Ammonia and greenhouse gas emissions from a subtropical wheat field under different nitrogen fertilization strategies

Minimizing soil ammonia (NH3) and nitrous oxide (N2O) emission factors (EFs) has significant implications in regional air quality and greenhouse gas (GHG) emissions besides nitrogen (N) nutrient loss. The aim of this study was to investigate the impacts of different N fertilizer treatments of conventional urea, polymer-coated urea, ammonia sulfate, urease inhibitor (NBPT, N-(n-butyl) thiophosphoric triamide)-treated urea, and nitrification inhibitor (DCD, dicyandiamide)-treated urea on emissions of NH3 and GHGs from subtropical wheat cultivation. A field study was established in a Cancienne silt loam soil. During growth season, NH3 emission following N fertilization was characterized using active chamber method whereas GHG emissions of N2O, carbon dioxide (CO2), and methane (CH4) were by passive chamber method. The results showed that coated urea exhibited the largest reduction (49%) in the EF of NH3-N followed by NBPT-treated urea (39%) and DCD-treated urea (24%) over conventional urea, whereas DCD-treated urea had the greatest suppression on N2O-N (87%) followed by coated urea (76%) and NBPT-treated urea (69%). Split fertilization of ammonium sulfate-urea significantly lowered both NH3-N and N2O-N EF values but split urea treatment had no impact over one-time application of urea. Both NBPT and DCD-treated urea treatments lowered CO2-C flux but had no effect on CH4-C flux. Overall, application of coated urea or urea with NPBT or DCD could be used as a mitigation strategy for reducing NH3 and N2O emissions in subtropical wheat production in Southern USA.

NH3, N2O, CO2 and CH4 emissions from the control (CK), one-time application of urea (U), one-time application polymer-coated urea (CU), split application of urea (SU), split application of ammonia sulfate-urea (SASU), urea plus urease inhibitor NBPT (U + N) and urea plus nitrification inhibitor DCD (U + D) treatments. The arrows indicate the time of fertilization for the split application.140