Growth and Energy Characteristics of Arboreal Wood Irrigated with Treated Effluent in Degraded Soil of Semi-Arid Regions

The management of forest species in the recovery of degraded areas of semi-arid regions is mainly limited by the availability of water and nutrients. Thus, the objective of this research was to evaluate the growth, yield, and energy characteristics of the wood of two forest species of the Brazilian semi-arid region subjected to deficient irrigation with sewage effluent by drip in degraded soil. For this, a field experiment was conducted in an agroforestry system with two native species of the Caatinga biome: sabiá (Mimosa caesalpiniifolia Benth) and aroeira (Myracrodruon urundeuva Allemão), intercropped with forage palm (Opuntia stricta (Haw) Haw). The wastewater used was domestic, coming from kitchen and bathroom sinks, which underwent primary and secondary treatment. The irrigation treatments were applied in the first two years: in the first year, water supply in the volume of 0.5 L/plant/week (WS0.5), treated effluent in the volume of 0.5 L/plant/week (TE0.5), and treated effluent in the volume of 1 L/plant/week (TE1). In the second year, all treatments were leveled at 0.5 L/plant/week, and in the following two years, all irrigation treatments were discontinued. Growth variables were monitored and, at the end of the study period, wood production was calculated and energetic analyses were performed. The Richards model adjusted satisfactorily to the growth variables for the species studied. The treated effluent at a volume of 1 L/week increased the yield in condensed liquid and decreased the volatile materials (VM) of sabiá, while in aroeira it increased the basic density and VM, with a decrease in the gravimetric yield.