Characteristics and driving factors of acid-base buffer of typical tobac-co-planting soils in western Hunan Province

To determine the characteristics of pH buffer of soils cultivated with tobacco in the mountain regions that are under long-term fertilizer application, a total of 28 soil samples were collected in areas of typical flue-cured tobacco cultivation in mountain regions in western Hunan Province. The pH buffer characteristics of collected soils were analyzed using both titration curve and gray correlation methods. Then quantitative relationships and the driving factors of soil acid-base buffer characteristics were also investigated. The results showed that the range of pH buffer of soils cultivated with tobacco in western Hunan Province was 11.35-43.29 mmol·kg^-1 and the average was 17.26 mmol·kg^-1. Acid-base buffer of yellow brown soil (11.35-43.29 mmol·kg^-1) was significantly higher than that of yellow soil (11.79-20.70 mmol·kg^-1). While the sensitivity of yellow soil to acid was determined by the content of soil organic matter, that of yellow brown soil to acid was closely related to pH and organic matter content. Also while 78.57% of the samples were sensitive to both acid and base, soil type, organic matter contents, and clay content were positively correlated with pH buffer capacity. For yellow brown soil, pH buffer capacity was also positively correlated with pH and cation exchange capacity. However, it was negatively correlated with exchangeable acid and aluminum. The performances of pH buffer of two soil types were quite different. pH buffer capacity of yellow soil was mainly affected by soil organic matter content, cation exchange capacity, and clay content. Then pH buffer capacity of yellow brown soil was mainly affected by pH, cation exchange capacity, and organic matter content. For production, it was necessary to use chemical fertilizers properly, to add organic fertilizer, to adjust soil acidity and to take other measures to improve pH buffer capacity of soil cultivated with tobacco. This will create a good ecological environment for the production of high quality tobacco leaves.