Effects of Partial Replacement of Chemical Fertilizers with High Carbon Base Fertilizers on Soil Characteristics and Tobacco Leaf Quality in Chongqing

In order to explore the effects of combined application of chemical fertilizers and high-carbon base fertilizers on the characteristics of acid tobacco-planted soil and tobacco leaf quality in Chongqing, a field experiment with different treatments was conducted:the high-carbon based fertilizer replacing 0 (CK), 9% (T1), 18% (T2), 27% (T3) and 36% (T4) chemical fertilizers, respectively. Soil organic carbon content, enzyme activity, flue-cured tobacco growth and development and tobacco leaf quality characteristics of tobacco field under different treatments were studied. The results showed that the T3 treatment significantly increased the contents of soil organic carbon, soluble organic carbon, microbial biomass carbon and oxidizable organic carbon. With the increase of high-carbon base fertilizer substitution, soil sucrase and cellulase activities showed a trend of first increasing and then decreasing, and both were the highest in the T3 treatment. Compared with CK, the T4 treatment significantly improved soil pH and available potassium content. The correlation analysis showed that the activities of soil cellulase and polyphenol oxidase were significantly positively correlated with oxidizable organic carbon, microbial biomass carbon and available potassium content. Principal component analysis showed that compared with CK, the application of high-carbon based fertilizer treatments significantly changed soil organic carbon and enzyme activities, and it became more obvious with the increase of high-carbon base fertilizer replacement. The application of the high-carbon base fertilizer significantly increased dry matter accumulation and yield at the late growth stage of tobacco plants, and yield and yield value of tobacco leaves treated with T3 increased by 19.19% and 23.24%, respectively, compared with the control. The treatments of high-carbon based fertilizer increased the reducing sugar, total sugar, potassium content, two-sugar ratio and sugar-base ratio of tobacco leaves, and improved the sensory quality. In summary, when the nitrogen was applied at a rate of 102.4 kg/hm² in the tobacco-planted area of Chongqing, the application of 73% chemical fertilizer nitrogen and 27% high-carbon base fertilizer nitrogen could improve the soil environment and yield and quality of tobacco leaves.