Most of us know—in the same way that we “know” a great many things that we’ve merely been told—that adding certain amendments to our soil will make it easier to grow plants there. So we add fertilizer and lime with great abandon and wait for it to do whatever magic lies in its power. That can lead to misapplications that actually end up harming your plants.
Amending soil need not be so mysterious, though. A more scientific approach would be to analyze the composition of the soil, and measure how much of its nutrients are available to your plants. That’s just what a soil test allows you to do. Armed with that knowledge, you can then prepare your soil more effectively for the planting season that lies ahead.
If you’d like to test your soil at home, there are two kinds of test: electronic and chemical. Both varieties of soil test kits are available at The Home Depot. For best results, follow the instructions that come with the kit, but here are some general methods you can follow.
Electric kits consist of a meter attached to two metal prongs, and are useful mostly for checking the pH levels of your soil. To get a sense of the overall consistency of pH in your landscape, pick several spots in the area where you want to plant and average together your measurements. At each sample site, use a spade and/or cultivator to loosen the soil to a depth of about 4 to 6 inches. The prongs of the tester can be pushed directly into the soil. If the meter consistently measures the pH at 7, it may need a new battery.
For a more precise view of the nutrient composition and deficiencies of your soil, you’ll need a chemical test. The more traditional kit consists of several vials and capsules containing a chemical powder. When dissolved in water, that powder reacts to different nutrients by changing color. By comparing the solution to a color-coded chart, you can estimate the relative levels of nutrients in your soil.
To get an accurate sense of the average health of your landscape, you’ll want to blend together small samples from several sites in the area you want to plant. Dig to a depth of four to six inches and take about a tablespoon of soil from each site. Don’t use brass, copper or galvanized tools, as they may contaminate the sample with traces of copper or zinc. Combine the samples in a plastic bucket by stirring them together. In each vial of the kit you’ll combine water, a pinch of soil, and the test powder. Seal the vials and let them stand for about 10 minutes, then compare them to color-coded chart for your results.
Finally, many county extension offices perform soil tests, sometimes charging a nominal fee. Contact your local extension for specific instructions, but as a general rule, you’ll need to collect a mixed sample as you would for a chemical test, mixing small samples from several spots in your yard.
Once you’ve determined your nutrient needs, head down to the Home Depot where our Associates can advise you on the best way to amend your soil.