Abstract
Interaction between two diazotrophs (Rhizobium and Azospirillum) and one phosphorus -solubilizing bacterium (PSB), Pseudomonas was studied in laboratory using soil extract agar plates and carrier models. On soil extract agar medium, the three microbes grew without inhibiting each other. In the carrier, all three microorganisms sustained their population equal or more than 107cfu/ g of carrier (effective enough for successful inoculation) after eight weeks storage at 28°C, irrespective of in what combination they exist. Rhizobium maintained highest population at the end of 8 weeks and seems to play a probiotic role for PSB, as population of PSB was higher in the presence of Rhizobium as compared to PSB alone after 8 weeks. Maize seed germination was 25% higher than in control after 24 h of inoculation when seeds were inoculated with coinoculant, Azospirillum + PSB or with Azospirillum+Rhizobium + PSB than in un-inoculated seeds. In field maize crop model was used to study the performance of three microbes in the presence of each other. Increase in grain yield ranged from 27%-50% over the control due to inoculation. Of all the inoculated treatments, highest increase was recorded when inoculant containing all three microbes Rhizobium, Azospirillum and Pseudomonas were inoculated in the presence of nitrogen @30kg/h and phosphorus @20kg/h. The grain yield in this case was equal to that when 120kg N and 80kg P was applied without bacterial inoculation. Highest seed nitrogen as well as seed phosphorus was recorded when Pseudomonas was applied in the presence of 120kg nitrogen and 40 kg phosphorus. Grain yield showed good correlation with straw Phosphorus (r0.0= 0.58) and leaf nitrogen (r0.0=0.63).
