The Differences in Lawn Fertilizers

Fertilizer Types

• There are many different ways to categorize fertilizers, but one of the most useful categorizes them according to their concentration, by weight, of three essential plant nutrients: nitrogen (N), phosphorus (P) and potassium (K). Gardeners and farmers commonly have their soil tested to see which of these three nutrients their soil lacks and purchase a fertilizer that can effectively supplement the right amount of these nutrients. These so-called "NPK ratings" are always printed on the bag of fertilizer as three numbers that indicate the concentration of each nutrient. For instance, a 10-15-20 fertilizer would contain 10 percent nitrogen, 15 percent phosphorus and 20 percent potassium by weight.

Fertilizers and Lawns

• All three of the above-named elements are important to healthy lawn growth. Nitrogen helps grass grow vigorously and establishes its green color. A healthy amount of phosphorus establishes new root systems and a healthy amount of potassium in your grass helps keep it resistant to disease and damage from extreme weather conditions. By choosing a fertilizer that has the perfect mix of all three of these nutrients involves knowing the specific nutritional needs of both the type of grass you grown in your lawn and of the soil beneath it.

Choosing a Fertilizer

• The only way to determine what fertilizer to use for your lawn is to have the fertility of the soil tested. Soil fertility tests are typically offered by private laboratories or by university agricultural departments and extension services. Test results should inform your choices when buying fertilizers. For instance, if your soil is high in nitrogen but lacking in phosphorus and potassium, a 5-20-20, 5-10-20 or even 0-10-10 fertilizer would be sufficient. Similarly, a nitrogen-deprived soil should receive treatment from a fertilizer that is higher in nitrogen than in the other two elements.

Other Considerations

• Regardless of what type of fertilizer you choose, there are a few general rules of thumb regarding application that can yield noticeable results in your lawn grass. All lawns respond well to a light fertilizer application in spring and again in early summer followed by a heavy fertilizer treatment during the fall. Newly established lawns will grow more healthily when given half a pound of fertilizer per 1,000 square feet of lawn grass. Other application guidelines should be tailored specifically to the species of grass you are growing and the nutritional needs of your lawn soil.