A New Technique Examines Soil Pressure on Cropland

A new sensor is helping Agricultural Research Service scientists and cooperators develop an alternative approach for detecting compacted soil on cropland.

Soil can become compacted as farm equipment repeatedly passes over fields. When this happens, crop roots are restricted from reaching water and nutrients. Less water infiltrates the soil, resulting in increased runoff and soil erosion. The consequences are limited yields and reduced profits.

Complicated electronic equipment is now needed to measure compaction. The new approach uses a sensor developed at the Agricultural Technology Centre, or AgTech Centre, a division within Alberta Agriculture, Food and Rural Development (AAFRD), the provincial agriculture ministry in Alberta, Canada. AgTech project engineer Reed Turner developed the device and is working with ARS agricultural engineer Randy L. Raper to evaluate its performance.

A standard method to test for soil compaction is to measure peak stress of vehicle traffic. Peak stress is the measured difference between the soil pressure existing before a vehicle approaches a sensor and the highest pressure achieved as the vehicle passes it. The new device is used to determine residual stress, the difference between the pressure before a vehicle approaches the sensor and the pressure after it has passed. Studies performed at ARS’ National Soil Dynamics Laboratory in Auburn, Ala., and at the AgTech Centre in Lethbridge, Alberta, showed that the residual stress remaining after a vehicle passes is proportional to peak stress.

The AgTech sensor is buried in the soil. A fluid-filled rubber bulb is connected by a high-pressure hose to either a gauge or a pressure sensor that measures the maximum pressure exerted on the soil and the residual pressure remaining after vehicle traffic has passed. If a pressure gauge is used, no electronic or computer equipment is required. Raper says the device is quick and easy to use.

Raper says that as equipment used in agriculture has become increasingly heavy, soil compaction also has increased on average.

ARS is the chief scientific research agency in the U.S. Department of Agriculture.