Effect of Nitrification Inhibitors on N2O Emissions after Cattle Slurry Application

Abstract

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.

Using the Nitrification Inhibitor Nitrapyrin in Dairy Farm Effluents Does Not Improve Yield-Scaled Nitrous Oxide and Ammonia Emissions but Reduces Methane Flux

“…This effect is comparable with the lower mean annual N 2 O emissions (up to 46%) reported when cattle slurry was injected with commercial NIs, including 2-chloro-6-(trichloromethyl) pyridine (nitrapyrin), on Haplic Luvisol under silage maize in Germany (Herr et al, 2020). This medium-term comparison between the five commercially available NIs showed no difference in N 2 O fluxes, crop yield, or N removal when cattle slurry was mixed with NIs before injection (Herr et al, 2020). A metaanalysis on the use of nitrapyrin with slurry in corn production concluded that the manure applied with this inhibitor increased the crop yield by 7%, improved the N retention in the soil by 28%, and decreased N 2 O emissions by 51% (Wolt, 2004).…”

“…It has been reported that NIs applied to cattle slurry decrease N 2 O losses by 60% after its surface application in grassland soils from temperate regions and NI efficiency was lower in spring than that in autumn (Merino et al, 2002(Merino et al, , 2005. This effect is comparable with the lower mean annual N 2 O emissions (up to 46%) reported when cattle slurry was injected with commercial NIs, including 2-chloro-6-(trichloromethyl) pyridine (nitrapyrin), on Haplic Luvisol under silage maize in Germany (Herr et al, 2020). This medium-term comparison between the five commercially available NIs showed no difference in N 2 O fluxes, crop yield, or N removal when cattle slurry was mixed with NIs before injection (Herr et al, 2020).…”

Effect of cattle slurry application techniques on N2O and NH3 emissions from a loamy soil

“…For the calculation of annual N 2 O emission, N 2 O fluxes from each treatment and experimental year were cumulated, assuming constant flux rates between two gas samplings. Methane (CH 4 ) fluxes were also detected but are reported elsewhere ( Herr , ).…”

“…In the injection treatment, the circular base frames (inner diameter: 0.3 m) were placed area‐representative; 7% of the base frame area was covered by the area above the injection slot, 93% by the area next to the injection slot. Methodological evaluation and area‐representative placement of the dark, vented chambers were described in detail by Herr (). All frames were installed close to the maize row ( Gassner , ).…”

Field Application of Organic Fertilizers Triggers N2O Emissions From the Soil N Pool as Indicated by 15N-Labeled Digestates

“…According to IPCC (2019) 1% of NH 3 -N losses was assumed to be re-deposited as N 2 O-N. Soil organic C stocks were presumed to be stable over the experimental period, thus, CO 2 fluxes were not considered for the calculation of total GWP (Herr et al, 2020). Water filled pore space (WFPS) was calculated by Equation (6) using the measured volumetric water content (WC vol ) and porosity (P),…”