[en] Crack formation and development has been a general concern in the agricultural science. Cracks contribute to the soil aeration, aggregate formation, and easy root penetration. However, cracks accelerated the soil desiccation, allowed deep infiltration of pesticides/pollutants through preferential flow, and polluted the shallow water-table in Belgium. Cracks were mostly studied on pure clay or on high clay content soil (Vertisol). Yet in Wallonia, cracks were present even on silt-loam soil (Luvisol). This study tried to cover this gap by analysing crack dynamics and evaporation process, during drying kinetics of the Luvisol found in Gembloux.
Soils were collected right from the agricultural field and processed on a small drying chamber in which evaporation test was taking place. Ceramic-IR-emitter heated the chamber while sensors (DHT22) measured the temperature and relative humidity. Digital camera took photos of the soil surface at 30min interval. Balance and tensiometer were linked to datalogger (CR800) and recorded the soil hydraulic properties (evaporation, water retention, etc.). Cracks were assessed from small samples (~5cm x 1cm thick) and big samples (~20cm size x 1.6 cm thick). Three treatments were considered including: disturbed soil, conventional tillage and reduced tillage.
For big samples, results showed higher cracks formation on disturbed soil > reduced-tillage > conventional-tillage due to loose of soil cohesion, soil organic content, soil aggregation, biological activities, and soil porosity. The soil evaporation rate was also greater in disturbed soil > reduced-tillage > conventional tillage. Cracks opening exposed profound-soil-water to the atmosphere without passing through the soil matrix. For small samples, the repetitive drying experiments increased cracks length/width, especially for the dense samples. Future study is needed to assess the presence of pre-(micro)-cracks in soil using X-ray microtomography.
