Availability of Nonexchangeable Soil Potassium to Plants as Affected by Added Potassium and Ammonium

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Abstract
Undried Marshall and Clarion surface and subsoil samples were cropped in the greenhouse (short‐term cropping) to determine the effect of NH4 and K additions on the availability of nonexchangeable soil K to corn plants. When 0, 10, 25, 50 and 100 mg. of NH4 was added to 100 g. of soil, the corn absorbed 21.8, 16.4, 11.6, 4.96 and 0.12 mg. of nonexchangeable K from the Marshall surface soil and 5.19, 4.74, 3.55, 0.91 and −1.44 mg. from the Clarion surface soil. This reduction in the uptake of non‐exchangeable K by plants was due to the blocking effect of NH4 on the release of K, and was not an effect of NH4 on the absorption of available K. Similar results were obtained with the Marshall subsoil. The Clarion subsoil, however, did not release K even in the absence of added NH4.K additions also reduced the release of nonexchangeable soil K. When NH4 and K were both added, the order of addition proved to be important because NH4 also blocked the release of added K that was fixed by the soil.
Funding Information
  • American Potash Institute

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