2017 年 8 巻 1 号 p. 77-84
In Japan, cadmium (Cd), copper (Cu) and arsenic have been designated as specific harmful substances in the Agricultural Land Soil Pollution Act. Though the safety standards of these substances have not been provided for upland field crops in Japan, it is important to minimize the concentration of these contaminants in agricultural products for both international trading and our health. The objective of this study is to clarify the effects of controlling groundwater levels on Cd and Cu uptake and growth and yield of soybeans. For this experiment, three plastic containers were prepared, and then 14cm-thick of non-contaminated gravel, 15cm-thick of non-contaminated soil (0.12 mg Cd kg-1; 2.4 mg Cu kg-1) and 25cm-thick of contaminated soil (2.24 mg Cd kg-1; 43.4 mg Cu kg-1) were placed in this order from the bottom of each container. Then the groundwater level of each container was maintained as 5cm (GL5), 10cm (GL10) and 40cm (GL40) during the growing period. As a result, Cd and Cu concentration of soybean seeds of GL5, GL10 and GL40 were 0.25, 0.52 and 1.07 mg Cd kg-1, respectively, and 5.08, 5.82 and 9.96 mg Cu kg-1, respectively. Significant difference in both Cd and Cu concentration of soybean seeds were found among three models at 5% level. On the other hand, growth and yield of soybeans tended to decrease with the rise of the groundwater level. Noticeably, plant heights and weights of a hundred grains were significantly different among these three models. From the above, it can be concluded that controlling groundwater levels can reduce Cd and Cu uptake and affect growth and yield of soybeans.
