The role of chicken manure on the production of Nile tilapia, Oreochromis niloticus (L.).
In experiment 1, 280-m2 ponds 60 km north-west of Bangkok, Thailand stocked with (Oreochromis niloticus) about 10 g at pH 8.4 and at 27°-34°C were fertilized weekly with chicken manure 20, 60, 100, 140 and 180 kg dry weight/ha plus urea and triple superphosphate (TSP) for 21 weeks from October to March. In experiment 2, ponds stocked with tilapia about 6 g at 3.2 fish/m2 were fertilized weekly with fresh layer-chicken manure 60 kg dry weight/ha, dissolved inorganic carbon (DIC) at 3.5 kg NaHCO3/ha, chicken manure plus NaHCO3 or no manure. All ponds received urea and TSP and ponds in experiments 1 and 2 had an equivalent nitrogen input of 4.0 kg/ha daily and a nitrogen:phosphorus ratio of 4:1. Addition of chicken manure to inorganic fertilization did not increase production of tilapia. Net fish yield (NFV) in experiment 1 increased with decreasing manure loading, which corresponded to increasing TSP input. Regression analysis suggested that chicken manure-P was about 10% effective as TSP-P at increasing NFY. NFY was linearly correlated to net primary productivity (r2 = 0.62, P<0.001), which was linearly correlated to total alkalinity (r2 = 0.77, P<0.001). Treatment differences in alkalinity, community respiration or dissolved oxygen concentrations at dawn were not related to manure input. Simple economic comparisons discourage the purchase of chicken manure as a source of soluble N and P for increasing algal productivity in Thailand.