Reliance of soil fertility management on biological processes

A major difference between conventional cropping systems and organic systems is the role of biological processes in organic systems. Most synthetic fertilizers are immediately available to plants. They do not require biological processes to make them available. And they do not enhance the biological health of the soil. In fact, several synthetic fertilizers degrade soil by drying it out or making it acidic or saline.

In contrast, a primary principle of organic farming is to feed the soil so that the soil can feed the plants. A healthy soil has good tilth and mineralizes organic matter efficiently, to provide plants with their required nutrients. It also has a diverse population of soil organisms that enhance plant growth in various ways, such as through symbiotic relationships with the plant, exuding enzymes into the soil, degrading toxins, and competing with pathogenic organisms.

Practices and inputs used by organic producers (as well as many others in sustainable agriculture) promote biologically healthy soils that sustain fertility in ways different from conventional systems. Organic systems use legumes and algae to fix atmospheric nitrogen in the soil. They promote the decomposition of plant and animal residues to make nutrients from them available to plants. Additionally, soil organisms produce bacterial gels and microbial threads that bind soil into aggregates, form humates that hold water and nutrients, and develop symbiotic relationships with plant roots to help them reach and use water and nutri-ents.(7) Recent research indicates that enzymes formed by soil microorganisms can enhance the growth and nutritional value of plants.(8, 9) Managing soil fertility with biologically-created inputs ensures that organic production is a dynamic biological process. Fertility management that relies on nitrogen fixation, recycling the nutrients from plant and animal wastes, and stabilizing nutrients in the soil profile will also help ensure that production practices are environmentally sustainable.

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