Although considerable research has examined the effects of soil respiration and erosion on soil organic carbon (SOC) loss, understanding of SOC loss through both gaseous and runoff-related pathways remains limited in sloping agroecosystems. In this study, a two-year field experiment under a wheat-maize rotation was carried out on sloping purple soil croplands to assess the effects of different fertilization regimes on SOC losses. The experimental treatments consisted of a control (CK), mineral fertilizers (NPK), organic manure combined with NPK (OMNPK), and crop residues combined with NPK (RSDNPK). The results indicated that organic fertilization significantly increased SOC loss through gaseous emissions and dissolved organic carbon (DOC) leaching, while reducing losses through sediment runoff, reflecting contrasting responses among SOC loss pathways. The three fertilization treatments (NPK, OMNPK, and RSDNPK) showed total SOC losses ranging from 8280.79 to 12,516.77 kg ha-1, which were substantially higher than those observed in the control treatment (6068.51 kg ha-1). Across all treatments, more than 98% of SOC loss originated from soil heterotrophic respiration, whereas the control treatment exhibited the highest proportion of runoff-related carbon loss (1.1%). By jointly assessing gaseous and runoff-related SOC loss pathways within a single field experiment, this study reveals contrasting regulatory mechanisms for SOC losses in sloping purple soils, with soil factors directly influencing gaseous SOC losses and climatic factors-especially rainfall-mainly controlling SOC losses via runoff pathways. The combined influence of soil and climatic factors accounted for 42% of the variation in gaseous SOC losses. Overall, the results suggest that organic fertilization leads to trade-offs among different SOC loss pathways and may enhance net ecosystem carbon balance under suitable management, highlighting the need to consider soil properties together with climatic conditions when developing sustainable carbon management strategies for agricultural ecosystems.