A Comparison of Some Extractants Used for the Assessment of Available Potassium in Some Hamadan Soils

Potassium (K) is an element essential for plant growth, playing a significant role in physiological and biochemical processes in plant. The relationship between a soil testing extractant vs. plant nutrient uptake should be a determining parameter in the selection of a soil testing method. The objective of this study was to evaluate different extractants employed for extracting available K in 10 Hamadan soils. The extractants used, were: 0.025 M H2SO4, 0.1 M BaCl2, 0.01 M CaCl2, 1 M NH4OAC, and 1 M NaCl. Potassium uptake and yield by wheat (Triticum aestivum L.), wheat shoots and dry matter content (grown in the greenhouse) were the factors used to assess plant available K. There were significant correlations observed between 0.025 M H2SO4 method with other methods expect for the case of 1 M NH4OAc. There were significant correlations observed between K extracted through different methods and K uptake by wheat shoots. Potassium extracted by 0.025 M H2SO4, 0.1 M BaCl2, and 1 M NaCl showed significant correlations with wheat dry matter yield. The 0.01 M CaCl2, 1 M NaCl, and 0.1 M BaCl2 extraction methods seem to be superior to 0.025 M H2SO4, and 1 M NH4OAC methods in evaluating plant K availability.