Photo: Nutri-lawn

Soil compaction is the compression of soil, resulting in reduced airflow and higher density. 

The mineral salts in fertilizers can cause a compaction layer in soil. A symptom of compaction is visible in ‘sun spills’ in lawns — areas where grass grows poorly due the soil being compacted, leaving the soil exposed to the sun. 

Photo: Jonathan Green

One of the major problems with compaction is that it reduces the abilities of grass and other plants to grow roots and creates an environment that is inhospitable to earthworm burrowing. Earthworms normally tunnel through the soil at various depths, creating holes throughout the soil that allow air, water, and nutrients to travel down through the soil. A healthy lawn can collect about 7 inches of rainwater. With a robust community of earthworms, that same lawn can hold 9 inches of rainwater. 

Compaction, combined with little earthworm activity, greatly reduces the natural sponge-like capability of lawns to absorb water. This increases the risk of flooding as water is forced to remain on the surface. This is of particular concern in areas prone to flooding and sea level rise. 

Photo: The Lawn Institute

Manually aerating, or creating holes in the soil (as earthworms do), alleviates compaction. This is often done by machines on agricultural fields, but a simple rake can be used for lawns. 

For healthier soils, put a stop to soil compaction by pledging not to spread fertilizer or chemicals on lawns. This will save you money in lawn care expenses and will benefit earthworms as well as their red-breasted winged consumers.