暗管与竖井排水工程改良新疆盐渍土的设计与效果评价

为探讨干旱区盐渍化农田水利改良措施的可行性，在新疆玛纳斯河流域安集海灌区进行了田间暗管与竖井排水工程试验，分别在距离暗管0.5 m（P1）、7.5 m（P2），距离竖井0.5 m（S1）、30 m（S2）和60 m（S3），以及未铺管区（CK）域设置7处观测区，评估农田排水措施在盐渍土改良期间的排水功能、土壤脱盐效果，同时监测棉花生长与地下水位动态。结果表明：5 a排水改良期间，0～80 cm深度土壤含盐量的总体降幅达到29.2 g/kg，棉花干物质量和籽棉产量年际增幅分别为22%和28%，浅层地下水位年际降幅1.16 m；改进的暗管与竖井协同排水相比单独应用暗管排水量与地下水位年际降幅分别增加了118%，进一步减少了盐分淋溶时期的深层渗漏量。研究结果可为干旱盐渍区的水土资源合理利用提供科学和理论依据。

Design and effect evaluation of subsurface pipe and vertical shaft drainage project to improve saline soil in Xinjiang

Soil salinization has greatly threatened agricultural productivity and land resources in arid desert regions. The field soil improvement needs to meet the large-scale production requirements fully. Soil salinization can affect 20% of the irrigated land on a global scale, leading to a noticeable reduction in crop growth and yield. One of these regions include the Xinjiang province, China, which is located in the inland arid desert regions of Central Asia. The desert covers an area of 4.3×105 km2. The saline-alkali land area is 3.02×104 km2, accounting for 37.72% of the total cultivated land, with the annual increase of saline-alkali land accounts for 0.26%. It is a high demand to mitigate soil salinity. The impact of soil salinization can be reduced to involve water conservancy, farm management (deep-ripping, backfilling of guest soil), chemical amendments (gypsum), and biological measures (cultivation of salt-tolerant crops). The water conservancy measures include the subsurface pipe (Pa) and vertical shaft (Sa) drainage. Specifically, the Pa approach uses the surface fresh water to leach the salt from the saline-alkali soil, whereby the water enters Pa buried in the soil and flows into a drainage ditch. The Sa drainage approach uses the subsurface wells to pump out groundwater in order to effectively lower the groundwater level and discharge saline water out of the planting area. The purpose of Sa is to regulate the distribution and balance of the soil water and salt in the planting area. Previous empirical studies on soil salinization was focused mainly on the water and salt transport, physical and chemical properties of saline-alkaline soil, and technical parameters or salinization improvement. However, the Pa and Sa drainage approaches are still in the exploratory stage for the improvement of saline-alkali lands due mainly due to the secondary soil salinization. In addition, the previous studies did not provide sufficient evidence on the effect of the combined Pa and Sa drainage measures. Moreover, previous studies have focused on the 0-100 cm soil layer depths rather than the groundwater recharge on the soil salinity. In this study, a soil improvement was conducted in the five-year growing season field to evaluate the agricultural soil ecosystem under Pa and Sa drainage approaches. The main objective of this study was to evaluate the desalination and drainage effect of the drip irrigation and leaching that combined with Pa and Sa in the process of improving saline-alkali soil conditions, including the soil desalination rate, drainage flow, salt discharge, and groundwater level. This study shows that saline-alkali soils were improved to assess the effects of the combined Pa and Sa drainage measures on the agricultural soil ecosystem. The average annual decline of groundwater level from 2016 to 2020 was 1.16 m. More importantly, the seed cotton yield increased by 3.2 t/hm2. It infers that the value of saline-alkali soil can be improved by combining the Pa and Sa drainage measures. This finding can provide a strong reference for the sustainable development of future saline-alkali soil improvement and agricultural land resource utilization for cotton production in arid desert regions.