Effect of NPK fertilization on the physicochemical characteristics of water and soil and on the dry weight of planktonic and benthic biomass in carp ponds

Abstract

The effect ofNPK fertilization on water and bottom soil properties and on the biological productivity of culture ponds was investigated. The monthly nitrate and phosphate concentrations in fertilized ponds were higher than that in control ponds to which no fertilizer was added, illustrating a rapid utilization of these nutrients by growing phytoplankton. There was a significant relationship between average chlorophyll-a concentration and phytoplankton abundance through NPK treatments. The regression results showed significant interaction between transparency and dry weight of planktonic biomass and the same was observed between organic carbon and benthic biomass. The coefficients of determination (R²) of planktonic biomass on water physicochemical factors showed 35.66 and 64.34% contribution in control and treated ponds respectively. The overall contribution of soil physicochemical factors to benthic biomass was 35.14% in control ponds and 64.88% in treated ponds. Water temperature significantly affected transparency through planktonic biomass. Organic carbon had simple correlation with pH, phosphorus and calcium and inverse but direct correlation with total nitrogen. It strongly affected the benthic biomass in fertilized ponds. Based on the dynamic interactions among nutrient concentration, planktonic biomass and benthic bionlass, it is suggested that rate of inorganic nutrients addition may influence the biological production-potentiality of fish pond waters through the indirect contribution of temperaturse and transparency.