ABSTRACT Application of organic fertilizer is a key strategy for soil carbon sequestration, yet its impact on the erosion selective transport and chemical quality of eroded organic carbon (OC) remains unclear. We investigated this using laboratory rainfall simulations on sloping cropland under three treatments: no fertilization (CK), chemical N/P (NP), and organic substitution (OMNP). Our results reveal a critical trade‐off between erosion quantity and carbon quality: (1) While OMNP significantly reduced total runoff and sediment fluxes (by 10.00% and 17.37% vs. NP), it enriched the remaining sediment with particulate and mineral‐associated carbon. However, the reduction in bulk sediment yield outweighed this enrichment, resulting in a net 13.97% decrease in the total loss of stabilized MAOC. (2) Fluorescence analysis identified a divergence in dissolved organic matter (DOM) composition. Runoff was dominated by highly labile, tryptophan‐like components (Peak T) derived directly from manure inputs, whereas sediment‐associated DOM was characterized by high aromaticity and humification due to selective mineral sorption. (3) The linear correlations between OC loss and runoff/sediment transport confirm that physical erosion processes govern OC mobilization. Overall, organic substitution effectively reduces physical soil carbon loss but intensifies the release of chemically reactive organic matter fractions, posing distinct risks for aquatic eutrophication and pollutant transport.
Feng et al. (Fri,) studied this question.