Migration of Salt in Plough Layer and Its Determinants in Farmlands in Eastern Henan Province

【Objective】 Soil salinization due to shallow groundwater table is a main abiotic stress facing agricultural production in eastern Henan province. In this paper we analyze the migration of salt in the plough layer and its relationship with geochemistry of both surface water and groundwater at different seasons. 【Method】 The experiment was conducted in areas adjacent to the National Agro-ecological System Observation and Research Station of Shangqiu. We measured salt content, depth of groundwater table, as well as surface water runoff from 2010 to 2020. The relationship between salt content and these environmental factors was calculated using the descriptive statistics and Piper figure analysis method. 【Result】 The increased salt content in the top 0~20 cm soil layer was mainly induced by the increased precipitation. The maximum electric conductivity of the topsoil layer occurred between October and November, but it is linearly correlated to precipitation in August (y=0.794 3x+126.65, R2=0.631 3, P<0.05). The content of Ca2+, Mg2+, Na+, HCO3-, SO42-, Cl- and electric conductivity of water in the topsoil layer and the 0~100 cm soil layer, as well as depth of the shallow groundwater table in 2020 was significantly higher than those in 2015 (P<0.05). We also found that the leachate from the topsoil was geochemically similar to that of the shallow groundwater and the surface runoff in 2020, indicating that the soluble salt in the topsoil was related to both surface water and subsurface water. 【Conclusion】 The electric conductivity of water in the topsoil layer and the 0~100 cm-depth soil layer in October was both positively correlated to precipitation and the depth of the groundwater table, suggesting that salt in the topsoil was hydraulically connected to soluble salt in the surface water and the subsurface water.