Cadmium Immobilization In Tobacco Field Soil Using Various Chemical Amendments

Hunan province is an important tobacco-producing region in China. The existing research does show that Cd has considerable ability of enrichment to tobacco. High levels of Cd concentrations in soils made the yield and quality of tobacco reduced, and influenced tobacco production of some tobacco planting base in Hunan, as well as effects human healthy when Cd transfer to human by tobacco. Therefore, the research of scientific using soil amendments to reduce bioavailability of Cd in the soil where plant tobacco, and control the migration and transportation of Cd towards tobacco has very important practical significance. By sampling and analyzing, this study made a preliminary survey on contamination of heavy metals of soil, irrigation water and tobacco in Chenzhou tobacco-producing region of Hunan province. The field experiment was carried out to explore the inhibition effect of sepiolite, calcium-magnesia phosphate fertilizer and calcium carbonate on tobacco absorbing cadmium of soil. The main conclusions of the study are as follows:1. In Chenzhou cigarette-producing areas, there is no obvious heavy metal pollution in irrigation water, most of the soil sampling points exist no pollution of Pb, Cu and Zn, Mn content in partial soil points are on the High levels, half of the soil sample points has obvious Cd contamination, the transfer of Cd to tobacco is relatively serious, Mn is also much, Cu and Zn are general, and Pb is rare.2. Under the application amount designed in this experiment, sepiolite and calcium-magnesia phosphate fertilizer this2kinds of control materials both can effectively reduce the available form content of Cd in the tobacco-producing soil, reduce the migration and transportation of Cd in soil to each part of the tobacco, and the larger application amount the better. There is no significant difference in comparison with the effect of these two kinds of materials. Sepiolite and calcium-magnesia phosphate fertilizer both made the soil pH slightly increase, soil pH increase is also one reason for the reduction of soil available form content of Cd, and this is helpful to control the tobacco’s absorption on Cd. However, tobacco growth needs suitable pH range,2kinds of materials cannot be used excessive application. Low quantity (400g/m2) calcium-magnesia phosphate fertilizer treatment can improve tobacco fresh weight,800g/m2calcium-magnesia phosphate fertilizer and sepiolite such two treatments have no significant effect on tobacco fresh weight, plant height and available leaf number.3. Calcium carbonate treatment made the soil pH obviously improved, significantly reduced the available form content of Cd and the exchangeable Cd content in soil, thus significantly reduced the Cd content in root, stem and leaf. Therefore, calcium carbonate can be used to control cadmium pollution in tobacco-producing field, reduce tobacco on cadmium accumulation, and reduce the health risks of tobacco to human body. But the calcium carbonate also has a significant effect on tobacco absorbing soil nutrients at the same time. Calcium carbonate increased available P and Ca exchangeable content in soil, reduced the soil available Fe, available Cu, available Zn content, made the tobacco total Ca content increase considerably, total Fe content reduce.(4)Sepiolite, calcium-magnesia phosphate fertilizer and Calcium carbonate can reduce uptake of Cd in tobacco, within the scope of addition of sepiolite, calcium-magnesia phosphate fertilizer≤533.3kg/mu, and calcium carbonate≤150kg/mu ware not negative impact on the growth of tobacco in this test. But all three materials increased the pH of the soil, which will bring to bad impact of growth of tobacco. So adjusting befittingly the amount of three materials applied is agreed in order to reducing cadmium in tobacco depending on the actual situation of soil cadmium pollution, and acidic fertilizer should be applied to be against increasing of pH resulting from the three materials used.