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Wisconsin | P is tightly bound to the soil particles. If you lose soil, you lose P. K is a more soluble salt and will be in any run off, but filtering through the ground a couple feet will hold onto more. That's the available P and K that we measure. There is far more P and K locked up in soil that is not measured by soil tests, but can become available as the soil becomes more chemically or biologically active, either through warming and aeration from tiling, or from run off and dissolving in Lake Erie.
In fresh water, P is the limiting nutrient so the most critical to control for water quality. Salt water has plenty of P because it doesn't evaporate, or run downstream, so N is more important for salt water quality. | |
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