Soil taxonomy and suitability assessment on typical tobacco-planting farmlands in Guizhou, Southwest China

The classification accuracy of tobacco soil in Guizhou Province remains to be verified. In this paper, 36 typical tobacco-planting farmlands were selected in various regions of Guizhou, and soil taxonomy of the farmlands was identified according to the information of soil-forming factors, profile morphological characteristics and measured data of soil physiochemical properties. Meanwhile, the suitability of the farmlands for tobacco planting was also briefly assessed. The diagnostic horizons of the surveyed farmlands include anthrostagnic epipedon, ochric epipedon, hydragric horizon, Fe-leachic horizon, LAC-ferric horizon, argic horizon, agric horizon and cambic horizon. The diagnostic characteristics included anthrostagnic-, perudic-, aquic- and udic-soil moisture regimes, gleyic features, redoxic features, lithologic character of carbonate rocks, humic property and ferric property, etc. Their soils of the farmlands belonged to Anthrosols, Ferrosols, Argosols, Cambosols and Primosols in soil orders, and there were 4, 8, 7, 5 and 1 soil subgroups in Anthrosols, Ferrosols, Argosols, Cambosols and Primosols, respectively. Soil textures of the farmlands included sandy loam, silt loam, loam, silty clay loam, clay loam, silty clay and clay, and 29 (80.6%) farmlands were unsuitable in texture for tobacco planting due to the clayey texture; 34 (94.4%) farmlands were unsuitable in plough thickness (less than 30 cm) for tobacco planting. For soil chemical properties of plough layer, pH ranged from 4.7 to 8.5, SOM from 12.3 to 55.5 g/kg, available nitrogen from 51.5 to 257.3 mg/kg, available phosphorus from 4.3 to 99.94 mg/kg, available potassium from 95 to 885 mg/kg, available Zn from 0.04 to 3.97 mg/kg, available Mo from 0.68 to 7.45 mg/kg and available B from 0.07 to 1.76 mg/kg; all spanned from the low grades to high grades. 16 (44.4%), 17 (47.2%), 13 (26.1%), 26 (72.2%), 30 (83.3%), 26 (72.2%), 20 (55.6%) and 30 (83.3%) of the farmlands were unsuitable in pH, SOM, available nitrogen, available phosphorus, available potassium, available Zn, available Mo and available B for tobacco planting, respectively. This study provides a theoretical basis for the sustainable development of tobacco field soil conservation and flue-cured tobacco production.