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Fertilizing Lawns


A healthy lawn needs nutrition to stay strong and fight against invading weeds. The best way to find out what type of fertilizer program you need is to have your soil tested. Your local county Extension office can tell you how to take a soil sample. Then send it to a soil testing laboratory. They will in turn, send you test results which tell you what your soil may need.

lawn fertilizing

Understanding Fertilizers

Grass needs to be fertilized with "the trinity," which is nitrogen, phosphorus and potassium or N.P.K. as it is also known. You will need to choose a fertilizer that has the proper formula for your specific needs. Fertilizers will state the percentage by weight of N.P.K. on the package in that exact order. A 20-10-10 fertilizer has the minerals in a ratio of 2 parts nitrogen to one part phosphorus and one part potassium or a 2-1-1 ratio. A fertilizer package that says it has a 10-5-5 has the same ratio of N.P.K. Pay attention now, watch this...the difference is that the 10-5-5 has half as much actual fertilizer than the 20-10-10. So if you require a 50 pound bag of 20-10-10, it would take a 100 pound bag of 10-5-5 to get the same results.

A 100-pound bag of 10-5-5 fertilizer contains 10 pounds of actual nitrogen (100 lb x 10 percent nitrogen = 10 lb), five pounds of actual phosphorus (100 lb x 5 percent phosphorus = 5 lb), and five pounds of actual potassium (100 lb x 5 percent potassium = 5 lb). The amount of nutrients in any other fertilizer can be determined in the same way. The amount of fertilizer to apply is based on the percentage of nitrogen, the first number in the sequence.

The Ohio State University Extension recommends a 3-1-2, 4-1-2 or 5-1-2 ratio for Ohio lawns. The ratio need not be exactly 3-1-2, 4-1-2 or 5-1-2. For example, 24-6-6 grade is close to a 4-1-2 ratio, and a 10-3-7 grade is close to a 3-1-2 ratio. Substitutions of this type can be made without too much concern.

There are basically two types of nitrogen. Water soluble and water insoluble. Water soluble is quick release and water insoluble is slow release. A good fertilizer will have each. Somewhere in the range of 30% to 50% insoluble or slow release is recommended. Slow release provides nitrogen over a period of time but is not available to the grass in cool weather. The soluble or quick release is available immediately and in cool weather.

University studies show that fall or Late August and September to late fall September to October is ideal for home lawns. You will get the most benefit during these times. Too many people place an emphasis on spring and summer fertilizing. Some is needed during spring and summer but too much can bring on disease and other lawn problems.

Disease and pest problems are less severe with fall applications. And lawns are able to withstand drought patterns in weather with a good fall application as this encourages deep root systems.

A good schedule to keep would be to fertilize at 8 to 10 week intervals during the growing season.

Here is a good fertilization schedule for home owners provided by The Ohio State Extension

(Pounds fertilizer per 1,000 sq. ft.)
Examples of some fertilizer Grades Available* April May June July August September Oct. Nov.** Dec.
10-6-4 5 5 to 10 10 10 to 20
15-3-3, 15-5-10 3 3 to 7 7 7 to 13
19-3-3, 19-5-10, 20-4-8 3 3 to 5 5 5 to 10
24-4-8, 24-4-12 2 2 to 4 4 4 to 8
28-4-12, 28-3-3, 29-3-5 2 2 to 4 4 4 to 7
34-5-5, 34-5-10 2 2 to 3 3 3 to 6
*Fertilizer ratios of 3-1-2 to 5-1-2 preferred
**Earlier date for northern Ohio and later date for southern Ohio

Keith L. Smith, Associate Vice President for Ag. Adm. and Director, OSU Extension.

Understanding the Roles of Nitrogen, Phosphorus and Potassium

Basically nitrogen gives the plant it's greeness. It is a part of the chlorophyll molecule. It maintains the plants health. Phosphorus helps the plant transfer energy between each part which make up the metabolic process. It is necessary for growth and root development. Potassium also helps in the metabolic process and it is responsible for balancing water pressure in and around the plants cells. A "complete" fertilzer has all three of these components. When at least one of these is missing it of course, is an incomplete fertilizer.


Great fertilizing information helps maintain a healthy soil for a safe, barefoot lawn.



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