Document Type : Research Paper
Authors
Department of Soil Science, Faculty of Agriculture, Malayer University, Malayer, Hamedan, Iran
Abstract
The purpose of this research was to investigate the release of non-exchangeable potassium (K), magnesium (Mg), and calcium (Ca) from vermiculite clay soil using different extractants as a natural source to achieve sustainable agriculture. The treatments included four extractants: hydrochloric acid, calcium chloride, citric acid, and oxalic acid, each at a concentration of 0.01 M, applied in ten half-hour intervals. The cumulative release of K, Mg, and Ca from the vermiculite clay soil was measured, and the data were fitted to five kinetic equations. The results of the analysis of variance indicated that the effect of the extractant on the release of K, Mg, and Ca was significant (p < 0.01). The maximum cumulative releases for HCl, calcium chloride, citric acid, and oxalic acid solutions were found to be 160.7, 62.1, 140.1, and 95.2 mg kg-1, respectively, for K element and 192, 1872, 1776 and 528 mg kg-1, respectively, for Mg release and cumulative release maximums for HCl, citric acid, and oxalic acid solutions were estimated to be 1600, 3040, and 1120 mg kg-1 respectively, for Ca release. The highest and lowest release amounts for K were related to HCl and calcium chloride, respectively, as the extractant. The power function (r = 0.95 to 0.99, p<0.01), parabolic diffusion (r = 0.76 to 0.99, p<0.01), and Elovich models (r = 0.85 to 0.89, p<0.01) were identified as the most effective equations for predicting the release of three elements from vermiculite clay soil. Mineralogical results indicated that the component of the vermiculite was transformed to smectite clay in two HCl and citric acid extractants. In conclusion, vermiculite clay soil can serve as a natural source to meet the K and Mg requirements of plants.
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