Phosphate-solubilizing microorganisms: A critical review

Abstract

Nitrogen (N), phosphorus (P) and potassium (K) are the three important nutrients required by any plant for healthy growth. Among these, P stands as the second limiting nutrient next to nitrogen. Even though different forms of P are abundantly present in soil, its availability in plant-utilizable form is limited. This defi ciency is usually compensated by adding chemical fertilizers. However, the chemical fertilizers are expensive and are not eco-friendly. Nonjudicious and irregular usage for a long time leads to decreased soil activity and soil microfl ora leading to imbalance in equilibrium. Usage of microorganisms to augment the Pavailability is the best alternative. Phosphate-solubilizing microorganisms (PSMs) when applied in appropriate numbers into the rhizosphere help the plant by supplementing P in plant-utilizable form by several mechanisms. In addition, few PSMs also possess added features as plant growth-promoting rhizobacteria (PGPR) and biocontrol agents conferring protection from phytopathogens. Improvement in soil characters by PSMs is an added advantage. Recent advances in technology paved the way for modifying PSMs with desired qualities. In spite of these, several areas in this area of research suffer different lacunae. Efforts are being made to discuss all major areas pertaining to PSMs in the present review.