Effect of Straw Returning on Soil Aggregate Characteristics and Tobacco Yield and Quality

The effects of rice straw returning on soil physical and chemical properties, aggregate characteristics and yield and quality of flue-cured tobacco in tobacco-rice rotation areas were studied through a two-year field positioning experiment. The experiment was set up with four treatments: no straw (CK), straw covered returning (T1), straw smashing (T2) and straw charring (T3). The results showed that all the rice straw-returning methods could improve soil physiochemical properties. Soil pH, soil alkali nitrogen, available phosphorus and potassium contents were significantly (p≤0.05) improved in the straw rushing and carbonizing treatments compared with those in the control treatment, and the effect of straw carbonization returning on soil fertilization was better. Meanwhile, all the three straw returning methods improved soil aggregate structure and stability in a certain degree, and the total amount of >0.25 mm soil water-stable aggregates, the values of average weight diameter (MWD) and geometric mean diameter (GMD) of soil aggregates were found to be the highest in the straw smashing treatment, which also had the lowest fractal dimension (D) values, followed by the straw charring treatment. From the perspective of the quantity and quality of flue-cured tobacco leaves of C3F class, the economic benefits of flue-cured tobacco, the chemical composition and sensory quality of C3F grade tobacco leaves were optimal in the straw smashing returning treatment, followed by rice straw covered and charring treatments. Taken together, rice straw smashing returning is a better way of straw utilization in the tobacco-rice rotation area of southern Anhui Province, followed by improved straw conversion into biochar returning to the field and then the mulching returning.