Do you know how to harness the power of the mighty soil steward known as the earthworm? In the November 2019 issue of Crop Talk, the Ontario Ministry of Agriculture, Food and Rural Affairs’ (OMAFRA) digital journal dealing with production issues in field crops, soil management specialist Sebastian Belliard discussed the many benefits of earthworms in maintaining soil health and nutrient levels. He refers to them as “the ecosystem engineers of the soil,” as their actions in the soil create the conditions by which decomposition and cycling occur.
“They help to break down and incorporate plant residues, bringing them in close contact with microbes that further decompose them and release their nutrients, and with soil particles to which that organic matter can be adsorbed and incorporated into microaggregates,” Belliard writes in the article. “Their burrowing creates channels in the soil that improve aeration and water movement and makes room for plant roots and other organisms to grow.
“Earthworms have been shown to improve soil structure by increasing stability and reducing runoff, mineralize and stabilize organic matter, increase nutrient availability, and even affect plant health by inducing the production of hormone-like substances.”
Earthworms are divided into three groups: surface-living (epigeic), topsoil (endogeic) and deep-burrowing (anecic). All three play a role in cycling and decomposition of crop residue, soil organic matter and mineral soil, which get mixed in the earthworm gut to produce highly fertile, highly concentrated bits of soil in their casts (which is a polite way to say earthworm poop).
“Realizing the potential benefits of earthworms on nutrient cycling and fertility requires nurturing their populations,” Belliard writes. “One of the most well-established facts about soil management is that tillage reduces worm populations. Intensive tillage can kill worms directly, expose them to drying and predators, destroy their burrows, and remove their food source.”
Belliard states that any reduction in tillage depth, intensity or frequency will benefit earthworm populations, as will the addition of organic amendments, such as compost and especially manure. As earthworms are a simple but telling measure of soil health, any increase in their presence and activity translates to an improvement in the health of crops.
For the full discussion of this and other production issues, visit the OMAFRA Crop Talk page.