Soil salinity dynamic change and desalting effect under different improvement measures in severe salinity soil in Xinjiang

Abstract: Soil salinization can directly affect crop production, and threaten the sustainable utilization of irrigated land. This problem is particularly prominent in Xinjiang Uyghur Autonomous Region, where has much uncultivated arable land, and soil saline and secondary salinization after land development. In this study, field experiments were conducted to investigate the influence factors and characteristics of soil salt movement, as well as elution desalination in different improvement measures treatments of severe saline soil through 3-year experiment. Five improvement treatments were designed including agricultural improvement (mainly including mulched with plastic film, deep plowing, returning straw and organic fertilizer), salt-isolation to root zone plus agricultural improvement, subsurface pipe drainage plus agricultural improvement, chemical modified plus agricultural improvement, and control without any human activity on new reclamation farmland in Xinjiang Province. The results indicated that salt content of the soil was mainly affected by evaporation, irrigation amount and groundwater depth; the soil salt content was significantly negative correlated with irrigation amount (correlation coefficient=-0.871, P=0.0039) and groundwater depth (correlation coefficient=-0.831, P=0.0072), positively correlated with monthly evaporation (correlation coefficient=0.754, P=0.0084), but not significantly correlated with mean monthly temperatures; The effect of irrigation amount on the 0-80 cm soil salinity in entire growth period was the most prominent. In the 3-years, dynamic changes in soil saline content varied with different improvement methods: high salt content accumulated in the top and deep layers of soil throughout the growing period for agricultural improvement treatment; obvious salt accumulation in the top layer of soils for salt-isolation to root zone plus agricultural improvement; the salt content at the deep layer higher than in subsurface layer for pipe drainage plus agricultural improvement, and chemical modified plus agricultural improvement treatment. The desalination rate of soils after the first-year was not satisfactory, and that after the second-year was significantly improved. The desalination rate of soil in the treatment of salt-isolation to root zone plus agricultural improvement and subsurface pipe drainage plus agricultural improvement treatment was up to 44% in the second year, but was significantly decreased in the third-year due to the reduction of the total salt content of the soil. Overall, all the treatments could result in the decrease of soil salt content. Among them, the soil desalinization rates of agricultural improvement plus subsurface pipe drainage and salt-isolation to root zone plus agricultural improvement were 61.33% and 59.37% respectively in the 0 to 80 cm layers, which were better than the other treatment. The soil desalinization rate of chemical modified plus agricultural improvement treatment was 55.32% in the 0 to 40 cm layers, higher than agricultural improvement 45.42%. The results can provide valuble information for saline soil improvement and rational development and effective utilization of saline soils in the Xinjiang arid zone.