EFFECT OF ZEOLITE AND WETTING AND DRYING TREATMENT ON THE AMOUNT OF DIFFERENT FORMS OF SOIL POTASSIUM IN VERTISOLS OF FARS PROVINCEFatemeh Jaberian, Shahla Mahmoudi, Ali Abtahi and Mehrdad Esfandiari
Zeolite as an amendment for physical soil characteristics can affect different forms of soil potassium and therefore can affect the cycling and availability of this element. The aim of this study is to evaluate the effects of different amounts of zeolite and wetting and drying treatment on 6 Vertisols that were collected from different regions of Fars province. Experiment was a completely randomized 3*2*4*6 factorial arrangement. The samples were incubated for 90 days at 22±2 °C. Humidity of the samples were controlled daily. To determine the effects of wetting and drying, 50 mL of distilled water was added to 50 g of zeolite treated samples and shaked for 24 hours and finally was dried in oven. The other groups were equilibrated at room temperature and tried to prevent evaporation from them. The different forms of potassium (soluble, exchangeable and non exchangeable) were determined in the samples. The results showed that zeolites application can increase the amounts of soluble and exchangeable potassium while it has no effect on non exchangeable potassium, which could be due to the high amount of potassium in zeolite and great tendency of zeolite to absorb potassium. Highest concentrations of exchangeable potassium were observed in soils with less amounts of smectite. Wetting and drying treatment caused the reduction of soluble and nonexchangeable K and increase of exchangeable k. The increase of soluble K as a result of zeolite application can enhance the possibility of potassium leaching, buton the other hand it is also able to prevent the leaching and fixation of potassium by retention of potassium in exchangeable sites.
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