Comparison of calcium and sodium in the release and re-fixation of potassium in various soils with distinct physical, chemical, and mineralogical characteristics in southern Iran

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Document Type : Research Paper

Authors

1 Department of Soil Science, College of Agriculture and Natural Resources of Darab, Shiraz University

2 Department of Soil and Water Science, College of Agriculture and Natural Resources of Darab, Shiraz University, Shiraz, Iran

Abstract

The exchange of mineral interlayer potassium (K) with soluble cations in the soil can release this form of K and supply a portion of the potassium required by plants in K-depleted soils. In the present study, the ability of 0.01M CaCl2, NaCl, and a mixture of CaCl2 and NaCl to extract non-exchangeable K from four soils with distinct characteristics over twelve 15-minute extraction periods, and the changes in soil’s capacity to re-fix K were investigated. The studied soils contained a high amount of smectite in the clay fraction with smaller amounts of chlorite, illite, and palygorskite minerals also present. Overall, in all soils, NaCl extracted more K than CaCl2 (up to 24, 64, 68 and 83% for soils 1, 2, 3 and 4, respectively). The highest amount of K was extracted from soil 3 (Ustorthents), while the lowest was from soil 4 (Torriorthents). Although, there was no significant difference between CaCl2 and NaCl in terms of K extraction in the initial three extraction stages, NaCl extracted a greater amount of K from all soils in the subsequent nine stages with increases ranging from 47 to 149%. This enhanced extraction may be attributed to the effect of Na on the clay dispersion, which increases the contact of the solution with the exchange sites and preventing the re-fixation of K by smectites. The capacity to fix K in soil 1 (Haploxerets) was significantly higher than in the other soils, while soils subjected to NaCl extraction exhibited a reduced ability to fix K.

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Iranian Journal of Soil and Water Research

Articles in Press, Accepted Manuscript
Available Online from 21 May 2025

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