| Effects of different nitrogen fertilizer applications on water quality and fish production were evaluated in ponds at the Auburn University Fisheries Research Station, Auburn, Alabama, in 1999. In the first study, a new sodium nitrate-based, water-soluble fertilizer (8% N, 24% P2O5, 15% K2O) containing trace elements was used as a sportfish pond fertilizer at rates of 8 and 16 kg/ha per application. This fertilizer was formulated by SQM North America (formerly Chilean Nitrate Corporation) according to specification provided by Auburn University researchers. The SQM fertilizer was compared with a standard, a 10-34-0 liquid fertilizer in bluegill sunfish (Lepomis macrochirus) ponds. Net production of bluegill averaged 368 kg/ha in the liquid fertilizer treatment, 288 kg/ha in the high rate SQM fertilizer treatment, and 224 kg/ha in the low rate SQM fertilizer treatment. At 16 kg/ha application, SQM fertilizer was as effective in increasing net phytoplankton productivity and sunfish production as a standard liquid fertilizer program commonly used in the southern United States.; In the second study, effects of ammonium sulfate (21% N), and sodium nitrate (16% N) application on water quality, sediment condition, and fish production were evaluated in 0.1-ha earthen ponds stocked with golden shiners (Notemigonus crysoleucas). Nitrogen fertilizer applications providing 9 kg/ha N were initiated on 30 March 1999 and continued at 2 weeks intervals until 15 October 1999. Four ponds served as controls and received no nitrogen fertilizer but phosphorus. Net production of golden shiner averaged 298 kg/ha in the ammonium sulfate treatment, 338 kg/ha in the sodium nitrate treatment, and 321 kg/ha in the control. Phosphate-only fertilization was as efficient as fertilization with phosphate plus ammonium sulfate or phosphate plus sodium nitrate in stimulating golden shiner production. Phosphate-only fertilization is less expensive and more “environmentally friendly” fertilization than both nitrogen and phosphorus. |
