Soil sampling

Late summer and early fall is a timely season for gardeners for many reasons. One reason is that it is the preferred time for taking soil tests in the flower bed, the vegetable garden, the lawn, and orchard. Soil tests play a major part in establishing a new flower bed or garden spot or providing the proper maintenance on existing garden sites.

What does a soil test tell us, and why is it so important to the success of our gardens? A soil test is like a blood test, revealing the strengths and weaknesses of the soil, including the levels of elements such as phosphorus, potassium, and magnesium, pH (a measure of the soil’s acidity or alkalinity), and recommendations on the amounts of lime and fertilizer to add, depending on the crop. Soil pH is critical because it determines the availability of the nutrients present in the soil.

Now is indeed the time to take a soil sample for a couple of reasons. First, if a test indicates that our soil needs lime, it will require several months for the lime to actually have time to take its full effect on raising the pH. Also, it is the time of year that the soil’s fertility level will be the lowest, thus giving us gardeners a truer picture of the soil’s needs than any other time of year.

How is a soil sample taken? The following points will help you take good soil samples if you have not already tended to this important task.

Use the right sampling tools. A soil probe, auger, spade or shovel may be used effectively. Use a paper bag or clean plastic bucket for soil. The zinc in metal buckets can contaminate soil samples.

Avoid uncharacteristic areas in the field or garden. Stay away from old fence lines, hedgerows, wet spots and trees.

Make up a composite sample from each area. A composite is made of sub-samples from 15 to 20 spots in the area to be tested. Sample soil to plow depth (six to eight inches) for gardens and flowers beds and four inches for lawns.

Remove any surface litter or thatch. To use a trowel or spade, push the tool to the desired depth into the soil. Then push the handle forward, with the trowel or spade still in the soil, to make a wide opening. Cut a thin slice from the side of the opening that is of uniform thickness, approximately one-fourth inch thick and two inches wide, extending from the top of the ground to the depth of the cut.

Mix the composite sample well. Then fill a special soil sample bag provided by the Cooperative Extension Service, supplying all the information asked for on the bag.

Then drop samples off at your local county extension office for mailing to the soil testing laboratory. A detailed soil test analysis will be mailed and/or emailed to you, complete with recommendations for growing particular crops.

Once medium or high soil fertility levels have been established, lawn areas need only to be sampled every two to three years. Vegetable gardens should be sampled at least every other year.

Happy soil sampling!

Tim Lewis is a Georgia Green Industry Association Certified Plant Professional, gardening writer, and former Perry High School horticulture instructor. He and his wife, Susan, own and operate Lewis Farms Nursery and Lewis Farms Produce located on Georgia Hwy 26 two miles east of Elko, where he was born and raised. He can be reached at (478)954-1507, timlewis1@windstream.net and at LewisFarmsNursery.com.

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