Selecting the correct lawn fertilizer for your lawn takes more than just grabbing a bag at the store. Many factors need to be taken into consideration including the size of your yard and time of year. Being informed about the many varieties of lawn fertilizer and what they have to offer can help you to make the best decision for your yard.
Check the nutrient percentages on the label. Lawn fertilizer contains three important nutrients: nitrogen, phosphorus and potassium. Nitrogen is represented with the letter N, Phosphorus with the letter P and potassium with the letter K. The nutrients always appear in the same order on the label, typically in a series of numbers such as 18-6-12, with the first number representing the nitrogen followed by phosphorus and potassium in that order. The percentage of nitrogen in the fertilizer is the most informative number as this determines how much fertilizer will be needed to cover your lawn. In general, you want one pound of nitrogen for each 1,000 square feet of lawn.
Decide how often you want to apply your fertilizer. Liquid fertilizers will only last for two to three weeks before another application is needed. Quick release granular fertilizers last a little longer, usually about four weeks. If you want a fertilizer that doesn't require frequent application, a slow-release granular fertilizer is your best choice. These will last from eight to 12 weeks depending on the specific composition of the fertilizer and the rainfall in your area.
Evaluate the need for weed control in your yard. If you are concerned about weed prevention, you will want to consider a fertilizer which also provides weed control. Pre-emergents should be used in the spring time to kill off weeds before they germinate. If the weeds in your yard are already growing, you will need a post-emergent to kill them.
Consider the time of year when you will be applying the fertilizer. In late fall and early spring, opt for fertilizers with high levels of potassium, often labeled as "winterizers." For new lawns, look for a lawn starter fertilizer which will have a higher level of phosphorous.