Organic gardening has become more popular in recent years due to increasing public interest in eating healthier food and in protecting the environment, which includes the soil in which we grow our food. Organically-produced foods bear no pesticide residue, and, due to healthier soil components, are more nutritious and better tasting.
Nature creates topsoil in forested land at a rate of about an inch every hundred years. Intensive organic agriculture in the home garden can put down an inch or more a year. When you grow organically, you are building topsoil by adding partially-decomposed organic matter to the soil.
Organic matter like compost gives the soil tilth and texture, and makes the grains more porous, allowing water and air to penetrate. As this organic matter continues to decompose, it slowly and steadily releases soluble nutrients to the plant roots in the soil. The major nutrients Nitrogen (N), Phosphorous (P), and Potassium (K), as well as the micronutrients are released. This results in healthier plants. Organic matter in the soil holds moisture and keeps plants from drying out as quickly. It also buffers the soil pH from abrupt changes in acidity or alkalinity.
Healthy soil is full of microorganisms, generally referred to as flora. These microflora, which include bacteria, fungi, and actinomycetes, are responsible for the breakdown of organic matter and the release of soluble inorganic compounds of nitrogen, potassium, phosphorous, and other nutrients. The soil is really a living structure which includes these microflora as well as earthworms (which also break down organics), other beneficial soil organisms, and organisms which can be harmful to crop plants. When you feed the soil with organic matter, you are feeding beneficial soil organisms, which in turn compete with the pathogenic organisms, helping to prevent plant disease. Plants grown in soil which is organically enriched are more naturally resistant to disease than crops grown in soil using only inorganic fertilizer.
Organic matter can be added to the soil in the form of animal manures or plant wastes laid directly on crop fields and either turned in or allowed to decompose on the surface. This is called sheet composting. It can be added in the form of mulches, like straw, built up around the plants to increase moisture, keep weeds and pests down, and control soil temperatures. It can be added in the form of compost prepared using various composting methods from organic materials like manure, plant wastes, and kitchen scraps, and then applied to the garden or farm field. In all these methods, the organic matter applied gradually breaks down by microbial decomposition and becomes available in soluble form to the plant roots at a rate that they can use.
The best thing the home gardener can do to start gardening organically (besides stopping the use of pesticides and inorganic fertilizers) is to make and use compost, or, at the very least, mulch with hay, straw, bark, or any of a number of other organic mulches. Save raked leaves and lawn clippings (not treated with pesticides) in a pile and add kitchen scraps like coffee grounds and egg shells. Turn occasionally or allow to sit for a year. Then add to the garden. Compost does not have to be turned into the soil, but you can if you want. Organic soil ammendments can also be purchased at garden centers. Read what you can about organic methods and talk to other gardeners. The more you practice the organic method, the better your soil will be.