Effect of Soil-climate Conditions,Tobacco Varieties and their Interactions on Heavy Metal Contents of Tobacco Leaves in Zhaotong,Yunnan Province

Field experiments were carried out at ten tobacco-planting eco-regions in Zhaotong,Yunnan Province,to investigate the contents of heavy metals in tobacco leaves and their association with soil and climate conditions.The tobacco leaves in Zhaotong were characterized with lower contents of copper,mercury and arsenic and higher content of nickel,while the contents of zinc,lead and cadmium were similar to other tobacco-planting regions.The influencing degree of soil-climate and other factors on heavy metal contents of tobacco leaves varied.The relative contribution of soil-climate,tobacco variety and their interaction and leaf grade to total variation of the seven chemical components in tobacco leaves was 57.3%,3.4%,22.3% and 17.0%,respectively.This indicated that soil-climate conditions had the strongest effect on the heavy metal contents of tobacco leaves while the effect of variety was negligible.As to the soil-climate conditions,soil played a predominant role in controlling heavy metal contents of tobacco leaves while climate was secondary.