Nitrogen Losses in Field Irrigated with Domestic Sewage Through Subsurface Drip Irrigation for Sugarcane in Brazil

Conflicts over water use and the high demand for food and biofuels have motivated the use of wastewater in irrigated agriculture. The study aimed to evaluate the nitrogen losses through nitrate leaching and nitrous oxide emission for sugarcane first ratoon irrigated by subsurface drip (SDI) with fresh water and treated domestic sewage (TDS) and traditional crop management under rainfed conditions. Therefore, the following treatments were implemented: T1—non-irrigated and topdressing fertilization; T2—irrigated with TDS, with fertigation; T3—irrigated with TDS, without fertigation; T4—irrigated with fresh water, with fertigation; T5—irrigated with fresh water, without fertigation. The nitrogen ( N ) fertilizer applied corresponded to 120 kg ha −1 to all treatments, with broadcast fertilization for nonirrigated cropping and, for the irrigated plots, it was performed by supplementing the concentration of the nutrients in the TDS and freshwater. All the fertigated treatments had lower leaching losses than nonirrigated treatment with topdressing fertilization, the total N loss for nonirrigated plots differed significantly from irrigated treatments, with a total loss of 16.36 kg N ha −1 . The application of TDS by SDI to meet the needs for water and nutrients resulted in a decrease of N losses by NO 3 − leaching and N 2 O emissions, compared with traditional sugarcane cultivation under non-irrigated with topdressing fertilization (total of 16.36 kg ha −1 for T1), being the nitrate leaching the main factor that contributed to the N loss with a loss of 71% for T1 (11.50 kg ha −1 ). Irrigation with TDS, in addition to providing nutrients and water for sugarcane cultivation, can help minimize nitrogen contamination compared to conventional management methods through SDI systems.