Chapter 15 - Phosphate solubilization by microorganisms

Abstract

The agricultural sector is a means to promote considerable socio-economic advances in a sustainable manner, with Brazil as an example; however, the productivity of cereal crops such as corn, rice, wheat and sorghum is below its potential. Among the factors that contribute to these crops lower productivity, the low availability of phosphorus (P) in the soils stands out. The most limiting nutrient in tropical soils is P and is less efficient for use by plants. Up to 75 percent of the P applied to the soil, as a fertilizer, becomes unavailable to plants by fixing it to the iron and aluminum oxides present in tropical soils. Due to this high phosphorus adsorption in the soil, the application of phosphate fertilizers in large quantities has become increasingly expensive due to the increase in the input in reprise recent years. For annual crops such as corn, soluble P sources such as single and triple superphosphates are usually. These sources are produced from the treatment of rock phosphate with sulfuric acid, a process that, in addition to the high cost, can lead to contaminants and toxic by-products. The direct use of rock phosphates as a fertilizer has not been recommended for annual crops due to its low content of soluble P. Many soil microorganisms can transform insoluble forms of P to an accessible soluble form, contributing to plant nutrition such as plant growth-promoting microorganisms, action solubilize different inorganic P forms, contributing to the use of low reactive P sources. The selection of microorganisms capable of solubilizing phosphorus (P) from rock phosphates (RP) may contribute to reducing the dependence of imported fertilizers in grain crops, reducing the costs of agricultural production, and also the environmental impacts.The inoculation with phosphate solubilizing microorganisms (PSM) on plant growth has been beneficial in several plant species. This chapter focuses on the Phosphorus behavior in soil, mechanism of P-solubilization, Microbial Phosphate Solubilization, and phosphate solubilizer’s physiological functions to better understand PSMs ecophysiology and, consequently, to gather knowledge for managing a sustainable environmental system. Conclusively, PSM are likely to serve as an efficient bio-fertilizer, especially in areas deficient in P, to increase crops’ overall performance as an example of the product developed by the Brazilian research microbiology group at Brazilian Agricultural Research Corporation (Embrapa).