Optimized fertigation mitigates N2O and NO emissions and enhances NH3 volatilizations in an intensified greenhouse vegetable system

Gaseous reactive nitrogen (GNr) losses (N2O, NO emissions and NH3 volatilization, etc.) in greenhouse vegetable fields (GVF) have received considerable critical attention. Much uncertainty still exists about GNr losses reduction under increasing vegetables demand and environmental policies in China. An experiment spanning four greenhouse vegetable growing seasons (cucumber and tomato) was conducted in North China Plain (NCP). It included four treatments, i.e., flood irrigation with no urea-N application (FU0), flood irrigation with conventional urea-N application (FUN), drip fertigation with conventional urea-N application (DUN), and drip fertigation with 50% reduction of urea-N application (DRUN). Obvious emission peaks of N2O, NO and NH3 flux were captured in the GVF after each fertilization and irrigation event. For FUN treatment, the mean annual area-scaled emissions of N2O, NO, and NH3 were 11.48, 1.66, and 44.90 kg N ha−1 yr−1, respectively; and the mean annual yield-scaled emissions of N2O, NO, and NH3 were 181.86, 23.04, and 800.07 g N t−1 yr−1, respectively. On the mean annual area-scaled and yield-scaled, the N2O emissions were significantly (P < 0.05) lower by 40.1 % and 32.3 %, and the NO emissions were lower by 23.5 % and 28.5 %, but the NH3 volatilization were significantly (P < 0.05) higher by 31.7 % and 49.0 %, respectively, for the DUN treatment than FUN. Also compared with FUN, in DRUN treatment, the mean annual area-scaled N2O emissions, NO emissions and NH3 volatilization were significantly reduced by 46.7 %, 52.4 % and 22.0 %, respectively; and the mean annual yield-scaled N2O emissions, NO emissions and NH3 volatilization were significantly reduced by 40.7 %, 57.1 % and 24.5 %, respectively. Moreover, compared with FUN treatment, DUN and DRUN treatment both alleviated the global temperature potential (GTP) at 20- and 100-year timescales. Overall, compared with conventional water and fertilizer regimes, only changing irrigation mode reduced N2O and NO emissions but increased NH3 volatilization losses in greenhouse cucumber-tomato cultivation system; reducing N application while changing irrigation methods had significant emission reduction effects on N2O, NO and NH3 at both the area-scaled and yield-scaled, and which is an effective water and fertilizer managements for greenhouse cucumber-tomato cultivation system.