By legal definition, the term fertilizer refers to a soil amendment that guarantees the minimum percentages of nutrients (at least the minimum percentage of nitrogen, phosphate, and potash).
An organic fertilizer refers to a soil amendment derived from natural sources that guarantees, at least, the minimum percentages of nitrogen, phosphate, and potash. Examples include plant and animal by-products, rock powders, seaweed, inoculants, and conditioners. These are often available at garden centers and through horticultural supply companies
Advantages of Organic Fertilizers
- Organic fertilizers commonly are mild, noncaustic materials, and if they come in contact with a crop, the fertilizers likely will not burn or desiccate foliage or roots.
- The slow release of nutrients makes them available for a longer period of time than water-soluble chemical fertilizers, which may be leached with the downward movement of water.
- Use of organic fertilizers with high organic matter contents can improve the physical properties of soils in ways such as imparting higher water-holding capacity and better structure and good tilth or physical condition of soil for crop growth. Some of the organic matter of fertilizers is converted to humus in soil by a process known as humification.
- Organic materials are sources of many essential elements.
- The use of organic fertilizers, such as composts, is a method of recycling materials that might otherwise be wasted
Growers may find it practical to use a balanced approach in uses of organic and chemical fertilizers. Organic fertilizers may be used for building soil fertility over a long period of time. Initially, growers may rely on supplemental use of chemical fertilizers with organic fertilizers in poor soils. As the fertility with respect to nutrient supply increases with prolonged application of organic materials, use of chemical fertilizers may be tapered off. A grower may use chemical fertilizers in the making of organic fertilizers. Chemical nitrogen fertilizers often are added to compost piles to accelerate the rate of decomposition of organic matter. Chemical phosphate fertilizers also are added to composts and to farm manures to fortify the phosphorus concentrations of these otherwise phosphorus-poor materials. Certified organic growers, however, have limitations on the use of chemical fertilizers in crop production. Certifying organizations require a time period of 3 years between the discontinued use of chemical fertilizers and issuance of certification as an organic