Using a penetrometer to detect soil compaction

Summary

In this video, Francisco Arriaga, a soil scientist from the University of Wisconsin Extension, demonstrates how to use a soil penetrometer to assess soil compaction. The penetrometer measures resistance as it is pushed into the ground, providing valuable insights into soil structure and potential compaction issues. Factors such as soil moisture and clay content affect readings, so it's important to calibrate the device using a nearby uncultivated area. The tool is essential for managing compaction in fields, particularly after heavy traffic, like during corn silage harvest.

Takeaways

• 🧑‍🌾 The speaker, Francisco Arriaga, is a state soil scientist with the University of Wisconsin Extension Service, discussing how to use a soil penetrometer.
• 🌱 A soil penetrometer helps determine soil compaction levels, which affect root growth and overall soil health.
• 🛠️ The device consists of a T-handle, a shaft, interchangeable tips, and a pressure gauge for measuring resistance.
• ⚙️ Two tip sizes are available: a half-inch tip for harder soils and a three-quarter-inch tip for looser soils with better structure.
• 📏 The gauge measures resistance in PSI, with green (0–200 PSI) indicating good conditions, yellow (200–300 PSI) suggesting some resistance, and red (above 300 PSI) showing possible compaction issues.
• 💧 Soil moisture and clay content affect readings—dry or clay-heavy soils will show higher resistance, even if not truly compacted.
• 🌾 A good practice is to test an untrafficked area (like a fencerow) as a baseline for comparison with field readings.
• 🚜 Compaction is often worse in fields with heavy traffic, such as those used for corn silage harvests.
• 📊 The penetrometer rod includes 3-inch depth markings to help identify the depth and thickness of compacted soil layers.
• 🧰 This information is valuable for properly setting tillage equipment to address specific compaction depths.
• 🔍 Testing should be done in a zigzag pattern across the field, similar to soil sampling, to identify compaction variability.
• 🌐 For further assistance or information, users are encouraged to contact their local county extension agent or visit the extension website.

Q & A

What is the purpose of using a soil penetrometer?

The soil penetrometer is used to assess soil compaction by measuring the resistance encountered as a rod is pushed into the soil. This helps identify potential compaction issues and understand soil conditions for better root growth.

What are the main components of a soil penetrometer?

A typical soil penetrometer consists of a T-handle, a shaft, interchangeable tips (half-inch and three-quarter-inch), and a gauge that measures the resistance in PSI.

How does the size of the tip affect the readings?

The smaller half-inch tip is used for harder soils, while the larger three-quarter-inch tip is used for looser, well-structured soils. The choice of tip depends on the soil type being tested.

What does the gauge on the penetrometer display?

The gauge displays the resistance in pounds per square inch (PSI). It includes a green zone (0-200 PSI), yellow zone (200-300 PSI), and red zone (above 300 PSI), where higher PSI indicates more compaction and potential root restriction.

Why is moisture a factor in soil compaction readings?

Soil moisture affects the resistance readings because dry soil is more compact and harder to penetrate, while moist soil is softer and easier to penetrate. This variability should be considered when interpreting the results.

How can soil moisture and clay content affect penetrometer readings?

Soil moisture and clay content are factors that influence soil hardness. Dry, clay-heavy soils will give higher resistance readings, whereas moist, loamy soils are easier to penetrate. These variables should be accounted for when using the penetrometer.

How can you calibrate the penetrometer to get accurate results?

To calibrate the penetrometer, you should first test in an area that has minimal traffic, such as a fence row, to establish a baseline reading. This will help you understand the normal resistance for your soil type, which can be used for comparison when testing areas of suspected compaction.

Why is it important to test soil compaction in a zigzag pattern across the field?

Testing in a zigzag pattern ensures that you sample a variety of soil conditions across the field, providing a more comprehensive assessment of potential compaction issues. This method helps you detect areas that may be more compacted due to equipment traffic.

What does the penetrometer’s rod marking system help with?

The rod has markings at three-inch intervals, which allows users to measure the depth of the compacted layer. This feature is useful for determining the thickness of compaction and adjusting tillage practices accordingly.

What does a high resistance reading on the penetrometer indicate?

A high resistance reading, particularly above 300 PSI, indicates significant soil compaction, which can hinder root growth and soil health. This may be a result of heavy traffic, such as from farm equipment during harvest, especially in fields like corn silage.