The Natural Resources Conservation Service defines soil health as “the capacity of a specific kind of soil to function, within natural or managed ecosystem boundaries, to sustain plant and animal productivity, maintain or enhance water and air quality, and support human health and habitation”.1 Of the living organisms that inhabit soil, earthworms are likely the most important for improving soil health because of their ability to increase soil aeration, infiltration, structure, nutrient cycling, water movement, and plant growth (Figure 1).1
When trying to improve soil health and crop production, we often think about how we can physically or chemically modify the soils with fertilizers, chemistry, or different tillage practices, but often overlook how soil can be improved biologically. Conservation tillage practices can help increase earthworm populations and because of the increased residue, their ability to help breakdown residue becomes increasingly important. Let’s take a deeper dive into how earthworms can improve the biology of our soils.
Earthworms serve many purposes in helping build healthier soils. Surface residue provides a moist and shaded environment for their survival. The bacteria and fungi growing on the residue are excellent food sources. In breaking down residue, they recycle the nutrients it contains and help increase microbial activity in the soil, which helps build organic matter levels in the soil. The burrowing of earthworms helps increase soil porosity which allows for better water and air movement, water infiltration, and helps improve soil water holding capacity (Figure 2). The burrows or channels helps roots improve growth and structure and allows for the roots to penetrate deeper into the soil profile. Earthworms also help with plant nutrient availability because their casts have higher available macro-nutrient contents than surrounding soil and a higher cation-exchange capacity. Their chelation of micro-nutrients can help increase their availability for plant uptake.
How can earthworm populations be positively affected through cultural practices?
Reduced or minimum tillage practices provide an environment conducive to increased earthworm populations as they thrive in high residue environments.
Crop rotations, proper pH, and fertility levels can help improve the environment for earthworms.
Manure is a great food source for earthworms and its nutrients can improve crop growth which can help increase earthworm friendly crop residues.
Many agronomic practices that improve row crop performance can help improve the environment for earthworms.
1Labenz, A.T. Earthworm activity increases soil health. Newsroom. Natural Resources Conservation Service, Kansas. United States Department of Agriculture (USDA). https://www.nrcs.usda.gov/wps/portal/nrcs/detail/ks/newsroom/features/?cid=stelprdb1242736.
Website verified 6/14/21.