Greenhouse gas emissions from an irrigated dairy forage rotation as influenced by fertilizer and manure applications

Authors: Dungan, Robert - Rob; Leytem, April; Tarkalson, David; IPPOLITO, JAMES - Colorado State University; Bjorneberg, David - Dave

Submitted to: Soil Science Society of America Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/21/2016
Publication Date: 6/30/2017
Publication URL: https://handle.nal.usda.gov/10113/5801848
Citation: Dungan, R.S., Leytem, A.B., Tarkalson, D.D., Ippolito, J.A., Bjorneberg, D.L. 2017. Greenhouse gas emissions from an irrigated dairy forage rotation as influenced by fertilizer and manure applications. Soil Science Society of America Journal. 81:537-545.

Interpretive Summary: Agricultural soil management accounts for 4.6% of total U.S. greenhouse gas (GHG) emissions. Nitrous oxide is a GHG of particular interest, as it has a global warming potential 298 times that of carbon dioxide and it is an ozone-depleting substance. Because of continuing concerns with impacts from agricultural GHGs on global climate change, there is a need for improved emissions inventories, especially from irrigated cropping systems in semiarid environments. In this study conducted in south-central Idaho, our main objectives were to determine the effectiveness of various nitrogen (N) sources (including conventional granular urea, urea with inhibitors [sold as SuperU], dairy manure, and composted dairy manure) and timing (fall versus spring application of manure) on GHG emissions. The treatments were applied to silage corn (2013) and barley (2014) during the first two years of study. During corn production, cumulative nitrous oxide emissions were 53% lower with SuperU when compared with granular urea and crop yields were unaffected. Under barley, crop yields were also unaffected by treatment, but nitrous oxide emissions were not lowered by SuperU. It was also discovered that there was no timing effect on nitrous oxide emissions when dairy manure was applied in the fall or spring. Overall, nitrous oxide-N emission losses as a percentage of total N applied were less than 0.21%. Cumulative carbon dioxide emissions were similar from fall and spring manure and greater than the other N treatments during the first two years. Methane emissions were similar among the treatments during all years and negative values indicate that oxidation of atmospheric methane was greater than production in soil. This work demonstrates that SuperU can potentially reduce nitrous oxide emissions from irrigated cropping systems. The data generated from this study will also be useful for improving GHG emissions inventories from agricultural production in semiarid states.

Technical Abstract: Information is needed regarding the effect of nitrogen source on greenhouse gas (GHG) emissions from irrigated semiarid agricultural soils. We report nitrous oxide, carbon dioxide, and methane 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 nitrous oxide 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 nitrous oxide than urea with corn, whereas no emission reductions occurred in 2014 with barley. The nitrous oxide -N emission losses as a percentage of total nitrogen 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, nitrous oxide fluxes from fall and spring manure were statistically similar and greater than the other nitrogen 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 nitrogen treatments. This work demonstrates that SuperU can reduce nitrous oxide emissions from irrigated cropping systems in the semiarid western United States without affecting yields.