Short-Term Dynamics of Soil Aggregate Stability in the Field

Aggregate stability is a key property affecting the movement and storage of water, seedling emergence, and soil sensitivity to erosion. Many studies have shown that aggregate stability changes through time. Field monitoring studies performed with a relatively large (monthly) time step showed the seasonal trend of aggregate stability. However, shorter time step monitoring is required to explore dynamics of aggregate stability at short term. For now, biological activity was recognized to be the main factor of aggregate stability dynamics, but previous studies were currently based on the external stimulation of aggregate stability. The objectives of this study were to assess variations in aggregate stability at short time steps in the field and to identify the factors controlling these variations of stability. A 6-mo field monitoring was performed at short time step (2-5 d) on a bare field of Luvisol without organic amendment. Aggregate stability was measured for both on surface and subsurface materials by the ISO 10930 (2012) method. Rain amount and intensity, air temperature and humidity, soil temperature, water content and hydric history, and soil water repellency were measured as explanatory factors. The results showed that aggregate stability varied greatly (up to 40%) over a few days for both surface and subsurface. Short term dynamics of aggregate stability were already shown by laboratory experiments, but such dynamics was never observed in the field for a bare soil without external stimulation of biological activity. For the surface, short time step variations of surface aggregate stability were primarily controlled by soil water content (WC0 and WC1/2), hydric history (Delta WC4 and API), and rain intensity. While large changes in aggregate stability were found for the subsurface, explanatory factors remain to be found.