What Are the Numbers on Lawn Fertilizer?

Nitrogen

• Nitrogen, denoted as "N," is one of the three primary nutrients essential for plant growth and is indicated by the first number on the fertilizer bag. Nitrogen is found in all living cells and supports the critical processes conducted by proteins, enzymes and metabolism, which in turn synthesize and transfer energy in plants. Nitrogen is found in the green-plant pigment chlorophyll, which conducts photosynthesis. The nutrient directly helps rapid, healthy growth of plants and optimizes leafy growth and quality of forage crops. Plants mostly get their nitrogen from fertilizers and air. Water is a poor source of nitrogen for plants, according to the North Carolina Department of Agriculture.

Phosphorus

• Phosphorus, or "P," is the second of the three essential plant nutrients and is indicated by the second number on the fertilizer bag. Phosphorus is an important part of photosynthesis and produces rapid growth, leads to prolific blooming and helps roots stay healthy. Phosphorus supports the formation of sugars, starches and oils in plants and helps convert solar energy into chemical energy. Plants with adequate amounts of phosphorus are more tolerant to stress and mature more quickly. Fertilizer is among the best sources for phosphorus.

Potassium

• Potassium, or "K," is the third number on the fertilizer bag and among the three essential plant nutrients. Potassium is absorbed by plants in just as large an amount as nitrogen or sometimes calcium. Potassium optimizes the health of plant proteins and supports photosynthesis, leading to better fruit quality, and better resistance to diseases. This resistance is especially critical in crops. The use of potassium in grain crops also produces a higher concentration of starch in the grains. Potassium is made available to the plant mostly through the applications of organic or inorganic fertilizers and soil minerals.