Release of Fixed Potassium from Soils by Plant Uptake and Chemical Extraction Techniques1
- G. E. Richards and
- E. O. McLean2
Three Ohio soils of fine sandy loam, silt loam, and clay loam textures were subjected to treatments of comparable levels of potassium as KCl and K-soil (exchangeable plus fixed K prepared by adding 1000 pounds per acre of K as KCl to portions of the same soils followed by successive wetting and drying). The soils were cropped to alfalfa in pots in the greenhouse for a period of six harvests. Potassium uptake by alfalfa was 76 to 95% as great from soils treated with K-soil as from those with similar rates of KCl.
Following removal of the third crop, soil samples were taken and subjected to various chemical extractions. They included 1.0N NH4OAc extraction of both moist and dry soils, and extractions with 1.0N boiling NHO3. In general, none of these extractions gave a consistent indication of the residual K available to succeeding crops of alfalfa following initial K treatments and removal of the first three crops (cuttings). The results suggest some inadequacies in existing soil analyses for indicating residual K available to crops.Please view the pdf by using the Full Text (PDF) link under 'View' to the left.
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