Preliminary studies on the effects of fresh and fermented pig manure on fish production

The growth of several cultivated fishes of Cyprinidae was studied using cognate fresh and fermented pig manure and the equivalent fertilizers N and P as sole inputs to different experimental groups of fish ponds. Experiment I was conducted from June to October 1986, experiment II from March to October 1987. The proportions of fish production from chemical-fertilized ponds (C), fermented pig manured ponds (F1), and fresh pig manured ponds (F2) were 100:156:226 and 100:294:382 respectively. The ratio of fish production of F1 ponds to F2 ponds was 100 to 145 in experiment I and 100 to 130 in experiment II, respectively.The chlorophyl content, zooplankton biomass, bacterial activity and BOD were lower in the C ponds than in the F1 and F2 ponds, while the DO concentration was higher. There was little difference in the concentration of NH4-N and PO4-P among the experimental ponds. The physico-chemical parameters in the F1 and F2 ponds were not always in conformity with the fish production. Some parameters were contradictory in these two experiments. In the experiment I, the content of NH4-N in the F1 ponds was lower than that in the F2 ponds, and the content of chlorophyl and the biomass of zooplankton in the F1 ponds were greater than those in the F2 ponds. In contrast, in experiment II all these three parameters were reversed in the F1 and F2 ponds. These results indicate that part of the fish production in the C ponds came from the natural planktonic food chain, while in the F1 and F2 ponds, much of the production was derived from the manure detritus as well as from the planktonic food chain. The nutrient value of fermented pig manure is probably less than that of fresh manure because of bacterial decomposition during fermentation. There is a complicated relationship among various physico-chemical factors after manure application in the F1 and F2 ponds.