Jane Martin, Franklin County Horticulture Agent
Many gardeners forego soil testing until something looks wrong with their lawn--it may gradually become light green in color, be less dense than desired or rapidly decline during summer stress periods. Or, a new lawn may not establish well. Then the gardener wonders about the soil and if it "needs something."
Soil testing is the only real way to know the fertility level of the soil; you can't determine nutrient levels or the pH by simply looking at it.
If a new lawn is being established, start with a soil test. It's easiest to add and incorporate corrective levels of fertilizer and pH adjusters (lime or sulfur) before the seed is sown or sod is laid. Most lawn grasses grow best in a slightly acid soil with a pH range of 6.1 to 6.9. Yearly applications of lime (an old tale) is discouraged since alkaline conditions could develop. Apply lime only if soil test results show it is needed.
The results of a soil test are only as good as the sample submitted, so take the time to sample correctly. Use a hand trowel or soil probe to take 10 to 15 small samples in a zigzag pattern across the lawn. Have a clean bucket or box handy to collect the samples.
Remove the top debris or thatch from the soil surface and sample at a 3-inch depth, taking the same volume of soil from each site. Mix this soil together into a composite sample, breaking up clods and letting it dry at room temperature. Then submit 1.5 cups of this soil to the OSU testing lab in Wooster--contact your local Extension office for the mailer and form. Currently, the cost of a "Lawn and Garden" test is $12 per sample.
Soil test results and recommendations are usually returned within two weeks. Results include pH, lime deficit, available phosphorus, exchangeable potassium, calcium, magnesium, cation exchange capacity and percent base saturation. Other tests are available upon request, with additional fees.
Gardeners should think about testing the soil every three years, especially if they are adding many soil amendments, fertilizers or wood ashes to the soil. Sample more frequently if you want to monitor the fertility levels more closely. Soil testing is an excellent measure of soil fertility and an inexpensive way to maintain good plant health.
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Keith L. Smith, Associate Vice President for Ag. Adm. and Director, OSU Extension.
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