Crop residue management options in rice-rice system: a review

Rice is the most residue-producing crop in Asia (826 million tons) contributing 84% of total production of the world. Traditionally, rice straw is removed from fields for use as cattle feed and other purposes in South Asia. On average, rice crop residues contain 0.7% N, 0.23% P and 1.75% K. Therefore, the amount of NPK contained in rice crop residues produced is about 22.13 x 10(6) and 26.26 x 10(6) t year(-1) in Asia and the world, respectively. Recently, with the advent of mechanized harvesting, farmers have been burning in situ large quantities of crop residues left in the field which interfere with tillage and succeeding operations for the subsequent crop, causing loss of nutrients and soil organic matter (SOM). On-field residue retention benefits soil health, soil water conservation, soil productivity and environment but there are several challenges in residue incorporation - physical problem of soil incorporation, labor intensive, fallow period and N immobilization. There are several off-field options for managing rice crop residues - palatable livestock feed, economic roof thatch for rural poor, rural residue composting, edible mushroom cultivation, biogas production and packaging of non-consumable items for transport.