The efficiency of subsurface acidity alleviation by surface liming in the presence of crop residues is controversial and needs more information. The study aimed to quantify the contribution of cover crop residues, regarding their contents of low molar mass organic acids and soluble nutrients to the mobilization of reaction products of surface-applied lime in the soil profile. Two experiments were conducted under laboratory conditions using 30 cm high PVC cylinders filled with acid and clayey red latosol. Treatments consisted of sole application of lime to 80% soil base saturation (6.1 t ha -1) or lime in combination with radish ( Raphanus sativus) or black oat ( Avena strigosa) [ Avena nuda] crop residues (20 t ha -1), as well as the equivalent amounts of organic acids and inorganic salts present in the plant materials. The application of lime alone or in combination with plant material reduced soil acidity in the 0-8 cm surface layer only. The low recovery of organic acids added to the soils (?7.2%) indicates that the acids were rapidly metabolized or adsorbed to the soil colloidal fraction, which explains the small effect on cation mobilization. A substantial part of the ion mobilization in the soil and leached solution after application of crop residues was probably due to the plant-own inorganic ion content due to the high water solubility: 65 to 71% for cations and 84% for anions. The greatest amount of aluminium displaced from the soil was due to the application of inorganic salt solutions. The presence of plant residues had little effect on the mobilization of the reaction products of surface-applied lime.
