Studying the ability of potassium solubilizing bacteria (KSB) inoculants to partially replace the convential potassium mineral fertilizer (KMF) in carrot fertilizing program, in addition to, clarifying their potential cytotoxicity on mitotic chromosomes division of carrot were conducted in the present investigation. According to field and laboratory experiment results, using the potassium solubilizing bacteria (KSB) as biofertilizer positively affected yield and quality of carrot especially, KSB3 inoculate. On the same direction, KSB and KMF combinations were more efficient than those of KSB and KMF alone. Regarding to the cytotoxic studies,  data reveled that carrot root tips treated with KSB and their combinations improved cell division and exhibited low cytotoxicity on mitotic division than those treated with KMF alone. So, it could be concluded that potassium solubilizing bacteria (KSB) inoculants could be used alone or mixed with low doses of KMF as alternative of potassium mineral fertilizer (KMF) in carrot fertilizing programs. In addition, it had less cytotoxicity and ecologically safer than KMF.