Effects of Different Crop Straws on Organic Carbon Mineralization and Humus Composition of Tobacco-Growing Soil

In view of the common flue-cured tobacco rotation system in Southern China, the characteristics of soil organic carbon mineralization and changes of humus content after adding different crop straws (tobacco, rape and rice) were studied to provide theoretical basis for rational utilization of tobacco field wastes. Indoor constant temperature incubation experiment was adopted in which three kinds of straw were applied by covering the soil surface or mixing with the soil, and the changes and correlation of CO₂ release pattern, total organic carbon content (TOC) and humus content of soil under different treatments were analyzed. The results showed that the addition of crop straw in different ways had significant influence on soil CO₂ release, and the mineralization intensity of soil organic carbon under the mulching treatment was higher than that under the mixing treatment, reaching an extremely significant difference. The addition of the three kinds of straws can significantly increase the soil CO₂ release rate and cumulative emission amount, and the mineralization intensity of soil organic carbon in each treatment is shown as rape straw > tobacco straw > rice straw. After 180 days of culture, the contents of TOC, humus composition and PQ value of soil treated with straw were significantly increased. Through correlation analysis, it can be found that the cumulative emission of soil CO₂ was significantly correlated with the content of soil TOC, HE (total humus that could be extracted) and FA (fulvic acid). Therefore, the addition of three crop straws can improve the soil organic carbon content and humus degree, and the straw mixing treatment has a better effect of carbon sequestration and emission reduction.