Choosing Fertilizers for Home Lawns

Fertilizing is an important lawn care practice, as it influences grass color, ability to recover from stress, and helps prevent weed invasions and disease. There are important features to consider when choosing lawn fertilizers at the local garden center.

Nitrogen (N), phosphorus (P), and potassium (K) are the three major nutrients needed by lawns. Nitrogen is the nutrient required most, although too much nitrogen can cause excessive topgrowth, leading to assorted problems. Percent nitrogen (by weight) is always the first of three numbers on the fertilizer bag, followed by phosphorus and potassium. For example, a 18-6-12 fertilizer contains 18 percent nitrogen. This number is important because it determines how much fertilizer is needed. In most cases, a rate of 1 pound of nitrogen per 1,000 square feet is suggested for each fertilizer application to the lawn. If high percentage nitrogen fertilizers are used, then less actual fertilizer product is needed to supply that one pound compared to fertilizers with low percent nitrogen. Recommended ratios of N-P-K for lawn fertilizers include 3:1:2 or 4:1:2.

Another important factor in choosing nitrogen fertilizers is what kind of nitrogen is actually in the product. Nitrogen fertilizer may consist of fast-release or controlled-release nitrogen. Advantages and disadvantages are outlined in the table below. For lawns, fertilizers containing controlled-release nitrogen sources are suggested for most applications. Check the guaranteed analysis information on the fertilizer label for information on what forms of nitrogen are in the product. Water insoluble nitrogren in slow-release.

Characteristics of Nitrogen Fertilizers for Home Lawns

Nitrogen Type	Advantages	Disadvantages
Fast-Release (i.e. urea, ammonium nitrate, ammonium sulfate)	1. Quick response (greening) 2. Provide nitrogen when soils are cold 3. Relatively inexpensive	1. May cause undesirable large flush of growth 2. Likely to burn grass 3. Losses through soil or air more likely
Controlled-Release (slow-release) (i.e. ureaform, sulfur-coated urea, activated sewage sludge, IBDU, water-insoluble nitrogen or WIN)	1. More uniform grass growth 2. Not likely to burn grass 3. Losses through soil or air less likely	1. May not work on cold soil 2. Most are expensive 3. May not see quick color change in grass

In addition, a variety of special lawn fertilizers may be found. Winterizer fertilizers are typically high in potassium, and although advertised for fall application can be applied in spring as well. Potassium is used all year by grasses, and is involved in heat and cold tolerance, disease resistance, and other stress tolerances. Weed and feed products contain a broadleaf weed killer for weeds such as dandelions (fall application); others contain a preemergence herbicide to control crabgrass (spring application). Lawn starter products, typically high in phosphorus, are intended for newly seeded lawns.