The contribution of cattle urine and dung to nitrous oxide emissions: Quantification of country specific emission factors and implications for national inventories

Publication history: Accepted - 10 April 2018; Published online - 24 April 2018.Urine patches and dung pats from grazing livestock create hotspots for production and emission of the greenhouse gas, nitrous oxide (N2O), and represent a large proportion of total N2O emissions in many national agricultural greenhouse gas inventories. As such, there is much interest in developing country specific N2O emission factors (EFs) for excretal nitrogen (EF3, pasture, range and paddock) deposited during gazing. The aims of this study were to generate separate N2O emissions data for cattle derived urine and dung, to provide an evidence base for the generation of a country specific EF for the UK from this nitrogen source. The experiments were also designed to determine the effects of site and timing of application on emissions, and the efficacy of the nitrification inhibitor, dicyandiamide (DCD) on N2O losses. This co-ordinated set of 15 plot-scale, year-long field experiments using static chambers was conducted at five grassland sites, typical of the soil and climatic zones of grazed grassland in the UK. We show that the average urine and dung N2O EFs were 0.69% and 0.19%, respectively, resulting in a combined excretal N2O EF (EF3), of 0.49%, which is b25% of the IPCC default EF3 for excretal returns from grazing cattle. Regression analysis suggests that urineN2O EFs were controlledmore by composition than was the case for dung, whilst dung N2O EFs were more related to soil and environmental factors. The urine N2O EF was significantly greater from the site in SW England, and significantly greater from the early grazing season urine application than later applications. Dycandiamide reduced the N2O EF fromurine patches by an average of 46%. The significantly lower excretal EF3 than the IPCC default has implications for the UK's national inventory and for subsequent carbon footprinting of UK ruminant livestock productsThe authors are grateful to the UK Department for Environment, Food and Rural Affairs (Defra), the Department of Agriculture and Rural Development (now the Department of Agriculture, Environment and Rural Affairs) in Northern Ireland, and the Scottish Government and the Welsh Government for financial support via the InveN2Ory project (AC0116). The work by Rothamsted Research was additionally supported by the Biotechnology and Biological Sciences Research Council (BBS/E/C/000I0320). We would also like to thank Jon Moorby (IBERS, Wales, UK), Reading University, SRUC (Scotland, UK) and Conrad Ferris (AFBI, Northern Ireland, UK), for provision of cattle urine and dung

Ammonia and nitrous oxide emission factors for excreta deposited by livestock and land-applied manure

Manure application to land and deposition of urine and dung by grazing animals are major sources of ammonia (NH3) and nitrous oxide (N2O) emissions. Utilizing data on NH3 and N2O emissions following land-applied manures and excreta deposited during grazing, emission factors (EFs) disaggregated by climate zone were developed and effects of mitigation strategies evaluated. The NH3 data represents emissions from cattle and swine manures in temperate wet climates, while the N2O data includes cattle, sheep and swine manure emissions in temperate wet/dry and tropical wet/dry climates. The NH3 EFs for broadcast cattle solid manure and slurry were 0.03 and 0.24 kg NH3-N kg-1 total N (TN), respectively, while broadcast swine slurry was 0.29. Emissions from both cattle and swine slurry were reduced between 46 and 62% with low emissions application methods. Land application of cattle and swine manure in wet climates had EFs of 0.005 and 0.011 kg N2O-N kg-1 TN, respectively, while in dry climates the EF for cattle manure was 0.0031. The N2O EF for cattle urine and dung in wet climates was 0.0095 and 0.002 kg N2O-N kg-1 TN, respectively, which were three times greater than for dry climates. The N2O EFs for sheep urine and dung in wet climates were 0.0043 and 0.0005, respectively. The use of nitrification inhibitors reduced emissions in swine manure, cattle urine/dung and sheep urine by 45 to 63%. These enhanced EFs can improve national inventories; however, more data is needed across multiple livestock species and climates

Greenhouse gas and ammonia emission mitigation priorities for UK policy targets

Acknowledgements Many thanks to the Association of Applied Biologist’s for organising and hosting the ‘Agricultural greenhouse gases and ammonia mitigation: Solutions, challenges, and opportunities’ workshop. This work was supported with funding from the Scottish Government’s Strategic Research Programme (2022-2027, C2-1 SRUC) and BBSRC (BBS/E/C/000I0320 and BBS/E/C/000I0330). We also acknowledge support from UKRI694 BBSRC (United Kingdom Research and Innovation-Biotechnology and Biological Sciences 695 Research Council; United Kingdom) via grants BBS/E/C/000I0320 and BBS/E/C/000I0330. and Rothamsted Research's Science Initiative Catalyst Award (SICA) supported by BBSRC.Peer reviewedPublisher PD

Emission factors for ammonia and nitrous oxide emissions following immediate manure incorporation on two contrasting soil types

We carried out four replicated field experiments to measure the impacts of immediate incorporation of solid manures on emissions of ammonia (NH3) and nitrous oxide (N2O). Four manures: cattle farmyard manure (FYM); pig FYM; layer manure and broiler manure were applied to the soil surface or immediately incorporated by mouldboard plough, disc or tine. Two of the experiments were carried out on a clay soil and two on a sandy soil to find out whether soil type interacted with incorporation technique to influence emissions of NH3 or N2O. Ammonia emissions were measured for 1 or 2 weeks while N2O emissions were measured for 60 days in one experiment and for a complete year in the other three experiments. Immediate incorporation by plough reduced NH3 emissions by c. 90% and by c. 60% by disc and tine (P < 0.001). There was no effect of soil type on NH3 abatement efficiency by plough or tine but the disc was less effective on the coarse sandy soil. Cross-site analysis indicated no effect of incorporation by disc or tine on emissions of N2OeN after 60 days but incorporation by plough increased direct emissions of N2OeN compared with surface application of manure (P < 0.001). Direct emissions of N2OeN, at c. 0.67% of total N applied, were substantially greater at the coarse-textured site than at the heavy clay site (0.04% of total N applied; P < 0.001). The impact of incorporation on total annual direct emissions of N2OeN differed in the three experiments where emissions were measured for a full year. There was no effect of incorporation on N2OeN emissions in the first experiment on the clay soil, and in the second experiment at this site incorporation by plough or disc, but not tine, reduced direct emissions of N2O (P ¼ 0.006). However on the sandy soil direct emissions of N2OeN were increased when manures were incorporated by plough (P ¼ 0.002) but not when incorporated by disc or tine. These results confirm that immediate incorporation of solid manures by plough is the most effective means of reducing NH3 emissions following the application of solid manures. The results also indicate that immediate incorporation of solid manures to reduce NH3 emissions does not necessarily increase emissions of N2O. However, the impacts of immediate incorporation on emissions of N2O may be related to soil type with a greater possibility of emission increases on coarse sandy soils