Effect of high phosphate fertilization rate on pond phosphate concentrations, chlorophyll a, and fish growth in carp polyculture Amtul Bari Tabinda Æ Mohammad Ayub Received: 8 September 2008 / Accepted: 26 January 2009 / Published online: 21 February 2009 Ó Springer Science+Business Media B.V. 2009 Abstract The effect of different application rates of triple superphosphate (22.4, 44.8, and 67.2 kg P 2 O 5 ha -1 ) was observed on total and available phosphorus concentrations in pond soil, total and filterable orthophosphate concentrations in pond water, chlorophyll a, and fish growth in a carp polyculture system during summer (22–32°C) months to deter- mine the economical dose of P 2 O 5 . pH, hardness, calcium and alkalinity of soil and water did not differ significantly among treatments (P [ 0.05) and were within the desired ranges. Average total phosphorus concentrations in pond soil were not significantly dif- ferent between treatments but available phosphorus (P [ 0.05) in pond soil, total phosphorus (P [ 0.001), and filterable orthophosphate (P [ 0.0001) concentrations in pond water, chlorophyll a (P [ 0.0001), and net fish production (P [ 0.01) were signifi- cantly higher in fertilized ponds than in controls. Overall, fish yield did not significantly differ among treatments, suggesting that a very high dose of P 2 O 5 may not be necessary for high yields. Reducing the dose of P 2 O 5 could reduce cost without reducing fish production. Keywords Triple superphosphate Á Filterable orthophosphate Á Phosphorus fertilization Á Water quality Á Polyculture Á Chlorophyll a Introduction Dissolved inorganic P is important for plant uptake (Turner and Haygarth 2000) and phosphorus has more effect than nitrogen in regulating the productivity of ponds. Previous studies revealed that phosphorus fertilization was more critical than nitrogen fertilization (Boyd and Tucker 1998), and the response of fish production to increasing fertilization is thought to be related primarily to phosphorus rather nitrogen addition (Wudtisin and Boyd A. B. Tabinda (&) Sustainable Development Study Center, GC University, Katchery Road, Lahore 54000, Pakistan e-mail: amtulbaritabinda64@yahoo.com M. Ayub Department of Fisheries, 2-Sanda Road, Lahore 53000, Pakistan 123 Aquacult Int (2010) 18:285–301 DOI 10.1007/s10499-009-9243-9