Effects of irrigation with wastewater on soil fertility and growth of forage palm (Opuntia tuna) and sabiá (Mimosa caesalpiniifolia Benth) under degraded soil in semi-arid Brazil.

Background: Water scarcity is growing every day, especially in semi-arid regions. Consequently, the amount of groundwater used in agriculture is strictly limited, and it has become necessary to explore alternative water sources. This study aimed to evaluate the potential of wastewater in restoring the fertility of degraded soil and in the vegetative growth of forage palm (Opuntia tuna) and sabiá (Mimosa caesalpiniifolia Benth). The experiment was conducted in the semi-arid region of Paraíba in a randomized block design arranged in a 3x2 factorial arrangement, with three types of irrigation water: i) irrigation with a volume of 500 ml plant/week with water supply; ii) irrigation with a volume of 500 ml plant/week of domestic sewage wastewater; iii) irrigation with a volume of 1000 ml plant/week of domestic sewage wastewater/ and two plant species: i) forage palm and ii) sabiá, with 10 replications. The biometric variables of the forage palm and sabiá plants were assessed. Soil samples were taken before and after irrigation to characterize soil fertility. It was found that wastewater changed pH in water, cation exchange capacity, base saturation, organic carbon, Ntotal, and available phosphorus. The treatment with the highest level of wastewater favored the vegetative growth of the forage palm, while the sabiá plants showed no significant response.