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Synopsis Fertilizers have played a key role in the modernisation of Indian agriculture and in making the country self sufficient in food grain production. P is reported to be the limiting plant nutrient in soils and is considered to be the key to crop productivity. Most soils contain insoluble inorganic phosphates but they are of no use to crops unless they are solubilized. Much of the soluble phosphates applied to soils as fertilizers is fixed by the soil and rendered less available to plants. The long term application of P fertilizers has resulted in an accumulation of total soil P, most of which is poorly soluble. Phosphate Solubilizing Microorganisms (PSM) are capable of solubilizing tricalcium, aluminium and iron phosphates, as well as rock phosphate making the phosphorus present in the soil available to plants. Soils also contain organic phosphorus, which can be used by crops only if it is mineralized. Microorganisms play active part in the decomposition and mineralisation of organic matter and release of nutrients. Organisms that cause increases in plant available P in the soil system belong to a diversified group including bacteria, actinomycetes and several group of fungi. Huge investments would have to be made in fertilizer factories to meet growing demand of phosphatic fertilizers. The fertilizers so produced is not only high price, but the factories themselves have an adverse effect on the environment. Phosphatic biofertilizers offer a viable alternative. This book provides a comprehensive information on phosphatic biofertilisers including PSM and VAM.