Nitrous oxide emission reduced by coated nitrate fertilizer in a cool-temperate region

Abstract

Application of coated nitrate fertilizers is expected to be a possible strategy to reduce nitrous oxide (N2O) emissions from soils of croplands. To evaluate the effects of coated nitrate fertilizer application on N2O emissions from soils, N2O fluxes were measured in a carrot field from 2016 to 2017. Ammonium sulfate (AS), coated urea (CU; only in 2017), coated calcium nitrate (CC), and no-nitrogen (NN) fertilizers were investigated. No recognizable increase in N2O flux was observed for about 45 days after fertilization in all the plots in 2016. In 2017, significant simultaneous increases in N2O and nitric oxide fluxes (up to 142 and 436 µg N m−2 h−1, respectively) were found only in the AS plots in spring, indicating enhancement of N2O production via nitrification. After mid-July, the N2O fluxes increased temporarily with the increase in soil water content after rainfall in all the plots including the NN plots in 2016 (up to 183–342 µg N m−2 h−1) and 2017 (up to 56–86 µg N m−2 h−1), indicating N2O production mainly via denitrification. Cumulative N2O emissions did not differ significantly among all the treatments in 2016, whereas that in the CC plots was significantly lower than that in the AS plots by 36% in 2017. These results suggest that the application of coated calcium nitrate fertilizers can reduce emissions of N2O produced via nitrification and can thus reduce cumulative N2O emissions in fields where nitrification is the major N2O production process in the soil.