Nitrogen is an essential element for all living things and the mineral element needed in the largest amounts by turfgrasses. Although nitrogen is abundant in the atmosphere (about 80 percent of the air surrounding us is nitrogen gas), it is in limited supply in soils and available to plants only after it has been converted to nitrate (NO 3 - )or ammonium (NH 4 + ) by microorganisms or industrial processes. In most cases, nitrogen fertilizer must be applied regularly to maintain high quality turf.
Although nitrogen fertilizer is required for healthy lawns, it can also contaminate ground- and surface waters through leaching and runoff. Excessive nitrate concentrations in drinking water are a health risk, especially for infants, pregnant and nursing mothers, and young children. Nitrogen movement into water can also accelerate degradation of ponds, lakes, coastal bays, and estuaries through a process called eutrophication. Eutrophication refers to the addition of nutrients to surface waters, resulting in algae blooms, dense aquatic plant growth, depletion of oxygen, and, in advanced stages, fish kills.
The goal of a nitrogen fertility program is to optimize plant uptake while minimizing leaching, runoff, and gaseous losses.