Optimized application of combined nitrogen and microbial decomposing inoculants increases wheat (Triticum aestivum L.) physiological growth and mitigates global warming potential under different water regimes

Excessive nitrogen fertilizer (urea) application has caused several environmental problems, such as increased greenhouse gas (GHG) emissions, leading to global warming (GWP). Monitoring nitrogen fertilizer is crucial for winter wheat production. Very limited studies have comprehensively evaluated the influences of microbial decomposing inoculants on global warming potential from winter wheat experiments under different fertigation modes and water regimes. A pot experiment was conducted to determine the effects of co-application of nitrogen fertilizer and microbial decomposing inoculants (MDI) on GWP and winter wheat physiological growth under different water regimes. The two water levels were: W1 (85–80% θFC) and W2 (55–50% θFC). The six fertigation modes were: F1 (Normal irrigation water), F2 (MDI), F3 (MDI + 100% nitrogen), F4 (MDI + 50% nitrogen), F5 (Normal irrigation water + 100% nitrogen) and F6 (Normal irrigation water + 50% nitrogen). The total nitrogen rate was 240 kg ha−1. The results revealed that the co-application of nitrogen and MDI significantly (p < 0.05) affected GHG (N2O, CH4, and CO2) emissions, GWP, and physiological growth. Compared with W1F3, the fertigation mode of W1F4 significantly (p < 0.05) reduced GWP by 62%, while sustaining wheat growth and photosynthetic rate (Pn). Water deficit significantly (p < 0.05) reduced wheat Pn and dry mass by 68% and 46%, respectively when comparing the well-watered (W1F1) to the water-stressed (W2F1) treatment. Co-application of 50% nitrogen and MDI significantly (p < 0.05) increased wheat Pn and dry mass under water deficit conditions by comparing W2F4 to W2F1. Therefore, the co-application of 50% nitrogen and MDI would be recommended in field experiments for sustainable wheat production and at a mitigated GWP in the North China Plain.