Objective The aims were to investigate the specific effects of different acidification control measures on the fertility and organic carbon stability of red soils and their underlying mechanisms, in order to select to the suitable acidification control measures.

Methods This study was based on a 9-year long-term field experiment at the National Agricultural Environment Yueyang Observation and Experiment Station. The effects of measures, including single chemical fertilizer application, bone meal combined with chemical fertilizer, lime combined with chemical fertilizer, and straw mulching combined with chemical fertilizer on the soil fertility and potential fertility characteristics were investigated, organic carbon fractions and their stabilities of acidified red soils were tested.

Result The results showed that, compared to the single chemical fertilizer application, lime combined with chemical fertilizer significantly increased pH, the exchangeable magnesium, conductivity organic carbon stability index and strength by 45.68%, 5.35%, 106.58%, 47.67% and 43.90%, respectively. Bone meal combined with chemical fertilizer significantly increased total nitrogen and total phosphorus by 14.11% and 11.56 %, respectively. Both treatments significantly reduced exchangeable hydrogen, exchangeable aluminum and exchangeable acid (all below detectable levels), and significantly increased exchangeable calcium (by 363.79% and 66.95%) and available phosphorus (by 108.36% and 33.98%, respectively). The straw mulching combined with chemical fertilizer significantly reduced the content of exchangeable ammonium and mineral-bound organic carbon, but significantly increased the stability index and strength of organic carbon by 36.85% and 46.97%, respectively. Path analysis further showed that acidification control measures affected the strength of organic carbon stability mainly by affecting the ionic characteristics, and lime application was more effective in enhancing soil fertility and organic carbon stability and acidification control.

Conclusion Lime and bone meal effectively mitigated red soil acidification, improved soil fertility and the stability of organic carbon. Straw mulching also increased carbon stability. Among the three measures, lime showed the best performance.