I listened to some interesting podcasts recently, with soil scientists Dr. Christine Jones, and Nicole Masters discussing microbial interactions in the soil: Diversity is the key! Not only does this apply to vegetable gardens, but also to orchards and fruit trees. And it also can apply to our own health, through the nutritional aspects of what we are eating. More research is exploring the link between soil microbiome, human microbiome, and human health.
Quorum sensing is a function that happens when there are sufficient soil microbes to communicate with each other, perhaps through electrochemical receptors on their surfaces. To understand quorum sensing it was helpful to me to have the example of having a quorum of people; for example a sufficient number of members to vote on an issue. So it is with microbes, when a sufficient number and diversity exists, they can sense one another and communicate with the plants, helping to meet the nutritional needs of the plants. The microbes are able to recognize friends and enemies, and can switch on gene expression and production of chemicals.
Seeds of plants, and plants themselves, have their own microbiome, communicating with and making requests of the soil microbiome through the rhizosphere. This communication can be requesting nutrition, or disease suppression.
Quorum quenching involves a diversity of beneficial microbes being present in the soil and in the plant which can then interfere with potentially damaging microbes. In an orchard it may be that improving the diversity of plantings around the trees can help with pollination, water infiltration, and disease limitation. Though perhaps controversial, compost tea or extract treatment of seeds, or spraying these on leaves, may be helpful for limiting disease.
Soil microbial life influences root health, which influences photosynthesis, which in turn drives the carbon cycle. The ability of plant root exudates to store carbon in the soil is directly related to diverse microbial life, which is directly related to diversity of plants. For more information, an interview with ACRES magazine discusses the carbon cycle and topsoil formation.
What does this mean for us as backyard growers? In a veggie garden it may be better to grow a wide variety of plants in one area, rather than having all the tomatoes together. In an orchard, we could promote more microbial diversity with integration of cover crop, living mulches, and flowering plants. It is easy to also imagine the benefits of flowering plants helping with beneficial insects and pest predators as well.
Some things to think about
difficult to have other plants root and grow. Presently, flowering perennials and annuals are along the fence line plantings instead. A debate goes on as to which is better; wood chips alone as a ground cover, or some living green mulch for root exudate diversity. Either way, at a minimum the ground is covered and protected.
The vegetable area is planned with diversity and “companion planting” for each raised bed. Beans and lettuce are growing alongside the tomatoes, etc. Calendulas and bachelor buttons are blooming, and the African blue basil has started flowering. Agastache, and scabiosa have reallly long blooming seasons. Soon the weather will be warm enough to add some zinnias and marigolds as well.
At a minimum, the potential beauty of the hoped for diversity will feed my soul.