Abstract:
Objective This study aims to understand the distribution characteristics and the relationships among soil pH, Ca2+, Mg2+ and CaCO3 in tobacco-planting fields in Guizhou and then scientifically to guide the adjustment of soil acidity or alkalinity as well as the application of calcium and magnesium fertilizers.
Method Topsoil samples (0-20 cm) were collected from 500 typical tobacco-planting fields widely distributed in Guizhou. Soil pH, exchangeable Ca2+, Mg2+ and CaCO3 were determined, and then the content changes and correlation regression models among different parent materials, soil types and regions were analyzed and discussed with SPSS.
Result According to the suitability for tobacco-planting, 20.0%, 18.2% and 56.4% of samples were lower and 37.0%, 55.8% and 29.6% were higher in pH values, Ca2+ and Mg2+ contents, respectively. 88.4% and 6.2% of samples were lower than 10 g kg−1 or 10 ~ 30 g kg−1 in CaCO3 content. Soil pH, Ca2+, Mg2+ and CaCO3 were differed with different parent materials. Soil pH and Mg2+ contents of paddy soil and lime soil were significantly higher than those of other soil types. The differences of pH, Ca2+ and Mg2+ in regions were larger than that of CaCO3. Correlation analysis showed that there were significant positive correlations among pH, Ca2+, Mg2+ and CaCO3 (P < 0.01), and the linear regression model of pH with Ca2+, Mg2+ and CaCO3 was as follows: pH = 5.065+0.393Mg2++0.081Ca2++0.001CaCO3 (R2 = 0.578, P < 0.001, MAE = 0.58, RSME = 0.71).
Conclusion The contents and distribution of soil pH, Ca2+, Mg2+ and CaCO3 in Guizhou tobacco-planting fields are affected by parent materials, soil types and regions, and pH is affected by Ca2+, Mg2+ and CaCO3. For soil pH adjustment and the application of calcium and magnesium fertilizers, soil pH, Ca2+, Mg2+ and CaCO3 should be simultaneously considered due to their close relationships.