Effects of soil redox condition on the transformations of Fe and Cd in soils and their uptake by rice
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    Abstract:

    In a pot experiment rice seedlings were planted in mesh bags that were filled with vermiculite to simulate rhizosphere and the bags were imbedded separately in submerged red, paddy and saline soils for cultivation for 13days. Results show that during the rice cultivation period, pH in the red, paddy and saline soils varied in the range of 6.05~6.78, 6.47~7.33 and 6.47~7.44, respectively. In the OM (organic matter) treatments, all the soils, regardless of rhizospheric or nonrhizospheric, decreased in pH, except for rhizospheric red soil, which increased significantly. Eh in all the rhizospheric soils of the control treatments lingered within 233~385 mV, and treatment with OM reduced rhizospheric Eh, but increased nonrhizospheric Eh of the red and paddy soils. Oxide-Fe fraction accounted for more than 90% of the reductively dissolved Fe and vermiculite-absorbed Fe, which was significantly correlated with soil solution Eh and pe+pH, indicating that Fe redox reactions occurred simultaneously on the surfaces of the soils and the vermiculites, but in opposite directions. The formation of iron plaque on root surface of the rice seedlings was related to redox conditions in rhizosphere. In the rhizospheres of CK (higher in Eh), Fe content on the root surface decreased with increasing pH, whereas in the rhizospheres of OM treatment (lower in Eh), Fe increased with increasing pH. In the red soil, iron plaques on the root surface retarded Fe absorption, while in the paddy and saline soils it acted reversely. Cd content on the root surface was significantly and positively related to Cd in root and in shoot. In the red soil iron plagued on the root surface retarded adsorption and uptake of Cd by rice, whereas in paddy and saline soils, it acted reversely too.

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Chen Xue, Liu Danqing, Wang Shu, Yang Yazhou, Li Yujiao, Hu Hao, Zhang Chunhua, Ge Ying. Effects of soil redox condition on the transformations of Fe and Cd in soils and their uptake by rice[J]. Acta Pedologica Sinica,2013,50(3):548-555.

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History
  • Received:May 22,2012
  • Revised:December 26,2012
  • Adopted:December 28,2012
  • Online: March 04,2013
  • Published: