Effect of P- Solubilizing Bacteria on Microbial Biomass P and Phosphatase Activity in Groundnut (Arachis hypogaea L) Rhizosphere

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 (H2PO4 ) and monohydrogen orthophosphate (HPO4 -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