Garden Myth Busted! Don’t Add Sand to Clay

October 16, 2009 | By | Comments (10)

Clay soil curses most gardeners in the South. It drains poorly, dries hard as a rock, and restricts the movement of air, water, and plant roots. It’s a pain in the butt to garden in. So naturally, we look for things we can add to it to loosen it up and save our aching backsides.

Clay

A lot of people think you can loosen up clay by mixing in lots of sand. It’s sounds logical. After all, among all the constituents of soil, clay particles are smallest and compact the most, while sand particles are biggest and compact the least. Adding lots of sand will therefore break up that clay, right?

Wrong, wrong, wrong, rototiller-breath! Sand mixed with our Southern clays forms a sort of nasty concrete. When it dries, just try digging in it. You can jump from a tree onto the shovel blade, but the blade won’t move and you’ll lose your dentures.

Instead of adding sand, add organic matter — lots of it. Any kind will do — sphagnum peat moss, garden compost, composted cow manure, grass clippings, chopped up leaves, chopped pine bark, potting soil, worm castings, whatever. Organic matter coats the clay particles, opening up pores in the soil through which air, water, and roots can freely move. It also makes the soil comfy for earthworms and other organisms that loosen the soil even more.

So forget sand. Add organic matter to your soil every year, in gross quantities if you can. Organic matter can turn even the worst clay soil into good soil within a couple of years.

The Grump hath spoken!  

 

Photo by Jared.

COMMENTS

  1. Frank

    ps @Dona – kinda late but I’ve had good luck with suspensions like that and of all kinds of things (sand, clay, organic matter etc). I always try to shoot for loam in dug out out self-filled areas (which is a combo of things – you can google the ratio to find more info) along with a lot of organics as a base and then tailor it as needed (more acidic for rose gardens, for example). One trick I’ve heard that is said to work for people in high rain areas where migration and separation can be a problem when things get soppy a lot – which might be a good place for sandy soil, though I’m big on perlite as well because it lightens the soil as opposed to adding sand – or a combo, is to add a layer of weed barrier cloth to the bottom of raised boxes (breathable but fine mesh), though I haven’t tried it myself.It’s also supposed to work as a good segregator for people who don’t feel safe eating from their yard (like if you life on a landfill that’s covering an old dump – who knows what the mercury content of some of those are – a little study can be scary when you find out just how much of the stuff they used to put into products like face creams. If I were doing that I’d put a few inches or more of sand atop the weed barrier as well – look up ‘sand filter’ and you’ll see why – and sand filters in both directions

    Also I got to wondering if some of you might be able to dig out beds and surround them (below or at ground level) with sand (because it does indeed get like hard as long division when mixed with clay) and then fill the beds in with an airy loamy topsoil and organic material. Same for walkways but fill with just ‘fill dirt’. The excess clay could be ‘rammed-earth’-style formed into small hills and barriers (or statues of neighbors you don’t don’t like – add lots of seed and make a chia-neighbor). I’ve been doing hills in one of my yards (made of silt – and ain’t it funny how weeds don’t seem to mind clay or silt? Buggers…) And the other, a smaller one, I covered the previous owner’s lawn with weed barrier and 20% clay (in addition to whatever clay was already in the topsoil from the same supplier – I didn’t test it). I was expecting a mess with every rain but to my surpise it’s not only got a superb breathable – heavy yes, but easy to move even after drying folliwing rain). I’m getting all manner of things popping up and I haven’t watered it once. Things from seed or bulb that have made their way from neighor’s gardens via wind or squirrel (the love bringing us all bulbs from … who knows!? around here). I wish I knew what was in that topsoil but I got lucky. I’m planning to xero-scape it to some degree but if nice things want to grow without asking for any help (like water or fertilizer) then far be it from me to complain. Anyay – hills and large rocks and a few concrete projects I’m working on are what’s in the plans. My dog LOVES the hills I make for her.

    November 29, 2014 at 9:58 pm
  2. Frank

    Better yet – sell your clay to people like who are dealing with large yards that are very high in silt. I have been adding organics for five years (in high doses) and have been purchasing clay from a local supplier (at $12/lb – dry). Many with low clay yards don’t realize it and would laugh at the idea. Many gardeners regard clay the way they would a tax hike – even those whose problems are largely caused by lack of clay – because it has such a bad rep. In addition to that I have high alkaline in most areas and the two combined are bad enough that even worms are taking a long time to migrate in (with my amendments they are slowly breaching the perimeter this year). Oh – and for the alkaline problem I’ve been adding lots of peat and low grade iron pyrite (cheap if you catch what local rock shows sell cheap as the toss-asude from what they mine and then sort while on the road with shows). Anyway – in many places there really is an agricultural need for it and as well folks who work with “rammed-earth” projects require lot of usually. That and lots of city folk who throw clay but can’t get out and dig their own (but love working from scratch) would be some of many potential customers. So – just remove that nasty clay yard of yours and sell it ;)

    November 29, 2014 at 9:23 pm
  3. Steve Bender

    Dona,
    I see no point in adding a layer of sand atop a layer of organic matter in your raised bed. I would just add a 50-50 mixture of topsoil and organic matter.

    August 27, 2012 at 1:10 pm
  4. Dona

    what if you are adding sand to a say one foot 6″ raised bed that is above clay? will the sand fall through the organic matter eventually and make concrete around the deeper reaching root? or does it stay suspended? it is a permanant bed that will not be tilled.

    August 27, 2012 at 12:22 pm
  5. Grumpy Gardener (His Benevolence)

    I think the best way to improve clay soil is by adding lots of organic matter — like, for instance, Canadian sphagnum peat.

    April 30, 2011 at 8:16 am
  6. canadian sphagnum peat

    I have tried mixing clay and sand. And I found out, that still, the clay was very sticky. There was no good result when we mix clay and sand. I don’t have any idea on what to do with clay. What I’m using now is pure loam It is very effective.

    April 26, 2011 at 7:59 pm
  7. Grumpy Gardener (aka His Excellency)

    Good advice, Emmit. You guys up north certainly know your….uh….manure.

    November 28, 2009 at 10:36 pm
  8. Emmit up north

    You said it! Clay plus sand is the recipe for adobe, so if you want to grow a garden on a brick, add sand to your clay. Here’s a quick test to try on your clay soil. take a bit of damp or wet clay between your fingers. If it feels gritty, then it already has all of the sand it needs, you need to add humus. If it feels silky smooth, then it would probably benefit with some sand, But!! First raise the humus level. If this is a new garden, with nothing planted yet, you might try an old technique called “green Manure” plant a quick growing annual crop like rye or soy very thickly. then when the plants are only about a foot high, rototill them under. repeat this as often as needed to produce a humus rich topsoil. And don’t forget the old fashion Brown manure, the kind that comes from cows and horses, It’s till a good source of humus. Whatever you do, it’s always easier to improve the soil in a new garden when you don’t have to contend with working around old plants.

    November 24, 2009 at 6:33 pm
  9. Grumpy Gardener (aka His Excellency)

    Don’t argue with Daddy!

    November 4, 2009 at 5:32 pm
  10. carolyngail

    And spoken well, Grumpy! My daddy knew that from farming on Alabama clay. Three words : Cotton burr compost. It breaks up clay better than just about everything and Daddy would always plow it back into the soil.

    November 4, 2009 at 8:49 am

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