Effect of Forms and Application Rates of Potassium Fertilizers on Exchangeable and Water-Soluble Potassium Content in Soil

This study investigated the effect of different application rates and forms (K₂SO₄ and KCl) of potassium fertilizers on exchangeable and water -soluble potassium contents in soil during sunflower cultivation. The application of potassium fertilizers significantly increased the levels of mobile potassium forms in the soil. Plots treated with K₂SO₄ showed higher contents of mobile potassium than plots treated with KCl, particularly at application rates of 180 -210 kg/ha and during the budding stage. Soil potassium content decreased toward the end of the growing season as a result of active potassium uptake by sunflower plants. The highest values were recorded with potassium sulfate at an application rate of 210 kg/ha.