Impact of neem (Azadirachta indica A. Juss) seed cake upon selective nutrient cycling bacterial population in fish culture

With an objective to examine neem seed cake as bactericide, three treatments—10, 20, and 30 mg L^?1—were applied in outdoor experimental Labeo rohita culture tanks for a period of 120 days. Nitrifying, ammonifying, and denitrifying bacteria declined directly with increasing dosage. Ammonifying and phosphate solubilizing bacteria recovered within a month, nitrifying and denitrifying bacteria after 45 days. A positive relationship was established between soil available-N and ammonifying, nitrifying, and denitrifying bacteria in 10 mg L^?1 (R² = 0.68–0.83). Phosphate solubilizing bacteria responded directly with dosage and contributed significantly to the orthophosphate pool (R² = 0.66–0.78).