Effects of iso-nutrient fertilization on plankton production in earthen ponds of Bangladesh.

The experiment was conducted to evaluate the effects of iso-nutrients fertilization on fertilizer combinations, containing a similar amount of nitrogen (N) and phosphorus (P) were the production of plankton in earthen ponds for a period of eight weeks. Two different were tested in triplicate using six earthen ponds of 100 m2 each. The fertilizer combinations of cow manure, urea and Triple Super Phosphate (TSP) at the rate 5000, 125 and 100 kg ha(-1), respectively, containing approximately 102 kg N and 65 kg P was used for treatment-1 (T-l). Another combination of poultry-manure, urea and TSP at the rate of 2000, 125 and 100 kg ha(-1), respectively, was considered as the treatment-2 (T-2). The application rate of poultry manure was adjusted to make the nutrient (N and P) content of fertilizer combination in T-2 similar to that in T-1. Four groups of phytoplankton namely, Bacillariophyceae, Chlorophyceae, Cyanophyceae and Euglenophyceae and two groups of zooplankton namely, Crustacea and Rotifera were identified. The mean abundance of both phytoplankton (78.25 +/- 6.33 x 10(4) cells L(-1)) and zooplankton (57.63 +/- 4.59 x 10(4) cells L(-1)), were significantly higher (p < 0.05) in earthen ponds which treated with poultry manure. The result showed that despite iso-nutrients content, the nutrient status of poultry manure proved to be superior to cow manure.