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Title:   Author  item
                                            MAHARJAN, BIJESH - University Of Minnesotaitem
                                            Venterea, Rodney

                                                         - *Rod*item
                                            ROSEN, CARL - University Of Minnesota
  Submitted to: Agronomy Journal
                                    Publication Type: Peer Reviewed Journal
                                    Publication Acceptance Date: 6/13/2013
                                    Publication  Date: 2/19/2014
                                    Publication URL: https://handle.nal.usda.gov/10113/59593Citation: Maharjan, B., Venterea, R.T., Rosen, C. 2014. Fertilizer and irrigation management effects on nitrous oxide emissions and nitrate leaching. Agronomy Journal. 106(2):703-714.Interpretive Summary: Management of irrigation and nitrogen fertilizer can affect crop yield, nitrogen use efficiency, and nitrogen losses to the environment in the form of nitrous oxide gas emissions and nitrate leaching to groundwater. Using multiple ("split") applications of conventional urea fertilizer over the course of the growing season can help to reduce environmental nitrogen losses, especially in sandy soils, but this requires additional labor and energy.  Another option is to use single applications of specialized nitrogen fertilizers such as urea containing urease and nitrification inhibitors and polymer-coated urea products that help to release nitrogen more gradually over the growing season. The objective of this study was to compare effects of these different fertilizer management practices on soil-to-atmosphere nitrous oxide emissions and nitrate leaching as well as their effects on corn grain yield and nitrogen use efficiency. We looked at these different practices under both irrigated and non-irrigated conditions for corn production in a loamy sand in Minnesota over two growing seasons. We found that urea containing urease and nitrification inhibitors was more effective in mitigating N2O emissions than polymer-coated urea. Irrigation significantly increased nitrate leaching, grain yield and nitrogen use efficiency; however, irrigation was beneficial in reducing nitrous oxide emissions per unit of grain produced. We also found that the nitrate that leaches into aquatic ecosystems and subsequently gets converted to nitrous oxide can be an important consideration when assessing the net greenhouse gas impacts of agricultural practices. These findings will be useful to farmers, regulators, and scientists interested in reducing the environmental impacts of agriculture while maintaining crop productivity.
                                Technical Abstract: Irrigation and nitrogen (N) fertilizer management are two important factors affecting crop yield, N use efficiency (NUE), and N losses in the form of nitrous oxide (N2O) and nitrate (NO3-). Split-application of conventional urea (SCU) and/or one-time application of specialized N fertilizers such as urea with urease and nitrification inhibitors (IU) and polymer-coated urea (PCU) may mitigate N2O emissions and NO3- leaching and improve NUE especially in sandy soils. The objective of this study was to compare effects of PCU, IU and SCU on direct soil-to-atmosphere N2O emissions, NO3- leaching, grain yield and NUE for irrigated and minimum-irrigated corn in a loamy sand in Minnesota over two growing seasons. Indirect N2O emissions due to NO3- leaching were estimated using a published emission factor. SCU increased yield and NUE compared with PCU or IU and decreased NO3- leaching compared with PCU. Direct N2O emissions were significantly greater in PCU than in IU or SCU and there was a trend for greater emissions with SCU than with IU. Irrigation significantly increased NO3- leaching, grain yield and NUE, but had no significant effect on both direct and total (direct plus indirect) N2O emissions. PCU had  significantly greater area- and yield-scaled total N2O emissions compared with IU or SCU. Thus, irrigation was beneficial when N2O emissions were considered simultaneously with grain yield; and IU was more effective than PCU in mitigating N2O emissions. Indirect emissions due to NO3- leaching accounted for 26 - 45% of total emissions, thus signifying the potential importance of indirect emissions in evaluating management effects on N2O emissions.


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