Open access publications in the SLU publication database

Abstract

A 22-month incubation experiment was conducted to study the effect of lime on clay dispersion, wet aggregate stability (WAS) and dissolved reactive phosphorus (DRP), using a heavy clay subsoil with an initial pH of 7.0 and 7.3 g kg(-1) of soil organic carbon. Lime was applied to achieve soil pH values of 7.5, 8 and 8.4. Clay dispersion decreased linearly with increased pH (corresponding to an increase in lime amount) for both lime types (R-2 = 0.44 for CaO; R-2 = 0.53 for CaCO3, P < 0.05), with a decrease of 2-16 % (CaO) and 3-17 % (CaCO3) compared with the control.Both WAS and DRP followed piece-wise linear functions, with an increase and peak around pH 7.5-7.8, and a decline at higher pH (WAS: R-2 = 0.73 for CaO, R-2 = 0.68 for CaCO3, P < 0.001; DRP: R-2 = 0.84 for CaCO3, R-2 = 0.33 for CaO, P < 0.001). Wet aggregate stability increased on average by 13 % and 11 % at the lowest and intermediate levels, respectively, compared with the control. At the highest lime application rate, WAS was 6 % (CaO) and 8 % (CaCO3) lower than in the control. These differences were probably caused by changes in electrical charge and in concentrations of soluble calcium and dissolved organic carbon (DOC) as the pH increased. More studies are needed to understand the processes in detail and to draw conclusions that are more robust.