Soil surface applied lime shows low efficiency in alleviating subsoil acidity. Lime efficiency is increased through water-soluble organic compounds released from plant residues. A biological test was evaluated to verify the capacity of plant extracts on lime mobility in the soil. The test presents the following steps: plant material preparation; extraction of water soluble organic compounds; soil column preparation; soil surface lime addition; plant extract addition; irrigation with distillated water; biological test with an indicator plant (wheat, cultivar Anahuac); and root growth evaluation. Surface applied lime without plant residue increased pH and Ca, and decreased Al in the top 5 cm of soil. Lime with black oats and oil seed radish extracts increased pH and Ca and decreased Al up to the 20 cm soil depth. Wheat residue had no effect on lime mobility. Indicator root growth followed the effect of treatments on soil chemical composition: lime without plant residue enhanced root growth in the top 10 cm depth and lime with black oats and oil seed radish enhanced root growth up to the 20 cm depth. The biological test was efficient to evaluate the ability of plant residues in relation to lime mobility in the soil.
liming; subsoil acidity; biological test; leaching