Influences of shallow groundwater depth on N 2 O diffusion along the soil profile of summer maize fields in North China Plain

• Published in: The Science of the total environment Vol. 926; p. 171861
• Main Authors: Li, Zhao, Li, Xurun, Zhang, Qiuying, Li, Fadong, Qiao, Yunfeng, Liu, Shanbao, Leng, Peifang, Tian, Chao, Chen, Gang, Cheng, Hefa
• Format: Journal Article
• Language: English
• Published: Netherlands 20.05.2024
• Subjects: Nitrous oxide (NO); Shallow groundwater depth (SGD); Summer maize field; North China plain (NCP); Soil profile; Lysimeter
• ISSN: 1879-1026
• DOI: 10.1016/j.scitotenv.2024.171861

The emissions of nitrous oxide (N O) from agricultural fields are a significant contribution to global warming. Understanding the mechanisms of N O emissions from agricultural fields is essential for the development of N O emission mitigation strategies. Currently, there are extensive studies on N O emissions on the surface of agricultural soils, while studies on N O fluxes at the interface between the saturated and unsaturated zones (ISU) are limited. Uncertainties exist regarding N O emissions from the soil-shallow groundwater systems in agricultural fields. In this study, a three-year lysimeter experiment (2019-2020, 2022) was conducted to simulate the soil-shallow groundwater systems under four controlled shallow groundwater depth (SGD) (i.e., SGD = 40, 70, 110, and 150 cm) conditions in North China Plain (NCP). Weekly continuous monitoring of N O emissions from soil surface, N O concentration in the shallow groundwater and the upper 10 cm of pores at the ISU, and nitrogen cycling-related parameters in the soil and groundwater was conducted. The results showed that soil surface N O emissions increased with decreased shallow groundwater depth, and the highest emissions of 96.44 kg ha and 104.32 kg ha were observed at G2 (SGD = 40 cm) in 2020 and 2022. During the observation period of one maize growing season, shallow groundwater acted as a sink for the unsaturated zone when the groundwater depth was 40 cm, 70 cm, and 110 cm. However, when SGD was 150 cm, shallow groundwater became a source for the unsaturated zone. After fertilization, the groundwater in all treatment plots behaved as a sink for the unsaturated zone, and the diffusion intensity decreased with increasing SGD. The results would provide a theoretical basis for cropland water management to reduce N O emissions.