Impacts of inorganic and organic fertilization on soil organic carbon and crop production: a meta-analysis

Enhancing soil organic carbon (SOC) is critical for climate mitigation and stable crop production, yet the effectiveness of different fertilization strategies varies widely across environmental and management contexts. To clarify these inconsistencies, empirical field data from major grain-producing regions of northern China were synthesized using meta-analysis, regression models, random forest algorithms, and partial least squares path modeling to systematically evaluate the impacts of chemical fertilization (CF), organic fertilization (OF), and combined organic–inorganic fertilization (COF) on SOC dynamics. Results showed that CF, OF, and COF increased SOC content by 13%, 34%, and 39%, respectively, with long-term application (>20 years) further amplifying carbon sequestration. Pronounced spatial heterogeneity was observed. In Northeast China (NEC) with higher initial SOC, over 80% of sites showed absolute SOC gains exceeding 10 g C kg-1, with COF most effective. In Huanghuaihai Farming Region of China (HFR), characterized by lower baseline SOC, relative gains reached 63%, and OF showed stronger effects. Across soil textures, OF consistently achieved the largest SOC improvements, and under nutrient-limited conditions, SOC enhancement followed the order OF > COF > CF. Test duration emerged as the dominant driver of SOC accumulation, while climate, nitrogen availability, and initial SOC modulated responses under different regimes. Structural equation modeling indicated that SOC mediated yield responses under CF, whereas direct soil and management effects dominated under OF and COF. These findings emphasize that fertilization management strategies should fully consider regional initial SOC levels and integrate carbon-enhancing practices within broader conservation-oriented farming systems to simultaneously enhance soil carbon sequestration, sustain crop productivity, and provide actionable evidence for promoting sustainable agricultural intensification and national carbon neutrality goals.