Spatio-temporal distribution of reactive nitrogen species in relation to wheat cultivation in Bangladesh

Farmers generally use more nitrogen fertilizer than others for crop production in Bangladesh because of its visible growth symptoms. Such practice is responsible for extra reactive N (Nr) load to the environment, but data are not available. Nitrous oxide (N2O) data were collected from a field trial following static closed-chamber technique, which were used for calibration and validation of DeNitrification and DeComposition model along with soil clay fraction, pH, bulk density and organic carbon contents. The model was well fitted and estimated about 364 g N2O–N ha−1 emission in Rajshahi region and only 15 g N2O–N ha−1 in Barisal region. District-wise N2O–N emissions varied from < 1–15.96 t season−1. In 2011–2016, N2O–N emissions from wheat fields were about 103–129 t yr−1 in Bangladesh. The model estimated nitric oxide (NO), ammonia (NH3) and nitrate (NO3) fluxes varied from 0.012 to 0.447, 7 to 12.5 and 0 to 4.7 kg N ha−1, respectively, under ambient temperature condition. In about 79% yield variabilities were explainable by N2O emission. In dominant wheat growing areas, if sowing is started from 15 to 30 November, N2O emission could be reduced by 8–40% with 5–13% reduction in yields compared to 10 November sowing. In similar areas and same sowing date with 1.5 °C temperature rise, N2O emission may increase by 8–45% and wheat yield might reduce by about 4–8%. Time of seeding and other cultural management in wheat cultivation would be the main avenue for reducing Nr loads to the environment.