Synergistic association of Rhizobium with phosphate-solubilizing bacteria under different sources of nutrient supply on productivity and soil fertility in soybean (Glycine max)

A field experiment was conducted during the summer and rainy seasons of 1999 and 2000 to study the effect of Rhizobium and phosphate-solubilizing bacteria (PSB) on growth, yield, nutrient uptake and soil fertility of soybean [Glycine max (L.) Merr.] under different sources of nutrient supply (vermicompost, pressmud and composted coir pith, each at 75 and 100% N substitution and inorganic fertilizers. Association between Rhizobium and phosphate-solubilizing bacteria was synergistic and their dual inoculation improved the seed yield of soybean significantly (30.9 and 33.6%) over untreated control during summer and rainy seasons respectively. Significant increase in NPK uptake and post-harvest soil N and P levels was observed under combined inoculation of biofertilizers. Among the sources of nutrient supply, vermicompost at 75% N substitution excelled all others in improving the growth and seed yield of soybean. Organic manures tried at 75% N substitution gave higher seed yield than 100% N substitution. Application of organic manures resulted in desirable post-harvest soil status with more N and P.