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Predicting the critical point of the soil water retention curve


The transition point between capillary water and adsorbed water, which is defined as the critical point (included the critical matric potential and the critical water content) of the soil water retention curve, demarcates the energy and water content region where flow is dominated by capillarity or liquid film flow. Accurate estimation of the critical point is crucial for modeling water movement in the vadose zone.

In an article recently published in the Soil Science Society of America Journal, researchers develop a simple method to estimate the critical point of soil water retention curve and analyzed the relationship between the critical point and particle size distribution or specific surface area.

With increasing clay content, the critical matric potential became more negative initially but started to increase at clay contents above ~30%. Increasing the silt content resulted in more negative critical matric potential, whereas soils with higher sand content had less negative critical matric potential. The magnitude of critical water content increased linearly with specific surface area and clay content.

Our findings suggest that the critical point estimated from the new method could represent the actual situations, help us understand the retention and movement status of water in soil at different matric potential, and also be used to establish the hydraulic conductivity model from saturation to oven dryness.

Read the full article in SSSAJ. Free preview May 31 - June 7