Study shows soil infiltration can stabilize desert soils

Soils found in deserts are quite different from those found in other places. An unusual environment exists when there are extreme temperatures, limited flora, and less amount of water.

Desert soils are unique because they contain only a limited quantity of dead plant material to decompose and form a rich layer of organic matter.

Researchers measure soil infiltration in desert soils near Alkali Lake, NV. Image Credit: Judith Turk.

Judith Turk, who works as an assistant professor at the University of Nebraska-Lincoln, explores the vesicular horizon—that is, the top layer of desert soils. Found commonly in deserts, this surface layer of the soil contains pores of different shapes known as vesicles and vughs.

These horizons are important because of their role in many processes. Vesicular horizons determine how much water soaks into the soil and how much runs off. Since they occur in deserts, they control the distribution of the most limiting resource, which is water.”

Judith Turk, Assistant Professor, University of Nebraska

Vesicular pores are spherical in shape, slightly similar to bubbles, and are not associated with one another. Vughs are also similar to vesicular pores but have a more irregular shape, virtually resembling a lump of bubbles that have not completely separated from one another.

Turk wanted to find out how those vesicular horizons form over different soils in the desert. In an experiment conducted recently by researchers, small plots of soils were selected and samples were taken.

The soil was then crushed to allow the pores to form from the beginning. The porosity of the soils was checked by the researchers over the course of a year for comparison.

First, we found that infiltration rates were lowered as a result of disturbance. This would normally not be surprising, since disturbance compacts the soil, reducing porosity, and breaking up the pore networks that water flows through.”

Judith Turk, Assistant Professor, University of Nebraska

“However, the pores in V horizons are different,” Turk added. “Most of the pores are not connected with each other and therefore contribute little to the permeability of the soil. So, we weren't sure how disturbance would affect these horizons.”

According to Turk, she and the researchers were surprised how the texture of a soil governs the level of porosity sustained in this soil layer. The researchers believed that the soil containing more silt would be more suitable for the formation of vesicles, but found that the vesicles formed more quickly in comparatively sandy soils.

Turk added, “The capacity for vesicular pores to reform within a year after the V horizon is disturbed is something that is interesting. The post-disturbance V horizons being thinner with smaller pores tells us that what we observed in the undisturbed soils takes time to form.”

These soils should be studied because semi-arid lands span approximately one-third of the land area on the planet. Soils with vesicular horizons often get disturbed because of the growing urban populations in arid settings. Wind and solar farms are also being constructed, which are popular areas for military exercises.

The teams’ findings should be taken into consideration when planning to disturb the soil. This would allow people to understand the behavior of the soil after the disturbance.

Turk has planned to continue this study in the days to come and is expecting to conduct an experiment over a longer period of time to observe the newly formed layers merging into the undisturbed surrounding soil.

Many people are surprised to learn that there are interesting soils in the desert. When I moved to California for graduate school, I fell in love with the desert lands of the western US. In the desert you can see the land surface and it’s easy to imagine the processes that have built the soil landscapes that we see today.”

Judith Turk, Assistant Professor, University of Nebraska