THE AVAILABILITY OF SOIL POTASSIUM

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Abstract
On gray soils low in general productivity in southern Illinois, high crop yields were maintained only by addition of K. Lab. studies revealed that K fertilization increased amt. of exchangeable K of the A-1 layer until utilized by the crop, but did not affect exchangeable K of the A-3 or B-1 layer. K starvation was associated with low exchangeable K and high exchangeable Ca. The Ill. soil, 2N.Y. soils which had responded to K fertilization, and 2 N. Y. soils which had not responded to K fertilization were leached with distilled water. Sugar was added, the soils were incubated at favorable moisture and temp. conditions for several mo., and leached again with distilled water. The process was repeated. There was no significant difference in rate at which exchange-able, and water-soluble K were replenished from the reserve supply of the soils.