Nitrogen and Phosphorous Budget Analysis of Carp Based

An experiment was conducted in 12 earthen ponds of 200 m2 at Kathar VDC, Chitwan, Nepal for 270 days to analyze the productivity and nutrient budget in some carp based polyculture systems. The experiment was conducted in a completely randomized design with four treatments in triplicate each: a) Carps only or control (7000 fish/ha) (T1); b) Carps (7000/ha) + tilapia (3000/ha) (T2); c) Carps (7000/ha) + tilapia (3000/ha) + sahar (500/ha) (T3); and d) Carps (7000/ha) + tilapia (3000/ha) + sahar (1000/ha) (T4). Silver carp (Hypophthalmichthys molitrix), bighead carp (Aristichthys nobilis), common carp (Cyprinus carpio), grass carp (Ctenopharyngodon idella), rohu (Labeo rohita) and mrigal (Cirrhinus mrigala) of mean stocking size 3.0, 4.2, 10.0, 18.8, 10.5, 2.2 g, respectively were stocked in all ponds at the ratio of 4:2:1:1:1:1. The mean stocking size of Nile tilapia (Oreochromis niloticus) and sahar (Tor putitora) were 9.7 and 3.4 g, respectively. The ponds were fertilized weekly with urea and di-ammonium phosphate @ 4 g N and 1 g P/m2/day. Fish were fed with locally made pellet feed (20 % CP) once in an alternate day at @ 2 % body weight. At harvest, the extrapolated fish yield ranged from 1.5 to 1.