Effects of smash ridging on soil organic carbon and CO₂ emissions in straw mulching sugarcane field

【Objective】In order to study the effects of straw mulching under no-tillage conservation tillage on the characteristics of soil organic carbon and CO₂ emissions in sugarcane fields, and provide scientific basis for the regulation and management of soil organic carbon pool in dryland sugarcane fields.【Method】From 2018 to 2019, the second year of continuous straw mulching was used as the research object of ratoon sugarcane fields, with smash ridging no-tillage ratoon sugarcane straw mulching(SR1), smash ridging no-tillage ratoon sugarcane straw mulching(SR2), and conventional no-tillage ratoon cane straw mulching(CT1) and conventional no-tillage ratoon cane without straw mulching(CT2) four treatments.Soil samples of 0-15 cm and 15-30 cm soil layers were collected during the sugarcane tillering, elongation and maturity periods.Total organic carbon, easily oxidizable organic carbon, microbial biomass carbon and CO₂ emission flux were analyzed, and the sugarcane soil carbon pool management index(CPMI) was calculated.【Result】Straw mulching increased the total organic carbon content of no-tillage sugarcane fields.After sugarcane harvest, the soil total organic carbon of 0-15 cm and 15-30 cm soil layer was increased by 33.60% and 22.08% in SR1 treatment compared with SR2 treatment, respectively.Compared with CT2 treatment, soil layers of 0-15 cm and 15-30 cm in CT1 treatment increased by 18.13% and 42.22% respectively.Straw mulching increased the oxidizable organic carbon content of the soil in no-tillage sugarcane fields.After sugarcane harvest, SR1 treatment increased the oxidizable organic carbon content of 0-15 cm and 15-30 cm soil layers by 11.86% and 37.78% respectively compared with SR2 treatment.The content of oxidizable organic carbon in 0-15 cm and 15-30 cm soil layers in CT1 treatment increased by 54.84% and 31.03% respectively compared with CT2 treatment.Straw mulching increased the soil microbial biomass carbon content in smash ridging no-tillage sugarcane fields.After sugarcane harvest, SR1 treatment increased by 83.21% and 126.43% of soil microbial biomass carbon content in 0-15 cm and 15-30 cm soil layers compared with SR2 treatment, respectively.Straw mulching changed the CO₂ emission flux of no-tillage sugarcane fields.The peak CO₂ emissions of SR1 treatment increased by 26.26% compared with SR2 treatment.Compared with CT2 treatment, CT1 treatment increased by 79.18%.Smash ridging no-tillage improved the CO₂ emission flux of sugarcane fields.The peak CO₂ emission of Fenlong no-tillage was as 1.66-2.35 times as that of conventional no-tillage.Straw mulching improved the soil carbon pool management index of sugarcane fields.The carbon pool management index of 0-15 cm and 15-30 cm soil layers in SR1 treatment increased by 16.99% and 55.90% compared with SR2 treatment, respectively.Compared with CT2 treatment, CT1 treatment increased by 29.50% and 28.53%, respectively.Under the straw mulching, the carbon pool management index of the 0-15 cm and 15-30 cm soil layers of the smash ridging no-tillage soil layer increased by 67.58% and 102.54% respectively compared with the conventional no-tillage.【Conclusion】Straw mulching can increase soil total organic carbon, oxidizable organic carbon, microbial biomass carbon content and soil carbon pool management index in smash ridging no-tillage sugarcane fields.This model can be used as an important means to regulate the characteristics of soil organic carbon pool in dryland sugarcane field.