Study On The Transfer Characteristics Of Zinc And Cadmium Between Different Parts Of Soil-rice System

The zinc and cadmium contents of52pairs of surface soils and correspondingroot, stem, leaf and grain samples of rice collected from Liancheng County, FujianProvince were determined, the accumulation of Zn and Cd in the soils and the variousparts of rice, and the transfer characteristics of Zn and Cd in the soils to the root, stem,leaf and grains of rice were studied. The main results were as follows.1. The contents of total soil Zn varied from72.26mg.kg-1to444.15mg.kg-1withan average of199.12mg.kg-1. The DTPA-extractable (available) Zn of the soils werebetween5.89mg.kg-1and23.59mg.kg-1with a mean of15.52mg.kg-1. The DTPA-Znhad a highly significant correlation with the total Zn. Both the total Zn and theDTPA-Zn showed a highly significant correlation with soil pH2. The total Zn and DTPA-Zn of the soils were significantly correlated with theZn content in the roots, stems and leaves. The total soil Zn had a highly andnegatively significant correlation with the transfer factors (total Zn basis) betweensoil-to-root, soil-to-stem, soil-to-leaf and soil-to-grain. The DTPA-Zn was negativelyand significantly correlated with the transfer factors (DTPA-extractable Zn) betweensoil-to-root, soil-to-stem, soil-to-leaf and soil-to-grain. The Zn concentration of brownrice grains showed positive and significant correlations with root-to-stem transferfactors.3. The total soil Cd were between0.25mg.kg-1and6.66mg.kg-1with an averageof2.41mg.kg-1. CaCl2-extractable Cd was between0.040mg.kg-1and1.671mg.kg-1.Total soil Cd was highly and significantly correlated with CaCl2-extractable Cd andsoil pH. The CaCl2-extractable Cd showed a highly significant correlation with soilorganic matter content. The total soil Cd was significantly correlated with the Cdconcentrations of the root and leaf of rice. CaCl2-extractable Cd showed highlysignificant correlations with the Cd concentrations of roots, stems and leaves.4. Total soil Cd was negatively and significantly correlated with the transferfactors (total soil Cd basis) of soil-to-root, soil-to-stem, soil-to-leaf, and soil-to-grain.CaCl2-extractable Cd was negatively and significantly correlated with the transfer factors (CaCl2-extractable Cd basis) of soil-to-root, soil-to-stem and soil-to-leaf. TheCd concentration of rice grain showed a positive correlation with the transfer factorsof root-to-stem, stem-to-leaf and stem-to-grain.5. The above results showed that the reliability for total and available soil Zn orCd to predict the concentrations of Zn or Cd in the root, stem, leaf and grain of ricevaried greatly. It seems difficult for both total and available soil Zn or Cd alone topredict the Zn or Cd concentrations in rice grain because of the important roles ofphysiological and biochemical processes within rice plant. The concentrations of Znand Cd in brown grain were correlated with the transfer factors of Zn or Cd betweenrice organs, which should be considered when the concentrations of Zn or Cd in ricegrain would be predicted.