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Because of the presence of shallow water tables and consequent secondary salinization in irrigated areas of Xinjiang China, there is an urgent need for installation of drainage systems to control the salinity levels in the crop rootzone. The goal of this study was to compare the midterm effects of the open ditch (depth of 2.2 m) and subsurface pipe (depth of 2.2 m) drainages on soil salinity, drainage, groundwater, cotton biomass, yield, and economic benefits while using drip irrigation under mulch (plastic film). We conducted a field experiment for eight consecutive years (2012–2019) in Shawan County of Xinjiang, China. Our experimental results indicated that open ditch and subsurface pipe drainages each reduced total soil salinity, improved saline–sodic soils, and controlled groundwater level, which caused a significant increase in the cotton biomass and yield. The open ditch drainage treatment (ODDA) represented a better desalination effect than the subsurface pipe drainage treatment (SPDA) at 73% and 81%, respectively. The electrical conductivity and pH of ODDA and SPDA water samples decreased as the soil salinities decreased over time. We used the farmland conditions from 2012 as the baseline for our experiment and evaluated how these baseline conditions changed over time in response to these treatments. Compared to this baseline, the cotton yield of ODDA and SPDA treated farmland increased by 18.30 times and 19.96 times in 2019, respectively. The investment payback periods for ODDA and SPDA treatments were 7.59 and 6.34 years, respectively, and their returns on investment were 12% and 30%, respectively. The midterm economic benefits of subsurface pipe drainage were more prominent than those of open ditch drainage. These results provide a reference for improving, developing, and utilizing soil saline–sodic land, and the sustainable development of agriculture in arid areas. [ABSTRACT FROM AUTHOR]

Winter irrigation is an effective means of salt leaching, but the long-term effect on salinity is unclear. In 2008–2019, three different soil types of farmlands were selected as the study area by drip irrigation under film mulch combined with periodic winter irrigation in the non-growth period. The salinity of 0–150 cm as well as the survival rate and yield of cotton in the non-growth and growth periods were monitored, respectively. The mass fraction of soil salt decreased rapidly under winter irrigation, and then, the salt content in each observation layer increased with years of cultivation. After 10 years of application, the soil salt content basically stabilized at a low level. In 2008, the salinity of the 0–150 cm observation layer of loamy clay, loam, and sandy loam varied within 6–60, 10–65, and 4–22 g·kg−1; after four winter irrigations in 2019, corresponding values dropped below 5.74, 3, and 4.76 g·kg−1, respectively. The salinity returns rate of the different observation layers all exceeded 40%. The desalination rate of the different soils after four winter irrigations all exceeded 63.52%. Cotton survival rate and yield in different soils were directly proportional to each other. After the second winter irrigation, the survival rates on the different soils all exceeded 60%. The results of this study can provide technical support for the sustainable development of different types of soil, farmers' income increase, and salinization land improvement. [ABSTRACT FROM AUTHOR]