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Greenhouse Gas Emissions from an Irrigated Dairy Forage Rotation as Influenced by Fertilizer and Manure Applications

Robert S. Dungan, April B. Leytem, David D. Tarkalson, James A. Ippolito, David L. Bjorneberg
Soil Science Society of America journal 2017 v.81 no.3 pp. 537-545
Hordeum vulgare, Medicago sativa, Zea mays, agricultural soils, alfalfa, autumn, barley, carbon dioxide, composted manure, conventional tillage, corn, crop rotation, crop yield, dairy manure, forage, forage crops, greenhouse gas emissions, greenhouse gases, irrigated farming, methane production, nitrification inhibitors, nitrogen, nitrogen content, nitrous oxide, oxidation, semiarid soils, silage, spring, sprinkler irrigation, urea, urea fertilizers, urease, Western United States
Core Ideas Urea formulated with urease and nitrification inhibitors can reduce N₂O emissions. Nitrous oxide‐N emission losses as a percentage of total N applied were ≤0.21%. Timing of manure application did not affect N₂O, CO₂, and CH₄ fluxes. Soil was a CH₄ sink and emissions were not influenced by N source. Information is needed regarding the effect of N source on greenhouse gas (GHG) emissions from irrigated semiarid agricultural soils. We report N₂O, CO₂, and CH₄ emissions from a silage corn (Zea mays L.) (2013)–barley (Hordeum vulgare L.) (2014)–alfalfa (Medicago sativa L.) (2015) rotation under conventional tillage and sprinkler irrigation. We evaluated the effectiveness of an enhanced‐efficiency fertilizer (SuperU, a stabilized granular urea with urease and nitrification inhibitors) to reduce N₂O emissions compared with granular urea and to determine GHG emissions from fall‐applied dairy manure or composted dairy manure and spring‐applied dairy manure. Nitrogen was applied during the first 2 yr of the study. SuperU plots emitted 53% less N₂O than urea with corn, whereas no emission reductions occurred in 2014 with barley. The N₂O‐N emission losses as a percentage of total N applied were 0.21 and 0.04% for urea and SuperU in 2013, respectively, with losses of 0.05% from both urea fertilizers in 2014. On average, N₂O fluxes from fall and spring manure were statistically similar and greater than the other N treatments in 2014 and a lasting manure treatment effect on emissions occurred under alfalfa. Carbon dioxide fluxes were greatest from fall‐ and spring‐applied manure during the first 2 yr. Methane fluxes were negative, indicating microbial oxidation, and no differences occurred among the treatments. Corn, barley, and alfalfa yields were similar among all N treatments. This work demonstrates that SuperU can reduce N₂O emissions from irrigated cropping systems in the semiarid western United States without affecting yields.