Ammonia, pH, and Plankton in Sunshine Bass Nursery Ponds: The Effect of Inorganic Fertilizer or Sodium Bicarbonate

Abstract

When sunshine bass (female white bass Morone chrysops × male striped bass M. saxatilis) fingerling production ponds are filled and fertilized according to recommended practices, high pH and high un-ionized ammonia levels often develop at the time recommended for stocking of 5-d-old fry. These levels often exceed those found to be lethal to sunshine bass. We compared the effects of organic fertilizer only, both organic and inorganic fertilizer, and both organic and inorganic fertilizers with sodium bicarbonate on 0.04-ha culture ponds. Rice bran, the organic fertilizer, was applied at 278 kg/ha during the first week and 55.6 kg/ha during the second week. Liquid 9-27-0 NPK (urea and mono-ammonium phosphate), the inorganic fertilizer, was applied at 48 kg/ha during both weeks. Sodium bicarbonate was applied at 56, 112, or 224 kg/ha. Primary productivity, pH, and the concentrations of ammonia, chlorophyll a, phytoplankton, and zooplankton were compared among treatments. We include results from the 12-14 d after ponds were filled and fertilized, the period when fry are usually stocked. Sodium bicarbonate application did not reduce (P > 0.05) pH in culture ponds. However, ponds that only received organic fertilizer had pH values that were significantly lower than those of the other treatments on 75% of the experiment days. Chlorophyll-a, total ammonia nitrogen, and un-ionized ammonia nitrogen concentrations were also significantly lower in organic-only fertilized ponds than in the other two treatments on most days and were well below sunshine bass fry tolerance limits. For most water chemistry variables tested, use of sodium bicarbonate did not improve water quality. Although total nutrient input was lowest in the organic-only fertilized ponds, the densities of phytoplankton, rotifers, copepod nauplii, copepod adults, and cladocerans were not significantly different from those of other treatments. These results indicate that sodium bicarbonate does not ameliorate high pH; however, use of only organic fertilizer does reduce pH without reducing zooplankton standing crops.