QUALIDADE DA ÁGUA E FERTIRRIGAÇÃO COM EFLUENTE DE SISTEMA AQUAPÔNICO NO CULTIVO DE VARIEDADES DE RÚCULA

Abstract

Aquaponics is an integrated system for the cultivation of vegetables (hydroponics) and aquatic organisms (aquaculture) that can be used for consumption or ornamentation. The use of fish farming effluent through the aquaponics system is a very interesting solution for use in fertigation, as it does not have phytotoxicity and can be used as a biofertilizer as well as it has enough macronutrients to meet the demand of most agricultural crops. Based on the above, the objective of this study was to evaluate the water quality in an aquaponic system under arugula cultivation, aiming at adding value and sustainability of the production system, in edaphoclimatic condition of the Cerrado, as well as evaluating the growth and development of arugula cultivated under fertigation with fish farm effluent. The experimental design of Chapters I and II was completely randomized, analyzed in a 2 x 3 x 4 factorial arrangement, with three replications. The factors consisted of two filter volumes in relation to the tank (V1= 50 L and V2= 70 L); three stocking density (D1 = 30, D2=60 and D3=90 fish per tank) and four times (6, 12, 18 and 24 days after the environmental acclimatization of the fish), totaling 72 experimental units. The water physical-chemical parameters were evaluated. The experimental design of Chapter III was completely randomized, analyzed in a 2 x 2 x 3 factorial arrangement, with three replications. The factors consisted of arugula varieties (v1 = cultivated arugula and v2 = giant broadleaf cultivated arugula); filter volume in relation to the tank (V1= 50 L and V2= 70 L); and stocking density (D1=30, D2=60 and D3=90 fish per tank); totaling 36 experimental units. Morphological variables, chlorophyll contents and production components were evaluated. The parameters pH, electrical conductivity, dissolved oxygen, temperature, total dissolved solids, alkalinity, hardness and sulfate are within the established limits, in relation to fish density factors, filter volumes and days after fish acclimatization. The parameters phosphorus, chloride, iron, total nitrogen, ammonia, nitrate, nitrite, chlorophyll a, biochemical oxygen demand and chemical oxygen demand were above the permitted, in relation to fish density factors, filter volumes and days after fish acclimation. The trophic state index had high values, being classified as a hyper-eutrophic environment. In general, the density of 60 and 40 fish together with the filter volume of 50 L caused higher water quality degradation. On the other hand, the density of 20 fish together with a filter volume of 75 L provided better water quality. The variety Cultivated with a density of 60 fish and a filter volume of 75 L provided better results. Whereas the variety cultivated with giant broadleaf with a density of 20 fish and a filter volume of 50 L was the one that obtained the lowest results. The results observed in this work were expected because higher density of fish in the same space causes a greater number of residues and consequently greater degradation of the water in the system, being necessary for higher densities a filter with greater volume for total removal of residues or even a lower density of fish. Due to the unavailability of some information in this research, it is recommended for future work to incorporate it with different fish densities and different volumes, for a better understanding and recommendation.