How Can I Properly Test For Soil Compaction?

Soil compaction takes place when the small open cavities, or pores, in soil are squeezed out. This usually occurs when pressure is applied to the surface of the soil – such as from foot traffic, hard rain or equipment – and it can reduce the size of the soil pores or even eliminate them altogether.

Why Is Soil Compaction A Concern?

When soil does not have a sufficient number of sizable pores, the roots of plants will struggle to grow and penetrate into the dirt. This means that air, water, pesticides and fertilizers will not be able to make their way through the surface crust or plow pan layers.

The roots of the plant will therefore be unable to access the nutrients they need to thrive, nor will they receive adequate water and oxygen. This means that they will be unable to reach their full potential, and some may even die.

Soil compaction can explain why some plants might be showing symptoms of drought despite being exposed to plenty of watering or rain as it causes the water to be unable to go through the soil and reach the roots. It is also important to note that soil that is compacted is a lot harder to work and requires significantly more effort to plow.

How Can You Test For Soil Compaction?

Because soil compaction largely takes place below the surface, it can be difficult to detect it visually. Therefore, to properly test for soil compaction, it is necessary to use a compaction tester at a depth of around three to four feet. A test rod needs to be moved down through the soil using a steady and even pressure; soil that is compacted will resist penetration with the rod.

Many times, penetration will stop abruptly at a somewhat uniform depth throughout a landscaped area. This is what is commonly known as a plow pan. A quick way to check whether compaction is a problem for trees or shrubs is by comparing the root growth both inside and outside of the root ball. If there is evidence of compaction, you can dig down to the depth indicated and look for abnormal root growth.

What Should You Use To Test For Soil Compaction?

There is a broad range of soil compaction tools that can be used to test your soil, with everything from manual compaction rods to digital recording compaction meters available. A manual compaction rod will simply tell you when you have hit a compacted layer; it may also indicate the presence of a buried object such as a pipe, rock, drain tile or storage drum.

A dial compaction probe can indicate the amount of pressure in pounds per square inch that will be needed to penetrate the soil using a needle that moves across a scale on the display panel.

To use a standard portable soil compaction tester, the typical process involves driving a probe 36 inches into the ground using constant and even pressure and reading the display to see the pounds per square inch of pressure that it takes to penetrate the soil. These tools typically have depth marks every three inches for easy depth measurements, and they are very easy to use.

A digital compaction meter works similarly to a dial probe, but it provides the information in a digital reading. It is also capable of recording the depth and pressure for each test that is carried out.

A typical digital dial penetrometer will feature a stainless steel shaft with markings every 3 or 4 inches for easy depth reference and will automatically display the peak compaction value on a digital display when the probe has been extracted from the soil. It may also display the severity of compaction using simple color codes such as green, yellow and red, along with the readings in PSI or kPa.

You need to make sure that whatever type of tool you use features a probe with depth markings so that you will know how deep you need to go to correct any compacted layers that you find when carrying out the tests.

What Can You Do If You Find Soil Compaction?

If you discover soil compaction, there are a few approaches you can take to correct it. First, you might consider top-dressing repeatedly using compost or mulch to add some organic matter and preserve the moisture levels of the soil. Another option is radial trenching or drilling holes beneath the drip line of trees on the property and then backfilling using topsoil or compost.

To break up the plow pan, you might try core aerating, cultivating or subsoiling to the proper depth. You may also want to limit foot and machinery traffic in areas of the property that are suffering from a compaction problem.

How Can You Avoid Soil Compaction?

Outlined below are a few tips to keep in mind if you want to avoid soil compaction and the problems it poses.

• Use borders made of mulch, shrubs or fencing to keep foot traffic away from the planted areas in the landscape.
• Change the depth of cultivation that is used each year.
• Avoid working soil that is wet.
• Make a point of using the same number of passes throughout the field with machinery, and aim to use the minimum number necessary. Use dual tires, tracks or flotation tires on equipment and be sure that tires are always inflated to the lowest PSI that is safe.
• Consider building temporary roadways that equipment can use. For example, you could place a bed of dry wood chip mulch several inches thick across the areas that are being landscaped to cushion the soil.

Get In Touch With Dirt Connections

At Dirt Connections, we have built our entire business on our thorough knowledge and experience working with soil. We offer contractors, companies and individuals throughout Northern Virginia and the surrounding counties with all manner of fill dirt, topsoil and other materials as well as residential, commercial and heavy construction services. Call us today to discuss your project.