CALCIUM-POTASSIUM INTERACTIONS IN SOILS AND PLANTS

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Abstract
Relatively large amts. of K were fixed, in nonexchangeable forms upon addition of CaCO3 to acid Mardin silt loam. This fixation occurred in moist soil and was independent of the K fixation that took place when the soils were dried. Hydrogen-saturated Mardin silt loam was found to fix no K upon moist storage. Fixation by this soil increased in direct relation to the increase in pH. Lime-induced K fixation apparently is not an instantaneous reaction, since the fixation of K by the Mardin soil increased throughout 24 weeks of moist incubation. There was no evidence that lime-induced K fixation was related to increased microbial activity. No direct relationship between the amt. of K entering the exchange complex and the amount fixed by moist soils was found. Although additions of lime up to 78% base saturation resulted in a reduction of both water-soluble and exchangeable K, the presence of excess CaCO3 further reduced the exchangeable K while increasing the concn. of K in a water extract. Ca sulfate had no effect on the level of exchangeable K but increased the watersoluble fraction. The K fixed in limed soils upon moist storage as detd. by leaching with neutral ammonium acetate was found to be released upon a subsequent leaching with N ammonium acetate, pH 4.8. Furthermore, there was no evidence of lime-induced fixation when the soil was leached directly with the extraction soln. at pH 4.8.