THE SOIL ECOSYSTEM ORGANIC MATTER

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THE SOIL ECOSYSTEM ORGANIC MATTER

• Prepared by
• Dr. Roger Clay

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ReadingCharman Murphy 2nd ed. Ch. 14
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Organic matter

• Consists of
• Litter
• Humified organic matter
• Soil organisms

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A Generalised Ecosystem

• Producers (very important)
• Consumers
• Decomposers
• Usually driven by the suns energy.

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The Soil Ecosystem

• Producers (minor importance)
• Consumers
• Decomposers (very important)
• What is the energy source?

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Plant Litter

• Quantity (from Spain Hutson 1983)

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Plant litter (cont.)

• Quality
• Importance of climate/vegetation type
• Rate of turnover
• Role of non-soil fauna

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Humified Organic Matter - Humus

• Major component of organic matter
• Produced by humification of litter
• Chemically poorly understood
• Stable, but continued breakdown occurs

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Amount of OM in Aust. Soils
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Organic Matter Soil Properties

• Bioturbation
• Surface litter
• Humus colloids

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Humus improves every soil

• cohesiveness to sands
• mellowness to clays
• aggregation porosity
• infiltration percolation
• aeration
• resistance to erosion
• (adapted from Kohnke 1968)

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Major Ideas

• Organic matter consists of various components.
• Soil ecosystems are driven by plant litter -
  decomposers are important.
• Litter quantity quality vary are important.
• Litter is converted to humus by the living om.
• OM is beneficial to soils plant growth.