Abstract
This study was conducted to evaluate the effect of increasing soil pH on cadmium (Cd) uptake by soybean. We conducted our experiment in the Jinzu River basin in a low pH (around 5) soil in an upland field that was converted from paddy field and was slightly polluted with Cd. Base application was applied to some plots increasing the soil pH as high as 7; in the pH range above 6, the soybean seed Cd concentration decreased from around 0.5mg kg^<-1> to around 0.25mg kg^<-1>. The Cd concentration and accumulation in the shoots decreased linearly with increasing soil pH in the full bloom stage and the full seed stage. Therefore, soil pH amendment was effective in restricting Cd uptake in the early reproductive stage. The Cd concentration in the soil solution decreased exponentially with increasing soil pH; we attribute the reduced Cd uptake by soybean roots to the decreased Cd concentration in the soil solution. The soil pH amendment often increased the dry matter production, main stem length, and grain yield. However, there remains a possibility that grain yield was not as high as it could have been because of the rough weather conditions during the reproductive stage or manganese deficiency when pH was around 7. In conclusion, amending soil pH with base effectively restrained Cd uptake by soybean in a field slightly polluted with Cd.
