Status of chlorine content in tobacco-planting soils in Hunan province and tobacco responses on chlorine application

The analysis results of water-soluble Cl- contents of 3329 soils samples from main tobacco-planting areas of Hunan province showed that the mean values of water-soluble Cl- content was 16.6 mg/kg for these samples.There was a huge difference of Cl- contents between the soils of different tobacco-planting areas.Soil with low water-soluble Cl- content in western Hunan and central Hunan accounted for big portion.The results of field experiments showed that rational Cl- application was favor of increasing chlorophyll content in leaves and root activity in tobacco plants at vigorous growth stage,and promoting NRase activity in leaves at early growth stage of tobacco plants.In lower Cl- content soils,when dose of KCl(K2O) accounting for 15%30% of total potassium fertilizer,flue-cured tobacco yield increased 5.2%16.9%,production value added 1911.07348.5 yuan/hm2,and the proportion of middle and superior tobacco leaves raised 10.2%11.5%.The quality of flue-cured tobacco was also improved without causing Cl- accumulation in soils.We could concluded that KCl should be partly be applied instead of K2SO4 from the soils with low Cl- content in Hunan and south China from the point view of input cost and economic benefit of flue-cured tobacco.