Productivity enhancement through rice–fish farming using a two-stage rainwater conservation technique

In order to increase the productivity from an unit volume of rainwater, a two-stage rainwater conservation technique was conceptualized and tested, in which part of the rainwater was conserved in rice field up to the weir crest level and the remaining in a refuge for rearing of fish (Catla catla, Labeo rohita, Cirrhinus mrigala and Cyprinus carpio) and prawn (Macrobrachium rosenbergii). Experimental study for 3 years (1999–2001) was conducted in Bhubaneswar, India. Swarna variety of rice was grown in plots of 300 m2 each with weir heights of 10, 12.5 and 15 cm as treatments having three replications each. Weir height of 12.5 cm, provision of peripheral trench on three sides of rice fields (0.5 m width and 0.3 m depth), a refuge occupying 9% of field area and fish stocking density of 25,000 ha−1 were found suitable for this system and resulted in rice equivalent yield of about 4.4 t ha−1 without application of pesticides. A net profit of Rs. 10,781.00 ha−1 was obtained from this dual production system.