Modeling impacts of N sources on N2O emissions in long-term crop rotation system in Brazil’s Cerrado using DNDCv.CAN

Predicting N2O emissions can help identify crop production practices and environmental conditions for mitigation. The objectives were to calibrate and validate the DeNitrification-DeComposition (DNDCv.CAN) model to simulate N2O emission in crop rotation (CR) systems in Brazil’s Cerrado biome, using different N fertilizer sources. Field data were obtained from a CR experiment with maize and common beans cultivated under no-till for 10 years. Treatments were: Zero-N, calcium ammonium nitrate (CAN), urea (UR), and ammonium sulfate (AS), with 5 replicates. Measured data including N2O fluxes, NH3 volatilization, soil NH4+ and NO3-, water-filled pore space (WFPS), and grain yields were used to calibrate and validate the DNDCv.CAN. The model acceptably captured the daily N2O emissions associated with different N sources, although episodic peaks were over or under-predicted. Correlation coefficient was 0.62 during calibration, with a mean absolute error of 17 g N2O-N ha-1 day-1, close to average measured (18 g ha-1 d-1), and simulated (17 g ha-1 day-1) emissions. Accumulated measured N2O-N emissions were 1.19, 4.38, 3.17, and 2.56 kg N2O-N ha-1 for Zero-N, CAN, UR, and AS, respectively, whereas the simulated were 1.13, 3.44, 2.24, and 3.32 kg N2O-N ha-1. The NH3, NH4+, NO3-, WFPS, and yields were also fairly simulated. Soil hydrologic parameters were adjusted in the model using a built in pedotransfer function to improve the simulations, which should be further investigated. The DNDCv.CAN effectively simulated cumulative N2O emissions from different N sources applied to CR under tropical conditions, making it valuable for evaluating potential emissions and mitigation strategies.