Imagine a garden with few pests and weeds, lush plant growth, and soil that maintains its moisture. Of course, it is buzzing with bees and aflutter with butterflies too. Here’s the secret—a garden like this can only be made possible with healthy soil.
Our members and Conservation@Home participants know how important it is to support a robust ecosystem in our neighborhoods. You might begin by planting native flowers, grasses, and trees in your yard. Those native plants then offer a welcoming buffet for caterpillars and other insects. In turn, those critters draw in birds and other wildlife. Before you know it, your gardens are supporting a dazzling array of life!
However, what’s under the soil deserves attention too. There is a whole web of life in the soil that is foundational for the rest of the ecosystem. Certainly, healthy soil allows plants to flourish, but good soil has other benefits too.
The Benefits of Healthy Soil
Healthy soil benefits plants, people, and the environment at large. Some of the benefits of healthy soil include:
- Healthy soil creates healthy plants that are less vulnerable to pests and disease.
- Healthy soil sticks together and has a sponge-like structure. It holds moisture and prevents erosion.
- Healthy soil captures, filters, and infiltrates stormwater.
- Healthy soil suppresses weeds.
- Healthy soil captures and stores carbon.
- Healthy soil produces high yields without the need for harmful chemical inputs—for vegetable gardens and large farms alike.
- Healthy soil produces the highest-quality, most nutritious vegetables!
Features of Healthy Soil: The Soil Food Web
All those benefits are fantastic—but how can healthy soil do all these things? These benefits are the result of a vibrant ecosystem within the soil. Healthy soil depends on a delicate balance of living organisms working together to decompose organic matter, recycle nutrients, and support plant growth.
This complex living system in healthy soils is called the “Soil Food Web.” Basically, nutrients cycle through the web from plants to beneficial microbes to larger creatures such as earthworms—and back again to the start. In the Soil Food Web, one organism’s trash is another one’s treasure. Nothing goes to waste as nutrients cycle through the web. Each level of the web contributes to the health of the whole system.
A Thriving Soil Food Web Creates the Healthiest Plants
Healthy plants depend on the Soil Food Web. Plants are able to make sugars from photosynthesis, but they need other nutrients too. Yet, a lot of these nutrients are locked away in the soil in forms that plants can’t use directly. So, they enter into an exchange with beneficial fungi and bacteria. These microbes break down nutrient-rich organic matter into a plant-available form. In exchange, the plants provide sugars to the microbes. Therefore, plants that are part of the Soil Food Web are well-nourished, healthy plants.
Without the Soil Food Web in place, plants have a hard time getting the nutrients they need. As a result, they are less nutritious to wildlife and people. They are also more vulnerable to pests and disease. When plants are undernourished, they produce less phytochemicals that inhibit pests. In healthy soil, beneficial fungi and bacteria cover the surface of plant roots, protecting pathogen-causing microbes from reaching infection sites on roots.
If you’re a visual learner, watch an animation that explains this concept in more detail.
The Soil Food Web Creates Well-Structured Soil
Healthy soil sticks together. When the soil is teeming with life, beneficial bacteria release sticky secretions that bond soil particles together. Beneficial fungi also produce exudates that further hold the soil aggregates together. These sticky exudates give soil structure—the soil sticks together but has plenty of air spaces between the soil aggregates.
Worms and other insects also improve soil structure. For example, earthworms burrow through the soil, creating channels that allow air, water, and roots to penetrate more deeply.
Well-structured soil has key environmental benefits:
- Well-structured soil is porous and oxygen rich. Life in the Soil Food Web (plant roots, microbes, worms, and more) is further nourished by oxygen. An oxygen-rich environment is also inhospitable to anerobic microorganisms—which thrive in oxygen-poor environments—that cause plant diseases. As a result, aerobic, beneficial microorganisms outcompete them in the soil.
- Porous soil allows excess stormwater to infiltrate down into groundwater reserves. Stormwater is filtered as it seeps down through the soil.
- Structured soil holds moisture, making plants more resilient to drought.
- There is much less erosion of precious topsoil when the soil sticks together. Less soil erosion also creates better air quality and water quality—wind isn’t able to blow soil into the air and stormwater doesn’t bring loose soil into local rivers.
- Well-structured soil sequesters carbon. Carbon is pulled out of the atmosphere by plants and exchanged with beneficial fungi. These fungi store carbon in their mycelium (the root-like structure of fungi) as well as in their exudates (called glomalin) that contribute to the soil structure. In fact, 50-70% of sequestered carbon in the soil is in tree roots and the fungi that are in symbiosis with them!
How to Start Building Healthy Soil in the Home Garden
The benefits of healthy soil are vast and deep! There are many practices we can do to start building healthy soil at home, including:
- Incorporate diverse plantings. A diversity of plants builds vibrant ecosystems above and below ground. For instance, different kinds of plants bring different nutrients down into the soil for exchange with microbes.
- Incorporate organic matter. Organic matter feeds many members of the Soil Food Web. Amend the soil with compost, leaf mold (composted leaves), wood chip mulch for perennials, and more.
- Inoculate plants with mycorrhizae. Your annuals and perennials alike will benefit from a symbiotic relationship with fungi, specifically mycorrhizal fungi. Simply mix mycorrhizal inoculant into the potting soil you use to start seeds, or dust the inoculant onto the roots of your purchased seedlings. Note that there are a few kinds of mycorrhizae. For example, ectomycorrhizal fungi enter into symbiosis with trees only. Do your research to make sure you get the right kind of inoculant for your plants. Pro tip: watering your inoculated plants with diluted seaweed extract will help inoculation by “awakening” the fungal spores.
- Reduce soil disturbance. Any tillage or disruption of the soil breaks apart mycorrhizal networks and soil structure. You may need to till to start your garden, but reduce disturbance thereafter. If you have more time and patience, try sheet mulching to smother grass to start a new garden.
- Avoid plastic mulch and landscape fabric. Plastic mulch and landscape fabric reduce the ability of air to reach the soil and limit stormwater infiltration.
- Always have roots in the soil. Beneficial microbes, the foundation of the Soil Food Web, need plant roots to survive. Long periods of time without plants in the ground will kill off life in the soil. For your annual garden beds, look into cover crops for the off-season.
- Intersperse perennial plantings into or along annual gardens. Beneficial fungal and bacterial networks can spread from perennials to nearby annuals each garden season! Try planting perennial native flowers or perennial foods (like raspberry canes) next to your annuals.
- Eliminate synthetic fertilizers. When plants have readily-available nutrients via synthetic fertilizer, they won’t enter into symbiosis with beneficial microbes. Consequently, the Soil Food Web falls apart, and you won’t get all the incredible benefits associated with healthy soil.
- Try holistic foliar sprays instead. Foliar sprays like liquid seaweed, fish hydrolysate, pure neem oil, compost tea, and others boost plant health and soil health.
Dig Deeper Into Soil
Soil health is complex, and we’ve barely scratched the surface in this blog. Here are a few resources that can help you dig deeper into soil:
- “Improving Soil Naturally” Webinar by Richard Hentschel
- Elaine’s Soil Food Web YouTube Channel
- Soil Science for Gardeners: Working with Nature to Build Soil Health by Robert Pavlis
- Mycorrhizal Planet: How Symbiotic Fungi Work with Roots to Support Plant Health and Build Soil Fertility by Michael Phillips
- Teaming with Microbes, Teaming with Fungi, and Teaming with Nutrients by Jeff Lowenfels (This is advanced level reading!)