Enlivening Soil (extract) by Carl Rosato – Soil Consultant
Fertile soil is a mixture of well-balanced minerals, high organic matter, humus, humic, fulvic and carbonic acids, good aeration and bountiful soil life. The biology or life in the soil is at its healthiest when the nutrients are plentiful and balanced, and there is sufficient oxygen and water. The top few inches of soil is the most vital, holding about 70% of the life and 70% of the organic matter. Below 6 inches the roots are feeding on mostly soluble nutrients since the micro-organisms are not able to thrive without sufficient oxygen. It is possible to create biological activity deeper with deep double dug or mechanical disturbance like spading. It is crucial to leave the soil as undisturbed as possible, although nontillage is very difficult in organic annual crops.
Increasing the quantity of earthworms and planting deep-rooted plants will let air into lower levels of the soil. Micro-organisms like bacteria, fungi, actinomycetes, algae, nematodes and protozoa, need oxygen to contribute directly to the release of nutrients to the plant. Some species of mycorrhizae tolerate very low oxygen levels, and infest roots much deeper than other species of beneficial microbes, providing nutrients and root protection. There are many symbiotic relationships going on between roots, organic matter, clay and micro-organisms to support the plant. Soil that is worked too wet annihilates air and water space, destroying the environment that microbes need. Soil that is worked too dry creates similar problems.