Soil testing can help keep unnecessary nutrients out of Kentucky streams

Garrard Coffey Agriculture and Natural Resources

How much fertilizer do you really need to use on your lawn and garden? If you are just making a guess, you could be using too much. But how can you know for sure? A simple and inexpensive soil test can tell you all you need to know to make your lawn and garden look great and to protect the environment from runoff of excess nutrients.

Soil fertility testing is a program designed to provide homeowners, landscape contractors, turfgrass managers, greenhouse managers as well as others with a soil management tool to determine fertilizer requirements of their lawn, garden, trees and shrubs. The University of Kentucky Division of Regulatory Services soil testing laboratory and Cooperative Extension Service offer soil testing services to every Kentucky citizen. Soil testing is the most important thing you can do before applying fertilizer. Fall and spring are the best times to take samples; and you should sample your lawn, landscape beds and vegetable gardens every one to two years, since your soil’s needs may change over time.

You can use the test results to determine the amount and kind of nutrients you add to your lawn and garden for best growth. A routine soil test from the University of Kentucky soil testing laboratory will provide you with information about the soil pH, plant available phosphorus, potassium, calcium, magnesium, zinc and cation exchange capacity of your soil. The results will include a recommendation about what amendments, if any, you may need to improve plant vigor and yield. Other special tests are available; however, this routine test will address most home lawn, landscape and gardening needs.

The County Extension Agent for Agriculture and Natural Resources at the Whitley County Cooperative Extension Service can help answer your questions about taking the sample and the testing procedure. Generally, to obtain a useful sample, you will want to map out the area where you plan to grow plants or where plants already exist. It is a good way to keep a record of your land use and results over time. Divide the area so that each soil sample represents one plant type or condition. Collect at least 10 samples for each area, mix them together and then take one composite sample (one or two cups) that represents that area for soil testing. For example, if you have a landscape bed that contains shrubs in one area and roses in another, collect two composite samples ‒ one composite sample from several sites under the shrubs and another composite sample from several sites under the roses.

For lawns, sample to a depth of about four inches. For gardens, ornamentals, mixed fruit trees and wildlife plots, sample to a depth of about six inches. Ideally, you should sample well in advance of any planting or spring green up to allow time for analysis, interpretation and then fertilizer and lime applications.

Use clean tools and never use a tool that you have previously used for fertilizer or lime. Shovels, trowels, spades, hand probes and augers are all good sampling tools. Clear the ground surface of any mulch or thatch. Take samples from several areas and mix them together in a plastic bucket to avoid metal contamination. If the soil is wet or damp, let it dry overnight or longer if needed. Collect about a pint (two cups) of the dry soil and place it in the University of Kentucky soil sample bag, available from any Cooperative Extension office; or a small, clean plastic sandwich or freezer bag can also be used. Identify your sample on the bag. An informational submission form will be completed at the Extension office for each sample. The Whitley County Cooperative Extension Service office will submit your samples to the lab for analysis.

For more information, contact the Whitley County Cooperative Extension Service at 549-1430; visit the office located in Cumberland Regional Mall, 965 S. Highway 25W, Williamsburg, Monday-Friday, 8 A.M.-12 P.M. and 1-4:30 P.M.; or e-mail at DL_CES_WHITLEY@EMAIL.UKY.EDU.