Technique Examines Soil Pressure on Cropland
November 13, 2001
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
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.