The World Beneath Your Feet (Part I)
OSGF
For the Oak Spring Garden Foundation’s horticulture staff, caring for the soil is just as important as tending to the plants it supports. Soil is alive and complex, and healthy soil is essential for the well-being of people, animals, and the environment.
In honor of World Soil Day, an international observance day established to raise awareness of the importance of soil quality, we’re bringing you two dirt-encrusted blogposts about soil in the formal garden. In this first post, assistant gardener Jordan Long discusses the process of revitalizing the soil in Oak Spring’s potager garden, and why healthy soil matters.
When standing in a garden bed, there is a whole world beneath your feet, and this world needs care and attention in order to thrive. About two years ago, our team of gardeners started to think critically about the long-term soil health in the potager garden and which strategies and practices we could implement in order to improve growing conditions for years to come.
The Oak Spring Garden was first planted over half a century ago, and until recently had seen constant tilling and synthetic fertilization. The soil in the potager garden was, as I like to say, exhausted: it was sandy, even dusty, with hardly any organic matter like compost or microorganisms (rhizobia, nematodes, mycorrhizal fungi, good bacteria). It was also largely absent of macroorganisms like worms, spiders, and millipedes. We knew this meant the soil had poor structure. A delicate balance of sand, silt, clay and organic matter constitutes healthy soil; these components must be at proper ratios for the soil to aggregate, stick together, have good pore space, good permeability, aeration, and nutrient exchange capacity.
The potager garden, fall 2020
In our case, the soil was heavy on sand and low on everything else. This indicated a severe lack of organic matter and macro and microorganisms, which help break down nutrients and make them more available to plants. It also meant that our soil had a low water holding capacity, which meant we wasted lots of water trying to keep our poor plants hydrated. Over tilling had been so disruptive, and the soil had become so weak, that compaction was also an issue - a particular problem when you’re trying to plant small plants and their fragile roots are unable to spread.
We knew immediately that we had to stop using the bagged stuff (the synthetics) because even if they are labelled “organic”, they really do nothing to build up the soil structure. It’s putting a Band-Aid on the issue. We needed to remediate and heal the soil.
We began by adding compost, which stimulates the soil as it breaks down and feeds critical microorganisms. In turn, microorganisms digest the organic matter that plants are unable to take up and release nutrients that are now more available to your plants. These guys need compost, leaf litter, and decaying matter to survive so that they can create critical symbiotic relationships with your plants. This relationship benefits nutrient mineralization and availability (the plant gets more “good stuff”), it stimulates plant growth hormones (your plant gets bigger), and prevents the plants from being the targets of plant pests, parasites, and diseases (weak plants are a buffet for pests). Microorganisms are the tiny guardians of the garden. And they are found in healthy soil!
Maintaining the presence of these microorganisms is the reason many farmers and growers have adopted the no-till method, which was the next step for our team. After an initial addition of compost to our beds, we did a very shallow tilling and let the compost sit over the winter. This spring, we began to plant our plants in a much healthier soil. It wasn’t quite where we wanted it, but we were on the right track.
Another practice we implemented was leaving the roots of our plants in the soil for a few months, instead of ripping the entire plant out of the ground when it was time to plant the next crop of vegetables. That way, beneficial microorganisms, macroorganisms, and nutrients were allowed to stay with the root ball, and as it decayed, it fed them and helped to improve the soil structure.
You might be asking yourself, why worry so much about soil health in a small space like the potager garden? While such a space may seem diminutive to humans, it’s a big deal for the organisms it supports. Every bed works together in a garden, and if one suffers, it has a ripple effect on your surrounding landscape. A bed with poor soil could be a breeding ground for viruses, bad bacteria, weeds, and plant pests that then make their way to your healthy plants.
Healthy soil is also important for beneficial wildlife. It gives birds, butterflies, and bees a safe space to visit, hunt for food, burrow, overwinter, pupate, and populate. It also stores more carbon from the atmosphere, and will require less water to hydrate your plants.
In this way, having healthy soil also benefits your wallet. You won’t be running up the water bill, and you won't find yourself lugging around countless bags of fertilizer from the store. Healthy soil will also give you an abundance of nutrient-rich herbs and vegetables far superior to what you find at the local supermarket, benefiting your health and that of your family. (Even though Oak Spring’s potager garden is mainly aesthetic, it grew enough vegetables this year that we were able to donate some to local food banks.)
Whether you’re creating a kitchen garden or just a few raised beds, healthy soil matters. So reduce tilling, add compost and leaf litter mulch, plant your plants, and enjoy the fruits (and veggies) of your labor!
All photos by Jordan Long. Jordan also selected the plants for the potager garden.