The Q&A Archives: Soil test results

Question: I religiously add compost and manure to my garden each year, but a recent soil test showed that my organic matter content was 9.9% and the potassium levels were 1,209 ppm. Are these amounts too high? Leslie Motz Olympia, WA

Answer: Your organic matter content is fine, but the potassium levels are high, says Craig Cogger, soil scientist at Washington State University in Puyallup. As long as your phosphorus, magnesium and calcium levels are adequate, high potassium levels aren'tnecessarily a problem, says Cogger. They may indicate, however, that you're applying too much manure, which could mean you have high nitrogen levels, he adds. Excessive nitrogen can cause delay in fruiting and may also leach into the groundwater.I'd suggest you stop adding manure for two years, says Cogger. Then test the soil again. If the potassium levels are closer to normal (500 ppm in your area), begin adding manure at half your previous rate, he says.

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