Biological nitrogen fixation as a source of nitrogen input in fishponds
1988
Kwei Lin, C. | Tansakul, V. | Apinhapath, C. (Asian Inst. of Technology, BangkoK (Thailand). Div. of Agricultural and Food Engineering)
The potential input of nitrogen derived from natural biological fixation in water of fertilized tilapia grow-out ponds in Thailand was determined by the acetylene reduction technique for 12 ponds over a 15-month period. On average, nitrogen fixation ranged from undetectable levels of N to 105 microgram/l/day in water column, compared with 200 microgram/l/day input of N from chicken manure loading at a rate of 500 kg/ha/week. Estimated total nitrogen fixation in fishponds during a 5- month grow-out cycle ranged from 8.8 to 85.7 kg N/ha. The nitrogen fixation primarily occurred in daylight; it was inhibited in the dark and suppressed by elevated ammonium concentrations present in pond water. Nitrogen fixing blue-green algae commonly present in the pond water were Anabaena, Cylindrospermum and Nodularia.
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