Integração aquicultura-agricultura: reúso do efluente de piscicultura na fertirrigação de minitomate, tipo grape, em cultivo protegido

Abstract

The management of natural resources, especially water, is one of the greatest challenges in the world. The disposal of effluents from aquaculture in rivers and streams has the potential to change water quality, with possible eutrophication. The integration between activities, with the use of fish farming effluents for irrigation of agricultural crops, allows to optimize the water resource. The objective of this research was to evaluate the reuse of fish farm effluent from pangasius rearing to fertigate mini-tomato, grape type. Two experiments were carried out, the first one in 2019 and the second on in 2020: 1st) Raw fish farm effluent for fertigation of minitomato, grape type, in protected cultivation; 2nd) Cultivation of mini tomato, grape type, fertigated with nutrient solution prepared in pangasius fish farm effluent. The experiments were installed in a randomized block design, the first with five treatments: nutrient solution (control) and four concentrations of raw fish farm effluent: 25%, 50%, 75% and 100%, with four replications; and the second with four treatments in tomato fertigation: nutrient solution prepared in water supply and nutrient solution prepared in pangasius fish farming effluent (EPCP) in three concentrations of nutrient solution salts (25%SN/EPCP, 50% SN/EPCP and 75%SN/EPCP). The fish farm effluent was characterized in relation to NH4+, NO2-, NO3-, Ca++ and PO4-, concentration. The biometric trait evaluated in the minitomato were plant height, stem diameter and yield. Tomato leaf analysis and evaluation of the relative chlorophyll index were performed for nutritional diagnosis purposes. The fruits of the mini tomato, grape type, were evaluated for quality. An economic analysis was realized considering the price of fertilizers and the sale value of minitomatoes. The average pH of fish farm effluent was 8.2 and EC of 0.77 dS m-1 for the first experiment, and for the second the pH was 8.1 and the EC was 1.2 dS m-1. The total nitrogen content was 10.42 ± 4.94 mg L-1 and 6.2 ± 8.8 mg L-1, for the first and second experiments, respectively, with a predominance of nitrate. Plants fertigated with 100% nutrient solution had a higher relative chlorophyll index. For yield (number and mass of fruits), in the first experiment, the treatment with 25% of raw effluent was similar to the control. The average soluble solids content was 7.6 ºBrix. In relation to the second experiment, the productivity and fruit mass of the treatment fertigated with 50%SN/EPCP had no difference in relation to the control. The results indicated the possibility of reducing up to 50% of the amount of fertilizers used in the nutrient solution in combination with fish farming effluent from pangasius farming, providing similar productivity to the control. The tomato plants fertigated with 75%SN/EPCP had higher yields and better economic return without interfering in fruit quality, which had a maximum value of 10.76 ºBrix and 7.1 mg ascorbic acid 100 g-1 of fruit.