effect of different bacterial and fungal populations on release of soil potassium

potassium is an essential plant macronutrient. various microorganisms including bacteria and fungi, algae, yeast and mosses are able to decompose silicate minerals and to dissolve nutrient such as k, fe, zn and si. aamong them bacteria are more important. the aim of this study was to determine the ability of microbial populations for releasing soil potassium. this study was carried out as a factorial experiment in completely randomized design including two factors, with three replications. to do so, 12 treatments including full combination of two bacterial geniuses (azospirillum lipoferum and azotobacter chrococoum) and two fungal geniuses (asperigilus niger and trichoderma hazarum) were inoculated into soil and the potassium was extracted by nh4oac over four different times (0, 10, 20 and 30 days). results indicated that the quantity of k released by soil inoculation with bacteria and bacteria plus fungi treatments, so that the treatment b1 (azotobacter chrococoum) could covert about 6% of the soil potassium to available form by plants and released potassium content increased with elapsing of time. in all treatments, the most quantity of potassium was released 30 days after inoculation. thus the biological potassium fertilizers can be a good substitute for chemical fertilizers.