Effects of roadside soil extracts on seed germination and root elongation of edible crops

Aqueous extracts of soils from three areas near major roads with marked differences in annual average daily traffic (AADT)—Tai Po (commercial and residential area with AADT 23730), Man Uk Pin (minor agricultural area with AADT 1150) and Shek O (recreational area with AADT 1590)—were prepared for testing their effects on seed germination and root elongation of three vegetable crops, Brassica chinensis, Brassica parachinensis and Daucus carota. It was discovered that the aqueous extracts of soils from the minor agricultural area had the highest content of various heavy metals (Pb 3·41 ppm, Zn 7·21 ppm, Cu 0·47 ppm, Cd 0·13 ppm and Mn 0·5 ppm) and were the most prominent in suppressing the root elongation and seed germination of the crops. In view of the low value of AADT for the agricultural area, it is suggested that application of fertilizers and pesticides might contribute to the input of metal contents. Copyright © 1983 Published by Elsevier Ltd.