Nutritional balance and production of sugarcane irrigated with treated wastewater through subsurface drip

Low sugarcane productivity in Brazil is due to insufficient rainfall and would benefit from irrigation. Thus, the application of treated wastewater, such as treated domestic sewage (TDS), becomes an alternative water and nutrient source for sugarcane cultivation. The objective of this research was to evaluate the productivity, soil fertility, fertilizer savings and nutritional balance during 2 years of sugarcane crops using TDS applied through subsurface drip irrigation. The experiment was conducted in the field under a randomized block design with five treatments, with two dripline depths and two water qualities (domestic sewage and surface reservoir) and finally non-irrigated plots. Productivity, nutritional balance, and soil fertility were measured during two harvest cycles. The irrigated treatments presented greater productivity in both ratoons (28.5% and 42.8%) and, consequently, higher nutrient extraction compared to the input, which provided a reduction of average soil fertility during the cycles evaluated. The dripline depths and the water qualities applied influenced concentrations of sodium in the soil profile, with highest levels in TDS treatments. Treatments with TDS also showed, in both cycles, significant savings of up to 100% on the application of nitrogen and phosphorus. Therefore, TDS applied by subsurface drip can be used as an irrigation alternative in sugarcane cultivation.