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Elevated Phosphorous in Soil #749377

Asked May 11, 2021, 6:14 PM EDT

My husband and I have a large, deep planter box that we filled with bagged soil last year. Last year, we planted a number of seeds, which sprouted beautifully but then failed to grow further/thrive. I tested the soil with a home test kit, and it showed a surplus of phosphorous. So, we replaced most of the soil in the box, but when I tested again this year, the phosphorus level is still showing up as “surplus.” (Perhaps this is a problem with Alaska soil?)  Are there any steps I can take short of replacing the soil (which is time consuming and expensive) that would help address this issue? Nitrogen and potassium levels are normal, and pH is a bit high (~7.5), but not crazy.

Anchorage County Alaska

Expert Response

Those home test kits are incredibly inaccurate.  Surplus phosphorus is probably not your problem.

I recommend getting a soil test from Brookside Laboratory (blinc.com).  You'll have to call them to get a quote and mailing instructions.  You'll want test package S001AN.

When you get the results back send them to me at <personal data hidden>.  I'll tell what the numbers mean and make a recommendation for improving the soil.  I doubt you'll need to replace the soil. 

Stephen Brown, Ph.D. Replied May 11, 2021, 7:29 PM EDT

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