The prospect of working to improve my garden soil excites me about as much as shopping for socks. But after talking with Mark Weathington, director of the JC Raulston Arboretum in Raleigh, about his book, Gardening in the South, I’m renewing my enthusiasm for improving my garden soil.
Mention soil to any gardener in our region and we are likely to hang our heads muttering about clay. But Weathington points out, “Red clay is so full of nutrients. It’s wonderful stuff if it isn’t like concrete when it dries out. So the key is to add organic matter.”
Explaining the need for organic matter Weathington continued, “It’s the single best way to be successful in the garden. Make it easier on yourself. You’ll have fewer weed problems and you won’t have to water as much. Everything about it will make gardening that much easier for you.”
Clay soil is comprised of small particles, so small they can only be seen with an electron microscope. These particles tend to be flat and they lay close together preventing water or air from circulating through it. That inability of water to easily flow through clay soil means it can become waterlogged or alternatively a rock-hard surface which water runs across rather than infiltrating.
Adding compost improves the physical characteristics of your soil. It opens up the space between the individual soil particles allowing water and plant roots to move through it more easily. Adding compost to clay soil can help achieve that Goldilocks moment when everything is just right—nutrient-rich soil that retains moisture but drains well.
Compost can come from many sources. Plants contribute to organic material. Fallen leaves break down faster than twigs or limbs. Topdressing garden beds with mulch also contributes organic material to the soil as the mulch breaks down; shredded bark decomposes faster than wood chips but it all ultimately becomes part of our garden’s soil. Gardeners can also make or buy compost to add to their beds.
Mine is a new garden. There was little topsoil left behind when our house was built so I am anxious to speed up the accumulation that will occur from decomposing mulch and leaf litter. But my yard is small and I have no room for a compost bin. So I keep a vermicomposting box going for my kitchen scraps. While my worms work hard they can’t produce enough castings to amend all of my beds so I purchase compost to supplement their output. But not all compost is the same.
The Organic Materials Review Institute (OMRI) is an international non-profit organization that determines which materials can be used in producing compost that qualifies for the USDA’s National Organic Program. Established in 1997, OMRI provides an independent review of products allowed for use in organic production.
I’m not seeking organic certification, but if I’m adding something to my soil I want to choose amendments that won’t introduce unknown components. OMRI-certified products display the OMRI logo, and I’m looking for that logo when I go shopping for compost. Now I just have to work up my enthusiasm to shop for some new socks.
You can learn more ways to improve your soil on our podcast.
Featured image – Shovel in soil / Lise Jenkins
Dr. Lise Jenkins produces the Triangle Gardener’s radio show and podcast. She also volunteers her time as a Master Gardener in Durham.