Long-term tillage and straw returning practices enhance soil humus composition, carbon sequestration, and ecological–economic benefits

Abstract

While straw return is widely promoted, its specific effects on soil humus composition, structure, and ecological functions are not fully understood. This study investigates the long-term impacts of different straw types and farming practices on humus composition, carbon sequestration, and ecological–economic benefits. In Hunan Province’s paddy fields, six soils with 5–30-year farming histories were selected. Treatments included a blank control, corn straw return, and rice straw return, each replicated three times. Humus structure was analyzed via infrared spectroscopy, component contents were determined by alkali extraction, and a carbon footprint model assessed emissions. Ecological economic analysis integrated soil carbon pool dynamics, crop yields, and input costs. By 2023, soil nutrient levels had significantly increased compared with 2018. Corn straw return significantly increased humic acid, fulvic acid, and humin contents by 38.6%, 67.3%, and 25.6%, respectively, outperforming rice straw return. Soil carbon storage under straw return was, on average, 4.5 tons per hectare higher than nonreturn treatments, with no-till combined with straw return showing the highest annual carbon fixation rate. No-till treatment reduced rice season carbon emissions by 25% compared with conventional tillage. Ecological–economic analysis showed that no-till with deep loosening rotation increased the annual rice–corn system yield to 8.65–9.97 t per hectare and achieved an ecological carbon surplus. Corn straw was superior to rice straw in enhancing humus content and activity, with a 10.0% greater increase in activity. Returning corn straw is more effective than rice straw for increasing soil humus content and activity. Optimized tillage methods, like no-till with deep loosening, significantly enhance soil organic carbon storage and reduce the carbon footprint. This study provides a scientific basis for optimizing straw management and formulating soil health-centered farming systems, supporting regional agricultural sustainability.

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