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Grass is best left to fertilize itself

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Thursday, March 15, 2007

Does it matter which fertilizer I use on my lawn? I usually buy what's on sale and fertilize once in the spring and again in the fall. I don't want to use the combination pest control and fertilizers on my lawn. I am concerned with using pesticides on the lawn with two young children who spend a lot of time playing there. -- A.C., Red Bank

First, I would recommend taking a soil test to determine the acidity (pH) and nutrient level in your soil. Lawns in our area grow best in a soil with a pH between 6.2 to 6.5. Unless the soil acidity is properly adjusted, the grass roots may not be able to take up the fertilizers that are being applied. So without first adjusting pH, you could be wasting your time and your money on fertilizers that will not be properly absorbed.

An accurate and comprehensive soil test can provide information on the right formulation of fertilizer to use on your lawn. For instance, if phosphorus levels are already high according to your soil test, then you should use a fertilizer with little or no phosphorus.

The three numbers on a fertilizer bag represent the percentage by weight of nitrogen, phosphorus and potassium -- N-P-K. So, a 10-6-4 fertilizer has approximately 10 percent nitrogen, 6 percent phosphorus and 4 percent potassium. As a rule of thumb, we never recommend adding more than one pound of actual nitrogen per 1,000 square feet in any one application. For example, with a 10-6-4 fertilizer, we would need 10 pounds of this 10 percent by weight of nitrogen per 1,000 square feet to provide 1 pound of actual nitrogen.

In environmentally sensitive areas, near bodies of water or on steep slopes, fertilizer rates should be reduced by 50 percent or eliminated depending on individual circumstances.

Recycling grass clippings back to the lawn can reduce fertilizer needs by 25 to 30 percent. This is one of the best ways to add nutrients to the lawn and maintain valuable organic matter in soils.

On average, many cool season grasses will perform well with two to three applications of fertilizer each year to maintain a healthy lawn. The first application can be applied in late March through April and should contain at least 50 percent slow release, organic fertilizer. A second application can be applied in early September and a third in October or early November.

It is wise to use fertilizers that release nutrients over a longer time period. I'd recommend using slow release fertilizers that have uniform particle size. These formulations are often more expensive, but can be applied more accurately and will provide a longer period of nutrition for grass roots.

If you have concerns with pesticide use, there are many things that you can do to avoid pests and diseases without using pesticides. Proper lawn care strategies can significantly reduce the need for pesticides.

Be sure to look for Cooperative Extension workshops on proper lawn care. I teach an Earth-Wise lawn care workshop and we will be conducting workshops at the EARTH center this spring. Call Denise at (732) 398-5262 or log on to www.ifplantscouldtalk.rutgers.edu for more information on lawn care or soil testing.