Isolation of phosphate solubilizing bacteria from vermicompost and determination of their microbial fertilizer potential

The fact that applications of chemical fertilizer cause problems such as water and soil pollution has led researchers to seek alternatives suitable for the concept of sustainable agriculture. One of these alternatives is microbial fertilizers. Numerous studies have been conducted on the use of microorganisms obtained from different environments as microbial fertilizers. However, there are no detailed studies on the presence and effectiveness of microorganisms that have the potential as microbial fertilizers in vermicompost and vermicompost-treated soil. This thesis aimed to fill this gap in terms of phosphate solubilizing bacteria. In this study, bacteria isolated from vermicompost and a vermicompost-treated soil based on their phosphorus solubilizing abilities were purification and 5 of these isolates were selected for the pot experiment, according to their phosphorus solubilizing capacity and 16S rRNA gene sequences. The pot experiment was carried out according to the randomized plot design with 3 replicates under greenhouse conditions and lettuce (Lactuca sativa var. Crispa) was used as the test plant. Bacteria solutions were applied to the soil on the 7th and 14th days after seedling plantation. The experiment also included a treatment receiving only chemical fertilizers and a treatment with no chemical and biological application. Biological analyzes (Alkaline Phosphatase, β-Glycosidase, Dehydrogenase, Urease activity analyzes and Mesophilic Heterotrophic Bacterial Count) and chemical analyzes (pH, EC, macro and micro nutrient analysis) were performed on the soil (bulk soil and rhizosphere soil) samples taken at the end of the experiment. Yield and quality parameters, and macro and micro nutrient contents of plants were also determined. According to the results obtained, the most effective isolates in rhizosphere soil were PBV-A9, PNB-B3 and PNB-B46, while PBV-A9, PHB-A8 and PNB-B3 isolates were prominent in terms of their effects on plant. It has been concluded that PNB-B3 and PBV-A9 isolates can adapt better to the rhizosphere region, and their potential as microbial fertilizer can be high when evaluated in terms of their effects on both soil and plant.