SOIL ACIDITY EFFECTS ON WHEAT SEEDLING ROOT-GROWTH

Soft red winter wheat (Triticum aestivum L. cv Hart) was used as a test crop in a bioassay technique to assess acid soil chemical constraints in major hill land soils of the Appalachian Region. Seedling root growth was related to amounts and forms of A1 in soil solution and A1 extracted by 0.01M CaCl2, 1M KCl, 0.5M CuCl2, and 0.33M LaCl3. Aluminum determined in the various extractants, total soil solution Al and soil solution Al reacting with 8-hydroxyquinoline, pyrocatechol violet, and aluminon showed large differences in root growth prediction ability. In general, Al extracted by 0.01M CaCl2 was a good predictor of root growth. Root elongation was more inhibited in subsurface horizons than in surface horizons. Although surface horizons had the lowest mean pH, the presence of high levels of exchangeable cations tended to ameliorate the Al toxicity. The root bioassay technique adapted here should be useful in assessing the potential Al toxicity of diverse soil types.