Practical Aspects of Chemistry in Pond Aquaculture

Abstract

Abstract Relationships among liming, fertilization, water and soil chemistry, phytoplankton response, and aquatic animal production are still poorly understood. There is considerable confusion about critical nutrients and fertilizer formulations for pond fertilization. The literature does not support the high application rates of nitrogen often used. Nitrate is more desirable than ammonium or urea as a source of fertilizer nitrogen. Problems in ponds with water and soil quality that are related to feeding result primarily from high inputs of feed. Organic matter is decomposed mostly to stable humus during a growing season, and there is little accumulation of highly decomposable organic matter from one crop to the next. High input of fresh organic matter to the bottom during a crop period can cause high oxygen demand in sediment, but sediment removal between growth cycles does not greatly reduce soil oxygen demand for the next crop. Organic matter resuspension without erosion of mineral soil has the potential for improving bottom soil condition during crops. This can possibly be achieved by new approaches to mechanically induced aeration and water circulation and the use of sodium nitrate as a soil oxidant. Chemical precipitation of phosphorus by application of aluminum, iron, or calcium ions has the potential for reducing phytoplankton blooms that result from feeding. The most important principle regarding water quality and soil management is that a pond has a finite capacity to assimilate nutrients and organic matter. When this capacity is exceeded, water and soil quality deteriorate. Sediment removal and water exchange only transfer pollution problems from pond environments to surrounding environments.