Enhanced‐efficiency nitrogen fertilizers reduce winter losses of nitrous oxide, but not of ammonia, from no‐till soil in a subtropical agroecosystem

Nitrogen (N) gas losses can be reduced by using enhanced‐efficiency N ( EEN ) fertilizers such as urease inhibitors and coating technologies. In this work, we assessed the potential of EEN fertilizers to reduce winter losses of nitrous oxide (N 2 O‐N) and ammonia ( NH 3 ‐N) from a subtropical field experiment on a clayey Inceptisol under no‐till in Southern Brazil. The EEN sources used included urea containing N ‐( n ‐butyl) thiophosphoric triamide ( UR + NBPT ), polymer‐coated urea (P‐ CU ) and copper‐and‐boron‐coated urea (CuB‐ CU ) in addition to common urea ( UR ) and a control treatment without N fertilizer application. N 2 O‐N and NH 3 ‐N losses were assessed by using the static chamber method and semi‐open static collectors, respectively. Both N 2 O‐N and NH 3 ‐N exhibited two large peaks with an intervening period of low soil moisture and air temperature. Although the short‐term effect was limited to the first few days after application, UR  + NBPT urea decreased soil N 2 O‐N emissions by 38% relative to UR . In contrast, urease inhibitor technology had no effect on NH 3 ‐N volatilization. Both coating technologies (CuB‐ CU and P‐ CU ) were ineffective in reducing N losses via N 2 O production or NH 3 volatilization. The N 2 O emission factor (% N applied released as N 2 O) was unaffected by all N sources and amounted to only 0.48% of N applied—roughly one‐half the default factor of IPCC Tier 1 (1%). Based on our findings, using NBPT ‐treated urea in the cold winter season in subtropical agroecosystems provides environmental benefits in the form of reduced soil N 2 O emissions; however, fertilizer coating technologies provide no agronomic ( NH 3 ) or environmental (N 2 O) advantages.