Fertilizers are essential to a garden or lawn's success. As plants grow, they require nutrients to feed their systems. If a plant's need is great, it will quickly remove nutrients from the soil. If the use of nutrients is greater than the replenishment, plants will stop growing, lose color and potentially die. Fertilizing prevents this.
Chemical fertilizers are mixed chemicals that create the correct nutrients readily absorbed by plants, according to the Michigan State University Extension. Commonly used synthetic fertilizers mainly consists of nitrogen, phosphorous and potassium with little micronutrient composition. Micronutrients are nutrients used in small amounts by plants, such as calcium and iron. Chemical fertilizers tend to release their nutrients at a faster rate than their organic counterparts because of less reaction with micronutrients, report horticulturists at the Clemson University Cooperative Extension.
Organic fertilizers are made from plant or animal sources such as bone scraps, manure, bone or fish meal, ground plant stalks, or leaves and compost. Micronutrients supplied with organic fertilizers are not always absorbed, but react with nitrogen, creating ammonium and nitrate. When organic fertilizer is applied at an incorrect rate, not all of the important nutrients are released, causing a build-up of these materials. Most plants require a specific amount of nitrogen to grow; for example, lawns usually require 1 pound of nitrogen per 1,000 square feet. Organic fertilizers do have the added benefit of adding organic matter to the soil, improving texture and preventing soil erosion.
Slow-release fertilizers are available in both organic and inorganic forms. These fertilizers break down slowly, giving a long-term release of nutrients. This prevents burning of plants and less runoff. Slow-release fertilizers are comprised mainly of nitrogen and come in several varieties. Urea-formaldehyde slow-release fertilizers are released by microbial degradation; isobutylidene diurea is released through moisture; sulfur-coated urea is released at a rate determined by the granule coating thickness; and plastic-coated fertilizers are released according to the temperature and their coating thickness.
Quick-release fertilizers come in water-soluble form and release the nutrients at a fast pace. Chemical fertilizers usually indicate on the label whether the fertilizer is a quick-release formula. Quick release is best used for blooming plants to force flowering vegetables around the time of production and on high maintenance lawns.
Chemical fertilizer is often made in a granule form. Granules degrade into the soil when made wet or when temperatures rise to a point where the coating breaks. Fertilizer in granule form is spread onto plants either by hand or through the use of a fertilizer spreader.
Liquid fertilizer is also available. Usually mixed with water, liquid fertilizer is applied by a hand-held sprayer, through a garden hose attachment or from a watering can.