Fixed ammonium and potassium release from two soils

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Abstract
Release of native and added K+ and NH4+ from 2 soils was monitored during a 166-day incubation/leaching experiment. One soil (Brookston) represented a major soil series in Ontario [Canada] whereas the other (Harriston) was suspected having a relatively large fixation capacity. Treatments were imposed involving addition of 50 .mu.M g-1 soil of K+ (KCl) or NH4+ (NH4Cl) only or one added after the other on successive days. The addition of either K+ or NH4+ on day 2 tended to inhibit the release of the other added on day 1. Also the addition of either K+ or NH4+ on day 1 tended to inhibit the sorption or fixation of the other on day 2. The release rate of K+ during the 10-166 day period was almost constant and not affected by the addition of NH4+. Alternatively, the addition of K+ on day 2 slowed the release rate of NH4+ by NO3- appearance from day 10 to 40 but had no effect thereafter. At the end of the experiment considerably more K+ than NH4+ was retained suggesting that K+ was more firmly fixed. However, the continuing nitrification of NH4+ must be contrasted with periodic removal of K+ by leaching with 0.01 M CaCl2 solution since the equilibrium between exchangeable and fixed ions was affected. There were no notable differences between the 2 soils despite a considerable difference in clay content.