Split N application and DMP based nitrification inhibitors mitigate N2O losses in a soil cropped with winter wheat

Nitrogen (N) fertilization to crops might lead to formation and release of reactive N—e.g. nitrate, ammonium, ammonia, nitrous oxide (N2O) —, contributing to eutrophication, atmospheric pollution, and climate change. Use of nitrification inhibitors and splitting of N fertilizer may reduce the N2O emission from arable soils cropped with winter wheat. We tested different N fertilizers treated with 3,4-dimethylpyrazol phosphate (DMPP) and 3,4-dimethylpyrazol succinic acid (DMPSA) by applying 180 kg N ha−1 in different N splitting strategies in a full annual field experiment on a loamy soil in Southwest Germany. A threefold split fertilization led to an emission of 2.3 kg N2O–N ha−1 a−1 (corresponding to a reduction of 19%) compared to a single application of ammonium sulphate nitrate (ASN) (p = 0.07). A single application rate of ASN with DMPP resulted in an emission of 1.9 kg N2O–N ha−1 a−1 and reduced N2O emissions from an ASN treatment without NI by 33%. Calcium ammonium nitrate (CAN) with DMPSA reduced N2O emissions during the vegetation period by 38% compared to CAN without a nitrification inhibitor, but this was offset by high emissions after harvest, which was driven by soil tillage with an annual reduction of 26% (CAN: 2.9 kg N2O–N ha−1 a−1; CAN + DMPSA: 2.1 kg N2O–N ha−1 a−1; p = 0.11). Among our tested treatments, a twofold split application of ASN with DMPP efficiently reduced N2O emissions and maintained grain yield when compared to the traditional system with threefold application without nitrification inhibitor. Despite resulting in lower protein contents in the twofold split application, this treatment should be further investigated as a potential compromise between wheat yield and quality optimization and climate protection.