Soil salinity distribution and its relationship with soil particle size in the lower reaches of Heihe River, Northwestern China

Abstract

Recognition of the vertical and spatial distribution characteristics of soil salinity and its influencing factors have become a prerequisite for formulating strategies for the utilization and sustainable development of soil resources. The changes and characteristics of the particle size distribution (PSD) and its relationship with soil salinity were studied using the combined methods of laser diffraction analysis, the textural triangle and fractal analysis in the lower reaches of Heihe River, Northwestern China. The soil salinity showed clear surface accumulation characteristics. Soil salinity profiles in the area were classified into four types: Equably distribution profiles, bottom accumulation profiles, surface accumulation profiles, and oscillation profiles. In the study area, moderate salinized soil, heavy salinized soil and saline soil accounted for 5.71, 25.71, and 42.87 %, respectively. It was shown that soil salinization in the lower reaches of Heihe River is severe. Soil salinity and its spatial distribution is mainly controlled by SO4 2−, Cl−, Na+ + K+, Mg2+, and Ca2+. The soil texture of the topsoil can be classified as sand, sandy loam, silt loam, and silt. The silt and sand occupied the majority of the PDS at different soil depths. There was a decrease in soil salinity and soil particle size with increasing soil depth. The fractal dimension of PSD ranged from 2.503 to 2.555, the higher the sand content, the lower the fractal dimension. A considerable linear relationship also exists between the fractal dimension and the contents of soil clay, silt, sand and the soil salinity. Results show that the soil texture features dominated the soil salinity distribution.