On clay

Clay soil: it absorbs water and expands, then expels water and contracts. This ability is called “plasticity.” I can’t throw a pot with the stuff, though, thankfully.

I thought rather naively that I would have sand at our farm. Being this close to the beach, I figured it was a part of the picture. Glacial movements are a funny thing, though, and I am sand-free here and instead have lots of clay.

This is both good and bad. Clay is wildly productive stuff. There’s a chemical reason for that: its tiny, flat particles, though notorious for other reasons, are great at binding with good metals in the soils itself through an electrochemical exchange of cations. Clay is negatively charged, the metals positive, thus the binding. Sure, we all need to go back to high school chemistry to understand it fully, but let’s just say if there’s some calcium or potassium floating around, the clay will get ahold of it and keep it.

It’s a bear to work with though as a gardener. This is Season #4 on the farm, so I have had three years of observation. Not nearly enough years, but…at least now I can at least speak a form of clay pidgin (har). My first year, I was so worried about the water-soaking potential of this soil that I did not mulch at all. Well, that was a huge mistake. Water from a hose or from the sky loves a plant-free (weed-free) bed of clay soil: it smashes the top layer into an amazing flatness that then gets baked by the sun. Nothing wants to go through that, and if you think of Death Valley you can understand what it begins to look like.

Clay is a problem because of how heavy it is: there is not much air in the space between the particles, unlike sand. Incorporating lots of stuff in with the soil is one way to lighten them, but in my experience it’s only a temporary fix. My first raised beds were made with a ton of compost, manure, leaves, grass clippings and then that native soil that I tilled beforehand, all mixed together. (Never work wet clay soil is another cardinal rule, incidentally.) These are still the materials I use to make new beds, but I tend to layer things instead: tilled earth, 2″ compost, 4″ dried grass, earth from the paths between the beds, more compost, more grass, and a topcoat of some of that big truckload of (clay) dirt I got earlier this spring. Unless I am planting seeds directly into the bed, the new transplants I stick into the new beds then get mulched to the hilt: 4-6″ of grass clippings, usually green. They turn brown eventually, and get refreshed every time Tom mows (which is about every 2 weeks).

Once the beds are made, I never till them again (a near impossibility anyway considering the beds are raised) and I never work them at all except to mix in the top inch or two in the spring. Vegetables are annuals in the main: in the clay soil elsewhere on the farm, perennial roots of grasses, trees and flowers (and weeds) are always present and thus humus is made in situ. Veggies are annuals, though. I tend to lop off the tops of my spent plants (not the brassicas or tomatoes but everything else) and leave the roots in place to rot and thus claw through that tough stuff.

Mulching is entirely necessary, however. It keeps the weeds down to zero, or near enough; it reduces my need to water down to near zero too. The worms and other wriggly things, which flee to subsoil level in an uncovered bed, are right under the mulch (and right at the top root zone) in a mulched bed. Last August we had so much rain that the beds DID drown, and I lost most of my cole crops; I pulled the mulch off to dry the soil out. I am not sure it worked, but the garden is now an island surrounded by a ring of perforated drain pipe, 300′ total, as a form of insurance. As I harvest the last veggies in the fall, I immediately sow green manures (a mix of rye, oats, hairy vetch) that will grow fairly slowly and will winterkill (sometimes). This creates a mass of vegetation a couple of inches thick. In the spring I use a three-tined cultivator and mix it in.

Can I say I love clay soils? Not really. Considering, though, that my kitchen garden is where there has been a kitchen garden for the last 90 years…and has not had fertility, rust, mildew, or wilt issues…I think I will keep it.

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12 responses to “On clay

  1. I love it when you talk dirty.

  2. Oh cookiecrumb, that’s too funny!
    My soil is heavy and sometimes pure (can make a pot out of it) clay, and my next-door neighbor has sand. Michigan. Go figure.

  3. I just wanted to say Hi! I discovered your blog yesterday and have been having a great time reading it. I live south of GR and have clay, a garden and chickens. I have always wanted a greenhouse so I am following your progress with that…I might just have to get one going myself this year!

    I look forward to seeing your garden progress. I have found that my clay is great for transplants (much less watering than I would expect) but the poor little seeds have a hard time with it. I should take a picture of the pile of dirt I had delivered this year…as fun for me as shoe buying is to some of my friends!

    I am also thinking of trying meat chickens again this year, maybe with your chicken tractor idea. I found my meat chickens to be VERY uncivilized and not fun to have around. I would like some home raised chicken again though…

    Thanks for the great ideas!

  4. Interesting POV on clay. Never thought of it as a (somewhat) desirable commodity. I’ve got plenty of it too & it’s always there, no matter where I dig in the yard. But still, everything is lush & growing so something must be going right.

  5. You want clay, come try to deal with this red clay of Georgia! ALL the outdoor animals at the Atlanta zoo are red!

  6. Oh yes, clay. We had horses pastured on our land by the previous owners and thankfully they did us a favor :). We have fairly aerated clay for most of the land, but it is still clay.

    I’ve liked the coconut coir fiber in our soil and am using it for the sunflower house because the sunflowers do NOT like the clay for some reason. Our blueberries, lilacs and hydrangeas love it though.

    Your advice about layering is great. I’m just getting ready to go out and plant some more in the ground and I think I’ll try that layering thing.

  7. OMG CC as usual you are a SCREAM.

    Anne: Really and truly I had NO idea (and it didn’t even factor into the home purchase) that there was clay here. It’s wacky! I first tried to get my brother to shovel up a few clods of grass so I could transplant my precious few plants brought down from MN (and this was November) and he kind of came inside laughing, saying he couldn’t do it. And I can see the sand dunes from my house.

    Anne! You are quite welcome, near-neighbor. I have a few more greenhouse posts floating around in my head now, so stay tuned. You should do a greenhouse! And a meat-bird tractor! Ah hah hah…you’ve fallen into my web! 😉

    Artemisia, I know: believe me I had to look hard to find an upside to this mucky stuff too, but really, the plants do love it. Weeds too, unfortunately.

    Pattie, what is it, iron in the soil that makes it red? I know it’s not just GA because my friend from NC has it too. That’s understandable about the poor zoo critters though; they can’t exactly import stuff from elsewhere I would imagine.

    Jennifer, yeah, the layering trick is the only thing I have found that works long term (okay, so my scale of “long” means two seasons). You are right about the sunflowers though. Mine always flop over when they’re at their tallest and sunniest in August. We usually get a couple of big soaking rains and they just give it up, roots and all. But maybe I will try it in the kid’s new garden bed (in the veg garden: she’s got seedlings to transplant soon, she’s so excited).

  8. Oh, how I would love clay. Here in Florida, it’s sand on top of limestone. Excellent drainage for the heavy summer rains, but it means heavy watering at least once a day from February to June. And it doesn’t hold a thing as far as nutrients go. I have to add a thin layer manure every week or it’ll just wash out. No calcium either, so tomatoes can be a pain. And the light, aerated soil (and good drainage) means everything has roots and runners crisscrossing the patch extensively, so turning in the spring and the fall is a huge pain. This is my first garden at this house, and layers are definitely in order for next season.

  9. B, can you mulch? My mom lives in the sand dunes and it’s awful. I ended up bringing in a truckload of topsoil and tilling it in when I made her big perennial garden a few years back. And I have turned her into a mulcher with grass clippings and wood chips. It seems to have helped but she certainly has problems keeping things wet too. Maybe you can start your new beds this fall with heaps of layers of things, so it will be ready for you when you start it up again next year.

  10. We have heavy clay soil too, and I decided to be lazy and build a raised planter to avoid all the work you’ve done with your soil. With the heavy May rains and now the June heat, the photo you included could easily be in our back yard instead of on your farm. So, I’m looking to mulch the veggies in rapid order. Out of curiosity, what kind of mulch do you use?

  11. Hi Lori. Grass clippings! It’s the one thing we have in abundance. They let water in, but not light, so weeds won’t grow. They rot to a nice light brown. I usually put 2-6″ of the fresh stuff down on each bed. Sounds like a lot but it disappears in no time.

  12. Oooh, that’s a great idea! We probably have just enough grass to support my single raised planter. Thanks for the inspiration for next year. For now, I have straw…

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