Water relations and productivity of sugarcane irrigated with domestic wastewater by subsurface drip

The water scarcity is one of the main factors contributing to the reduction of productivity in agricultural crops, and the use of alternative water source in the irrigation is an option to minimize water stress. The objective of this study was to evaluate the water relations, vegetative growth, productivity and technological quality of sugarcane irrigated with treated domestic sewage by subsurface drip during its second ratoon. The research was performed at the School of Agricultural Engineering of the State University of Campinas-SP, through a randomized block design with five treatments, with two depths of dripper lines installation and two water sources, which are: irrigation with wastewater from domestic sewage applied to 0.20 m depth, and to 0.40 m, irrigation with fresh water from a surface reservoir to 0.20 m depth and to 0.40 m and finally non-irrigated plots. Irrigation management was performed following the soil water balance through the time-domain reflectometry technique and all irrigated treatments were fertigated according to the water source applied. Leaf water potential, chlorophyll, gas exchange, leaf nutrition, vegetative growth, productivity and quality technological were measured during the second ratoon of sugarcane. Soil moisture changed according to the depth of the dripper lines installation, being higher for irrigated treatments. The leaf water potential, chlorophyll, gas exchange and nitrogen and magnesium concentration in the leaves also were higher for irrigated plots. The irrigated treatments with sewage had the largest stem and sugar yield compared with the rainfed, being the dripper line irrigated with sewage to 0.20 m presenting the greatest differences reaching 95% and 86% with a productivity of 233.69 Mg ha−1 and 37.06 Mg ha−1 for stem and total recoverable sugar, respectively; however, there were not significant differences between the irrigated plots. The technological quality of sugarcane was considered appropriate to all treatments.