Earthworms part of good soil health

Courtesy photo: A good earthworm population is considered good for soil health.

Sow and Grow

“Soil health” has become common terminology in the agronomy scene the last few years. 

Although trends come and go, I think soil health is here to stay. According to a 2001 paper (Land degradation: an overview), it is estimated that the total annual cost of erosion from agriculture in the USA is about $44 billion per year, i.e. about $100 per acre of cropland and pasture. 

On a global scale, the annual loss of 75 billion tons of soil costs the world about $400 billion per year, or approximately $70 per person per year (Eswaran, H., et. al. 2001).

Every producer has their own unique way of operating in a way that is most effective and familiar to them. However, nearly everyone has room for improvement within their business model. One of the changes I challenge growers to strive for is better soil health management and planning.

In South Dakota we have adopted five “principles of soil health.” These include:

1. Soil Cover - keeping plant residue on the soil surface at all times.

2. Limited Disturbance - minimize or completely avoid tillage in order to allow soils to build aggregates, pore spaces, organic matter, and improve biological activity.

3. Plant Diversity - mimic nature by using cool and warm season grasses and broadleaf plants. For example, this includes adding a mixture of cover crops and/or small grains to a strictly row crop rotation.

4. Living Roots - allowing cover crops to grow in the off-season provides carbon to the soil and serves as a food source for microorganisms.

5. Integration of Livestock - allowing livestock to graze cash crop and cover crop residue provides more forage options for producers at a time of year when forage quality and supply begins to drop. In turn, livestock grazing increases soil biological activity, improves nutrient cycling, and helps improve overall soil health if grazing is properly managed. 

Using these principles, how could a focus on improving and retaining soil health be of value to you or the next generation on your operation? The five principles listed above work synonymously with one another, and the more regenerative-type practices that are added to a cropping system, the more benefits your soils will experience. Essentially, the more we can mimic nature, the better our cropping systems should function.

There are many different ways to measure soil health such as water infiltration, soil compaction, soil biological testing, organic matter, etc. One unique way to get a big picture view of soil health is to look for earthworms (believe it or not)! Healthy soils are full of natural organisms that range from rabbits and insects, to microscopic beings.

Earthworms fit into a very special category in reference to soil health. They have the capability to do ‘tillage’ in no-till soils; as they move through the soil searching for food and water, tunnels are created. These tunnels improve soil porosity and ultimately soil health. 

Their existence above and below ground speed up the breakdown of organic materials in the soil and improve the carbon and nutrient status, making them more available to crops.

Each time a tillage pass runs through a field, soil structure is broken down, but what often isn’t noticed is that earthworm populations are significantly affected. A recent study conducted by SDSU Extension personnel looked into earthworm populations. They selected sites that were no-till for 15 years or longer and where cover crops were planted in the fall of 2019 after small grain harvest. A control plot was established by spraying out 15x30’ plots at each site. In the spring of 2020, project coordinators returned to count earthworm populations using an established protocol that involved pouring mustard-vinegar solution into rings to bring worms to the soil surface (Chan and Munro, 2000).

Earthworm populations varied due to soil conditions from just over 285,000 up to 2,000,000 worms per acre. The study found that on average, cover crops had more than twice as many earthworms as the control plots with no cover crops. 

As one might expect, soils won’t vastly improve overnight, but by slowly adding the principles of soil health to your operation, a more resilient and healthy cropping system (with increased earthworm activity among other positive soil health indicators) should emerge. For more information on this study visit https://extension.sdstate.edu and search ‘earthworms’; for further resources on transitioning to no-till and other soil health systems search ‘soil health’ on the SDSU Extension website or visit https://www.sdsoilhealthcoalition.org/ or http://sdnotill.com/index.htm.

New Extension Agronomy Info and Events:

• To request a printed copy of the SD Pest Guides or other printed SDSU Extension publications, visit https://publicationrequest2021.questionpro.com. This will be available through March 31.

• Sign up for our free Crop Hour Webinar series every Tuesday through Friday through the last full week of March at https://extension.sdstate.edu/agriculture/crops. March 2-5 focuses on "Sunflowers," and March 9-12 focuses on "Understanding SDSU Extension Agronomy Research."

• The 2021 Ag Economics Dialogues for March will take place March 19. Sign up free by March 18 on the events page at https://extension.sdstate.edu.

• For a full listing of all SDSU Extension activities, visit the events page on the Extension website.

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