A healthy ecosystem starts with healthy soil. Soil plays a foundational role in supporting life — anchoring and nourishing plants and trees, cycling nutrients, recharging groundwater, and boosting the resiliency of plants.
Planting for clean water and pollinators begins below the surface—with our soil. “I am involved in organic lawn care, pollinator planting and ecological restoration work and soil health is the bedrock of all these endeavors,” shares Bob Dahm from Organic Lawns by LUNSETH. “A ‘soil health first’ approach is vital to the success of all of these projects.”
Human development can contribute to soil health issues like compaction and erosion. In this blog post, we’ll hear from Dahm about some common soil challenges and strategies for improving soil health in your yard. Along with Divine Islam of Divine’s Urban Gardens, Dahm is helping Blue Thumb develop a new soil health workshop that we will be rolling out in the next few months!
Getting to know your soil
Soil is more than just “dirt” — it’s a rich mixture of organic matter, clay and rock particles, minerals, and microorganisms. You can begin getting to know your soil by simply observing. “Careful observation will provide a lot of info,” says Dahm. Dahm says observing the presence of weeds and insects, as well as plant disease and overall plant health, can give you a general sense of your soil’s health.
Understanding your soil type can inform what plants might do well at your site and if your soil might benefit from a compost amendment (more on that in a bit). Soil comes in many textures, with three main types: silt, sand, and clay. A quick way to determine your soil type is with the Ribbon Test or the Mason Jar Test.
Soils can also be characterized by pH, which measures the availability of nutrients in the soil. Most native plants can tolerate a wide range of pH and soil types. However, if you’re concerned about your soil, you can order a basic soil test from a service like the University of Minnesota Soil Testing Lab. You can also bring a sample of your soil to your local native plant nursery and ask them what plants would do best in your soil.
If you’re planning a rain garden, it’s important to find out the infiltration rate of your soil (how well it soaks in water), which will determine how deep your rain garden can be. Rain gardens that are not the correct depth for the soil can result in standing water that does not drain in a timely manner. (Visit our Rain Gardens page for instructions on how to conduct an infiltration test).
Dealing with Soil Compaction
Compaction is a common soil health challenge. “Compacted soil has little capacity to support beneficial life,” Dahm shares, adding that it reduces the ability of soil to soak up water and makes it harder for plant roots to grow.
Compaction presses soil particles together, reducing the natural air pockets. Without these air pockets, oxygen can’t reach plant roots and microorganisms in the ground. Some causes of compaction include foot and vehicle traffic, construction equipment, and tilling.
If you notice that water doesn’t easily soak into your soil (running off your property or creating standing pools of water), if it’s hard to pierce a shovel in your soil, or if there are areas without any plant growth at all, your soil may be compacted.
Here’s what you can do:
- Add compost. “I usually assume that soil health has been compromised and begin by adding quality compost that contains carbon and beneficial organisms,” says Dahm. Compost makes the soil lighter and fluffier, adds nutrients, and helps the soil better retain water.
- Add a diversity of native plants. As plant roots grow into the soil and partially die back each winter, they contribute organic matter and leave channels to percolate through the soil and work against compaction.
- Minimize soil disturbance to prevent compaction from happening in the first place. When weeding or prepping your garden, avoid tilling. “Tilling is like a tornado going through ‘soil town,’ shares Dahm. “It kills microbes, destroys soil structure that allows air and water to move into the soil.” Instead, hand pull weeds and turn your soil with a shovel.
Preventing Erosion
Rain beating down on soil and runoff from precipitation can carry away soil particles. This erosion contributes to water pollution and robs plants of needed nutrients and organic material. Some signs of erosion include exposed tree roots, small gullies in the ground, and silt accumulation in low areas.
Keeping your soil covered can prevent erosion and compaction. Start by keeping shredded hardwood mulch, dried leaves, grass clippings or groundcovers on your soil. Avoid using dyed mulch, rock, or plastic landscaping fabric. Some good low-growing options for living groundcover include wild ginger, Penn sedge, wild strawberry, violets, creeping phlox, and wild geranium.
Adding native plants is also a great way to manage erosion. Their extensive root networks hold soil in place while absorbing water and nutrients. Along shorelines, plants slow down incoming waves and anchor soil on the shore. When planting new plants, covering your soil with mulch has additional benefits like reducing weeds, holding in moisture, and adding organic matter to the soil as the mulch breaks down.
With that in mind, keep a few areas of your site bare, especially sunny or south-facing areas with loose, well-drained soil. Why? 80% of Minnesota’s native bees nest in the ground, including the rusty patched bumble bee. In winter, bumble bee queens hibernate in undisturbed soil, a few inches below the surface.
Supporting Living Soil
Teeming with bacteria, fungi, nematodes, worms, and insects, the billions of organisms that reside in our soils represent the greatest concentration of biomass anywhere on the planet. They make up a soil food web essential to the growth and flourishing of plants and animals dwelling above ground—including us.
“Soil is alive!” shares Dahm. “If the biology is healthy, soil will sequester incredible amounts of carbon and regenerate our planet.” Soil biology supports ecosystems through strengthening soil structure, boosting nutrient availability, and promoting decomposition.
There are many ways you can encourage a community of healthy microorganisms in your soil, Dahm shares. If you want to start from scratch, you can use sheet composting or cardboard smothering (also known as the “lasagna method”). You can also work towards maximizing biodiversity in your choice of native plants.
Growing plant roots contribute sugars and proteins to the soil that feed beneficial bacteria and fungi, which provide nutrients to the plants in return. To create an environment where roots can be active at different soil depths, incorporate a mix of flowers, groundcovers, shrubs, and trees in your planting. You can also add compost. Besides reducing soil compaction, it also supports the beneficial microorganisms in your soil.
If you want to give your plants an extra boost, consider adding mycorrhizae, which are the underground parts of fungi. Mycorrhizae forms a network of filaments that are associated with plant roots. These networks transfer water and nutrients to plant roots, which provide sugars to the mycorrhizae in return. Inoculating planting and seeding projects with mycorrhizae is sort of like kombucha for soil! It helps new seedings and plantings germinate and get established.
Back to the Basics
Dahm likes to think of soil as the “gut” of ecosystem and plant health. “If there are bad organisms growing in our digestive tract, we will have chronic health problems, auto-immune problems and even mental health issues,” says Dahm. Similarly, if soil isn’t healthy, it won’t store water, cycle nutrients, or support beneficial, symbiotic organisms. Prioritizing soil health creates a foundation for all life that stems from it — including us.
Stay tuned for the release of our new soil health workshop and other new offerings by subscribing to the Metro Blooms newsletter. In the meantime, check out our free, self-paced Resilient Yards Online Learning Series at bluethumb.org/events.
– Megan Reich, Metro Blooms Communications and Program Manager