Organic Matter
What it is: Organic matter comprises all carbon-based constituents of the soil, including living organisms, decaying plant material, and humus. Indicators include measures of total organic matter, specific fractions of organic matter, or ratios of organic matter to mineral constituents.
Why it is important: The amount of organic matter in the soil is an important indicator because it is the storehouse for the energy and nutrients used by plants and soil organisms.
Specific problems that might be caused by (too little, too much etc.):
Too little: poor soil structure, poor aggregate stability, inefficient cycling of nutrients
Too much (as result of excessive manure applications): nitrate leaching, phosphorus runoff
What you can do: You can increase your soil's organic matter levels by reducing tillage (in some soils), including deep and heavily rooting crops in the rotation, planting cover crops, applying manure, and not over fertilizing.
For more information go to Soil Management Practices.
Ways that soil organic matter can be measured include:
| Method | How Performed | Comments |
|---|---|---|
| Total organic carbon (TOC) | ||
| Soil organic matter (SOM) | ||
| Total Kjeldahl nitrogen (TKN) | ||
| Total nitrogen (TN) | ||
| Labile carbon | ||
| Particulate organic matter (POM) | ||
| Carbon:Nitrogen ratio | ||
| Microbial biomass carbon (MBC) | ||
| MBC/TOC | ||
| Decomposition |
The different methods have different levels of accuracy and precision.