Effects of different fertilization and feeding regimes on the production of integrated farming of rice and prawn Macrobrachium rosenbergii (De Man)

An experiment was conducted in rice field plots each of 30 m(2) to determine the appropriate combination of feeding and fertilization regimes for the giant freshwater prawn Macrobrachium rosenbergii (De Man, 1879) cultured along with rice in rice fields. There were four treatments: rice culture only with regular fertilization (A, control); rice-prawn integrated culture with regular fertilization (B); rice-prawn integrated culture with basal fertilization and commercial feed (C) and rice-prawn integrated culture with regular fertilization and commercial feed (D). Juvenile prawns of 1.5-g size were stocked on the third day after rice transplantation at a density of 2 prawns m(-2) and fed twice daily at 5% reducing to 2% of body weight during the experiment. The rice yield in treatment D (0.42 kg m(-2)) was significantly higher than that in other treatments (0.34, 0.36, 0.34 kg m(-2) in treatments A, B, C respectively). Prawns grew significantly faster (P<0.05) in treatments C and D (23.8+/-0.9 and 22.0+/-1.7 g prawn(-1) respectively) than in treatment B (14.7+/-1.6 g prawn(-1)). Prawn production in treatment C (347+/-13 kg ha(-1) crop(-1)) was significantly (P<0.05) higher than that (234+/-30 kg ha(-1) crop(-1)) in treatment B, while in treatment D (296+/-53 kg ha(-1) crop(-1)) it was not significantly different from that in treatments B and C (P>0.05). Treatment C gave the highest economic returns among all treatments, followed by treatments D and B, indicating that the combination of basal fertilization and commercial feed is the most appropriate nutrient input regime for the rice-prawn integrated culture system.