Posted 11/13/2012 10:45 (#2694726 - in reply to #2694423) Subject: Re: Some thoughts on fungi and nutrients
Nutrient removal is simple. It's easy to measure and is somewhat consistent.
NATURAL nutrient addition is what's complicated, by physical and then biological breakdown of minerals. Many think of the soil as simple dirt, and the fertilizers and nutrients we add to the field are directly taken up by the plant. It's not that simple.
It's amazing how much of the mineral form is present in the soil of both P and K. There is some merit to the ability of the soil to provide the nutrients the plants need without additional fertilizer, the minerals are there, they just need to be converted to plant available forms. I have seen many studies that suggests a natural floor exists in the availability of plant required nutrients. The problem is keeping that level high enough that an annual application of fertilizer is not economical over the long run.
From above publication-
"Note that eventually all the primary P minerals will weather. Walker and Syers (1976) suggested
that for the soil conditions they studied, this process would take about 22,000 years."