Amending Hardpan Clay Soil
By: Jessie Keith
“I have hard clay soil. I have been adding one plant at at time and even that is hard digging holes large enough to amend soil around roots. But now I want to start a large bed by putting down cardboard, putting a bed border around it, and using everything in our mulch pile to cover the cardboard and leave over winter. Would this help or is there a better way?” Question from Erin of Kirkwood, Missouri.
Answer: I used to live in the Midwest, and hardpan clay soils are the worst. Covering bad soil won’t help your plants or the soil down below. Plants grow and resist drought best when their roots can grow deeply, which means either transforming your clay bed or building raised beds. If you want to transform your bed, here’s what I suggest.
Dig Deeply and Amend Like Crazy: Wait until the soil is lightly moist (not wet), and dig deeply into your bed bit by bit, putting portions of the clay soil in a wheel barrow. Then add loads of organic matter into the dug area–compost, leaf mulch, peat moss, earthworm castings, etc. (Check out Black Gold’s amendments.) Then slowly mix your clay soil back in. If you have a small tiller to really work it in and blend it well, that would be best. Continue to add lots of organic matter over several seasons, and your soil will be wonderful.
I also recommend taking all of your leaves at the end of the season, chopping them up, and laying them thickly over your bed like mulch. Once springtime comes they will have begun to break down and feed the soil. Using compost instead of bark mulch will also give your soil more enrichment.
We also encourage you read this article about Double Digging!
Happy gardening! Jessie
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