follow up on soil test

Asked May 8, 2018, 12:54 PM EDT

I recently had a soil test done at the U of MN. The results showed phosphorus at 92 and Potassium at 271. To me these look like sky high results. Is it bad to have too much of these elements? the other results of the soil test are pH 7.3 and organic matter at 8%. A little history: The first thing I noticed a few years ago is that my tomatoes were not growing like they had. The vegetable garden in general did not produce like before. Last year, I brought in a trailer load of good looking compost and even that didn't help. Thus I did a soil test, are these results the cause of my problem? thanks, Diane Ringdal

Hennepin County Minnesota

1 Response

Although the addition of organic matter improves most soils, that's not always the case.

The following description of soil conditions and management at Persephone Farm seems to parallel yours in some respects and may be a useful reference for your purposes.
http://articles.extension.org/pages/74053/high-soil-test-phosphorus-and-potassium-levels-on-a-long-t...

Given the high organic content and excess nutrients shown by the soil test, adding compost (or other organic matter) and fertilizer will be counter productive. Nitrogen is the exception and should be applied in the amounts (if any) indicated in the soil test results.

In time, cropping without additional soil amendments will reduce the excess nutrients to optimum levels. Test the soil again occasionally to verify this.

The following excellent discussion about how to interpret soil tests may also be of interest:
https://extension.umaine.edu/gardening/manual/soils/interpretting-soil-tests/