Soil Care Basics: Increasing Organic Matter and Mineral Availability
The care of the Earth is our most ancient and most worthy, and after all our most pleasing responsibility. To cherish what remains of it and to foster its renewal is our only hope. ~Wendell Berry, The Unsettling of America
In Soil Ecology: The Basics of Fertility, I discussed soil ecology and concluded that our best soil-care strategy is the imitation of natural soil systems, which negatively means avoiding the destructive practices of industrial agriculture—monoculture, use of synthetic chemicals, and excessive tillage—and positively means increasing soil life diversity and population densities, feeding the soil from natural (and more home-grown) sources, and protecting soil structure. With those concepts as background, we can focus on specific practices to achieve these goals. Most soil-care strategies cluster around two key concepts: increasing organic matter and mineral availability—discussed in this article—and finding alternatives to the disruption of tillage—discussed in the companion piece “Protecting Soil Structure with Alternatives to Tillage”.
It has been said that organic matter in the soil consists of “the living, the recently dead, and the very dead.” The “living” portion consists of all the diverse forms of living organisms that make up the soil food web, but also plant roots themselves. It is a good thing to have lots of plant roots in our garden beds, because the most intense biological activity in the soil is found in the rhizosphere—the area in and immediately surrounding plant roots—largely because of important symbiotic relations between plant roots and soil organisms. “Recently dead” (or “active”) components include recently deceased soil organisms of all types, green plant material such as crop residues, and fresh manures. They decompose readily and make nutrients available quickly. The “very dead” portion is humus, the final residue of organic matter breakdown that is so important for soil structure, water retention, disease suppression, and nutrient-exchange pathways. All three forms of organic matter should be present in soil in goodly amounts, at all times, in order to cater to the specific “tastes” of the different classes of soil food web organisms, enlist their services in breaking down organic material into forms usable by plants, and improve soil structure. Our sources of organic matter should be as diverse as possible.