Cotton production is crucial for China's economy, with Xinjiang being the leading producer. However, Xinjiang's arid oasis agroecosystems face challenges like water scarcity and soil degradation, threatening sustainable cotton cultivation. Saline-alkali soils require continuous reclamation. Mulched drip irrigation (MDI), introduced in the 1990s, offers efficient water and salt management, preventing deep percolation and inhibiting evaporation. While MDI has improved production, concerns remain about its long-term effects on reclaimed saline-alkali fields. This research addresses these concerns by evaluating MDI's long-term impacts on soil salinity, crop productivity, and overall sustainability in Xinjiang's vulnerable agroecosystems. The study specifically addresses the potential for long-term soil salinization, plastic mulch pollution, and the disruption of soil microbiome communities due to prolonged drip irrigation, aiming to develop strategies for sustainable MDI implementation that balance agricultural benefits with ecological protection.

Existing literature highlights the benefits of MDI in improving water use efficiency and mitigating soil salinity in arid regions. Studies have shown its positive impact on crop yields and soil health parameters. However, there is a gap in understanding the long-term sustainability of MDI, particularly in reclaimed saline-alkali lands. Some studies indicate potential challenges associated with long-term use, including salt accumulation, plastic pollution, and impacts on soil microbial communities. This review underscores the need for a comprehensive, long-term evaluation to address concerns and guide sustainable MDI implementation.

A 12-year study (2009-2020) was conducted in Xinjiang using a space-for-time substitution approach. Five cotton fields with varying MDI implementation years (1998-2012) were selected. Soil samples were collected at regular intervals from different depths (0-140 cm during growth season, 0-200 cm during non-growth season) from three points in each field: under drippers, mid-row, and between membranes. Soil salinity (electrical conductivity), physical properties (bulk density, porosity, aggregate stability), chemical properties (carbon, nitrogen, phosphorus), and microbial community composition (16S rRNA and ITS1 sequencing) were analyzed. Soil quality was assessed using a minimum dataset (MDS) and a total dataset (TDS), employing principal component analysis (PCA) and correlation analysis to select key indicators. Statistical analysis (ANOVA, paired t-test, regression, path analysis) was conducted using IBM SPSS Statistics 26. Alpha-diversity indices were computed using QIIME, and distinctions in microbial communities were assessed through non-metric multidimensional scaling (NMDS).

The study found that long-term MDI significantly reduced soil salinity, with a desalination rate exceeding 60% after three years and stabilizing at 80-90% after eight years. Salt migration patterns showed initial vertical movement during the growth season followed by accumulation at the soil surface during the non-growth season. MDI improved soil physical properties, increasing the proportion of large aggregates and total porosity initially, although bulk density increased after ten years. Soil nutrient content (nitrogen, phosphorus, carbon) significantly increased under long-term MDI. The microbial community structure changed over time, with an increase in the relative abundance of beneficial bacterial and fungal genera after long-term MDI application, though diversity stabilized after 15 years. A positive correlation was observed between soil quality and cotton yield over the 22 years, suggesting MDI's contribution to long-term sustainable agricultural production. A novel water-saving and salt-control technology system was proposed comprising salt flushing during the growth phase, salt leaching during non-growth periods, and a coordinated irrigation and drainage strategy. Despite increased residual plastic film accumulation (annual rate of 15.69 kg/ha), the overall trend of soil quality was positive due to other implemented strategies.

The findings demonstrate that MDI is a sustainable practice for improving soil health and cotton yields in arid regions. The long-term reduction in salinity, enhanced nutrient levels, and improved soil structure contribute to increased productivity. Changes in microbial community composition indicate adaptation to MDI, suggesting enhanced ecosystem resilience. The proposed water-saving and salt-control system further enhances sustainability. The accumulation of residual plastic film poses a challenge, requiring integrated waste management strategies to ensure long-term environmental sustainability. The success of MDI highlights the potential for sustainable intensification in arid agriculture, but ongoing research is needed to optimize management practices and mitigate potential negative consequences.

This study provides strong evidence supporting the long-term sustainability of MDI for cotton production in arid regions. MDI effectively manages soil salinity, improves soil health, and enhances crop yields. However, addressing residual plastic film pollution is crucial for maintaining environmental sustainability. Future research should focus on optimizing MDI practices, developing biodegradable mulches, and further investigating the long-term impacts on soil biodiversity and ecosystem services. Integrating MDI with other water management and soil conservation techniques will be critical for enhancing the long-term benefits of this promising technology.

The study focused on a specific region in Xinjiang, and the results might not be directly generalizable to other arid regions with different soil types, climate conditions, or cropping systems. While the study covered a 12-year period, longer-term studies would provide further insights into the long-term trends and potential limitations of MDI. The impact of the proposed water-saving and salt-control system on soil health and yield needs to be further evaluated through field trials.