The Effects of Simulated Acid Rain on the Uptake of Mineral Elements in Soybean Plants

Abstract

Adverse effects of acid rain on the growth of plants include acidification of soils and the subsequent leaching of basic cations and release of certain elements in potentially toxic concentrations from soil. The present study describes changes in the elemental conditions of cultivated soil and soybean plants exposed to simulated acid rain.
The cultivated soil pH (soil: H₂O=1:2.5) at the upper layer (0-5cm) was significantly decreased with increasing acidity of simulated acid rain. At pH 2.0, the contents of soluble basic cations, Mn and Zn in water (soil: H₂O=1:5) were significantly increased in the upper soil layer (0-5cm) compared with pH 5.6. As a result of these changes on soil conditions, the uptake rate of basic cations, Cu, Mn and Zn by the soybean plants were increased by exposing the simulated acid rain at pH 2.0. These results suggested that the concentration of Mn and Cu in plant are available to estimate the acidification of soil with acid rain.
On the other hand, despite the contents of soluble Al in 1N CH₃COONH₄ was increased and of soluble P in water was decreased with decreasing pH of soil in the upper soil layer, P uptake rate by soybean plants was increased at pH 2.0. Any effects of toxic element were not observed at all pH treatments.
These results suggested that soil chamistry may change significantly in upper layer by simulated acid rain treatment at pH 3.0 or below, but the effects of such changes were not important on the growth and yield of soybean plants under the normal manuring practice.