Several gardening books I’ve read include the note that good garden soil is a sandy loam, rich in organic matter. My yard’s soil is naturally a massive gob of red clay — like in the nearby photo — not at all what is recommended.
Red clay is actually not all bad. It holds nutrients much better than sandy soil, so it doesn’t need as much fertilizer. It also holds water — sometimes too well! — which means it is slow to dry out. When it does get dry, it becomes brick-hard and tough to dig.
Plants benefit from the nutrient-holding and water-holding capacity of clay soil. The problem is that the clay compacts and does not allow roots to move easily through the soil, and it doesn’t have good air spaces (which roots need).
Not every yard in this area has such dense red clay as mine. When we first moved here (in 1990), and for years afterward, an older gentleman in Kennesaw grew roses, lots and lots of roses, out near the road on Cherokee Street.
I stopped to talk with him once, when I saw him out tending his roses. He said that a friend brought him a truckload of oak leaves to use for mulch each year, but that his yard had naturally good soil. That comment stunned me into speechlessness for a moment — my experience was so different!
Most people I talk to around here have soil like mine. This may be why so many new gardeners use raised beds filled with soil mixes that don’t include clay.
My gardens, though, are not in raised beds. They are in the ground, in that red clay. I add amendments like compost (from my yard) and soil conditioner (from a garden center) to increase the organic matter and microbial activity. The amendments make the clay soil a more welcoming place for the roots of my crops.
How to create good garden soil from red clay
A recommendation from Cooperative Extension’s “Ask an Expert” page for improving clay soil, is below. The picture of the compost bin nearby, though, is a clue about at least one important amendment.
Here is the Extension Expert’s recommendation:
- Choose an organic soil amendment like composted yard waste, rotten leaves, or well-rotted manure (make sure any composted manure does not contain residual herbicides!). Material that is well-rotted will not smell unpleasant; it will smell like the earth.
- Spread a 3 to 4 inch layer of your chosen amendment on top of the clay soil; work it down into the soil about 6 to 8 inches.
- After the compost has been worked into the soil, you can spread an inch or two layer of sand on top and gently spade it in.
- Before planting in spring, lay on another 2-3 inch layer of compost and work it into the soil, about 6 to 8 inches down (the depth of a shovel blade).
Walter Reeves, The Georgia Gardener, has an updated article on Soil – Bed Preparation that suggests bagged soil conditioner as an alternate for compost. His article also suggests adding Permatil to the mix, to keep the clay soil looser, as the composts and soil conditioner decompose and disappear.
Permatil is expanded shale, and it creates air spaces in the soil. I have added a similar product to part of my upper garden, an area I don’t re-amend as often as the veggie area because it has some perennials (permanent plants).
If you can’t find Permatil but are interested in trying something similar, look for Espoma’s Soil Perfecter, bits of kiln-fired “ceramic mineral” that works in a similar way to open up air spaces in the soil.
Nutrients and pH?
The Extension recommendation above does not address soil pH (acid level) or fertility/nutrients. The Expert who answered the question may have assumed that everyone will know to send a soil sample to their state’s soil lab (Georgia’s is at UGA, in Athens) through their local Cooperative Extension office.
If you are not sending a soil sample to your state’s soil lab, consider buying a pH test kit (see my article on Soil pH and Garden Success for more information). For fertility, if you don’t have a soil lab recommendation for fertilizer, choose an organic-approved garden fertilizer and follow the package directions. To learn more about nutrient sources for your garden, check out my articles on Potassium Sources for an Organic Garden and on Fish Emulsion Fertilizers.
Dig soil when ground is not soggy
You will know your clay soil is dry enough for digging when you can squeeze a handful of it and it breaks up into bits. You should not be able to roll it into the kind of snake-shapes that can be coiled to make pottery bowls.
Clay soil needs to be not-soggy at digging time, partly so you can get the clay to let go of your shovel and partly so it won’t reform into giant, brick-like clods when the lumps finally dry. Digging in wet clay soil also causes it to compact, making it lose the air spaces that are vital to healthy plant roots.
Winter is a great time to work on improving garden soil or to create new planting beds. Here in the South, we have some pleasantly cool afternoons mixed in with the cold ones, which means we have good opportunities for working outdoors.
Right now, though, the ground is squishy under my feet when I walk in the yard. I just need to wait for the rain to stop and the ground to get drier.