Many people hold a handful of soil and think "dirt," an inanimate substrate that provides structural support for plant roots. In fact, soil is a complex entity, teeming with microbial life and full of organic matter, minerals, water and air pockets, all of which aid plants as they grow. Organic gardening methods attempt to promote soil health and fertility by mimicking the means by which healthy soils develop in nature.
In the 1960s, agricultural scientists developed a wheat seed that responded exceptionally well to unnatural human inputs, such as synthetic fertilizers and intensive irrigation. The ensuing Green Revolution promised to eliminate world hunger through increased crop yields. Decades later, world hunger remains, but the reliance on synthetic fertilizers and pesticides that followed the Green Revolution has devastated the environment, creating aquatic dead zones and poisoning the soil with toxic chemicals. Organic soil treatment techniques seek to slow or reduce such damage by relying on agricultural methods that take into account the health of the whole system, not just crop yields.
One way that organic gardeners improve soil health is by adding organic matter to the soil. Organic matter promotes microbial growth, improves the soil's ability to retain water and nutrients, and replaces lost minerals. "Rodale's Ultimate Encyclopedia of Organic Gardening" estimates that healthy soil should contain 5 percent organic matter. Gardeners restore organic matter by spreading compost or working dead plant matter, like autumn leaves, into the soil.
Minerals and Nutrients
Synthetic fertilizers were developed to replace nutrients lost over time in agricultural soils; however, they did nothing to restore or preserve organic matter. Many of the techniques used to restore organic matter, such as compost or cover crops, also replenish lost nutrients. Gardeners can also heal specific deficiencies by applying certain organic materials as fertilizer. For example, bone meal and eggshells repair calcium deficiencies.
Because organic agriculture focuses on the health of the entire system, not just the productivity of crop plants, organic soil treatments enhance soil fertility--and, therefore, productiveness--over the long term. Organic solutions further protect local ecosystems, including groundwater supplies, that people rely on to stay healthy. Because of this long-term perspective, organic methods may also increase productivity over time. In a review of several studies comparing organic and conventional growing methods, University of California Berkeley biologist Christos Vasilikiotis found that, over the course of years, organic methods reached or even exceeded the crop yields derived from conventional methods.
"Rodale's Ultimate Encyclopedia of Organic Gardening" touts organic soil treatments as "almost like a miracle cure for soil problems," adding the caveat that they are slow-acting solutions. Building healthy soil, particularly under challenging conditions, can take years. Although the eventual benefits are significant, gardeners must be prepared to wait through several unproductive seasons before they begin to see results.