Long-term Sludge Applications on Cadmium and Zinc Accumulation in Swiss Chard and Radish1
- A. C. Chang,
- A. L. Page and
- J. E. Warneke2
Swiss chard (Beta vulgare var. Fordhook) and radish (Raphanus sativus var. Cherry Belle) were grown twice annually (spring and fall) on a Ramona sandy loam (fine-loamy, mixed thermic, Typic Haploxeralfs) soil treated with 0, 22.5, 45, 90, and 180 Mg ha−1 yr−1 of composted sludges from Los Angeles. The soil received two sludge inputs of equal amounts each year and crops were planted shortly after each sludge incorporation. Cadmium and Zn accumulation of the plant tissue from 1976 to 1985 was examined. Results from the analysis of variance indicated that effects due to sludge application rates, seasons plants were grown, number of years of sludge application, and their interactions were all significant. If the data sets were partitioned according to sludge application rates and seasons, metal concentrations of the plant tissue may be expressed as a nonlinear regression model, y = a + b (1 − e−cx), where y is the metal concentration of the plant tissue, x is the cumulative sludge loading, and a, b, and c are constants. All but two nonlinear regressions were significant at p <0.05 with R2 from 0.38 to 0.95. The deviation of the observed values from the predictions of the regression model indicated that other factors might have also affected the metal uptake by plants. Stepwise multiple regression analysis of the partitioned data sets indicated that soil pH, soil salinity, soil temperature, and length of growing season influenced the metal accumulation in plant tissue.Please view the pdf by using the Full Text (PDF) link under 'View' to the left.
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