Nitrogen stabilizers mitigate nitrous oxide emissions across maize production areas of China: A multi-agroecosystems evaluation

Abstract

N stabilizers such as urease and nitrification inhibitors are potential tools for mitigating N2O emissions and improving maize yield. However, the efficacy of N stabilizers is inconsistent across a broad range of agroecosystems. To enable the large-scale use of N stabilizers for sustainable agricultural development, it is necessary to identify the benefits of N stabilizers and the driving factors that regulate their efficiency. Here, we evaluated the efficiencies of 3,4-dimethylpyrazole phosphate (DMPP) and N-(n-butyl) thiophosphoric triamide (NBPT) in four typical ecological sites with contrasting climatic and soil conditions in the maize production area of China (Gongzhuling, Wuqiao, Xinxiang, and Wenzhou). Disparate ecological sites significantly influenced the N2O emissions (0.2–19.0 kg N2O-N ha−1) and maize yields (7.5–13.9 Mt ha−1). Also, N stabilizers reduced N2O emissions by 1.3–93.9 % across the four sites. Compared to NBPT, DMPP showed higher efficiency, but the joint inhibitor (NBPT+DMPP) had non-significant effects compared to DMPP. Although N stabilizers did not significantly increase maize yield, they reduced yield-scaled N2O emissions (YSNEs) by 3.1–83.4 % (p < 0.05) across study sites. Hotspots of N2O emission occurred within two weeks after N fertilization, and the mitigation of N stabilizers on N2O emissions was strongly reduced over time. This implies the degradation velocity of N stabilizers was critical for emissions mitigation efficiency. Meanwhile, environmental factors obviously influenced N stabilizers efficiency. Random forest and correlation analyses indicated that soil pH and sand content showed positive correlations and high importance for the N2O mitigation efficiencies of N stabilizers, whereas water-filled pore space and salt content showed negative correlations and high importance. In addition, N2O mitigation efficiencies of different N stabilizers showed a different response to environmental changes, wherein higher environmental sensitivity and easy invalidation under unsuitable conditions were observed in NBPT than in DMPP. In conclusion, DMPP effectively mitigated YSNEs in all study sites, and its efficiency was closely regulated by soil pH, water-filled pore space, and soil texture. Therefore, amending soil quality may enhance the benefits of DMPP and might decrease future N2O emissions in the maize fields of China.