Effects of liming on void space and aggregation in an upland grassland soil

The aim of this paper is to study changes in water-stable aggregation and void space in an upland grassland soil following a surface application of calcium carbonate intended to increase the diversity of soil fauna. Samples of the H and Ah horizons were collected at the time of the first lime application (June 1999) and 1 and 2 years thereafter. Void space in both horizons was quantified by image analysis of thin sections and the size distribution of water-stable aggregates in the Ah horizon was determined by laser granulometry. The effect of liming was largely seen in the H horizon where pH in CaCl2 increased from 3.4 to 4.1. Percentage void space and % voids >1000 μm2 increased significantly in the H horizon between 1999 and 2001, and there was a significant liming effect. In the mineral Ah horizon, only the change in void space over time was statistically significant. There were no significant differences in aggregate stability following liming or over time, despite a significant reduction in organic carbon concentration between 1999 and 2001. The change in void space with liming was consistent with reported changes in the abundance of larger enchytraeid genera such as Fridericia and with changes in earthworm abundance. Changes in void space with time may be linked to the cessation of grazing at the experimental site.