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 (NH ₃ ) and nitrous oxide (N ₂ O) emissions. Using data on NH ₃ and N ₂ O emissions following land-applied manures and excreta deposited during grazing, emission factors (EFs) disaggregated by climate zone were developed, and the effects of mitigation strategies were evaluated. The NH ₃ data represent emissions from cattle and swine manures in temperate wet climates, and the N ₂ O data include cattle, sheep, and swine manure emissions in temperate wet/dry and tropical wet/dry climates. The NH ₃ EFs for broadcast cattle solid manure and slurry were 0.03 and 0.24 kg NH ₃ -N kg ^-1 total N (TN), respectively, whereas the NH ₃ EF of 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 N ₂ O-N kg ^-1 TN, respectively, whereas in dry climates the EF for cattle manure was 0.0031. The N ₂ O EFs for cattle urine and dung in wet climates were 0.0095 and 0.002 kg N ₂ O-N kg ^-1 TN, respectively, which were three times greater than for dry climates. The N ₂ O 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 45-63%. These enhanced EFs can improve national inventories; however, more data from poorly represented regions (e.g., Asia, Africa, South America) are needed.
(© 2021 The Authors. Journal of Environmental Quality published by Wiley Periodicals LLC on behalf of American Society of Agronomy, Crop Science Society of America, and Soil Science Society of America.)