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 (N2O- N) and ammonia (NH3- 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-c oated 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. N2O- N and NH3- N losses were assessed by using the static chamber method and semi-o pen static collectors, respectively. Both N2O- N and NH3- N exhibited two large peaks with an intervening period of low soil moisture and air temperature. Although the short-t erm effect was limited to the first few days after application, UR + NBPT urea decreased soil N2O- N emissions by 38% relative to UR. In contrast, urease inhibitor technology had no effect on NH3- N volatilization. Both coating technologies (CuB- CU and P- CU) were ineffective in reducing N losses via N2O production or NH3 volatilization. The N2O emission factor (% N applied released as N2O) 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-t reated urea in the cold winter season in subtropical agroecosystems provides environmental benefits in the form of reduced soil N2O emissions; however, fertilizer coating technologies provide no agronomic (NH3) or environmental (N2O) advantages.