An assessment of the role of buffalo manure for pond culture of tilapia. III. Limiting factors

Abstract

Nutrient release and dose-response experiments evaluated buffalo manure as a source of soluble and particulate nutrients for Nile tilapia ( Oreochromis niloticus) culture and its adverse effects on water quality. Buffalo manure nitrogen (N) and phosphorus (P) content and release characteristics confirmed that manure was a poor source of both particulate and soluble nutrients. Only 6% of initial manure total Kjeldahl N of the 17 mg N/g dry matter (DM) was released as dissolved inorganic N, and 35% of the initial manure total P of the 1.3 mg P/g DM was released as soluble reactive P. Water quality deteriorated at higher manure loading rates of more than 100 kg DM/ha/day. Water color and total suspended solids increased steadily with manure loading rate, promoting light limitation of phytoplankton production at higher loading rates. The dark brown color imparted by manure to the water decomposed faster in the light than under dark conditions. Dissolved oxygen concentrations at dawn also declined to near 0 mg/l at higher manure loading rates.