Fertilizing lawns, forage grass or ornamental grasses with nitrogen helps them grow quick, thick and green. Nitrogen fertilizers come in many varieties and concentrations, so special attention should be paid to how much you use, what time of year you use it, and how much you use. Over-fertilizing wastes time, money and resources while causing pollution and other environmental damage.
Before the advent of chemical fertilizers, organic nitrogen fertilizer came in the form of animal manure, rain, compost and legume cover crops. Legumes have a mutually beneficial relationship with bacteria that fixes atmospheric nitrogen, converting it into ammonia that plants use as food. Chemical fertilizers provide easily measurable quantities of nitrogen to grasses. In theory, this should allow the user to apply as much as is needed without damaging the grass or wasting valuable fertilizer.
Timing nitrogen fertilizer application with the time of year when grasses are active is critical. Nitrogen fertilizer applied to frozen ground to dormant grass is wasted, because it either washes away with precipitation or leeches too deep into the ground for the grass roots to reach before it can be absorbed. Slow-release nitrogen stays in the ground longer, feeding grass continually, while quick-release fertilizers provide a quick burst of green and growth.
Test the soil for nitrogen content before applying fertilizer. If there is a nitrogen deficiency, add fertilizer according to package directions. Err on the side of too little. You can always add more later if necessary, but you can't reclaim wasted nitrogen that leeches into the soil or runs off during heavy rains. Don't fertilize right before a heavy rain, as the water can wash away granules or push liquid nitrogen farther into the ground than shallow grass roots can reach.
Excess nitrogen from pastures and home lawns leeches into groundwater supplies and often ends up in drinking water. Too many nitrates in drinking water is harmful to infants, causing blue baby syndrome. Nitrogen runoff ends up in waterways and lakes, where it causes algae blooms that suffocate fish and other aquatic organisms.
Using too much nitrogen fertilizer isn't fiscally or environmentally wise. It takes a lot of time, fossil fuel energy and transportation energy to produce and ship fertilizers, and costs you money. Add this to the fact that it takes time and effort to apply fertilizers. Applying too much too often can harm your grass, burning the leaves and stressing the plants. Use a mulching lawn mower to give your lawn the nitrogen lost from the leaves you just cut, and save yourself a few rounds of adding fertilizer.