Effect Of Plastic Film Mulching On Translocation Characteristics Of Heavy Metals In Soil And Crop System

The experiments was conducted in two different planting patterns (film covering and non film covering) with broad bean, maize and lettuce to study effect of plastic film mulching on translocation characteristics of heavy metals in the soil and crop system.The experiment results showed that by plastic film mulching, soil organic matter was decreased, plant weight was increased, soil pH was increased in soil-broad bean and soil-lettuce systems, however decreased in soil-maize system. And the amount of both soil bacteria and fungi was increased, while the behave of actinomycetes was more complex, it was increased by 51.2% and 27.5% in soil-broad bean and maize root soils respectively, but it was decreased by 46.2% in lettuce root soil. By plastic film mulching, the bioavailability of heavy metals was decreased in soil-broad bean and soil-lettuce system, however increased in soil-maize system.In soil-broad bean system, plastic film mulching influenced a little to the heavy metal enrichments of root, except Zn, and it obviously promoted the translocation of heavy metals from root to lamina, in particular, it greatly promoted the translocation of element Fe and Pb; however plastic film mulching reduced translocation of majority heavy metals from root to fruit, except Pb. In soil- maize system, plastic film mulching promoted the uptake of heavy metals (except Mn) of the root, and promoted the translocation of element Pb and Mn from root to caudex, lamina and fruit, and the translocation of other heavy metals (except Cu) from root to fruit. In soil-lettuce system, plastic film mulching promoted the uptake of heavy metals of the root, and reduced the translocation of heavy metals from root to caudex and from root to lamina (except Cu and Zn ).The experiment results showed that by organic fertilizer cultivation, soil pH was decreased, and soil organic matter and the amount of soil bacteria were increased, as well as plant weight. This cultivation also increased the bioavailability of heavy metals. In soil-broad bean system, the organic fertilizing cultivation promoted the translocation of element Pb from root to lamina and fruit. In soil-maize system, the cultivation increased the heavy metals of root and lamina, but reduced the heavy metals of caudex. the cultivation promoted the translocation of element Fe from root to caudex, lamina and fruit, and the translocation of element Cu from root to fruit.The experiment results showed that the effect mechanism of plastic film mulching on the migration of heavy metals from soil to the crop come from two aspects. The first is changing the distribution of heavy metals in soil, the second may be associated with promoting plant growth, thereby contributing to the crop uptake of certain heavy metals.