Aims Southern Hunan is the largest flue-cured tobacco-growing area in Hunan, China, aided by climate and soil conducive to the growth and development of tobacco. Our objectives were to evaluate climate feasibility, soil fertility and tobacco quality, and provide a scientific basis for classifying southern Hunan tobacco-growing areas.
Methods We obtained climate data for 30 years, including different growth and development periods and total sunlight hours during the field period, for the counties of Xintian, Yongxing, Jianghua, Jiangyong, Daoxian, Ningyuan, Guiyang, Jiahe, Hengnan and Lanshan from the Hunan Meteorology Bureau. We collected 1 225 soil samples from 2002 to 2003 and determined soil parameters, including pH, organic matter, nutrient elements and cation exchange capacity (CEC). We selected three or four flue-cured tobacco varieties from southern Hunan in 2004 and determined six appearance quality indexes and nine sensory quality indexes of 15 tobacco samples of C3F grades. We estimated climate feasibility index (CFI), soil feasibility index (SFI), appearance quality index (AQI) and sensory quality index (SQI) for tobacco by applying membership function and estimating weight values for each index by using principal components analysis.
Important findings The CFI was (79.59%±3.96%) and ranged from 74.71% to 83.98%. The areas had feasible temperature, a long period with average daily temperature ≥20 ℃, high accumulated temperature of ≥10 ℃, small day-and-night temperature differences, abundant precipitation, high humidity, and low sunlight percentage during field periods. The SFI was (43.92%±15.49%) and ranged from 13.32% to 82.82%. The soil had high nutrient storage capability and was rich in organic matter, total N, hydrolytic N, available P and most micro elements; however, pH was neutral to slightly alkaline and total P, total K and available K were insufficient for tobacco. Furthermore, the ratio of exchangeable Ca to Mg was unbalanced, available S was high and available B was lacking. The AQI and SQI were (86.65%±3.29%) and (63.08%±0.74%), respectively. Tobacco leaves had good maturity, open configuration and high quality of aroma; undesirable taste and biting taste were small.