Got Your Soil Test Back? Here Are 3 Things You Need to Know

Fine Gardening - Issue 197
Photo: Steve Aitken

Though immensely valuable, a soil test is not a crystal ball. A little knowledge goes a long way in making the most out of your test results. See 5 tips for better soil.

Nitrogen is complicated

Soil tests were invented by chemical agriculturalists to measure chemical nitrogen, which is often lacking from being leached out by rain or taken up by plants. The complex organic nitrogen of rich garden soil, however, is not captured by a standard soil test. Steady soil building (with the moderate-to-high phosphorous test results to prove it) means that the supply of organic nitrogen is likely sufficient.

PH is important

A home soil pH meter rarely is as reliable as a soil pH test. Though most plants tolerate a wide range of pH, a test gives a good baseline, as well as an indicator of how easy or hard it is to change. Clay soil resists change (and will need a lot of lime), while sandy soil reacts quickly to lime or acidity.

Ignore (or reduce) fertilizer recommendations

Fertilizer and lime recommendations are based on agricultural crops and rarely relate to your garden plants. Instead of fertilizer application rates, use the test result ratings. If they are low or moderate, consider adding some fertilizer. If they are high or very high, your ­organic soil is supplying enough nutrients to meet your plants’ needs.

Ea Murphy is a soil scientist in Tacoma, Washington, and the author of Building Soil: A Down-to-Earth Approach.

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