A Reassessment of Nitrogen Fertilization for Sunfish Ponds

Abstract

Experiments on the fertilization of sunfish Lepomis spp. ponds at Auburn University have been conducted since the late 1930s. These studies have demonstrated a large benefit of phosphorous fertilization, but less response to nitrogen fertilization (Swingle 1947; Swingle et al. 1963; Boyd 1990). One series of ponds used for this research was constructed in 197 1, and studies conducted in 1971 (Boyd 1973), 1977 (Boyd and Sowles 1978), and 1986 (Murad and Boyd 1987) did not demonstrate a need for nitrogen fertilization in sunfish ponds. Nevertheless, a number of recent studies at other locations have reported positive responses to nitrogen fertilization (Yusoff and McNabb 1989; Green et al. 1989; Diana et al. 1991) in pond culture of tilapia. Also, a study at Auburn University by Arce and Boyd ( I 975) showed that small applications of nitrogen fertilizer could increase tilapia production above that possible with phosphorus-only fertilization. Therefore, another study on the response to nitrogen fertilization was conducted in the series of ponds at the Auburn University Fisheries Research Unit that has been used in pond fertilization and feeding experiments since 1971.