Objective  To study the effects of drip fertigation on soil active organic carbon content and methane (CH₄) emission flux in sugarcane field, and investigate the relationship between soil methane emission flux and soil active organic carbon content.

Method  The field experiment with different irrigation and fertilization treatments under drip irrigation was conducted in Nanning Irrigation Experimental Station from March to December in 2018. Four fertilization levels were designed: Conventional fertilization (F₁₀₀, N 250 kg·hm⁻², P₂O₅ 150 kg·hm⁻², K₂O 200 kg·hm⁻²), incremental fertilization 1 (F₁₁₀, 10% increase based on F₁₀₀), incremental fertilization 2 (F₁₂₀, 20% increase on the basis of F₁₀₀), and reducing fertilization (F₉₀, 10% reduction based on F₁₀₀). Two drip irrigation levels were set: W₁₈₀ (180 m³·hm⁻²) and W₃₀₀ (300 m³·hm⁻²). Soil CH₄ emission flux and active organic carbon contents at different growth stages of sugarcane were measured using conventional method, and the relationships between soil CH₄ emission flux and active organic carbon contents in sugarcane field were analyzed by Pearson method.

Result  At tillering stage, W₃₀₀F₁₂₀ treatment increased soil soluble organic carbon (DOC) content by 156% compared with W₃₀₀F₁₀₀ but had lower CH₄ emission flux in soil than the other treatments. At maturing stage, W₃₀₀F₁₂₀ treatment increased soil DOC content and microbial biomass carbon (MBC) by 114% and 49.6% compared with W₃₀₀F₁₀₀, respectively. CH₄ emission flux in sugarcane field was only positively correlated with soil DOC content, with the correlation coefficient of 0.38.

Conclusion  Soil DOC content significantly affects CH₄ emission flux in sugarcane field. W₃₀₀F₁₂₀ treatment can increase soil soluble organic carbon content in sugarcane field at tillering and maturing stages, and reduce soil CH₄ emission in sugarcane field at tillering stage.