Uso da água cinza filtrada em cultivo irrigado na agricultura familiar no Sertão do Pajeú

Abstract

The water is a limited resource and the intensive use of this natural resource in the agriculture has put pressure on water reserves, making it necessary to search for sustainable alternatives make water available for other activities, with emphasis on the reuse from domestic gray water. Than, the this research aimed to characterize the quality domestic effluent and its effect on the irrigation of the grain sorghum crop IPA-1011, submitted to different conditions of available water in the soil. The research was carried out with filtered gray water collected in a rural residence that uses a physical treatment system for gray water reuse (RAC). The characterization of the effluent from the RAC was carried out, as well as the supply water used by the resident family, which parameters such as EC, pH, turbidity and the presence of the chemical elements calcium, sodium, chloride, bicarbonate, potassium, boron, copper were determined , iron, manganese and magnesium, tests were carried out with different configurations of filtering layers, in order to monitor the quality of the effluent after a second filtration, in addition to determining the flow time and instantaneous flow rate in saturated and unsaturated filtering layers. The filtered domestic effluent was also destined for sorghum irrigation, in randomized block design with a 5 x 2 + 1 factorial scheme with three replications, having how irrigation depths with filtered gray water as the first factor (Ɵ residual, 20%, 40%, 60%, and 100% of the water available in the soil), with the second factor referring to the irrigation shifts of 3 and 6 days, and an additional treatment that was conducted to 100% of the water available in the soil using water from urban supply. It was found that the supply water and gray water, both collected in the rural residence, were classified for irrigation purposes as C3S1 with high risk of salinization and low risk of sodicity, and the increase in chemical products used in the residence did not change the classification, but raised by 61.8% the salinity of gray water compared to the supply water. The introduction of wood shavings as one of the filtering elements proved to be efficient in improving the final flow of the filters, in addition to preventing water retention on the surface of the filters. The biometrics carried out during the sorghum cultivation showed that irrigation with filtered gray water favored the development of the crop when compared to plants of this plant species subjected to dryland conditions and that plants grown with 60% of the available water in the soil presented a satisfactory performance for the analyzed parameters, standing out as a promising reference level.