Biosolids as water fertilizer for plankton production / Biossólidos como fertilizantes de água para produção de plâncton

AUTOR(ES)
DATA DE PUBLICAÇÃO

2008

RESUMO

Aiming to evaluate the use of biosolid as a water fertilization strategy in the production of Daphnia sp., were conducted three experiments in the Fish Nutrition Laboratory of the Department of Animal Science of the Federal University of Viçosa (UFV). The first experiment, conducted during February and March 2008, to last for thirteen days, aimed to evaluate the use of different fertilizers - dicalcium phosphate (DF), biosolid (BS) and feces of quail (FQ). Were used 24 tanks of asbestos cement with useful volume of 100 L each, distributed in a completely randomized design, with four treatments (the three fertilizers and a control treatment without fertilization - WF) and six repetitions. As control variables were assessed the production of Daphnia sp. and the following water quality parameters: chlorophyll-a, electrical conductivity, pH, dissolved oxygen, temperature, ammonia nitrogen and organic nitrogen, total phosphorus and total hardness. The weight of the biomass of Daphnia sp. was measured at the end of the experiment (day 13). The control parameters of water quality were measured at three times during the experimental period: the first, eighth and thirteenth day. The maximum weight of the biomass of Daphnia sp. was found in tanks fertilized with FQ (35.6 grams), followed by the BS (16.8 grams), WF (6.8 g) and DF (5.2 g). There was a correlation between the values of chlorophyll-a and the weight of the biomass of Daphnia sp., which will very likely reflects interactions between phytoplankton and zooplankton communities. The results suggest that biosolids can be successfully used as water fertilizer, for production of phytoplankton and, consequently, of zooplankton. In the second experiment, carried out from February and March 2008, sought to evaluate the application of different levels of biosolids. Were used 25 tanks of asbestos cement with useful volume of 100 L each, distributed in a completely randomized design with five treatments (four levels of biosolids - 25 g, 50 g, 75 g and 100 g and a control treatment without fertilization) and five repetitions. The control variables and the sampling plan were the same as the first experiment. The weight of the biomass of Daphnia sp. was measured at the end of the experiment (day 13). The control parameters of water quality were measured at three times over the experimental period: first, eighth and thirteenth day. The average weight of biomass of Daphnia sp. found in the tanks were: 16.51 g to 100 g of biosolids; 14.63 g to 75 g of biosolids; 14.10 g to 50 g of biosolids; 12.85 g to 25 g of biosolids and 5.80 g in tank without fertilization. The results suggest that biosolids can be successfully used as water fertilizer for production of phytoplankton and, consequently, of zooplankton. The application of increasing quantities of biosolid not committed water quality to the point of making it unsuitable for the cultivation of aquatic organisms. However, despite the growing production of phytoplankton in line with increasing levels of biosolids, the production of Daphnia sp. tended to stabilize itself from the application of 50 grams of biosolids. The third experiment, conducted from March to April of 2008 with duration of fourteen days, involved the use of biosolid with different settings of NPK. Were used 25 tanks of cement and asbestos previous designs, with five treatments (five levels of NPK in 50 g of biosolids) and five repetitions. The control variables and the sampling plan was essentially the same of previous experiments, but measuring up nitrate and soluble phosphorus in place of organic nitrogen and total phosphorus. The application of biosolids with different formulations of NPK not compromised water quality to the point of making it unsuitable for the cultivation of aquatic organisms. However, despite the growing production of phytoplankton in line with increasing levels of phosphorus in the formulation of fertilizers, the weights average of Daphnia sp. biomass found in the tanks, around 10 grams, not statistically different for different treatments. In short, the results suggest that biosolids can be successfully used as water fertilizer for production of phytoplankton and zooplankton.

ASSUNTO(S)

fertilizantes producao animal fertilizers biossólidos biosolids

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