Reduction of aluminum toxicity to radish by alkaline oxygen treated kraft lignin

To obtain a soil-conditioning agent for acid soil containing excess aluminum ions (AL), kraft lignin was modified by alkaline oxygen treatment. The growth of radish root in solution and in soil containing AL with or without addition of these lignins under controlled pH was examined. We concluded the following. Growth inhibition of radish roots by AL can be removed by adding alkaline oxygentreated lignins in the range of pH 4.5–4.8 in soil. A similar result was obtained at pH 4.5 in a culture solution. The reduction of AL toxicity to plant may be due to the aggregation between AL and the modified lignin at low concentrations of modified lignin because soluble AL could not be detected. On other hand, elongation of radish root was not obviously inhibited, although the soluble AL in the solution culture was at an extremely high level when the dosage of a modified lignin was high. This suggests that the reduction in AL toxicity to plants was due to formation of a complex between AL and acidic groups of the modified lignin.Part of this report was presented at the 49th Annual Meeting of the Japan Wood Research Society, Tokyo, April 1999 and the 44th Lignin Symposium, Gifu, October 1999