Cotton/halophytes intercropping decreases salt accumulation and improves soil physicochemical properties and crop productivity in saline-alkali soils under mulched drip irrigation: A three-year field experiment

Abstract Soil salinization has become a severe threat deteriorating soil quality and restricting sustainable agricultural development in arid and semi-arid areas. The objective of this study was therefore to propose a new cotton/halophytes intercropping system [such as cotton/Suaeda salsa intercropping (CSSI) and cotton/alfalfa intercropping (CAI) systems] to improve soil salinization and crop production based on the traditional monoculture cotton (MC). A three-year field experiment was conducted to explore the effects of the MC, CSSI, and CAI systems on soil salt accumulation, salt removal, soil physicochemical properties, root mass density, aboveground biomass, seed cotton yield, and irrigation water productivity (IWP). Experiment treatments consisted of three cropping systems: MC, CSSI, and CAI systems, respectively. All treatments were designed using a randomized complete block with three replications. The result indicated that the CSSI and CAI systems could decrease soil EC1:5, salt accumulation, bulk density, Na+ content, and pH in no mulch strips and increase salt removal, soil porosity, and organic carbon content compared with the MC system. Compared with the MC system, the CSSI system increased root mass density in 0−20 cm soil depth. No significant differences in seed cotton yield and IWP were found among the MC, CSSI, and CAI systems in 2014. However, total aboveground biomass, seed cotton yield, and IWP were significantly higher in the CSSI and CAI systems than that of the MC system in 2015 and 2016. This study suggested that the cotton/halophytes intercropping system showed greater salt removal and crop productivity than the MC system. Therefore, the CSSI and CAI systems should be recommended as a long-term agronomic remediation method for improving soil salinization and increasing cotton yield in the arid area of northwest China.