Evolution of soil quality and microbial communities in arid pear orchards reveals pathways to sustainable management

Soil quality is fundamental to agricultural ecosystems sustainability, influencing crop productivity, nutrient cycling, and environmental health. However, soil quality dynamics in perennial orchard systems and their long-term evolution remain insufficiently understood. This study examined the soil physicochemical properties and microbial community structure of Korla fragrant pear orchards of different planting ages (0, 5, 10, and 25 years) through integrated field surveys and laboratory analyses. Soil organic carbon (SOC) significantly increased in the 0-100 cm soil layer, with average annual rates of 0.18-1.06 g C kg^-1. The total nitrogen (TN) and alkali-hydrolyzable nitrogen significantly increased in the 0-60 cm soil layer, with average annual rates of 0.01-0.03 g N kg^-1 and 0.09-1.45 mg N kg^-1, respectively. Nitrate accumulation in the 0-100 cm soil layer increased from 427 kg N ha^-1 before planting to 707 kg N ha^-1 after 25 years. The Olsen-P significantly increased in the 0-40 cm soil layer, with average annual rates of 0.42-0.84 mg P kg^-1. In contrast, the soil pH, electrical conductivity (EC), and total soluble salts decreased significantly with orchard age. Both bacterial and fungal alpha diversity increased, with bacterial communities stabilizing after 5 years and fungal communities continuing to succeed. Redundancy analysis revealed that the soil water content, SOC, TN, pH, and EC were the key environmental factors shaping microbial community assembly. These findings demonstrated that long-term pear orchard cultivation enhanced soil fertility and shaped microbial communities, while simultaneously revealing associated risks such as soil acidification and nitrate accumulation, thus providing a critical foundation for developing sustainable soil management strategies.