Soil organic carbon (SOC) depletion and stagnant crop productivity are key constraints to agricultural sustainability in arid northwestern China. Agricultural practices (APs) are key drivers of SOC dynamics and crop productivity. However, due to chronic water limitation, alkaline soils, and low initial SOC content in this region, the responses of SOC and crop yield to APs may differ fundamentally from those in more humid or temperate regions, making it challenging to coordinate soil carbon accumulation and nutrient supply. Therefore, using multilevel meta-analysis and random forest models, this study comprehensively analyzed 5245 paired observations from 267 publications, examined the response patterns and potential mechanisms of crop yield and SOC content to eight APs and predicted the spatial probability of achieving synergistic benefits. Multilevel meta-analysis results showed that no-tillage increased SOC content by 7.6% (P < 0.05) but had no significant effect on crop yield. Mulch planting significantly increased crop yield by 28.2% (P < 0.05) but did not significantly alter SOC content. In contrast, other APs exhibited significant synergistic benefits. The synergy index, quantifying coordination between crop yield and SOC content, was highest under mineral-organic fertilization (0.33) compared to mineral fertilizer alone, followed by biochar input (0.31), straw returning (0.20), subsoiling (deep tillage to loosen subsoil, 0.15), and green manure (0.15). Subgroup and random forest results demonstrated that the effectiveness of APs is significantly influenced by climatic and soil conditions. Regression analyses further indicated that changes in soil total nitrogen (TN) and available phosphorus (AP) were closely associated with the APs-driven synergies between crop yield and SOC content. Model-derived results suggest that biochar input and mineral-organic fertilization may be broadly promising for achieving the desired outcomes across the study region, while no-till and green manure show limited modeled suitability, particularly in arid and low-fertility areas such as Xinjiang, western Inner Mongolia, and southern Gansu. These findings establish that targeted APs can reconcile carbon concentration and productivity goals in arid farming systems, provided they are tailored to local pedoclimatic conditions. This study provides a scientific basis for policymakers to develop spatially explicit strategies aimed at promoting sustainable soil carbon accumulation and ensuring food security in Northwest China.