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Used to be anybody could farm.

All you needed was a strong back. . .

however nowadays you need a good education to understand all the advice
you get so you can pick out what’ll do you the least harm.
Vermont saying, mid-1900s

Although we focus on the critical role soils play in growing crops, it’s important to keep in mind that soils also serve other important purposes. Soils govern what percent of the rainfall runs off the field, as compared to the percent that enters the soil and eventually helps recharge underground aquifers. When a soil is denuded of vegetation and it starts to degrade, excessive runoff and flooding are more common.

Soils also absorb, release, and transform many different chemical compounds. For example, they help to purify wastes flowing from the septic system drain in your back yard. Soils also provide habitats for a diverse group of organisms, some of which are very important such as with those bacteria that produce antibiotics.

Soil organic matter stores a huge amount of atmospheric carbon. Carbon, in the form of carbon dioxide, is a greenhouse gas associated with global warming. We also build roads and buildings on soils; some are definitely better than others for this purpose.

The organisms living in the soil, both large and small, play a significant role in maintaining a healthy soil system and healthy plants.Some soil organisms can harm plants either by causing disease or by being parasites.

In other words, there are “good” as well as “bad” bacteria, fungi, nematodes, and insects. One of the goals of agricultural production systems should be to create conditions that enhance the growth of beneficial organisms, which are the vast majority, while decreasing populations of those few that are potentially harmful.

Human beings have been harvesting plants for food, medicines, and other purposes for over 9,000 years. This has resulted in extensive depletion of carbon and essential plant nutrients such as nitrogen, phosphorus, and potassium from the soil.

Begin by Feeding the Soil with Organic Matter

To enhance the soil and its surrounding landscape, cover crops create numerous synergistic and beneficial effects. Mostly because they produce carbohydrates from sunlight, water and CO2 (photosynthesis), and their residues are largely returned to the field, they will feed and energize a living, breathing soil containing everything from one-celled bacteria, to foot-long nightcrawlers.

Initially, it is primarily the soil micro-organisms (bacteria, fungi and actinomycetes) that devour easily digestible simple sugars and proteins from freshly incorporated plant residues. These materials, which contain high levels of nitrogen, as well as some phosphorus, potassium, and other essential nutrients, are then immediately available for subsequent crop plants.

The results will contribute to a more stable, humus portion of soil organic matter, and remain a part of the soil for a much longer time.

As soil microbes digest organic matter, they produce complex sugars known as polysaccharides, which are glue-like substances that cement soil particles into aggregates or “crumbs.” This crumb structure, along with the build-up of stable organic matter, leads to improved water and nutrient-holding capacity and to water infiltration. The soil begins to take on a spongy quality and is less prone to compaction.

Nitrogen can also be replenished in the soil by growing legumes such as vetch, peas, or clover; all of which support specialized bacteria known as rhizobia on their roots. The legumes provide the rhizobia with carbohydrates, and in return the rhizobia provide the legumes and the surrounding soil with nitrogen from the air.

Many other nutrients may be deficient because they are unavailable to most crops in their current form in the soil. Deep-rooted cover crops such as sweetclover and alfalfa can mine calcium, potassium, phosphorus, and other nutrients from deeper depths and transport them to the surface for future crops.

Cover Crop References:
Managing Cover Crops Profitably, 2nd edition.
USDA Sustainable Agriculture Research & Education Program (1998)

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