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Lawn fertility and maintenance

By John Fulton       Send a link to a friend

[APRIL 29, 2004]  Martha Smith, horticulture educator in Macomb, likes to say, "Horticulture is everyone's agriculture." Just think of the time, effort and money spent on lawn maintenance, and you can see where that statement is probably true.

Today's offering will deal with lawn maintenance. That means mowing, fertilizing and the like. We are way past recommended seeding and major renovation times but just hitting the swing for the maintenance operations.

Let's start with fertilization of the lawn. To begin with, it is important to know what the numbers on a bag of lawn fertilizer mean. The bag has numbers like 26-4-7 or 13-13-13. The first number is the percentage of nitrogen in the product, the second is percentage of P2O5 (commonly referred to as phosphorus), and the third is percentage K2O (commonly referred to as potassium or potash). This means that a 10-pound bag of 13-13-13 would contain 1.3 pounds of nitrogen, 1.3 pounds of P2O5, and 1.3 pounds of K2O.

It is also important to know what type of grass you have in your lawn. When looking at nitrogen application rates, improved bluegrass varieties (such as A-20 and Delphi) need 4-6 pounds of nitrogen per 1,000 square feet per year. Common bluegrass varieties (such as Delta and Park) need 2-4 pounds of nitrogen per year, and fine-leaf fescues need 1-3 pounds per year per 1,000 square feet.

Nitrogen should be put on at least twice per year, with ideal times being the first week of May and the first week of September. Resources vary on the amount of nitrogen that may be safely applied at any one time, with maximum ranges from 1 to 1.5 pounds per 1,000 square feet. Most current university information recommends 1 pound maximum per application.

Phosphorus and potassium should be applied on the basis of soil testing since these nutrients are not like nitrogen, in that nitrogen does not remain stable in the soil for long periods of time. Without a soil analysis, correct applications are about 1.5-2 pounds of P2O5 and 2.5-3 pounds of K2O per 1,000 square feet.


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Boiling this all down to practical terms means that a lawn of mixed common bluegrass and fine fescue should have about 12 pounds of 13-13-13 applied twice a year. I realize that you will build up phosphorus levels somewhat, but not very rapidly. And, the nice thing is that phosphorus will not be lost. It will remain in the soil until needed. Another option is to apply most of the phosphorus and potassium with one application and use one of the high nitrogen products for the other.

The last thing that we need to mention in soil fertility is lime. Ideal soil pH (which is a measure of relative soil acidity) is between 6.0 and 7.0. This is the range in which micronutrients are available in adequate amounts for your lawn. Another way to think of it is that a pound of nitrogen acidifies the soil enough so that about 4.5 pounds of lime is needed to counteract it. But unless you know the starting point, you have no idea whether you are in the range or not.

On to the mowing. Proper mowing height is rather simple. Bluegrass lawns should have the mower set at 1.5-2.5 inches tall, while fine fescues should be mowed at 2-2.5 inches tall. The kicker is to remove no more that one-third of the leaf blade at any one time (that way you don't need a mulching mower or collect clippings). Translation: Mixed species lawns should be mowed every time they reach about 3 inches tall with the mower set at 2 inches.

The last item to mention is water. Water should be applied only in the morning, applied only when Mother Nature doesn't provide it, and you can expect to pay a price for your luxurious lawn (such as getting all the grubs along with the water bill). If you decide to water, apply an inch a week in one application.

Hopefully these tips will get you on your way to a healthy and good-looking lawn.

[John Fulton,
Logan County Extension office]

Previous articles by John Fulton

Logan County Fair

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