Enhanced phosphorus fertilizer use efficiency with microorganisms

Abstract

Phosphorus (P) is an essential nutrient in plant development and growth, and its deficiency is one of the major factors limiting crop yields worldwide. Although soils generally possess a large amount of total P (400-1000 mg kg-1), only a small ratio (1.00-2.50%) is immediately available for uptake of plants since 75-90% of added P is precipitated by metal-cation (calcium, iron, and aluminum) complexes and quickly becomes fixed in soils. The nature of calcareous soils in the arid and semiarid regions of the world has made P use efficiency (PUE) low (10-25%) in this land. For this reason, farmers have added a significant amount of these chemical fertilizers to the cultivated land to achieve the desired result every year. Low-use efficiency of the P fertilizers and their continuous long-term use have led to environmental pollution. The use of chemical P fertilizers cannot be omitted at this time without intensely diminishing food production. However, it is known that the compound use of phosphate-solubilizing microorganisms (PSMs) and chemical P fertilizers can reduce the negative impacts of overuse of these fertilizers and improve PUE in an efficient and environmentally prudent manner. Among the PSMs, it can be mentioned arbuscular mycorrhizal fungi (AMF) and plant growth-promoting rhizobacteria (PGPR). AMF increase the growth, yield, and absorption of nutrients in the plant mostly by increasing the effective absorptive area of the roots by formation of an extensive extraradical hyphal network, and PGPR also contribute directly to increasing the solubilization of insoluble P compounds in the soil and thereby plant growth through mechanisms like producing organic and inorganic acids, increasing root surface area, and improving beneficial symbiosis with host plants at different stages of plant growth. In addition, it is known that the plants inoculated with a combination of PGPR and AMF can express synergistic effect to augment plant growth indices while maintaining safe natural resources such as P stocks. This chapter is a critical summary of the efforts in using phosphate-solubilizing bacteria (PSB) and phosphate-solubilizing-AMF for augmenting the use efficiency of P fertilizers.