Abstract: 【Objective】 Study on the assimilated carbon accumulation and distribution of maize under various fertilizer applications in fluvio-aquic soil, can not only provide a scientific basis for rational fertilization practices for increasing crop yield, but it also has important significance to the study of global carbon cycling. 【Method】 Based on a long-term experiment, samplings from various organs of maize were taken at maturity stage to measure the biomass yield under various fertilization applications. Organic carbon content, carbon assimilate distribution proportion, and C/N ratio of maize and its various organs under different fertilization conditions were also analyzed. 【Result】 The results showed that the averaged carbon content in maize was about 464 g?kg-1 under the long term combined application of fertilizers and organic manure (NPKM, 1.5NPKM). It was 3% higher than the applications of N and PK treatments. The carbon content of maize kernel was obviously improved in the NK treatment, which was about 3% higher than the control treatment. In all treatments, the distribution proportion of assimilated carbon biomass in stem and leaf of maize was about 57% in PK treatment, which was 73% higher than that of the N treatment. The distribution proportion of assimilated carbon biomass in crop stubble in the PK treatment was also the highest (about 7%). The distribution proportion of assimilated carbon biomass in maize grain under the PK treatment was the lowest (30%). The C/N ratio in maize stem and leaf, cob, and crop stubble was the highest in PK treatment whereas it was the lowest under the 1.5NPKM treatment. The C/N ratio in stem and leaf, cob, and crop stubble in PK treatment was 121%, 105% and 120% higher than that in the 1.5NPKM treatment, respectively. In all fertilization treatments, the fixed carbon content in whole maize was the highest in NPKM treatment in above-ground parts of maize, and that was the highest in NPK balanced fertilization treatment in under-ground parts of maize. The fixed carbon content of maize in the above-ground part in NPKM treatment was about 7.2 t?hm-2 higher than that of the control treatment, NPK balanced fertilization treatment was 0.3 t?hm-2 higher than that of the control treatment for the under-ground part of maize. 【Conclusion】 The combined NPK fertilization and organic-inorganic fertilization significantly enhanced the carbon biomass of crop. These balanced fertilizations improved the distribution proportion of assimilated carbon in grain and cob, and then reduced the distribution proportion of assimilated carbon and the C/N ratio in stem and leaf, and crop stubble. These changes in distribution proportion of assimilated carbon and the C/N ratio by the balanced fertilization were helpful for the decomposition and transformation of returned straw and crop stubble into the soil. It indicates that balanced fertilization is a sustainable and environment-friendly management practice and has great significance for soil fertility and soil carbon sequestration.

Key words: long-term fertilization, maize, carbon assimilates, distribution proportion