Abstract
Two kinds of soils were contaminated with cupric chloride and these soils were incubated at 20℃ for more than a month. Soil solutions were obtained from these soils with a centrifuge method. The toxicity of these soil solutions on the elongation of seminal roots of rice were compared with each other and that of cupric chloride in distilled water. The results showed that the soil solutions effected a decrease in the copper's toxicity, and there was a clear difference in the strength of this effect between these two kinds of solutions. This result was the same as that of the last paper, so it was assumed that the organic compounds and nutrient elements ions in the soil solutions effected a decrease in the copper's toxicity and also that the strength of these effects depends on the amounts of these substances in the soil solutions. There was a large difference in the copper concentration in soil solutions between these two kinds of soil-alluvial soil and volcanic ash soil. Copper concentration in soil solution of the former soil was more than ten times higher than that of the latter for the same added concentration of cupric chloride. It was assumed that this phenomenon depends on the difference in clay mineral content of these two kinds of soils, because there was no difference in the content of fumus between both soils.
