Response of some characteristics of selected beneficial soil microorganisms under different potassium fertilizer applications**

Abstract

Among the three important nutrients of (NPK) for plants, potassium plays a vital role in increasing disease resistance capacity and also in the activation of over 80 different enzymes responsible for plant metabolism. This article presents changes in the population of some soil beneficial microorganisms responsible for the nutrient cycling process in the soil and in their respiration activity as related to the application of different potassium (K) fertilizers (KCl and K2SO4) at different doses in a model incubation experiment. The application of KCl and K2SO4 fertilizers increases soil acidity at higher doses. The parameters describing the soil microbial community, i.e. microbial respiration and colony forming unit counts of free living N2-fixing bacteria, Rhizobium sp., Pseudomonas sp., potassium-solubilizing bacteria, and phosphate-solubilizing bacteria increased with the application of fertilizers at lower doses, but a minor decrease was observed for higher doses of fertilizers. The level of microbial activity showed a positive correlation with the application of different amounts of fertilizer but no effect was observed due to the use of different fertilizer types, thereby indicating that a substantial improvement in soil biological activities can be achieved regardless of the K fertilizer type at optimized doses.