THE GROWTH OF SILVER CARP AND BIGHEADIN POLYCULTURE PONDS FERTILIZED MAINLY WITH AMMONIUM CHLORIDE

Growth of the silver carp(Hypophthalmichthys molitrix)and bighead(Aristichthys nobilis)were studied in polyculture ponds with the two fishes as main cuIture species.Six fer-tilization regimes were employed among which four used ammonium chloride one usedammonium bicarbonate and urea,and one used organic manure as nitrogen source.The daily absolute growth,daily growth rate, instantaneous growth rate, relative growth rate inlength and weight, and condition factor were detennined for different periods of the growthseason,The resuIts indicated that ammonium chloride was a pond fertilizer with good quality and promoted the growth of the silver carp and bighead.Best growth was achieved whenthe ratio of N/ P2O5 in the fertilizer was about 2.Supplemental application of potassiumfertilizer did not improve the growth of the two fishes.