Biofertilizer Green Manuring
Ghai and Thomas (1989) have defined green manuring as "a farming practice where a leguminous plant which has derived enough benefits from its association with appropriate species of Rhizobium is ploughed into the soil and then a non legume is grown and allowed to take the benefits of the already fixed nitrogen". The practice of green manuring was started from several century B.C. in India and China. During the course of time availability of chemical fertilizers decreased the significance of green manuring. In recent years, due to hike in price of chemical fertilizers, the practice of green manuring is reemphasized.
Ghai and Thomas (1989) have given a list of various leguminous plants to be used as green manure. Some of them are: cultivated annual legumes (e.g. Crotalaria juncea, C. striata, Cassia mimosoides, Cyamopsis pamas, Glycine wightii, Indigofera linifolia, Sesbania rostrata, Vigna radiata), perennial legumes (e.g. Acacia nilotica, Cassia hirsuta, Sesbania aegyptica, Leucaena Jeucocephala), and wild annual legumes (e.g. Cassia cobanensis, Lathyrus sativus, Mimosa invisa, Mucuna bracteata). In a report of International Rice Research Institute (Philippines) it has been suggested that fast growing tropical legumes can accumulate more than 80 Kg N/ha when grown as green manures.
In India, for a small and marginal farmers, green manuring may be important because of high cost of chemical fertilizers. Moreover, reclamation of "Usar lands" can also be done by green manuring. In addition to nitrogen, green manures also provide organic matter, N, P, K and minimize the number of pathogenic microorganisms in soil (Sanford, 1926; Subba Rao, 1982; Ghai and Thomas, 1989).