The same highly sophisticated seismic tools and methods used to measure the severity of earthquakes show promise in determining the impact tillage has on soil moisture and water retention.

University of Washington scientists say these research results indicate tillage and compaction disrupt the intricate capillary networks within the soil in ways that affect how it soaks up water. 

While tillage is supposed to create holes for water to reach plant roots, David Montgomery, a Washington professor of earth and space sciences, says working the ground actually does the opposite. Instead, tillage breaks up these small channels in the soil, causing rain to pool on the surface and form a muddy crust. Over time, this can lead to increased erosion and flood risk.

Measuring Seismic Velocity

For the past decade, scientists have used distributed acoustic sensing that records ground motion based on fiber optic cable strain. Because the technology is extremely sensitive, it can capture the speed at which sound waves pass through substances such as soil.

The Washington researchers found that when soil gets wet, the seismic velocity changes. The result is that sound moves slower through mud than dry dirt. 

To collect the data, researchers placed fiber optic cables in fields at an experimental farm near Newport in the United Kingdom, affiliated with Harper Adams University. This turned out to be an ideal testing ground in existing plots that had been no-tilled for more than 25 years.

They recorded ground motion from no-till and tilled plots receiving different amounts of tillage and compaction determining by various tractor tire pressures. This data was combined with weather data over the same time period,which featured light to moderate rainfall and mild temperatures.

Vibrating Ground

By observing ground vibrations the scientists found the soil was extremely sensitive to numerous environmental factors, including precipitation. The soil’s response to rainfall was analyzed by comparing trends in seismic velocity. 

The researchers maintain this evaluation method is straightforward, inexpensive and offers far better resolution than previous used soil monitoring tools. They believe it could help no-tillers better understand how to more effectively manage their soils, provide real time flooding alerts and refine estimates of atmospheric water content. And probably warn you of potentially upcoming earthquakes, too.