钝化剂-锌肥降低烟草镉含量长期效果研究

EFFECTS OF LONG-TERM AMENDMENT WITH PASSIVANT AND ZINC FERTILIZER ON CADMIUM REDUCTION IN TOBACCO GROWING IN A CD CONTAMINATED FIELD

采用田间小区试验，通过外源添加 1.5 mg kg-1镉（Cd）模拟轻度 Cd 污染土壤，研究赤泥、油菜秸秆、玉米秸秆及其组合并配施硫酸锌降低土壤 Cd 有效性和烟草各部位Cd 含量的长期效果。结果表明，施用钝化剂后，烟叶产量增加了 7.0%~32.1%，中上等烟叶比例提高了 2.9%~20.2%，烟草经济效益提高了 6.6%~31.3%。钝化剂处理土壤有效态 Cd 含量降低显著，2012 年和 2013 年降幅分别为 18.6%~47.4%、16.0%~27.0%。烟草各部位 Cd 含量排序为下部叶＞中部叶、上部叶＞茎秆，且均与土壤有效态 Cd 含量呈极显著正相关关系。2011—2013 年钝化剂处理烟草叶片 Cd 平均含量较对照分别降低了 28.3%、28.1%、15.2%，烟草各部位 Cd 含量年变化幅度下部叶最大，茎秆最小，叶位间 Cd 含量差异随钝化时间延长逐渐缩小。钝化剂降低土壤-烟草系统 Cd 生物有效性效果稳定持久，其中油菜秸秆优于玉米秸秆，有机无机复合钝化剂效果最好。配施锌肥后，2011—2013 年烟草叶片 Cd 含量较对照分别降低了 19.1%、23.3%、17.9%，且下部和中部叶片降低效果达到显著水平；中部和上部叶 Cd、Zn含量呈显著负相关关系。因此，在轻度 Cd 污染土壤上，赤泥油菜秸秆复合钝化剂配施锌肥是降低烟叶镉含量兼顾高产的最佳生产措施。

With rapid industrialization and urbanization in progress over the recent decade in China, the issue of Cd contamination of agricultural soils has become more and more serious. According to the surveys and statistics available that show about 7% of the agricultural soils have already exceeded the National Standard for Environmental Quality in Cd contamination and relative to other heavy metals and metalloids, cadmium （ Cd ） should be deem as an element of the first priority for control. Besides, tobacco is a high Cd accumulator, storing Cd mainly in its leaves, which, if consumed by chronical smokers, would leave Cd accumulated in their bodies. Therefore how to decrease Cd content in tobacco plant, especially in its leaves, has been a hot topic in the fields of tobacco industry and public health. In a three-year field plot experiment, red mud and/ or plant straw was amended in addition, or not, to Zn fertilization to explore its long-term effect on Cd in-situ immobilization in the soil and Cd accumulation in tobacco plant, so as to find a best way to reduce cadmium content in tobacco growing in contaminated soils. The experiment was designed to have five treatments in terms of amendment （red mud, rape straw, corn straw, red mud plus rape straw, and red mud plus corn straw ） and two levels of Zn fertilization. The soil in the experiment was artificially contaminated with 1.5 mg kg-1 cadmium added to the soil. Results show that compared with control, the yield of tobacco leaves and the ratio of mid-high grade leaves in amendment treatments were significantly increased by 2.6% ~ 32.3% and 2.9% - 20.2%, respectively, which brought about an increase in economic benefit by 6.6% - 31.3%. Among the treatments, the amendment of red mud plus rape straw was found to be the highest in both yield and economic benefit. The amendments stably decreased soil available Cd contents by 18.6%- 47.4% in 2012, and 16.0% - 27.0% in 2013. The plants from the treatment were found to follow an order, i.e. bottom leaf 〉 middle leaf and upper leaf 〉 stem in terms of Cd content in plant. The contents of Cd in tobacco were most positively related to soil available Cd content. Therefore, the Cd content in tobacco leaves in 2011, 2012 and 2013 decreased by 28.3%, 28.1% and 15.2% on average, respectively in all the amendment treatments. The effect was the most apparent in bottom leaves and the least in stem. Rape straw, full of thiols, was higher in Cd immobilization capacity than corn straw. Application of zinc fertilizer in addition to the amendments further significantly lowered Cd content in different parts of the tobacco plant at different seasons. In conclusion, the treatment of red mud, rape straw plus zinc fertilizer is the most effective one in this experiment to decrease Cd phytoavailability in soil-tobacco system. Therefore it can be extrapolated as a high cost-efficient measure to decrease Cd content in tobacco plants and increase yield of tobacco leaves in lightly Cd contaminated soils.