| Soil quality is closely related to human health. Heavy metals in the soil can be harmful to human body health through the soil-plant system. It is significance that to control the farmland soil quality through pay attention to the dynamic change of farmland soil heavy metal. Based on two long experiments on application of nitrogen and phosphorus combined with organic fertilizers and the different ways of straw returned. Determined 8 kinds of heavy metals in the soil of all treatments and the heavy metal contents in stem, leaf, seed, cob of corn plant in 2013, In order to analysis the effects of balance and interannual and profile changes of heavy metal contents in cinnamon soil and corn plant on long-term fertilization. So it can prevent heavy metal pollution of the farmland soil and provide theoretical basis for the reasonable fertilization. Main conclusions are as follows:1. The absorption of eight kinds of heavy metal of maize grain are different. Except N3P3M0 and N0P0M6 treatments, fertilization treatments Cd and Hg contents are below N0P0M0. Fertilization treatments Pb contents in corn grains analyzed in 2013 were exceed their respective thresholds of the national food safety standard. Increasing organic fertilizer on corn grain cause As cumulation significantly than the single fertilizer. Production dilution effect could not add the grain Cu and Zn contents with increasing organic fertilizer. Corn grain Cr content rise before they are reduced with the increase of fertilizer rate. With the increase rate of chemical fertilizer corn grain Ni content increased significantly, increasing organic fertilizer can reduce the accumulation of Ni in corn seeds. All different ways of straw returned treatments of eight heavy metals in minimum accumulation in seeds, except Pb content, other elements are under the limited food safety standards. Straw returned grain Cu, Zn and Cr contents were higher than straw unreturned A1. Straw returned could reduce corn grain Cd, Hg, As, Ni contents.2. Long-term nitrogen and phosphorus combined with organic fertilizer: Soil heavy metal input and output in a rough calculation results showed that: The Cu, Zn, Cd,and Ni input and output calculation of no fertilizer N0P0M0 treatment and chemical fertilizer treatment showed deficit roughly by 22 years. Chemical with organic fertilizer treatments were increased. The Pb and Hg content of no fertilizer treatments showed a deficit, other treatments showed a surplus. N0P0M0 and NjPiMo. accumulation loss by 22 years, other treatments increased with add of fertilizer rate. Long-term different straw returned into filed:The Pb, Hg, As and Cr input and output calculation of treatments showed increase roughly by 21 years. The Cd and Ni of A1 treatment showed deficit by 21 years. Straw returned treatments were increased. Cu and Zn are different from the other six elements.3. Heavy metal inter-annual features of cinnamon soil showed that, Pb, Cr and Ni contents increased in 2013. Cd and Zn had no obvious change. Hg, As and Cu reduced. It is not significant difference between treatments that fertilization on soil Cd, Pb, Hg, As, Cr and Ni; Chemical and organic fertilizer effects Cu and Zn between treatments of soil significant, single chemical fertilizer was effects not significant. All nitrogen and phosphorus combined with organic fertilizer treatments and different straw returned into filed treatments Pb content of soil compared with foundation soil samples increased 4.42%～20.95%,10.22%～28.80% respectively. Cr content of soil increased 4.58%～13.69%,6.56%～8.79% respectively. Ni content of soil increased 1.09%～10.34%,4.63%～8.57% respectively. Nitrogen and phosphorus combined with organic fertilizer treatments Cd content of soil compared with foundation soil samples increased 0.05%～23.80%, except N0P0M0, N1P1M0 and N3P2M3 treatments. Different straw returned into filed treatments Cd content of soil changed-13.32%～22.77%. Two experiments Zn content of soil changed-6.84%～22.28%,-9.99%～2.56% respectively. Hg and As contents of soil reduced 29.30%～74.20%,50.00%～70.59% respectively. As content of soil changed-41.54%～-17.10%,-19.27% 1.21% respectively. Cu content of soil changed-19.75%～4.57%,-23.72% ～-7.53% respectively.4. Heavy metals variation characteristics of long-term nitrogen and phosphorus combined with organic fertilizer in the soil surface of 0～20 cm, 20～40 cm showed that: Cd, Pb, Cu, Zn and Cr contents in the soil surface of 0～20 cm is higher than that of no fertilizer treatment; Pb content of fertilization treatments in 20～40 cm is lower than no fertilizer treatment. Pb mainly gathered in the surface layer. Heavy metal content variation characteristics of different ways of straw returned in the soil surface layer of 0～20 cm,20～40 cm showed that: The content of Cd, Pb, Hg and As in the soil top layer of 0～20 cm is difference between treatments. It is not significantly affected by the returning straw in different ways, mainly because migration of heavy metal in 0～40 cm soil layer change; Both of them effect contents of Cu, Zn and Cr were significantly between treatments.5. In addition to the heavy metal elements Cr of foundation soil in the study area, other seven kinds of elements content are higher than the average background soil heavy metal elements in Shanxi Province. The contents of eight heavy metals in soil tested in 2013 did not exceed the upper limits of the grade Ⅱ criteria of the National Standard for Soil Environment. |
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