Distribution and Evolution Characteristics of Soil pH in Zunyi Tobacco Planting Areas

In order to understand the spatial distribution and evolution characteristics of soil pH in Zunyi tobacco-growing areas, 4816 soil samples were collected from 11 tobacco-growing counties in Zunyi for pH measurement in 2016-2017, and compared with the second soil survey data and the 2000-2005 survey data. The results showed that:(1) Soil pH in Zunyi tobacco areas varied from 4.4 to 8.8 in 2016-2017, with an average value of 6.6 and a coefficient of variation of 14.72%. The soil samples suitable for tobacco-growing accounted for 62.5%, and the alkaline soil samples for tobacco-growing accounted for 20.5%, the proportion of acid soil samples was 17.0%; (2) The average soil pH values of 11 tobacco-growing counties ranged from 6.2 to 7.4. There were significant differences of soil pH among these counties (p<0.05) and the frequency of distribution of different soil pH grades was significantly different. The spatial distribution of soil pH showed a regional character with soils from Southern parts being acidic and from Northern parts being alkaline; (3) Since the second soil survey, the soil pH in Zunyi tobacco areas showed a decrease in the proportion of the most suitable soil pH for tobacco-growing; the proportion of suitable soil pH also showed a downward trend, while the proportion of soil in the alkaline range increased continuously and the proportion of the acid-biased soil in Zunyi tobacco areas generally increased volatility. As a whole the soil pH of Zunyi tobacco field has obvious spatial-temporal heterogeneity, and further research on its evolution causes and control strategies should be carried out in the future.