- Author: Jane Callier, UC Master Gardener of Napa County
Every gardener has the ability to have a positive and significant influence on earth's warming climate. Improving soil by adding organic material like compost helps the life in earth's over-tilled and compacted soil.
Try thinking of the soil in your garden as a living body. If your body experienced something akin to digging and turning, you'd need a trip to the emergency room. Of course, we have to manipulate soil a bit to start new plants and seeds, but you can think of that kind of action as a good Swedish massage.
It's obvious that a plant needs healthy roots, but roots do more than keep plants healthy. Roots need carbon to grow and plants draw that carbon from the atmosphere. Carbon dioxide, of course, is a major contributor to greenhouse gas and global warming.
Through photosynthesis, plants create carbon sugars to feed their own growth. They also deliver carbon to the soil via their roots. As roots exude carbon sugar, mycorrhizal fungi are drawn to them. The narrow area around the roots is called the rhizosphere, where active chemistry and microbiology happen.
Mycorrhizae have hyphae, garden hose-like structures that can extend 300 yards. Hyphae attach to roots, creating an immense root system. As mycorrhizae metabolize more root sugar, plants grow and pull down more carbon from the atmosphere. Their roots transfer minerals absorbed from the soil into the plant. Both plants and soil structures benefit from the interaction.
You might compare the soil biome to a bustling city: busy freeways, construction workers, and lots of food trucks and bistros. What happens when we don't have plants, roots, and microorganisms creating all this life in the soil and performing this scientific, yet magical dance? As you might guess, the soil becomes a lifeless combination of minerals.
Food grown in soil with a healthy biome has higher nutritional value. It has higher concentrations of several minerals that contribute to overall health and may help prevent inflammatory ailments like Alzheimer's and heart disease.
Tilling the soil harms the soil biome. It destroys microorganisms in our bustling soil community and leaves us only lifeless dirt.
The hyphae in healthy soil make a protective coating called glomalin that literally holds the soil together, helping it aggregate. Soil that doesn't aggregate won't have a healthy biome.
Try this simple thought experiment. One plate has a mound of flour on it representing tilled soil. Next to it is a plate with a piece of bread on it representing aggregated soil. Pour water on the flour and it will run off without penetrating. Pour water on the bread and it will be absorbed, just as aggregated soil keeps carbon, nitrogen, and minerals in the ground. Aggregated soil is like a “carbon sponge.”
You can create aggregated soil by planting perennials and trees. Both have roots that remain in the ground a long time. You can intercrop your vegetable garden, planting cool-season vegetables like broccoli alongside mature warm-season crops, like tomatoes, that are nearing the end of their harvest.
Planting perennial fruits and vegetables—think artichokes, asparagus, and strawberries—is another increasingly popular way to keep roots in the ground year-round. Keeping more plants and their roots in the ground can be a lifeline for our soils as earth's climate heats up.
We need to overcome the habit of tilling the soil. As much as possible, we need to leave soil intact. Soil is made up of sand, silt or clay, water, and air. Only 5 percent of soil is organic matter. Of this 5 percent, only 5 percent is living organisms. This soil life is a precious commodity, and most of it is in the top two inches.
You can learn more about these concepts in the UC Master Gardeners of Napa County presentation, “Soil is the Solution: Healing the Earth One Yard at a Time.” You can watch this presentation on YouTube (https://www.youtube.com/watch?v=JqA8DqBtRuo). The presentation describes how we can help slow and ultimately reverse soil damage.
The takeaways are these: Protect the soil biome and the rhizosphere. Preserve soil aggregates. Retain healthy topsoil and protect it from erosion.
Food Growing Forum: Join the UC Master Gardeners of Napa County for a Zoom forum on “Dealing with a Hotter Climate” on Sunday, June 12, from 3 p.m. to 4 p.m. Register to receive the Zoom link at https://ucanr.edu/2022FoodForumJune
Guided Tree Walk: Join the UC Master Gardeners of Napa County for a free tree walk in Fuller Park in Napa on Tuesday, June 14, from 10 a.m. to noon. Space is limited to 12 people and pre-registration is required. Each attendee must register separately. Trees to Know in Napa Valley will be available for $15; cash or check only.
Gardening with the Masters: Join UC Master Gardeners of Napa County and Ole Health on Saturday, June 18, from 10 am to 1 pm at Ole Health South Campus, 300 Hartle Court, Napa, for a workshop on gardening. Children five years old or older, accompanied by an adult, are welcome. Attendance is limited. Register here: https://www.olehealth.org/our-services/community-outreach-resources
Got Garden Questions? Contact our Help Desk. The team is working remotely so please submit your questions through our diagnosis form, sending any photos to email@example.com or leave a detailed message at 707- 253-4143. A Master Gardener will get back to you by phone or email. For more information visit https://napamg.ucanr.edu or find us on Facebook or Instagram, UC Master Gardeners of Napa County.