Effects of different proportions of chemical fertilizer reduction combined with organic fertilizer supplements on organic carbon sequestration in Tobacco-planting soil

The long-term effects of different proportions of fertilizer reduction combined with organic fertilizer on organic carbon sequestration in tobacco-planted soil were explored. Based on nine consecutive years of field positioning experiments, treatments of no fertilizer (CK), 100% fertilizer (CF-1, local conventional recommended fertilizer), 80% fertilizer (CF-2), 80% fertilizer with organic fertilizer (OF-1), 60% fertilizer with organic fertilizer (OF-2), 70% fertilizer with organic fertilizer + bioorganic fertilizer (BOF) were applied to compare organic carbon storage profit and loss, carbon sequestration rate, organic carbon component content, organic carbon sensitivity index, soil carbon pool activity and soil carbon pool management index of tobacco-planting soil, and to explore the long-term effects of different proportions of fertilizer reduction combined with organic fertilizer supplements on organic carbon sequestration in tobacco-planting soil. The organic carbon composition, storage, and soil carbon sequestration rate of tobacco-planted soil under the continuous no-fertilization (CK) treatment were significantly lower than those of CF-1. Compared with CF-1, the organic carbon content of tobacco-planting soil increased by 9.6%, 20.9% and 13.9%, the labile organic carbon content of soil increased by 43.4%, 68.0% and 41.7%, soil dissolved organic carbon content increased by 14.8%, 19.1% and 25.4%, soil microbial biomass carbon content increased by 22.8%, 37.2% and 36.4% and soil organic carbon storage increased by 15.3%, 30.2% and 31.2%, respectively, in the OF-1, OF-2 and BOF treatments. Compared with CF-1, the average annual carbon sequestration rate was increased by 191.3%, 382.6% and 391.3%, the carbon pool management index was increased by 100.8%, 159.8% and 79.6%, respectively, among OF-1, OF-2 and BOF treatments. Continuous fertilizer reduction at different proportions combined with organic fertilizer significantly increased the sensitivity index of soil active organic carbon. Compared with CF-1, the yield of tobacco leaves increased by 10.3%, 33.5%, and 35.3%, and the proportion of medium- and high-grade tobacco leaves increased by 14.6%, 22.0%, and 18.0%, respectively, in the OF-1, OF-2, and BOF treatments. After nine consecutive years of fertilizer reduction and supplementation with organic fertilizer, the organic carbon content and soil organic carbon sequestration rate of tobacco-planted soil significantly increased, and the quality of tobacco production was promoted. This approach is an effective way to produce green and high-quality tobacco leaves and to increase the efficiency of soil carbon sequestration. Treatment OF-2 or BOF resulted in much better results.