Submitted to: Journal of Environmental Quality
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/7/2015
Publication Date: 11/6/2015
Publication URL: http://handle.nal.usda.gov/10113/62417
Citation: Watts, D.B., Runion, G.B., Nannenga, K.E., Torbert III, H.A. 2015. Impacts of enhanced-efficiency nitrogen fertilizers on greenhouse gas emissions in a coastal plain soil under cotton. Journal of Environmental Quality. 44:1699-1710.
Interpretive Summary: Recently, there has been interest in the use of commercially available controlled and slow released N fertilizers, also known as enhanced efficiency N fertilizers. These fertilizer sources are believed to decrease nitrous oxide (N2O) production in agricultural systems by increasing crop N uptake through improved synchronization of N release with plant growth. Thus, a study was conducted to determine if these new fertilizer sources could reduce greenhouse gas emissions from a cotton cropping system. Nitrogen sources evaluated included urea, ammonium sulfate, urea-ammonium sulfate, a control released polymer coated urea (Environmentally Smart Nitrogen; ESN), stabilized urea containing a urease and nitrification inhibitor (Super Urea), poultry litter + urease and nitrification inhibitor (AgrotainPlus), and an unfertilized control. Utilization of slow or controlled released fertilizers generally did not provide an advantage in reducing greenhouse gas emissions over the standard inorganic fertilizers presently being marketed for agricultural production.
Technical Abstract: Enhanced-efficiency nitrogen fertilizers (EENFs) have the potential to increase crop yield while also decreasing N loss from agricultural fields. However, effects of EENFs on emissions of greenhouse gases (GHGs) need to be studied at a variety of locations and cropping systems. The effects of these fertilizers on GHGs have not been examined in cotton; thus, we established an experiment on a Coastal Plain soil in Central Alabama to compare EENFs to traditional N sources. Nitrogen fertilizer sources evaluated included, urea (U), ammonia sulfate (AS), urea-ammonia sulfate (UAS), controlled-release, polymer-coated urea (ESN), stabilized urea (SuperU), poultry litter (PL), poultry litter + AgrotainPlus (PLA), plus an unfertilized control. Fluxes of carbon dioxide (CO2), nitrous oxide (N2O), and methane (CH4) were monitored regularly after fertilization through harvest from 2009 to 2011 using a closed chamber method. The PL and PLA treatments tended to have higher CO2 flux than did the other N treatments and ESN and SU tended to be lowest, particularly earlier in the growing season. Nitrous oxide fluxes were highly variable and rarely affected by N treatments; PL and/or PLA tended to be higher than other N treatments but only during the first two or three sampling days in 2010 and 2011. Methane fluxes were higher in 2009, which was a wet year, than in 2010 or 2011; N treatment had little impact on CH4 flux throughout the study. Cumulative fluxes of each GHG were used to calculate global warming potential (GWP) which was highest with PL and PLA and lowest for the control, UAS, ESN, and SU. Our results suggest that poultry litter increases GHG flux in cotton. The reduction in GHG flux from EENFs was infrequently different from the standard inorganic N fertilizers, suggesting their higher cost may render them impractical at present. However, more research is still needed on the rates and timing of EENF applications as a tool in agricultural production systems.