Effect of Vermicompost and Zeolite Applications on Potassium Transformation in Calcareous Soils of Fars Province

Although addition of amendment materials to soil is not for changing of soil K status, secondary effects of these materials can be important in K distribution among soluble, exchangeable and non-exchangeable forms. In this research, effect of addition of 2% zeolite, 2% vermicompost and 1% zeolite+ 1% vermicompost on 10 calcareous soils of Fars province belonging to five orders was investigated. The experiments were done as a randomized complete block with three replicates. Samples were incubated at 22±2 °C and 50% of saturated moisture content for 90 days. Then different forms of K were determined in the samples. Zeolite application induced 279 mg kg-1 increase in exchangeable K and 24 mg kg-1 decrease in non-exchangeable K, but it had not a significant effect on soluble K. Although vermicompost application increased soluble and exchangeable K, its effect was more sensible for soluble K (139 mg kg-1). Zeolite+vermicompost application increased all forms of K. Increase in soluble K with vermicompost application may increase risk of K leaching; but zeolite application can preserve K in exchangeable phase and inhibit K leaching and fixation.