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| DOI：10.13522/j.cnki.ggps. 2023468 |
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| Experimental study on the effects of groundwater depth on groundwater and soil moisture and salinity distribution in agricultural fields in Yucheng Area, North China Plain |
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LI Xurun, LI Zhao, ZHANG Qiuying, LI Fadong, FU Weizhang
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1. College of Resources and Environment, Shandong Agricultural University, Taian 271018, China; 2. Key Laboratory of Ecosystem Network Observation and Modeling, Institute of Geographic Sciences and Natural Resources Research, Chinese Academy of Sciences, Beijing 100101, China; 3. Shandong Yucheng Agro-ecosystem National Observation Research Station, Yucheng Comprehensive Experiment Station, Chinese Academy of Sciences, Yucheng 251200, China; 4. Chinese Research Academy of Environmental Sciences, Beijing 100012, China; 5. College of Resources and Environment, University of Chinese Academy of Sciences,
Institute of Geographic Sciences and Natural Resources Research, CAS, Beijing 100190, China
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| Abstract: |
| 【Background】Soil salinization is one of the greatest global challenges that seriously affects agricultural productivity and environmental sustainability, the severity of soil salinization is reportedly increasing in China, India, Pakistan, Australia, China, Middle Eastern countries and the US. The depth of shallow groundwater has an important influence on land salinization, and in the past, groundwater in North China Plain was constantly used for irrigation, leading to a continuous decline in the groundwater level. In recent years, both deep and shallow groundwater levels in North China Plain have risen as a result of the ban on excessive use of groundwater in North China Plain and the implementation of the South-to-North Water Diversion Project. Under the new situation of the rising groundwater level in North China Plain, how the characteristics of water and salt transport in the farmland of North China Plain will change, and its response mechanism to the depth of groundwater burial needs to be further explored. Shallow groundwater affects crop growth and yield by altering the moisture and salinity of the soil profile in agricultural fields, and the process is complicated by its hydro-chemical changes. 【Objective】In order to study the distribution pattern of soil water salinity content and its effect on crop yield at different shallow groundwater burial depths, as well as the changes in groundwater chemistry. 【Method】Relying on the volumetric evapotranspiration meter sample site, four groundwater depth treatments were set up, namely G0 (no groundwater burial depth), G1 (groundwater burial depth of 40 cm), G2 (groundwater burial depth of 70 cm), G3 (groundwater burial depth of 110 cm) and G4 (groundwater burial depth of 200 cm), and G4 (groundwater burial depth of 150 cm), using weekly as the monitoring frequency, to monitor changes in the content of various ions in shallow groundwater and changes in moisture and salinity in the soil of summer maize fields under evapotranspiration conditions.【Result】①The deeper the groundwater burial depth, the lower the water content and salinity of the surface layer (0-20 cm) soil. Compared with G0, the water content of surface soil in G1 and G2 increased significantly by 27.54% and 26.97%, respectively, and G3 increased by 8.25%, while G4 increased by only 2.18%; Surface soil salinity increased by 0.79, 0.47, and 0.43 g/kg in G1, G2, and G3 treatments, respectively, while it decreased by 0.01 g/kg in G4 treatment. Among them, salts in G1, G2 and G3 treatments mainly accumulated in the soil surface layer, while G4 treatment mainly accumulated in the 40~70 cm soil layer;② There was a linear relationship between groundwater depth and surface (0-20 cm) soil water content and salinity, with surface soil water content decreasing by 0.53% and salinity decreasing by 0.065 g/kg for every 0.1 m increase in groundwater depth. ③The main cations in shallow groundwater are Na+ and Mg2+, and the main anions are SO42- and HCO3-. Concentrated rainfall can change the ion type in shallow groundwater from Na-Cl-SO4 to Na-HCO3; ④ Under strong surface evaporation, the ion concentration in water rised faster the shallower the depth of groundwater table. Among them, HCO3- concentration fluctuated greatly in each treatment, with a general upward trend; while NO3-, due to the effect of fertilizer application, the shallower the depth of groundwater burial the faster NO3- peaked in the shallow groundwater and the higher the concentration. 【Conclusion】In this study, increasing the depth of shallow groundwater to 1.5 m can effectively reduce the water-salt content of the surface soil, reduce the influence of shallow groundwater by evaporation, precipitation, and other climatic conditions. A shallow groundwater depth of 1.2 m was optimal for summer maize growth and yield. The study of the effects of different shallow groundwater burial depths on soil moisture and salinity in agricultural soils helps to understand the migration of water and salt in agro-ecosystems and the mechanism of groundwater-soil interaction, which is of great importance for preventing soil salinization and safeguarding crop yields. |
| Key words: groundwater burial depth; soil water content, soil salinity; groundwater salt ions; North China Plain |
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