MODELING UPTAKE OF CADMIUM BY PLANTS IN SLUDGE-TREATED SOILS

Laboratory and greenhouse experiments were conducted to formulate pred ictive models for the uptake of cadmium by Jelly bean (Phaseolus vulga ris L.), grown in sludge-treated soils, on the basis of soil and plant -root properties. The values of the porous system self-diffusion co-ef ficient (Dp) of cadmium fulvic acid complexes in soils were higher tha n those when Cd was applied as inorganic salts. Pot experiments were c onducted with ten sewage sludge-treated old alluvium, non-calcareous, non-saline (Vertisol) soils of Patna wherein a Jelly bean crop was gro wn after soil treatment with 0 and 5 mgkg(-1) isotopically tagged and organically complexed Cd. The results indicated that the application o f Cd through Cd-FA in soils did nor influence the dry matter yield and root radius (r(0)), root density (L-V) and half distance between the roots (r(h)) of the crop, though if significantly increased the concen tration of Cd in the plants and its uptake by the crop. The soil organ ic carbon content, cation exchange capacity, clay content pH and EC we re used to predict uptake of Cd by the crop. The root parameters and p orous system self-diffusion co-efficient of Cd-FA in soils were able t o predict the Cd uptake by the crop with very high levels of confidenc e. The modified form of the mathematical model of Baldwin et al. (1973 ) (Plant Soil, 38, 1973, 621-35) was found to be useful in predicting the rate of uptake of Cd by Jelly bean grown in sludge-treated soils. (C) 1998 Elsevier Science Ltd. All rights reserved.