Lawn fertilizer feeds the grass and improves the appearance and color of the turf. Too much fertilizer causes a flush of growth that contributes to thatch buildup and ultimately reduces the health of the lawn. Excess fertilizer runoff is unhealthy for the environment, contributing to water pollution. Too little fertilizer leads to browning, bare spots and eventually the death of the grass. The goal is to use only enough of the right kinds of fertilizer for a healthy lawn.
Begin Fertilizing in the Fall
Begin a lawn fertilizer program in the fall to encourage deep roots more resistant to drought and cold weather. Apply fall fertilizer when the weather cools off to an average daily temperature of 50 degrees. Fertilize again at the end of May, June and August.
Apply fertilizer just before rain is expected, or water the lawn after fertilizing. Broadcast fertilizer evenly over the lawn by hand or use a mechanical spreader.
Understand the Numbers
Fertilizer nutrient percentages are indicated by three numbers, such as 18-6-12. The first number indicates the percentage of nitrogen in the formula, in this case 18 percent. The second number is the phosphorus content, 6 percent. The last number indicates 12 percent potassium.
The recommended ratio of N-P-K for lawn fertilizers is 3-to-1-to-2 or 4-to-1-to-2. A 3-1-2 ratio fertilizer would have numbers that are multiples of 3-1-2, such as 6-2-4 or 12-4-8. The higher the number, the less fertilizer is needed.
Use Controlled-Release Nitrogen
Nitrogen promotes vegetative growth. The recommended rate is 1 pound of nitrogen per 1,000 square feet of lawn. In most cases, controlled-release nitrogen is best for lawn applications. Fast-release fertilizers cause a quick flush of green growth before being rendered useless. Slow- or controlled-release nitrogen is less likely to burn the grass. It works slowly to produce a more sustained and healthy growth.
Special Formulas Are Available for Different Situations
A lawn starter fertilizer is used for newly planted lawns until the roots are established. Winter fertilizers are higher in potassium than regular lawn fertilizers. These formulas are useful in the fall and spring to improve heat and cold tolerance and disease resistance.
Use Combination Products Suited to Your Grass Variety
Weed and feed products contain a combination of fertilizer and weed killers to control undesirable growth. Use pre-emergent herbicides to control crabgrass in the spring. Broadleaf weed killers kill already growing dandelions and other broadleaf weeds.