Effects of practicing long-term mulched drip irrigation on soil quality in Northwest China

Assessing soil quality variation during the prolonged application of mulched drip irrigation (MDI) is critical to comprehend the sustainability of arid agriculture. To investigate the dynamics of crucial soil-quality indicators caused by the long-term application of MDI, the "space instead of time" methodology was adopted, and six fields were selected to represent the primary successional sequence in Northwest China. A total of 21 vital soil attributes from 18 samples were used as soil quality indicators. Based on the soil quality index calculated from the entire datasets, it was observed that long-term MDI practice enhanced soil quality by 28.21 %-74.36 % due to improvements in soil structure (e.g., soil bulk density, three-phase ratio, and aggregates stability) and nutrients (including total carbon, organic carbon, total nitrogen, and available phosphorus). Compared to natural unirrigated soil, soil salinity in 0-200 cm depth significantly decreased by 51.34 %-92.39 % in cotton fields with increasing years of practicing MDI. In addition, long-term MDI practice restructured soil microbial communities and augmented microbial activity by 259.48 %-502.90 % relative to the natural salt-affected soil. However, soil quality stabilized after 12-14 years of MDI application due to accumulated residual plastic fragments, increased bulk density, and reduced microbial diversity. Overall, practicing long-term MDI promotes soil quality and crop yield by promoting soil microbiome structure and function and soil structure. However, long-term mono-cropping with MDI would result in soil compaction and impair microbial activity.