If you haven’t thought about earthworms, you should

While growing up, I thought the only value earthworms had were as fishing bait. As growers and researchers dig into the details of the hidden world of the soil we are learning that earthworms provide multiple benefits to building and maintaining healthy soil. Here are five ways earthworms provide value to growers:

Earthworms digest plant matter, breaking it down and distributing nutrients throughout the soil profile. In fields with ample earthworm populations, farmers have found worms pulling corn leaves from standing corn stalks into worm middens, heaps of biological material left behind by the earthworms to protect their houses in the soil.

Building worm populations will dramatically increase plant residue decomposition. An average earthworm population will consume up to two tons of dry matter biomass per acre per year. It is important to note however, that worms will only process residue from the soil surface. Residue tilled into the soil profile will not speed up harvest and decomposition by worms. Also, worms process this plant material without exposing soil to oxygen, protecting soil from oxidation which causes soil organic matter and soil carbon loss.

Not only do worms process plant matter without causing oxidation of soil organic matter or soil carbon, but also they build soil structure (unlike tillage). Worm castings as well as the mucus they use to move through soil act as binding agents for soil particles. So, the more worms you have, the better able the soil is at holding up equipment despite wet conditions and the more resistant your soil will be to both wind and water erosion. 

Worm burrows provide excellent pathways not only for roots, but for water to move both vertically and horizontally through the soil profile. Earthworm castings also build soil particle size, creating more space for water infiltration and storage while decreasing saturated conditions. These burrows and larger particle sizes remain in the soil as long as the soil remains undisturbed. Studies show soils with earthworms drain 10 times faster than soils with low earthworm populations and also infiltrate surface water 6 times faster. Meaning that in years you experience drought or excess precipitation, earthworms will give your fields a big advantage.

Earthworm castings and mucus contain 10 times more bacteria than undigested soil. These bacteria then help in the plant-soil relationship. Further, earthworms eat harmful nematode populations that typically feed on cash crop roots. As an added bonus, earthworms consume and digest weed seeds.

So much to cover here. Earthworm castings contain over three times the nitrogen and phosphorus of undigested soil. The earthworm gut has a neutral pH, resulting in castings with a neutral pH. New research is showing that besides building soil organic matter and creating soil with higher fertility, earthworms also make the nutrients in the soil much more readily available to plants while optimizing soil pH. And considering that earthworm activity closely aligns with plant growth and nutrient needs, having a high earthworm population is like spoon feeding fertilizer to growing crops. 

As growers, we can gain significant advantages by building our earthworm populations. Our management can significantly impact earthworm populations. Reducing tillage, planting cover crops, and increasing crop diversity all help earthworms who, in turn, help us.

As a final value, earthworms can provide an indication of your progress on soil health. Dig a shovel full of soil and do a simple worm count, then track for changes in your worm counts over time. This will tell you not only the increasing benefits you receive from earthworms, but also provide an indication of overall soil health and soil biology.

-By Ryan Stockwell, Grower Engagement Senior Manager and Wisconsin farmer