Transcript Organic Matter In The Soil

Organic Matter In The Soil
Topic #2055
Megan Burgess
Overview
Chemical/Physical Influence on Soils
Organic Matter Components
Humus
Effects of Organic Matter on Carbon:
Nitrogen Ratio
 Benefits of Organic Matter
 Detrimental Effects
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Chemical/Physical Influence on
Soils
 Life in soils is dependent on organic
matter for energy and nutrients
 Accumulation of organic matter reaches
equilibrium in non-tilled soils
 Organic matter can be temporarily
added to increase to benefit soils for
farming and gardening
Organic Matter Components
 Living and dead plants
 Animal residues
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Insects
Earthworms
Macro and microorganisms
Organic Matter Components
 Most comes from plants
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90% of plant material made of Carbon (C),
Hydrogen (H), and Oxygen (O)
Moisture content of plants varies
• 60% - 90% (75% is average)
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Other plant elements include:
• Nitrogen, sulfur, phosphorus, potassium,
calcium, magnesium, micronutrients
Organic Matter Components
Carbon
11%
Water
75%
Solids
25%
Hydrogen
2%
Ash
2%
Organic Matter Components
 Animals - secondary sources of organic matter
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Consume plant tissue and leave waste products
and bodies when they die
Move plant residues (ex. earthworms, ants)
 Bacteria, Fungi, Microorganisms - bulk of
organisms
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Breakdown plant and animal residues
Die and decompose into organic matter
Humus
 Complex, amorphous, colloidal
substance in soil left after
decomposition of organic matter
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Resistant to further decomposition
Improves soil structure
Dark color to soil (top 10 inches)
Increases soil water-holding capacity
Effects of Organic Matter on
Carbon: Nitrogen Ratio
 Natural conditions:
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12 parts carbon : 1 part nitrogen
 Changes in components can change
C:N ratio
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Fungi and bacteria multiply rapidly
Temporary nitrogen deficiency for crop
As more organic matter is added the ratio
changes
Benefits of Organic Matter
 Source of 90-95% nitrogen in unfertilized
soils
 Major source of phosphorus and sulfur
 Supplies soil aggregating cements
 Contributes to cation exchange capacity
 Increase soil water-holding capacity
 Increases air and water flow rates
Benefits of Organic Matter
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Increase micronutrient availability for plants
Furnishes carbon supply
Reduces erosion
Shades soil
Prevents rapid water loss
Balances soil temperature
Detrimental Effects
 Energy source for disease organisms
 Excessive plant residues may hinder
planting operations
 Some plants contain phytotoxins
(poisons) in organic matter
 Increase organic matter changes C:N
ratio and limits availability to crops