Fertilizer is a material added to soil to make the soil more nutritious for plants. In agriculture, fertilizer comes from organic sources, such as manure, or is manufactured chemically. According to the U.S. Environmental Protection Agency, most fertilizers contain one or more of nitrogen, phosphorus and potassium, since these ingredients are most important for plant growth.
Organic fertilizers are derived from plant or animal waste and naturally contain important plant nutrients like nitrogen and phosphorus. Common organic fertilizers, such as cow manure are worked into the soil during crop planting. Plant wastes also make good fertilizers and can be made by composting plant remnants from crops. Organic fertilizers may also be called bulky fertilizers, since they take up a lot of space and are therefore difficult to transport. Because they cannot be transported easily, most organic fertilizers are used within the local area where they are created.
Inorganic fertilizers are synthesized by a manufacturer to include important plant nutrients in a small, non-bulky form so that they may be easily transported. Inorganic fertilizers can be designed to create specific results through variation in ingredients or in the proportion of ingredients. They can also be designed for specific crops or specific growing regions. For example, inorganic fertilizer with a high concentration of phosphate is created for use on soybean crops. Farmers should test soil to determine what nutrients are needed from fertilizer so that they can choose the correct balance of nutrients. Other inorganic fertilizers have additives to improve soil condition or to repel insects from crops. The International Fertilizer Industry Association produces a best-practices guide to assist farmers and the agricultural industry in choosing and using fertilizers in the best manner.
Industrial Waste Fertilizers
Some kinds of industrial waste are used to manufacture fertilizers because of their high nitrogen levels. Bio-solids left over from water treatment in wastewater plants are also used to create fertilizers. The U.S. Environmental Protection Agency, Food and Drug Administration and Department of Agriculture ensure that these fertilizers are safe for agricultural use.