Like all living beings, bacteria and fungus need food, water and shelter. In last month’s Grow Wild article, we explored how microbes function in garden soil and how they benefit future gardens. This month, we’ll explore various approaches to cultivating soil microbes and fostering their presence in your garden.

FEED THEM 

Preserve the roots. Soil microbes thrive on decaying plant material. After harvest, make sure to cut down stems, branches and unused plant material and lay it on the surface of your garden, but leave the roots in the soil. Avoid uprooting plants entirely, as the roots preserve the microbial populations that have been nurtured throughout the growing season. Decaying roots are also a valuable food source for microbes under the soil unless the plant is diseased, in which case, they should get cut down and removed.

Diversify your garden. A diverse array of crops serves as a crucial food source for soil microbes, as each plant releases different sugars through its roots to feed a varied population of microbes. It’s wise to plant 12-15 different cover crop species to enhance microbe feedstock diversity. Homeowners usually grow a variety of crops, including trees, shrubs, flowering plants and other landscaping. Research indicates that a garden surrounded by diverse vegetation not only supports more bacteria, fungi and protozoa but also attracts beneficial insects for pollination and pest control. To maximize microbial benefits, rotate vegetable crops to different areas of the garden each year. 

Companion planting. Introducing a mix of plants such as legumes, mustards, radishes and even grains like wheat and barley throughout the garden also feeds the soil. Even if these plants don’t get eaten, leaving them in the soil at the end of the season adds valuable organic matter. 

Use natural fertilizers. Natural fertilizers such as kelp and bonemeal are nourishing for microbes and their intended crops. Chemically derived fertilizers can have detrimental effects on soil inhabitants. Additionally, many chemical fertilizers are salt-based, which can adversely impact the microbial environment. 

WATER

Assess irrigation. Allowing the soil to go bone dry can kill bacteria and other microorganisms, while flooding the soil makes it hard for them to breathe. Maintaining optimal moisture levels is crucial for both soil microbes and plants, with the preferred range being around 40-70%. Use moisture probes to assess your irrigation needs, or simply dig around plants with a small shovel. Ideally, the soil should exhibit enough moisture to form a ball when squeezed, without water visibly coming out. 

Mulching. Mulched soils retain moisture more effectively than bare ground. Plus, leaves and straw breaks down into organic matter and also becomes a food source for the microbes.

Avoid soil compaction in the garden, as compacted soil limits water infiltration. Never walk in the garden after a heavy rain, and don’t leave equipment on the soil overnight in growing areas. The cultivation of a diverse array of crops, particularly those with thick or long roots like radishes, wheat or barley, helps create water channels as their decomposed roots leave spaces in the soil, further enhancing water absorption and soil aeration.

SHELTER

Plant cover. Ensuring continuous plant cover in your garden is essential for fostering a thriving microbial community. After harvesting crops like carrots or beets, consider planting other short-season or cover crop varieties in their place, especially if you leave the tops in the garden. This practice also helps regulate soil temperatures. In addition to mulch, plants provide shade, creating a favorable environment for microbes by preventing extremes in soil temperature.

Do not disturb. Reducing the amount of soil disturbance benefits soil microbiology. Tilling the soil shreds up fungal networks and nematodes. Turning up soil exposes bacteria to UV rays, killing them. As microbial populations build and secrete glomalin, the soil will begin to cling together and create good soil structure that has porosity. 

ADD MORE MICROBES

Start a compost pile. The best source of microbes comes from homemade compost. Incorporating a variety of food waste and leaves into the compost pile yields a more biologically diverse product, providing nourishment for our soils and crops. 

Worm composting, or vermicomposting, contributes to the diversification of microbes. Unlike traditional compost, vermicompost doesn’t require turning and doesn’t generate heat, so it attracts more insects cycling nutrients and enhances the soil food web.

Animal manure harbors microbes that won’t appear in traditional compost. Aged, weed-free manure can be added to the soil in the fall or early spring, ensuring it’s incorporated before plants go into the soil.

Microbial inoculants. While purchasing microbial inoculants is an option, it’s also a gamble. Some may adapt and thrive in the local environment, while others may not survive. To ensure the success of local microbes, finding quality garden soil from a friend or a well-vegetated native area and adding it to the garden is a reliable approach.