Effect of Pond Fertilization with Vermicompost and Some Other Manures on the Hydrobiological Parameters of Treated Pond Waters

摘要

Organic fertilizers are used to enhance the productivity of inland aquatic resources. These fertilizers directly influence the water quality parameters which in turn form the aquatic environment. Vermicompost is a new introduction to the list of organic fertilizers used in aquaculture production. However, its effects on water quality parameters have not yet been fully investigated. To accomplish this objective, the present study was undertaken. The experiment was carried out in 5.54×6.15 m size ponds with a stocking density of 30 fish per pond in a ratio of 3:4:3 of Indian major carps viz. catla ( Catla catla Ham.), rohu ( Labeto rahita Ham.) and mrigal ( Cirrhinus mrigala Ham.). Different organic fertilizers used as treatments were: untreated ponds as the control (T1), pig manure at 4,000 kg ha?1 year?1 (T2), poultry manure at 6,000 kg ha?1 year?1 (T3), cow dung at 10,000 kg ha?1 year?1 (T4), vermicompost at 10,000 kg ha?1 year?1 (T5) and vermicompost at 15,000 kg ha?1 year?1 (T6). One fourth dose of fertilizers was applied 15 days prior to the start of observations and remaining doses in equal amounts were given at fortnightly intervals. The water quality parameters like dissolved oxygen , pH, alkalinity, hardness, free carbon dioxide, nitrogen, potassium, phosphorous, temperature, turbidity and planktons were measured at monthly intervals. Pond waters treated with vermicompost at 10,000 kg ha?1 year?1 seemed to be the best among the six treatments. This was evident in case of DO, alkalinity, hardness, light penetration, free carbon dioxide, phytoplanktons and zooplanktons. For other parameters too, this treatment kept their values in the favorable ranges. On the basis of all permutations and combinations, therefore, vermicompost at 10,000 kg ha?1 year?1 came out to be the best among the six treatments used in this study. The results revealed that, except for temperature, values of all other water quality parameters in the treated ponds differed significantly between treatments as well as months. Despite this, the values of most of the chemical and physical parameters of all the treatments fell in the favorable ranges. Then, pond waters treated with vermicompost at 10,000 kg ha?1 year?1 (T5), were found to have the best levels of quality parameters as compared to those in the other treatments.