Visual screening of potassium solubilizing bacteria for increasing the solubilization of potassium minerals

Abstract

Research on potassium solubilizing bacteria (KSB) has recently gained attention, most of it has been focused on the size of the halo zone; however, information regarding KSB growth duration and their potential to reduce the use of chemical fertilizers for sustainable agriculture and to be used as a biofertilizer are still lacking. The aim of this study was to offer a complete, long-term observation of KSB growth. We monitored the growth of two KSB strains that were isolated from the rhizosphere for 7 days on Modified Aleksandrov Medium (MAM) plates. We specifically designed the observation times. These methods were used to distinguish KSB's capability to solubilize potassium minerals. The results indicated that KSB-12 isolate was capable of producing organic acid and thus solubilizing potassium faster than KSB-19 isolate at 1-4 days of incubation. Interestingly, the solubilizing zone of the KSB-12 isolate decrease after 5 days of incubation, while KSB-19 isolate continued to grow, maintain cell numbers, produce organic acids, and continuously release potassium. Different types of volatile and non-volatile organic acids have an effect on this phenomenon. In conclusion, we provided a well-designed time series study regarding the potassium solubilization efficiency of KSB, determining the fastest and longest strains of potential KSBs.