Manipueira tratada com peróxido de hidrogênio e seu uso em cultivo de coentro hidropônico

Abstract

Cassava wastewater is a liquid residue from cassava processing, rich in organic and mineral compounds, but its composition limits its use. The aim of this study was to evaluate the use of hydrogen peroxide (H2O2) in the treatment of cassava wastewater to make it a viable source of nutrients in hydroponic cultivation. In Test 1, carried out in the laboratory, a completely randomized experimental design was used in a 5x2 factorial scheme, with five concentrations of H2O2 - (0; 0.125; 0.250; 0.50 and 1 M) and two treatment times - (1 and 72 h), with four replicates. With increasing time and H2O2 doses, there was a reduction in P and NO3- levels. The amount of NH4+ and EC increased with treatment time. The presence of residual H2O2 was higher with high doses, but decreased over time. Analyzing criteria such as turbidity, organic matter, residual H2O2 and nutrient concentration for application in a hydroponic system, H2O2 concentrations of 0.125 and 0.250 M were shown to be more suitable. Trial 2 involved the cultivation of coriander using cassava treated with 0.125 M H2O2 and untreated, adapting a vertical aeroponic system. The experiment was conducted in randomized blocks with three replicates, with a total of 11 treatments, totaling 33 experimental units. The cassava reatments were inferior to the control treatment (Furlani's solution) in most of the variables analyzed. The use of 0.125 M H₂O₂ is not recommended to treat cassava for use in hydroponics due to its inviability for the development of the coriander plant. The treated cassava reduced the photosynthetic pigments of the plants, mainly with 100% replacement of the K+ requirement in the nutrient solution. The use of H₂O₂ at 0.125 M is not recommended to treat cassava wastewater for its use in hydroponics due to its unfeasibility. Treated cassava wastewater reduced plant pigments, especially with substituition of 100% K+ of requirement. The partial or total replacement of K+ with cassava starch reduced plant height and biomass. Untreated cassava starch, replacing 50% of the K+ requirement, stood out for increasing fresh mass, indicating its potential partial use as a source of potassium.