Illinois Study Reveals Soil Cracks Increase Water Loss in Drought

By Andi Anderson

Soil plays a major role in storing and supplying water, but drought conditions can significantly change its behavior. A recent study by the University of Illinois Urbana-Champaign explores how cracks in dry soil affect moisture loss and water movement.

When soils face prolonged drought, they develop desiccation cracks. These cracks alter soil structure and increase water loss. Lead author Kristelle Dela Cruz, a doctoral student in the Department of Agricultural and Biological Engineering, explained the process clearly. She said, “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.”

Co-author Maria Chu, professor in Agricultural and Biological Engineering, explained how soil composition changes. She noted that soil texture includes sand, silt, and clay, while structure refers to how these particles are arranged. Cracks disturb this structure and change how water moves within the soil.

To study this, researchers built a lysimeter, an instrument used to measure soil water balance. It contained silt loess soil, common in the Midwest. The team recreated real field conditions using controlled temperature and multiple cycles of wetting and drying.

Co-author Jorge Guzman, research assistant professor in Agricultural and Biological Engineering, described how they tracked water loss. He said, “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.”

The findings showed that cracked soil loses water faster. Guzman explained, “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.”

The study also suggests that current models should consider changing soil structure. Dela Cruz said, “Most hydrological models assume soil structure to be static, whereas we're trying to determine how changes in soil structure affect the hydrologic variables over time. This will be helpful in assessing drought impacts, as well as the soil water availability.”

Future research will examine how plants interact with cracked soil and compete for water.

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