Abstract
Effects of impulsive and/or continuous load of H_2SO_4 on soil environment were investigated by using indoor lysimeters filled with Tsukuba light-colored andosol to which limed sewage sludge had been applied at a rate of 40kg m^<-2>. One lysimeter, called 'LC' plot, received 31mm equivalent of 0.1 mol L^<-1> H_2SO_4. Then the plot was irrigated with dil. H_2SO_4. (pH 3.5) for 4y at a rate of 31mm week^<-1>. To another lysimeter, 'SW' plot, 13mm of 0.1 mol L^<-1> H_2SO_4 was applied at first and the same volume of distilled water as 'LC' plot was irrigated thereafter. Rape plants were cultivated on both plots for 17 times during the experimental period. The pH at the surface soil declined to 7.0-7.4 by the acid impulse, but recovered to around 8.4 within 4 months. The yield and Mn concentration of the crop became higher in the 'LC' plot relative to the 'SW' plot. The potassium level was parallel with the crop yield in the 'LC'plot. The load of 0.1 mol L^<-1> H_2SO_4 caused leaching of S, Ca and Mg down to the depth of 30cm ('SW' plot) or 80cm ('LC' plot). Continuous irrigation of pH 3.5 water slightly elevated the levels of these elements in the soil solution at the depths of 30 and 55cm. In accordance with the cultivation, S, Ca, Mg and especially NO_3-N concentrations in soil solution showed oscillation at the upper 10-55cm layers. At the 30cm depth of the 'LC' plot, Zn and Cd levels were increased during 300-500th day with a simultaneous increase of the TOC and pH values, suggesting mobilization of these metals as chelated forms.
