Effect Of Different Fertilization On The Bio-availability Of Cd In Soil With Facility

Heavy metal cadmium (Cd) pollution has become a global environmental problem which has caused great harm to the ecosystem and human health. Recently, with a large amount of fertilizer applied into soil and thus fertilizer application will exert a certain impact on Cd in soil, so affecting the migration and transformation of Cd in soil-plant system. In recent years, the facility agriculture in our country has become an important part of modern agriculture, while the substantial input of fertilizer and organic fertilizer in the facility agriculture has become a common phenomenon, which can easily lead to the accumulation of heavy metals in soil. At the same time, the facility environment has the characteristics of high temperature, high humidity, semi-closed and so on and when the conditions change, we have no clear understanding of the effect of Cd transformation in the soil and the operation in the plant. This experiment is conducted to study the effects of single and different fertilizers application on Cd fraction in soil and the absorption of Cd in different parts of tomato cultivated by greenhouse pot experiment and laboratory culture experiment. In addition, it has also been discussed that the correlation between Cd fraction and plant absorption, and the effects of different environmental conditions on the fraction of Cd in polluted soil. Under the conditions of this experiment, the conclusions are as follow:(1) Compared with the control, during the growth period, without added Cd, the contents of exchangeable Cd in each treatment with different fertilizations have increased. While Cd added into the treatment, the content of exchangeable Cd in the treatment of potassium fertilizer and NPK were slightly increased, and the rest of the treatment of its exchange state Cd content has reduced.(2) During the growth period, the content of exchangeable Cd in soil samples decreasing, the content of Fe-Mn oxides bound Cd form shows an increasing trend, and the content of carbonate form and organic bound Cd is not obvious with time.(3) The absorption of Cd in tomato shows a rising trend with the increase of the amount of exogenous Cd. The absorption of Cd in overground part of tomato is always higher than underground part. All fertilization treatment can promote the absorption of Cd in tomato roots whether added a low amount of Cd or not at all. All treatment significantly reduced the absorption of Cd in every part of tomato which add a high amount of Cd (p<0.05).(4) Exchangeable Cd is the main fraction to influence the bio-availability of Cd, and has a positive correlation with the absorption of Cd (p<0.05). Fe-Mn oxides Cd has a negative correlation with the absorption of Cd whether in low amount of exogenous Cd treatment of tomato leaves or the addition of high amount of exogenous Cd treatment of tomato root (p<0.05), however, it has a positive correlation with the absorption of tomato leaves in high amounts of exogenous Cd (p<0.05). Carbonate bound Cd has a positive correlation with the absorption of Cd in tomato roots which does not add Cd, and has a positive correlation with the absorption of Cd in leaves of tomato with high amounts of exogenous Cd (p<0.05).(5) The effect of pH on the fraction of Cd is in descent order that are residual, exchangeable, Fe-Mn oxide bound, carbonate bound, organic bound. With the increase of pH, exchangeable Cd content showed a decreasing trend,and the decline range among the 0.289-1.983 mg-kg’-1, carbonate bound, Fe-Mn oxide bound and residual Cd generally present the trend of upward, and the variation range followed by 0.488-0.871 mg-kg-1,0.63-1.315 mg-kg-1 and 0.336-2.16 mg-kg-1.(6) The change of soil moisture content deeply affect the content of the exchangeable, Fe-Mn oxides bound and residual of Cd, however, it does not work obviously to the content of carbonate bound and organic bound Cd.