Organic amendment substitution improves the sustainability of wheat fields changed from cotton and vegetable fields

Long-term excessive use of chemical fertilizers and continuous cropping in vegetable and cotton production lead to a decline in farmland soil quality and crop productivity, endangering sustainable agricultural development. Organic amendment substitution (OAS) or farmland use change or can potentially enhance soil quality and crop yield. However, it remains unclear whether their combined application can improve the sustainability of wheat fields when changing from cotton and vegetable fields. In this study, continuous cropping cotton and vegetable fields were changed to wheat fields (C-W and V-W), and then field fertilization experiments (non-fertilization, NF; chemical fertilizer alone, CF; chemical fertilizer reduced by 20%, RF; and organic amendment substituted 20% of inorganic nitrogen, OAS) were conducted for three years (2018-2020) to explore their effects on wheat productivity and soil quality. The findings revealed that the combined farmland use change and fertilization improved soil quality in wheat fields compared to pre-change cotton and vegetable fields. OAS improved soil quality index (SQI-TDS by 0.36-0.82 and 0.32-0.82; SQI-IDS by 0.37-0.90 and 0.40-0.88) by improving soil properties and increasing microbial diversity compared to NF, CF and RF in C-W and V-W. Meanwhile, OAS increased nutrient use efficiency, crop productivity index (CPI, by 13.69%-72.46% and 8.52%-41.45%) and the sustainability index (SI, by 14.14%-49.35% and 12.56%-40.00%). Moreover, microbial biomass carbon and nitrogen (MBC and MBN), pH, available nitrogen (AN), soil organic carbon (SOC) and ACE index were key soil factors affecting yield. These indicators can be used to construct important dataset to simplify soil quality evaluation systems. Overall, the present study revealed the mechanism by which OAS improved wheat field sustainability by increasing wheat productivity and soil quality after farmland use changes, contributing to sustainable agricultural development. Moreover, it provides valuable reference methods and evaluation ideas for future research on farmland soil quality and sustainability evaluation.