Effects of physicochemical factors on the dry weight of planktonic biomass in carp ponds through NPK fertilization

Abstract

Water quality parameters were monitored during controlled NPK fertilization of 6 ponds for 9 months. Four ponds were used for treatment and other 2 remained as control to which no fertilizer was added. Phytoplankton and zooplankton densities were measured monthly. The regression analysis of 18 physicochemical variables on dry weight of biomass showed significant (P<0.01) interaction between light penetration and dry weight of biomass. The coefficients of determination (R₂) of biomass on physical factors showed 39.6% and 55.9% contribution in control and treated ponds, respectively. The R₂ of biomass on chemical factors was 47.7% in control ponds and 67.7% in treated ponds, showing interdependence on each other. Average chlorophyll concentration significantly (P<0.01) responded the phytoplankton abundance through NPK treatments. Water temperature significantly (P<0.01) affected light penetration through the abundance of phytoplankton biomass. Thus water temperature plays an important role in the release of nutrients from inorganic manures.