Vermicompost Augmented with Plant Growth Promoting Rhizobacteria Improved Soil Fertility and Growth of Brassica rapa

The excessive use of chemical fertilizers in agriculture has created several health and environmental issues which necessitates the finding of alternate means for sustainable crop production. This study was designed to compare the effects of plant growth promoting rhizobacteria (PGPR)-enriched, and plain vermicompost on growth and yield of turnip (Brassica rapa L.) and soil fertility. Microbial strains were isolated from the previously manufactured vermicompost and characterized in vitro for plant growth promoting traits (e.g., phosphate (P) solubilization, growth hormone and enzyme production). Based on exhibition of maximum traits of PGPR, 11 out of 22 strains were selected for inoculating the vermicompost before its application to the turnip plants in pots under natural conditions. Results revealed that 3 strains i.e., MV-9, MV-17 and MV-21 showed significantly higher potential of plant growth promoting traits (mentioned above). Similarly, vermicompost enriched with these PGPR strains significantly improved germination rate (43%) and turnip yield (30%) along with increased number of leaves, leaf length, diameter, fresh/dry weights of plant shoot/root compared with control. PGPR treated vermicompost unquestionably improved the macro and micronutrients in plant and soil, despite a notable variability was observed between treatments regarding contribution towards soil and plant nutrients. Inter strain comparison affirmed that, MV-17 treated vermicompost resulted in 63% higher soil NO3-nitrogen compared with control, whereas in roots, same isolate increased phosphate (P) and potassium (K) contents, but not NO3-N. In general comparison of PGPR strains, MV-9, MV-17 and MV-21 significantly increased turnip fresh weight, soil macro and micronutrient contents. Overall, it is concluded that vermicompost augmented with bacterial strains; MV-9, MV-17 and MV-21 imparted beneficial effects on growth, yield and nutritional value of turnip and increased soil fertility.