Effect of application of a microbial fertilizer that contains phosphorus solubilizing bacteria on some soil biological properties and growth and nutritional status of tomato plant

Objective of this study was to investigate effects of a microbial fertilizer, which contains a phosphorus solubilizing bacteria (Paenibacillus polymyxa), on biological properties such as bacterial number and enzyme activity and some chemical properties in a soil on which tomato plants (Solanum lycopersicum L.) were grown. Its effects on nutrient content and yield of tomato plants were also in the scope of this study. For this purpose, applications of phosphorus in different rates (0, 25, 50, 75, and 192.52 ppm) alone and with the microbial fertilizer in a standard dose were comparatively evaluated. The experiment was set according to the randomized block design with five replicates and carried out for 128 days in total of 50 pots under greenhouse conditions. During the growth season, soil samples were collected in regular intervals (0, 1st , 4th , 13th , and 18th weeks). In the middle of the growth season, leaf samples, and in the harvesting time, fruit samples were collected and analyzed. At the end of the growth season (18th week) above-ground plant portion was removed from pots to determine plant dry weight and to calculate phosphorus efficiency level. Prior to the experiment, the test soil was analyzed for texture, pH, EC, lime content, organic matter content, total N, exchangeable K, Ca and Mg, available P, Fe, Mn, Zn and Cu. At the end of the experiment, macro and micro nutrient analyses were repeated in soil samples collected from treatments. Soil samples regularly collected from treatments during the experiment were used to determine changes in pH, EC, available P, urease, alkaline phosphatase and β-glucosidase activities, and bacterial number. These analyses were also conducted for soils collected from plant rhizosphere at the end of the experiment. Leaf samples were used the determine N, P, K, Mg, Ca, Na, Fe, Zn, and Cu contents of test plants. Total yield, average fruit weight, and average fruit number were also measured. During and at the end of the growth season, in general, available P content of soils receiving the microbial fertilizer was found to be lower than soils receiving no microbial fertilizer. However, these values were generally above the control value and the highest available P value was obtained from treatment with highest P application and the microbial fertilizer (PR+B). In addition, the highest level P application with microbial fertilizer (PR+B) was found to increase the most exchangeable K, Mg, Na, and available Zn, Mn, and Cu values in soil. In terms of soil urease, alkaline phosphatase, and β-glucosidase activities, no significant difference was observed between treatments with and without the microbial fertilizer. On the other hand, effect of time on these parameters was statistically significant. In terms of mesophilic bacterial number, high level of P applications alone and with the microbial fertilizer resulted in the highest values. The highest total yield and plant dry weight were obtained with PR+B treatment and the difference between treatments with and without the microbial fertilizer was found to be statistically significant. KEYWORDS: Alkaline Phosphatase, β-Glucosidase, Biofertilizer, Chemical Fertilizer, Microbial Fertilizer, Phosphate Solubilizing Bacteria (PSB), Plant Growth Promoting Rhizobacteria (PGPR), Soil Enzyme Activity, Soil Fertility, Tomato, Urease