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New soil sensor allows simple, in-field compaction measurements

Engineers at the AgTech Centre in Lethbridge have developed an easy-to-use sensor that can quickly show soil compactibility in the field.

For the first time, farmers, equipment manufacturers and researchers can make a simple on-the-spot measurement of the soil compaction caused by a given operation, says Reed Turner, the AgTech Centre engineer who led the development of the AgTech Centre (ATC) Ground Pressure Sensor. “Farmers could use this as a tool to help them decide when to initiate field operations.”

As farmers have adopted larger, higher capacity agricultural equipment, the loads, pressures and working forces applied to soils have increased, Turner says. “Hopefully, we can reduce soil compaction risks by giving producers and researchers tools to measure soil compactibility quickly and efficiently.”

Soil compaction occurs when soil particles are squeezed together and broken down as a result of pressure and loads from equipment travelling over a field. “Soil compaction can affect crop yield significantly, by inhibiting water infiltration and plant root development,” he explains.

The AgTech sensor is simply a fluid-filled 25 mm diameter rubber bulb attached to a pressure transducer by a short high-pressure hose. The bulb is inserted into the soil in a hole drilled using an adjustable drill fixture. The pressure on the bulb is read by either an electronic sensor or a simple dial pressure gauge.

The sensor measures a time history of the “in-ground” pressure produced as a vehicle moves over the placement site. Peak pressures can be used to judge the compaction force that a given event produces. Residual pressure, or net pressure remaining after a vehicle has passed over a sensor, can be used as an indicator of the compactibility and net compaction of the soil.

Readings from the sensor can show the effects of different contact surface geometries (such as lug patterns or inner tire surface), vehicle type and vehicle loads. Two people using the sensor and a simple placement fixture can place, drive over, and log 10 to 20 separate readings in 20 to 30 minutes. This data rate allows statistically significant measurements of peak, average and residual pressure under moving vehicles, both loaded and unloaded.

Since current methods for measuring soil compaction are complex and time consuming, farmers have typically relied on experience or rules of thumb, when trying to assess how much impact their equipment and operations have on the soil. Turner believes this simple sensor can be used as a tool to help farmers decide whether or not the soil is ready for a particular field operation, or whether to wait for less compactible conditions. “The sensor can also be a useful extension tool for demonstrating compaction effects of various operations and machinery.”

Currently, the AgTech Centre is seeking other researchers using traditional, more complex soil compaction measurement methods, who would be interested in putting the device through its paces and comparing it with their other measurement methods. “We want to ensure the sensor measurements are accurate and the protocols for using it are the most desirable,” says Turner.

For more information contact the AgTech Centre. Phone: (403) 329-1212. Fax: (403) 328-5562.

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