Earthworms Can Be An Indicator of Soil Health

Jul 04, 2016

By Christina Curell

Worms found in Sam Aultman Farm, Coleman Mich.

There are many different parameters that can be used to determine soil health. One common measure is the number of earthworms that are found in the field. To survive, earthworms need moist soils that have sufficient residue or organic matter for food.

Earthworms perform several important functions in soil. They improve soil structure, water movement, nutrient cycling and plant growth. They are not the only indicators of healthy soil systems, but their presence is usually an indicator of a healthy system.

There are some considerations that you need to be aware of when looking for earthworms. If earthworm counts are taken when the soil is dry, the earthworm numbers may not be a good representative of the field. Earthworms may have moved deeper or to areas of the field that have more moisture. Earthworm populations will be high around areas with high organic matter. If such an area is consistent throughout the field, go ahead and test. If it is not a good representative of the field, choose another spot to test that is more uniform with field conditions. To get the best results, it is advisable to test several times during the growing season, and then take an average of the earthworm numbers.

Materials that you will need to measure worms in the field:

Tape measure
2 liters of tap water
Hand trowel or shovel
Container to collect worms
Solution of 2 tablespoons of mustard powder dissolved in 2 liters of water

Once you have your materials gathered you are ready to count earthworms.

Step 1: Measure a square foot in the test area and dig down 12-inches.

Step 2: Collect and count the number of worms found. If possible, differentiate worms by type. For example, label as earthworms, red worms, etc.

Step 3: (Optional) Level out the bottom of the hole, and pour the mustard solution slowly. Deep burrowing worms should come to the surface within 5 minutes. Collect and count the worms that come to the surface.

Step 4: Count and record the total number of earthworms that are collected.

Another method to count earthworm populations takes more time but is less labor intensive.

Step 1: Measure a square foot in the test area.

Step 2: Slowly pour 2.5 gallons of the mustard solution in the test area, allowing the water to infiltrate through the soil without pooling and running off. This could take several minutes depending on soil type and moisture.

Step 3: Collect and count the earthworms as they come to the surface for ten minutes after the test area is saturated with the mustard solution.

Earthworm counting is only one way to determine soil health. There are other measures that farms can use, especially with soils that are sandy and droughty, to determine the health of their soil.

To learn more about soil health, join other farmers on Aug. 24 as Michigan State University Extension hosts an educational field day focusing on soils at the Saginaw Valley Research and Extension Center near Frankenmuth, Mich. The “MSU Agriculture Innovation Day: Focus on Soils” is a great opportunity for farmers to learn about the cutting-edge research conducted by MSU scientists on soil health topics ranging from nutrient management and soil quality to compaction and tile technology. The event is free and open to all. It begins at 8 a.m. with registration. Nine educational sessions will be conducted throughout the day, and attendees can also view displays and demonstrations. A lunch will be provided.