Impact of phosphate solubilizing bacteria on growth and yield of maize

Soil microorganisms are supportive in the transformation of soil phosphorus (P) and are thus an important component of the soil P cycle. These are effective in releasing P both from inorganic and organic pools of total soil P through their respective solubilizing and mineralizing abilities. To evaluate this, five promising strains of PGPR [PS-01 (Burkholderai sp.), PS-12 (Bacillus sp.), PS-32 (Pseudomonas sp.), PS-41 (Flavobacterium sp.) and PS-51 (Pseudomonas sp.)] capable of solubilization of both organic and inorganic phosphorus as investigated under in vitro conditions were evaluated in a pot trial for their rhizosphere phosphatase activity and mineralization potential of organic P in soil, plant growth and yield at different farmyard manure (FYM) levels i.e. 0, 8 and 16 Mg ha^-1. These bacterial strains were also monitored for other attributes like chitinase activities and root colonization ability in addition to phosphatase activity, auxin production and ACC-deaminase activity. In response to inoculation with these selected rhizobacteria, significant increases in plant height, root length, shoot dry weight, root dry weight and grain yield were observed which were up to 16, 11, 42, 29 and 33%, respectively, over uninoculated control in the presence of FYM at 16 Mg ha^-1. Similarly, there were significant increases in the rhizosphere phosphatase activity, mineralization of organic P and soil available P which were 189, 185 and 62% higher than uninoculated control in the presence of FYM, respectively. The study demonstrated that the use of PGPR having multifaceted beneficial traits would be highly effective for improving growth and yield of crops.