The importance of soil solution chemistry to nickel toxicity on barley root elongation

The influence of soil solution properties on nickel (Ni) toxicity and its effects on barley root elongation were investigated using 17 Chinese soils amended with Ni chloride, which may or may not have undergone leaching treatment. The Ni in the soil solution was recorded in the soil pore water and in the extraction with 0.01 M CaCl2. The ranges of effective concentrations for CaCl2 -extracted Ni that caused 10% root elongation inhibition (EC10) and for 50% inhibition (EC50) varied widely from 65 to 114 times between different soils. The EC10 and EC50 values for Ni toxicity thresholds in soil pore water for unleached and leached soils varied from 40 to 124 times. In most soils, the toxicity thresholds for Ni, based on 0.01 M CaCl2 or soil pore water extractions, were not significantly affected by leaching. Regression models between toxicity thresholds and soil solution chemistry were developed and showed that Mg and S in soil pore water were the two most important factors affecting the extent of Ni toxicity on barley root elongation. However, pH showed only a weak correlation with toxicity thresholds.