Soil carbon (C) is essential in improving the crop productivity and the quality of soils. However, the research reports on enhancing the system productivity and soil C status in the acid Inceptisol of north-eastern region (NER) of India under sustainable integrated nutrient management (INM) are not adequately available. Here, we studied a rice-rice system after 32-year (1987–2020) of continuous INM treatments with farmyard manure (FYM)/ rice stubbles/ Azolla and chemical fertilizer inputs. Yield data were measured yearly to derive the sustainable yield index (SYI) and soil samples were collected during the last three years to assess the different C fractions, C stocks and sequestration and C indexes. The recommended dose of fertilizers (RDF) + rice stubble significantly increased the total yield and the SYI over the unfertilized-control, followed by RDF + FYM and RDF + Azolla. The RDF + Azolla treatment effectively enhanced the very labile and labile C fractions, while RDF + rice stubble contributed to the less labile and non-labile C fractions in soil. The maximum SOC stock was found under RDF + FYM (67.1 Mg ha⁻¹) and RDF + rice stubbles (66.6 Mg ha⁻¹), whereas the lowest in the unfertilized-control (39.1 Mg ha⁻¹). The soil C sequestration followed the same trend ranging between -4.0 and 24.1 Mg ha⁻¹. The water soluble C and microbial biomass C fractions were found to be the most responsive to the different nutrient management practices. The INM treatments showed a higher lability index, C pool index, and C management index. While yield declined in the unfertilized control, the supply of organic and chemical fertilizers sustained rice-rice productivity with an enhancement in soil C status in the long-term.

土壤碳（C）对于提高作物生产力和土壤质量至关重要。然而，关于在可持续综合养分管理 (INM) 下提高印度东北地区 (NER) 酸性 Inceptisol 系统生产力和土壤碳状况的研究报告并不充分。在这里，我们研究了 32 年（1987-2020 年）使用农家肥 (FYM)/稻茬/ Azolla连续进行 INM 处理后的稻米系统和化肥投入。每年测量产量数据以推导出可持续产量指数 (SYI)，并在过去三年收集土壤样品以评估不同的碳组分、碳储量和固存以及碳指数。推荐剂量的肥料（RDF）+稻茬比未施肥对照显着提高了总产量和SYI，其次是RDF+FYM和RDF+ Azolla。RDF + Azolla处理有效地增加了非常不稳定和不稳定的 C 部分，而 RDF + 稻茬有助于减少土壤中不稳定和非不稳定的 C 部分。在 RDF + FYM (67.1 Mg ha ^-1 ) 和 RDF + 稻茬 (66.6 Mg ha ^-1)，而未受精对照中最低 (39.1 Mg ha ^-1 )。土壤固碳遵循相同的趋势，范围在 -4.0 和 24.1 Mg ha ^{-1 之间}。发现水溶性碳和微生物生物量碳组分对不同的养分管理实践最敏感。INM 处理显示出较高的不稳定指数、C 池指数和 C 管理指数。虽然未施肥控制的产量下降，但有机肥和化肥的供应维持了稻米生产力，长期提高了土壤碳状况。