The Importance of Organic Matter in the Soil
If you’ve read some of our materials in the website, you have probably seen me encourage you to try to continually have decomposing leaves on your woodland garden site. This strategy helps to increase the organic material in the soil, which in turn increases the water holding capacity of the soil, as well as increasing fungus, microbes, and other organisms. Woodland plants need all of these things to thrive. Interconnectedness between organisms in quality soil is key to healthy forests and to your woodland garden.
In a regular garden or in agriculture, you would be wise to use compost to increase organic matter, which is highly superior to commercial fertilizers! Greens, mixed with browns and water, become a compost that has more bacteria than fungus in it. Decomposing leaves have more fungus than bacteria. Fungus, other microorganisms, and organic material (humus) is the mainstay of healthy forest soil.
I know that this method has increased the fertility of the soil in some areas in my yard, which had the topsoil (previously farm land) scraped off and deposited elsewhere. Due to leaving the leaves and keeping a pile of leaves to replenish during summer months, I’ve been able to create a couple of successful woodland gardens, but I don’t have data to show the facts and figures. I still don’t have data for my yard, but I read something this week that was so fascinating.
My dairy farmer friends, Whitney and Dan Belprez of Two Sparrows Farm in Eaton Rapids send out a newsletter each month to update on things happening on the farm. The March newsletter had a section about their soil.
They practice regenerative agriculture which means that they compost the collected winter cow manure and spread it back onto the fields each spring, adding organic material to the soil. They have been doing this for the seven years they have been at this location.
Whitney has allowed me to quote the newsletter:
“We still have lots of compost to spread, although if the ground continues to thaw we may have to wait a few months to spread it. We're always so excited to add more fertility to the soil each spring. When we purchased this farm back in 2018, the organic matter percentage was around 2.5 - 3% (depending on the exact spot). in 2025, after 7 years of grazing perennial grasses, no tilling, and only adding composted manure to the ground, we are in the 5.5 - 6% range across the farm.
According to MSU research, every 1% increase in organic matter the soil can hold 16,500 more gallons of water per acre at a one foot depth (38,445 gallons at 6 inches deep!). So, with the 3% increase that' we've seen on our 65 open acres, our land now has the capacity to hold 49,500 gallons more per acre - a grand total of 3,217,500 MORE gallons of water on our farm, making us much more resilient to drought and weather changes throughout the season.
Increased organic matter also increased the land's capacity for growing and grazing - it is the best indicator of LIFE in the soil.”
This is how most ecosystems work. Everything in the system is “working together” in a sense to keep the foundation of the system, arguably the soil, in good health.
Many woodland plants rely on the tree leaves to keep them shaded or semi-shaded, leaf or plant cover on the ground to keep the soil shaded, and fairly constant moisture in the soil for their roots. Some even need a microhabitat of a dip or gully in the woods where they can have higher than average humidity (ferns, for example). One of the keys to the moisture is precipitation, but also the water holding capacity of the soil which, as seen above, is greatly increased by adding organic material.
My street has a lot of Norway maples on it. Additionally, the wind often blows from the west and I’m on a corner lot that catches the leaves that are blown around. I gather these leaves into a pile or two in my back yard. I watch the soil since earthworms (non-native) churn through leaves quickly. Then I add more as I see they are needed throughout the growing season. In the fall, I make sure my woodland gardens have a healthy dose of leaves as covering.
I’ve been known to rake my neighbor’s yard for leaves and occasionally scored some yard waste bags in the fall. These are ideas for if you want to “leave the leaves” or don’t have large trees.
The original source for data was an MSU extension article found here:
This article is geared toward agriculture and grazing and using compost. But the same principles apply in the forest. Add a legume to your area to help fix nitrogen in the soil as well! We carry two in our shop, hog peanut (no stock listed at this point) and groundnut. NOTE: We also sell Wild Senna, Wild Lupine and Partridge Pea that fix nitrogen, but this post is focuses on rich woodlands.