By Jamie Martin
A new University of Illinois Urbana-Champaign study is shedding light on how drought conditions alter soil structure and affect the movement of water beneath the surface.
The research focuses on desiccation of cracks, which commonly develop when soils experience prolonged drying.
These cracks form as water evaporates and stress builds within the soil. Once that stress exceeds the soil’s strength, the surface begins to split apart. According to the researchers, this process significantly changes how water is stored and lost.
"As moisture evaporates from the soil, it induces stress. Once this stress exceeds the tensile strength of the soil, the soil breaks and desiccation cracks form. The cracks open additional surface area for moisture to transfer from the soil to the atmosphere, causing soil with cracks to become even drier," said lead author Kristelle Dela Cruz, a doctoral student in the Department of Agricultural and Biological Engineering.
The study examined the relationship between soil cracking and hydrological processes. Researchers noted that soil texture is determined by the mix of sand, silt, and clay, while soil structure describes how those particles are organized.
Cracking alters that structure and influences the movement of water through the soil profile.
To recreate field conditions, the team designed a specialized lysimeter containing approximately one cubic foot of silt loess soil, a common soil type throughout the Midwest.
The experiment included controlled temperatures of 40 degrees Celsius and repeated wet-dry cycles to mimic drought conditions and crack development.
"We cannot directly measure evaporation, but we can estimate the total loss of water from the soil by tracking the changes in weight through time, which can indicate the amount of water that has been lost from the system," said co-author Jorge Guzman, research assistant professor in ABE.
By photographing the soil surface over time, scientists tracked crack expansion and compared it with water loss measurements. Results showed that cracked soils lose moisture more rapidly because the openings increase the amount of soil exposed to the air.
"Soil without cracks is more protected against water loss. We can see from our data that the cracks accelerate the process of water transfer from the soil to the air. Then, the soil area that contacts the air becomes drier, and it changes the dynamic of how water redistributes in the soil. Eventually, there is a decrease in evaporation, but that's because the water is already gone," Guzman explained.
Researchers plan to further investigate how vegetation and plant water use interact with cracked soils under drought conditions.
Photo Credit: gettyimages-neenawat555
Categories: National