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Soil organic matter
In most soils, organic matter accounts for less than 5% of the total weight. Soil organic matter (SOM) is the fraction of the soil composed of anything that once lived and includes plant and animal remains in various stages of decomposition, cells and tissues of soil organisms, and substances from plant roots and soil microbes [USDA Soil Carbon fact sheet]. Well- decomposed organic matter becomes humus, a dark brown porous, spongy material that has a pleasant, earthy smell.
As plants, insects and microorganisms that live in or on the soil die, they contribute to SOM. SOM may also be added to the system through incorporation of amendments such as compost or animal manure, or off-farm amendments such as rock phosphate and green sand. Beneficial fungi, bacteria and other soil organisms recycle SOM and convert it into nutrients and other substances that ultimately benefit your crop plants.
As soil organic matter levels increase, more of it gets converted into humus. Humus is a relatively stable form of soil left over after myriad soil organisms—from earthworms to arthropods—have used and digested the decaying organic materials. Carbon-rich humus:
• Is resistant to further decay.
• Acts as a reservoir for water and nutrients.
• Improves soil structure.
• Continues to feed beneficial soil microorganisms.
• Sequesters significant amounts of atmospheric carbon to mitigate climate change.
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Research
Humus can store carbon in the soil for decades or even centuries. Recent studies of pre-Columbian indigenous agriculture in South America suggest that natives of the region used charcoal to convert infertile red soils to deep, dark fertile earth. Even after hundreds of years, these terra preta soils are rich in carbon and improve crop production in an area larger than modern-day France.
Read more >> Carbon is the key
Farmer-to-Farmer"Including cover crops that produce lots of biomass (such as red clover), chopping straw from small grains back into the field and incorporating composted vegetable matter and manure will all contribute to active, healthy organic matter."
~Mary-Howell and Klaas Martens
Penn Yan, NY
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