
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
August 2008
Nitrogen Tie-up and
Composting
– 3. Matter with a low c:n ratio N rich
• A high c:n ratio is N poor
August 2008
Nitrogen Tie-up and
Composting
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Soil Humus 10
Young Alf 12
Rotted manure 20
Corn stalks 60
Sawdust 400
August 2008
Garden Soil 12
compost 15-20
Clover residue 23
Straw 60