N2O emissions from a loamy soil cropped with winter wheat as affected by N-fertilizer amount and nitrification inhibitor

Nitrogen (N) fertilization leads to the release of reactive N species, which can be detrimental to the environment. Nitrification inhibitors (NIs) are substances capable of retarding the oxidation of ammonium to nitrate, which can increase N use efficiency of applied N fertilizer and decrease N losses such as the release of the greenhouse gas nitrous oxide (N2O). Adaption of N fertilizer amount to plant demand might also decrease N surpluses and thus lower N2O emissions. We investigated the effects of N fertilizer amount (0, 120, 180, and 240 kg N ha−1 a−1) and the use of the NI 3,4-dimethylpyrazol phosphate, DMPP, on annual N2O emission from a soil cropped with winter wheat in a 2 year field experiment. N2O fluxes were affected by N level and by use of DMPP with higher fluxes under high N amounts and treatments without NI. Application of DMPP led to a reduction of annual emissions by 45%. Interestingly, also winter emissions (8–12 months after N fertilization) were decreased by DMPP. In this period, a complete degradation of DMPP was assumed. The reason for this effect remains unclear. Wheat yield and quality were unaffected by DMPP, whereas grain yield was increased with N fertilizer amount in the first year. Nevertheless, response curves of grain yield-related N2O emissions over all data showed lower optimal N fertilizer doses when DMPP was used. Application of DMPP at suboptimal N rates could help to achieve a better profitability with simultaneous reduction of the product scaled emission.