Liming and Fertilization of Brackishwater Shrimp Ponds

Agricultural limestone and burnt lime are applied either to the water during shrimp production or to pond bottoms between shrimp crops. However, unless the total alkalinity and total hardness of pond water is below 50 mg/L as equivalent CaC0₃ or the pond soils are acidic (pH < 7), liming is of little or no value. The use of burnt lime should be avoided because this material can cause high pH in water and soil. Chemical fertilizers or manures are used to fertilize brackishwater ponds. Fertilization programs for brackishwater ponds usually require more nitrogen (N) than those for freshwater ponds. Phosphorus (P) fertilization is important both in brackishwater and freshwater ponds. Because water is exchanged often in brackishwater ponds, fertilizer should be applied in small doses and at frequent intervals. Most managers of brackishwater ponds prefer a large proportion of diatoms in the phytoplankton community. An N:P application ratio of 20:l in ponds favors diatoms; in fiberglass tanks with water of low silica concentration, fertilization with silica encouraged an abundance of diatoms.