Movements of cations in forest soil solution enriched two anions

Abstract

NH₄Cl as a source of NO₃^--N and Cl^- was used to clarify the composition and changes in concentrations of cations in the soil solution of a forest. The investigation was conducted in a young (24-year-old) sugi (Cryptomeria japonica) stand, in Gumma Prefecture from May to October 1989. Soil parent materials were paleozoic strata of sandstone and phylite. The pH (H₂O) of the surface soil was relatively small (about 4.5) for a sugi stand. The soil solution was sampled at soil depths of 10, 20, 30, and 50cm using a soil solution sampler attached to a porous ceramic cup. The applied NH₄⁺-N almost changed to NO₃^--N early on. Leaching of cations from the soil colloid to the soil solution was affected by the sum of the concentrations of the main anions, not by a specific anions. Ca²⁺, Al³⁺, Mg²⁺, K⁺, and H⁺ increased in that order with increases in the sum of the concentrations of the anions. An exponential correlation was observed between H⁺ and Al³⁺ concentrations in the soil solution. When the H⁺ concentration in the soil solution was more than 0.1 me l^-1 (below pH 4). Al³⁺ concentration was increased greatly. Any increases in the concentration in soil with small pHs should be given attention in order to maintain the soil fertility.