Does Grass Need Nitrogen?

Nitrogen Basics

• Nitrogen helps plants form proteins and is part of chlorophyll, which grass uses to perform photosynthesis. Maintaining good levels of nitrogen encourages your grass to grow and helps your lawn stay green and healthy looking. However, too much nitrogen causes grass to become weaker and more susceptible to diseases and pests. Although nitrogen naturally returns to the soil in organic matter, leaf clippings and pet wastes, many lawns require additional nitrogen in the form of chemical fertilizers.

Nitrogen Fertilizers

• Chemical fertilizers usually list nitrogen (N) as the first ingredient, along with phosphorus (P) and potassium (K). Although soil tests can usually tell you which nutrients your grass needs, soil testing is less effective for nitrogen because the amount of nitrogen in the soil varies. Specific recommendations vary depending on your climate and type of grass, but most lawns require two to three annual applications of 1 lb. of nitrogen per 1,000 square feet.

Reducing Pollution

• Nitrogen and other nutrients in chemical fertilizers pollute the water supply when excess chemicals run off or when people spill fertilizer on hard surfaces, such as concrete, where it is eventually washed into the water supply. Pollution from nitrogen and other nutrients causes excess algae growth, which reduces the oxygen in lakes and rivers and kills fish. Reduce pollution by following directions carefully, never applying more fertilizer than recommended, choosing slow-release nitrogen, sweeping any spilled fertilizer and not fertilizing before heavy rainfall.

Grasscycling

• Grasscycling, the practice of leaving mulched grass clippings on the lawn after mowing, helps return nitrogen to the soil and reduces the need for chemical fertilizers. According to Ohio State University, 100 lbs. of grass clippings contain 3 to 4 lbs. of nitrogen as well as other nutrients. Grass clippings decompose rapidly, so they don't contribute to thatch buildup.