In 2008 there were over 843 million acres of U.S. farmland, of which over 4 million acres were certified by the USDA Organic Program. Organic farming averaged a 15 percent increase yearly between 2002 and 2008, according to the USDA and California is the leading state in organic farm acreage. Certified organic growers do not use synthetic fertilizers because their chemicals are harmful to health and they destroy the nutrient cycles in soil. Certified organic growers often use a combination of composted farm wastes, worm compost and compost tea to fertilize crops.
Compost is decomposed plant and animal waste that can be used as farm fertilizer to enrich soil. Large-scale farm composting uses decaying animal litter, poultry and other animal manure, crop residues as well as additional material such as rock phosphates, feather meal, bone meal and other mineral products. Water and air cause the compost pile to heat up and decay. Finished compost is then applied to growing crops as fertilizer. Compost is nutrient rich and it also "captures and destroys 99.6 percent of industrial volatile organic chemical in contaminated air", according to the EPA.
Compost tea is traditionally created by placing compost in a burlap sack and leaving it to soak in a barrel full of water. Modern methods for creating compost tea utilize aerating equipment to mix oxygen into compost infused water. Oxygen helps grow and multiply the microbes released from compost. As the microbe population multiplies, compost tea increases its nutrient content. Compost tea is used as a foliar spray that delivers nutrients directly onto plant leaves. Kirk Grace, vineyard manager at the Robert Sinskey Vineyards in Napa Valley, California, describes the value of using compost tea as "a way to apply the beneficial characteristics that are in compost such as its fertility and microbial populations and biological by-products and second, it can be an aid in disease management."
Red worms digest vegetable and fruit waste materials and leave behind their castings, which contain nutrients. Vermicompost is five times higher in nitrogen than common soil and seven times higher in phosphorus. Vermicompost is used in nurseries and the landscape industry as an ingredient in potting soil mixes, and on farms as a soil fertilizer. Farm-scale vermicompost operations are managed in large trenches. Worms are kept in fibrous bedding materials and fed large amounts of food waste products. Within four to six weeks, the vermicompost can be harvested for farm use.
Synthetic Nutrient Fertilizer
Nutrients are removed from soil through the growing process and can be replaced by synthetic nutrients. The N-P-K label on fertilizer identifies its nitrogen-phosphorous-potassium content. The International Fertilizer Association lists these ingredients as the most important for good crop growth and describes other elements found in soil as "beneficial to some plants" but not "essential to the growth of all of them."Best practices with inorganic fertilizers include knowledge of the rate of application, the right time to apply, the right product and the right place to apply it.