Naturally fertile soil maintains and creates plant life easily. Soil is fertile when it is filled with organic matter which has the nutrients that create strong plant growth. Good soil makes a good garden, and good soil makes for good food. Natural ways to increase soil fertility is the focus of organic gardening.
Most nutrients needed by green plants are available from air, water and soil. Twenty nutrients have been identified as essential for healthy plant growth by the University of the Virgin Island Extension Program. Nitrogen, phosphorus and potassium---called macronutrients---are the most important and are needed in relatively large amounts. Calcium, sulphur and magnesium are also macronutrients.
Macronutrients and trace elements are made available to plants through the addition of organic matter to the soil. Organic matter is the decayed and decaying plant and animal residue known as compost. Natural fertilizers are also a source for the nutrients necessary for soil fertility. In natural environments soil fertility is constantly replenished by the process of decay of plants and animals.
Soil fertility in a home garden is maintained by adding compost. Compost improves fertility and soil structure; good soil structure is essential to help roots spread and to prevent excessive water loss. The Cornell University Extension program recommends that clay soils have 4 to 5 percent organic matter and sandy soils have 2 to 3 percent. The most efficient way to add organic matter to soil is by adding compost.
Both commercial and homemade compost increase the organic matter content of soil, and therefore its fertility. Healthy soil contains 4 billion microorganisms per teaspoonful. Compost is easily made at home and many local recycling programs have composting workshops. Commercial composts are available at garden centers. Worm composting is a popular alternative for urban gardeners---it contains five times more nitrogen than ordinary garden soil.
There are economic benefits for home gardeners who maintain soil fertility as a gardening goal. The effect of adding compost and its micronutrients is cumulative, so soil improves each year. Fertile soil results in increased crop production in vegetable gardens, which reduces food costs. Fertile soil also reduces water costs. And compost is free when it's homemade.