Distribution Characteristics and Influencing Factors of Nitrogen in Unsaturated Zone in Salinized Area of Hetao Plain

Soil nitrogen plays an important role in plant growth, soil physicochemical properties and microbial activities. In order to identify the process and mechanism of nitrogen migration in the unsaturated zone in salinized areas, a typical salinized farmland in Hetao irrigation areawas selected to explore the difference of nitrogen distribution in soil profiles and the main influencing factors through monitoring the unsaturated zone and hydrochemical statistical analysis. The results showed that the soil nitrogen content in the 0-100 cm depth of the study area was at a low level, and the average contents of NO3⁃N, NH4⁃N and NO2⁃N were 4.88, 1.63 and 0.04 mg/kg, respectively. The spatial distribution of soil nitrogen is related to soil depth and physical and chemical properties. With the increase of soil depth, NO3⁃N content showed a trend of gradual increase. The high value area is mainly distributed in the soil layer with a depth of 40-80 cm, and the content of NH4⁃N mostly concentrates in the soil layer with a depth of 60-100 cm. Soil NO3⁃N content is mainly related to soil pH, water content and water⁃soluble salt content (TDS, Cl-, SO42-、Na+), while NH4⁃N content is mainly affected by water content, clay particles and TOC content. The accumulation of NO3⁃N and NH4⁃N in soil is related to the movement of water and salt, the electrostatic adsorption of soil minerals and the control of microorganisms, which are largely affected by soil particle size composition, pH, organic matter content and competitive anionsand cations content. © 2022, Editorial Department of Earth Science. All right reserved.