We determined N2O fluxes from an unfertilized control (CON), from a treatment with mineral N‐fertilizer (MIN), from cattle slurry with banded surface application and subsequent incorporation (INC), and from slurry injection (INJ) to silage maize (Zea mays, L.) on a Haplic Luvisol in southwest Germany. In both years, amount of available N (total N fertilized + Nmin content before N application) was 210 kg N ha−1. In the slurry treatment of the 1st year, 140 kg N ha−1 were either injected or incorporated, whereas 30 kg N ha−1 were surface applied to avoid destruction of the maize plants. In the 2nd year, all fertilizers were applied with one single application. We calculated greenhouse gas emissions (GHG) on field level including direct N2O emissions (calculated from the measured flux rates), indirect N2O emissions (NH3 and NO3 - induced N2O emission), net CH4 fluxes, fuel consumption and pre‐chain emissions from mineral fertilizer. NH3 losses were measured in the 2nd year using the Dräger‐Tube Method and estimated for both years. NH3 emission was highest in the treatment without incorporation. It generally contributed less than 5% of the greenhouse gas (GHG) emission from silage maize cultivation. The mean area‐related N2O emission, determined with the closed chamber method was 2.8, 4.7, 4.4 and 13.8 kg N2O‐N ha−1 y−1 for CON, MIN, INC, and INJ, respectively. Yield‐related N2O emission showed the same trend. Across all treatments, direct N2O emission was the major contributor to GHG with an average of 79%. Trail hose application with immediate incorporation was found to be the optimum management practice for livestock farmers in our study region.

Cattle slurry injection (INJ) has shown to be an efficient measure to reduce ammonia (NH3) losses from soils but it might also significantly increase nitrous oxide (N2O) emissions, which can dominate the total greenhouse gas (GHG) release in silage maize production (Zea mays L.). Nitrification inhibitors (NIs) are known for their potential to mitigate N2O. Therefore, we tested the effect of NIs added to cattle slurry before INJ on N2O fluxes from a Haplic Luvisol under silage maize in southwest Germany. We determined N2O fluxes at least weekly, with the closed chamber method over two full years. NIs differ in their chemical and physical behavior and we therefore tested a range of commercially available NIs: 3,4-dimethylpyrazole phosphate, 3,4-dimethylpyrazol succinic acid, a mixture of both, nitrapyrin, dicyandiamide, and 1,2,4 triazol and 3-methylpyrazol. Although not significant, INJ treatments with NI showed lower mean annual N2O emissions than the INJ treatment without NI in the 1st year. The emission reduction by NI of 46% in the 2nd year was statistically significant. In both years, we did not find any difference in N2O release, crop yield, or nitrogen removal between the different NI treatments. In the 1st year, which was extraordinary dry and warm, emission factors (EFs) for all INJ treatments were 4 to 8-fold higher than default EF from the IPCC. Even in the 2nd year, only three NI treatments reached EFs within the range provided by the IPCC. Direct N2O accounted for between 81 and 91% of the total GHG emission. Area- and yield-related GHG emission of the broadcast application with subsequent incorporation was in both years in the statistical class with lowest emission. In contrast, INJ with NIs showed similar GHG emissions in only one year, and consequently, incorporation was found to be the optimum management practice for livestock farmers in our study region.

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