Sustainability assessment of deep vertical rotary tillage for salinized farmland: Balancing salinity control, soil C–N stocks, and yield

Soil salinization severely limits sustainable agricultural development in arid regions, highlighting the need for integrated management practices to improve soil functions, crop yields, and environmental outcomes. This study conducted a four-year field experiment (2020–2023) to compare the effects of deep vertical rotary tillage (DVRT) at depths of 20, 40, and 60 cm, with continuous conventional tillage (CT) serving as the control. The sustainability of DVRT was assessed by measuring soil salinity, soil organic carbon (SOC), total nitrogen (TN), enzyme activity, microbial biomass, and CO 2 emissions. The results showed that, compared with CT, DVRT at depths of 40 cm and 60 cm reduced soil salt storage in the 0–100 cm soil profile by 59% and 68%, respectively, while soil water storage decreased by 5% and 8%, respectively. Furthermore, DVRT depths of 40 and 60 cm significantly increased SOC to 6.24–12.53 Mg ha −1 and TN to 0.62–0.96 Mg ha −1 , as well as enzyme activity, microbial biomass carbon, and microbial biomass nitrogen, resulting in an increased soil quality index (SQI). Although CO 2 emissions increased by 16%–22%, increased plant dry matter enhanced plant-derived carbon and nitrogen inputs, effectively mitigating the negative effects of CO 2 emissions. DVRT also significantly increased cotton yield by 24%–43% and economic benefits by 60%–79%. Entropy-TOPSIS analysis identified the DT60 treatment as the most effective approach for improving soil quality and promoting sustainable agricultural production, with a comprehensive evaluation index (CEI) of 0.78. Overall, DVRT improved soil quality, crop yield, and economic returns, while also facilitating carbon sequestration and nitrogen retention, thereby supporting the sustainable management of salinized farmland.