The effects of time of incubation on the relation between charge and pH of soil

Summary Samples of two Andisols and two Ultisols from southern Chile were incubated with acid or with lime for up to 60 d at 25°C or for 1 day at 40°C or at 60°C. The changes in positive and negative charge were measured. The Andisols reacted slowly at 25°C. They lost protons to the solution at high p H, thus increasing the negative charge on the soils and decreasing the pH of the solution. They gained protons at low p H, thus increasing the positive charge on the soils and increasing the p H of the solution. The Ultisols reacted more quickly but again charge and p H changed through time. For all samples, the rate of reaction was increased by incubating at 60°C. Brief incubation at 60°C produces a similar relation to that obtained after longer incubation at 25°C. This provides a convenient means by which measurements can be made more quickly.