A First Insight on the Interaction between Desiccation Cracking and Water Transfer in a Luvisol of Belgium

The present paper presents the interactions between water retention/evaporation and cracking during the desiccation of intact and disturbed Belgian Luvisol. The disturbed (DS) and undisturbed (NDS) samples (reduced-tillage-residue-in (RTRI) and conventional-tillage-residue-out (CTRO)) were collected from an agricultural field in Gembloux, Wallonia, Belgium. The drying experiment took place in controlled laboratory conditions at 25 °C. Moisture content, soil suction and surface cracks were monitored with a precision balance, a tensiometer and a digital camera, respectively. The image processing and analysis were performed using PCAS® and ImageJ® software. The results showed that crack formation was initiated at a stronger negative suction and a lower water content (Wc) in DS > CTRO > RTRI. The suction and the crack propagation were positively correlated until 300 kPa for the DS and far beyond the wilting point for the NDS. For the NDS, the cracking accelerated after reaching the critical water content (~20% Wc) which arrived at the end of the plateau of evaporation (40 h after crack initiation). The Krischer curve revealed that the soil pore size > 50 µm, and that it is likely that cracks are important parameters for soil permeability. The soil structure and soil fibre content could influence the crack formation dynamic during drying. The agricultural tillage management also influences the crack propagation. As retention and conductivity functions are affected by cracks, it is likely that the movement of fluids in the soil will also be affected by the cracks following a desiccation period (i.e., when the cracked soil is rewetted).