Mechanism of Saline–Alkali land improvement using subsurface pipe and vertical well drainage measures and its response to agricultural soil ecosystem

Salinization is recognized as a threat to agricultural productivity and land resources in global arid desert regions. To date, field soil improvement schemes have met with minimal success to date. We aimed to improve saline-alkali soils by assessing the effects of combining subsurface pipe (Pa) and vertical well (Sa) drainage measures on agricultural soils ecosystem. In a five-year field experiment, soil was sampled 0.5 m, 5 m, 7.5 m horizontally away from the Pa, and 0.5 m, 30 m, 60 m horizontally away from the Sa. Findings indicate that the soil electrical conductivity (EC) decreased from 16 dS m-1 to 3 dS m-1 at a 0-80 cm depth, and the soil desalination efficiency was great at the 0-300 cm depths (≥ 32%) than at the 400-700 cm depths (-14%-74.7%). The combined Pa and Sa drainage measures significantly decreased the species richness and quantity of soil microbial communities, and their negative impact on observed species was irreversible within 1 year. The farther the horizontal sampling conducted from the Pa and Sa, the greater the structural similarity of the microbial community at the genus level, higher the catalase, acidic protease, and neutral phosphatase activities, and lower the alkaline phosphatase activity. The overall decrease in groundwater level from 2016 to 2020 was 5.7 m. The seed cotton yield increased by 3.2 t ha-1. The results suggest that the value of saline-alkali soil can be improved by combining Pa and Sa drainage measures. Our research provides guidance for further effective utilization of agricultural water and soil resources and the sustainable development of the soil ecosystem in arid desert areas.