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This section defines healthy soils (see links in content) and discusses soil organic matter (SOM). There is also discussion on the economic benefits of healthy soils and how healthy soils lead to carbon sequestration and storage benefits. Co-benefits are another important factor of healthy soil.
Read the full overview HERE.
There is no one universally accepted definition of healthy soil. The commonality of the existing definitions reference healthy soil as a living ecosystem. The word “healthy” can only be used to refer to living things. Therefore, in reference to soil health, soil must be considered a living ecosystem full of life, like any other living complex system.
A preferred hybrid definition of healthy soil follows: Healthy soil exhibits sustainable productivity, promoting plant growth with optimal efficiency with little to no disease or pests and without a need for major soil disturbances (like plowing and tillage) and without a need for off-farm supplements.
The upper six inches of healthy soil over a one-acre surface area typically contains 10-20 tons or more of soil organic matter of which up to about 1 ton consists of living microorganisms.
Since this soil life is crucial for nurturing the next generation of plants, it becomes important for all working landowners to understand the factors that promote increased levels of soil organisms and organic matter.
These soil organisms are commonly referred to as the soil food web of life. According to the U.S. Department of Agriculture, the soil food web is the community of organisms living all or part of their lives in the soil. It consists of a complex array of microbes (bacteria, fungi, protozoa), arthropods, ants, spiders, worms, and some higher animals. Organic matter in the soil fuels this soil food web of life. “Climate smart agriculture” are those working land practices that lead to healthy soil conditions which means increasing the soil organic matter (SOM).
SOM is derived from all the living and dead forms of the soil food web organisms, plus fresh or dead and decaying plant components in and on the soil surface and the substances excreted from growing roots. Soil Organic matter is crucial to produce healthy soil. Soil organic matter is highly complex and is derived from all the materials (including minerals) found within living plants, insects, animals, microbial cells, and tissues.
SOM is the fuel that drives the health of soils and brings all the measurable co-benefits to healthy soil ecosystems. Farmers can increase soil organic matter using specific agronomic practices. A major percentage (about 58%) of SOM consists of carbon derived from atmospheric carbon dioxide through photosynthesis. Therefore, increasing SOM may lead to sequestering, or binding of carbon, for long periods of time within the soil ecosystem.
Increased SOM leads to healthy soil conditions with increased populations of the soil food web organisms. SOM contains about 58% carbon that originates from atmospheric carbon dioxide. This Greenhouse Gas (GHG) is converted to SOM through the processes of photosynthesis.
About 20-40% of the carbon contained within the SOM becomes sequestered soil carbon. Agronomic practices that decrease SOM content decrease soil health and release sequestered carbon from the soil in the form of carbon dioxide gas. Practices that decrease sequestered soil carbon (and reduce SOM) include aggressive plowing, tillage, and use of chemicals, including pesticides, herbicides, and synthetic fertilizers.
There have been numerous studies that illustrate the agronomic benefits associated with healthy soil conditions in the long term.
A comprehensive perspective from the Natural Resources Conservation Service of the USDA are presented HERE:
Storing SOM provides the benefit of carbon sequestration as mitigation to climate change, and are summarized HERE:
It should not be surprising therefore that farmers everywhere are using conservation agricultural practices that increase soil health with organic matter and carbon in their soils.
Sequestering carbon requires practices that bring long-term additions of soil organic matter (SOM) to the soil. When plants die, they decompose and 60-80% of the residues undergo short term decomposition (within a year or two) and this plant carbon re-enters the atmosphere. The rest (some 20-40% of the plant residues along with other dead or decaying matter) enter the soil and persist for years, decades, to hundreds of years becoming sequestered carbon.