Int.J.Curr.Microbiol.App.Sci (2017) 6(4): 1240-1260 1240 Original Research Article https://doi.org/10.20546/ijcmas.2017.604.152 Effect of P- Solubilizing Bacteria on Microbial Biomass P and Phosphatase Activity in Groundnut (Arachis hypogaea L) Rhizosphere Madhusmita Pradhan 1 , Chinmay Pradhan 2 and Santanu Mohanty 1 * 1 Department of Soil Science and Agricultural Chemistry, College of Agriculture, OUAT, Bhubaneswar, Odisha, India 2 PG Department of Botany, Utkal University, Bhubaneswar, Odisha, India *Corresponding author ABSTRACT Introduction Phosphorus is the second most essential macro nutrient after nitrogen required for crop growth (Lal, 2002). Various metabolic processes viz., energy transfer, signal transduction, macro-molecular biosynthesis, photosynthesis, respiration, etc. require P as the key ingredient (Shenoy and Kalagudi, 2005). Mostly soils contain only approximately 1 μmol l -1 soluble P, where as the P requirement by the crops is approximately 30 μmol l -1 soluble P for optimum productivity (Simpson et al., 2011). Plant roots usually absorb P as dihydrogen orthophosphate (H 2 PO 4 - ) and monohydrogen orthophosphate (HPO 4 -2 ) ion (Panda, 2009). Declined soil reaction (pH) increases the concentration of Fe and Al in soil solution thereby making complexes with aluminum and iron-free oxide sand hydroxides (Fearnside, 1998; Richardson, 2001). Soil acidity thus triggers and increases rate of P fixation as well as immobilization (Fankem et al., 2006). Unlike N, P availability is highly dependent on the type of soil reaction (pH) and no big atmospheric source is there to supplement the P requirement of crops. Again, compared to N and K, total phosphorus level of soils is low and usually one tenth to one fourth of N and one twelfth of K (Jones and Eva, 2011). Thus, P is also International Journal of Current Microbiology and Applied Sciences ISSN: 2319-7706 Volume 6 Number 4 (2017) pp. 1240-1260 Journal homepage: http://www.ijcmas.com Phosphorus plays a major role in growth and development of crops and is often found limiting in almost all types of soils. Phosphorus (P) solubilizing bacteria do the vital processes of mobilization of P from its poorly available sources. In this study, the potency of five bacterial strains (2 strains of Bacillus and 3 strains of Burkholderia) have been evaluated to solubilize P from complexes of Ca-P, Al-P, Fe(II)-P and Fe(III)-P. Bacillus amyloliquefaciens CTC12 (KT633845) solubilized P more efficiently from complexes of Ca-P, Fe(II)-P and Fe(III)-P where as Burkholderia cepacia KHD08 (KT717633) solubilized highest P from Al-P in vitro. All the five strains significantly enhanced soil phosphatase activities, microbial biomass P and plant P concentrations when combinedly applied with SSP. Bacillus amyloliquefaciens CTC12 and Burkholderia cepacia KHD08 in combination with SSP solubilized 63 and 61 per cent more P compared to pots treated with SSP only. When these five isolates were inoculated to groundnut enhanced the soil available P and phosphatase activity. Keywords MBP, Phosphatase, PSB, Groundnut. Accepted: 12 March 2017 Available Online: 10 April 2017 Article Info