Effects of sludge extracts on seed germination and root elongation of crops

Different concentrations of aqueous extracts of activated sludge were prepared by extracting with distilled water in an electric blender. They were then applied to the seeds of flowering Chinese cabbage, Brassica parachinensis and Chinese radish, Raphinus sativus var. longipinnatus, after being filtered through a Whatman No. 42 filter paper.
Seed germination and root elongation of the crops were retarded, especially at higher concentrations of sludge extracts (0.8 and 1%). Studies of root elongation clearly showed the effect of retardation, even at a concentration as low as 0.2%, although the percentage of seed germination at this particular concentration was similar to that of the control group which was treated with distilled water only. The seeds of flowering Chinese cabbage were more sensitive to the sludge extracts than the seeds of Chinese radish.
The harmful effects of substances other than heavy metals in the aqueous extracts of sewage sludge on seed germination and root elongation were revealed when the seeds of B. parachinensis were treated with mixtures of heavy metals with concentrations equivalent to those obtained in different portions of sludge extracts. Copyright © 1981 Published by Elsevier Ltd.