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

Minimizing soil ammonia (NH) and nitrous oxide (NO) 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 NH and GHGs from subtropical wheat cultivation. A field study was established in a Cancienne silt loam soil. During growth season, NH emission following N fertilization was characterized using active chamber method whereas GHG emissions of NO, carbon dioxide (CO), and methane (CH) were by passive chamber method. The results showed that coated urea exhibited the largest reduction (49%) in the EF of NH-N followed by NBPT-treated urea (39%) and DCD-treated urea (24%) over conventional urea, whereas DCD-treated urea had the greatest suppression on NO-N (87%) followed by coated urea (76%) and NBPT-treated urea (69%). Split fertilization of ammonium sulfate-urea significantly lowered both NH-N and NO-N EF values but split urea treatment had no impact over one-time application of urea. Both NBPT and DCD-treated urea treatments lowered CO-C flux but had no effect on CH-C flux. Overall, application of coated urea or urea with NPBT or DCD could be used as a mitigation strategy for reducing NH and NO emissions in subtropical wheat production in Southern USA.