Soil improvement for clay?

mad_gardenerFebruary 6, 2009

I live here in the land of the red clay, in a subdivision where any topsoil has gone the way of the bulldozer. Lately I've been trying to think of ways to improve the clay soil that I'm stuck with in my 1/4 acre yard (I do have raised beds for vegetable gardening, but I have dreams of a lush backyard that could act as a small slice of heaven for the local wildlife). I've heard of laying down newspapers and growing cover crops, but can anyone describe either method in detail? I'd also like recommendations as to the best cover crops to grow to improve clay soil. Please note that since I live in a subdivision, I would like to try to avoid cover crops that could easily become invasive and spread to my neighbors' yards.


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The best soil improvement for clay is organic material. Adding compost (which you can purchase in bags - mushroom or manure) several times a year in thin layers will help. Mulching with good organic material (shredded leaves, shredded pine mulch) will also help in the beds. Organic material attracts small critters (worms, tiny beetles) whose job it is to consume the material, enriching the soil as a byproduct of their efforts. By the way, these tiny bugs help feed birds - have you ever noticed the Brown Thrasher (our state bird) scratching around in the leaves? It is looking for bugs to eat.

I also add a little compost (or shredded leaves) into the bottom of the hole when I am planting something.

If you go into any wooded area, you will notice nice rich dirt - that is the result of years and years worth of dead leaves and branches that have been broken down. Underneath it all is the same red clay that you have - but it has been transformed.

Here is a link that might be useful: Brown Thrasher

    Bookmark   February 7, 2009 at 10:05AM
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I faced a similar situation, when I purchased this property 42 years ago. I am on top of a hill and the developer took 8-10 feet from the top of the rear of the property to fill in the gullies to build the roads. Some of the slopes that remained were at a 45°angle, which required terracing before anything could be planted.
I began, by tilling in composted ground bark, by the truckloads. In those days, you could purchase a truckload of Natures Helper for about $80, delivered. (100 - 3³ ft. bags or about 11³ yds). That would be cost prohibitive today.
Then I planted trees, Oaks, Maples, Pines, Hickory, Dogwood, Magnolia (both deciduous & evergreen) and some smaller conifers, Chamaecyparis sp. and later on, Azaleas (native & evergreen), Rhododendron, Anise, Camellias, Pieris

In recent times, I do as esh suggests, add a layer of compost, leaf mold and shredded pine needles to the area around the plants each year and leave the fallen leaves and conifer needles where they are, to decompose.

After all of the intervening years, I now have an established woodland, where once there was a red clay desert.

Just be sure the area drains well, because clay retains moisture for a long period of time and more plants die from too much moisture, than too little. (Assuming normal rainfall!)

    Bookmark   February 8, 2009 at 12:04PM
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If you can get the attention of a tree service in your area, they often need places to dump their chippings. I have found that beer is a good way of being remembered by those who operate the trucks. Anyway, this is a good, cost effective way of building soil structure. Even just sheet mulching is remarkably effective at loosening up the most recalcitrant clay soils!

    Bookmark   February 8, 2009 at 8:24PM
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I will add a suggestion.... We have big oak trees all around our neighborhood and those leaves are nearly indestructible! Today I am going out with my mower and rake. I pull all the fallen leaves out of the beds and put them in a big pile, mow over them a few times without the mower bag to chop them up. Then I replace the catch-bag on the mower, mow up the leaves, and dump the chopped up leaves back on the bed. I am going to add some mushroom compost and black cow as well, then cultivate it all into the top of the dirt in the bed. When I leave the leaves as they are, fallen from the tree, they take forever to break down. The chopped up leaves also look nice and "mulchy." Have fun!

    Bookmark   February 9, 2009 at 8:33AM
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10 yards of a mixture of topsoil and compost is about $350 delivered. That will add 4" on top of the clay in a 30' X 30' area and give you something to plant in. Mix the topsoil and clay well where you plant. Add a few scoops of mulch on top for under $100 and you have a great start. The trick is to have the $450, but the costs of the slower ways also add up.

    Bookmark   February 9, 2009 at 12:34PM
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I am seeking topsoil/compost delivery as you suggest. Much like Mad_Gardener, my builder left me with precious little to work with. I spent the greater part of the weekend trying to prepare soil beds only to find every space on the terraced area is riddled with tree roots fewer than 2"in! I made a few trips to HD to get Natures Helper and additional soil, but truckloads are in my future to properly build up. Any recommendations are most welcome. Am in the Marietta area.

Thanks in advance!

    Bookmark   April 13, 2009 at 3:37PM
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satellitehead(z8 ATL Metro)

I have been buying all of my mulch and "landscape mix" dirt from Atlanta Landscape Materials (Google for them).

This place was suggested to me by GW member 'vroomp'. I have been nothing but pleased by the quality of product they've provided, I've bought soil, hardwood mulch and stone by the tons from them in the last two years. I highly recommend their 'landscape blend' (or whatever), it has lots of manure and other stuff, and is generally weed seed free from what I can tell. The hardwood mulch is great as well, and they have a good stone choice.

(I know this sounds like a walking ad, but it took me weeks to find a good place, and this place has been GREAT)

They're in Duluth, about a mile north of I-85 on Buford Highway. Their website has numbers and directions.

    Bookmark   April 13, 2009 at 5:02PM
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Thank you, Sattelitehead!!! Just the type of recommendation I am looking for. The last thing I want is to unknowingly purchase poor material.

    Bookmark   April 13, 2009 at 9:25PM
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Also adding sand will help, keeping the clay from binding.

    Bookmark   April 13, 2009 at 9:34PM
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Well, amending clay soil will take time, effort and money.

You need to do a combination of things. First, You get a truck load (10 CY?) of mixture of top soil and compost ( I have seen places on Buford HW, Doraville).
Then till it in to get a mixture of clay and what you got.
That would be like 50/50.
There are people who want to get rid of their horse manure. Go ahead and get as much as you can and mix it to your compost/top soil/existing clay.

Now you can get started. After planting(shrubs, vegetable, etc always mulch them heaviliy with fine wood chips or pine straw. Do that every year. They will get mixed wit your soil little by little. If you have lots of trees, rake, collect their leaves, needly and chop them up by lawn mower, compost them or just spread them around. Do the same with your grass clipping after they sit for a while. It would be better to mix it with pine straw or leaves to provode cood water drainage.

I do not know how economical and practical is it, to mix sand along with top soil/compost. Sand does not have any value other than providing drainage.

As I said, it would take time. But if money was no object,
you could improve your soil in one shot; Just dumpy alot more of top soil and compost.

    Bookmark   April 13, 2009 at 10:28PM
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I would avoid using sand alone, to try improving drainage.
Clay+sand+water+hot sun=Adobe brick. You may as well pave the area, because that is what you will have!
It requires time to improve the tilth of a bare red clay palate. I have been working on mine for more than 40 years, to reach a point where I can sink a shovel in the ground almost anywhere and plant without further amending the soil.
I highly recommend annual applications of compost and/or leaf mold in flower beds and around shrubs and trees, in lieu of commercial fertilizers. It usually contains all of the nutrients needed to grow healthy plants. Mulch and the clay content of the soil help retain moisture during dry periods.
Until my trees became large enough to provide raw material for adequate supply of compost, I would go around the area in the fall and collect leaves/pine needles placed at the roadside for pickup, shred them with the lawnmower or shredder and pile them up to decompose. Some people in this area have the wood chips from tree removals dumped on their property for mulch and eventually compost. I don't have room today for that! I would need to add an upper deck to accommodate any more compost piles!
Don't become discouraged by slow progress, it's worth the time and effort, in the long run!

    Bookmark   April 14, 2009 at 2:55AM
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I agree with razorback about adding sand.

The whole purpose of sand is to improve drainage.
You can accomplish that with organic matter with better results. Organic matter will provide drainage while at the same time retaining right amount of mosture.

On the other hand, come to think of it, some Georgia red soil has already sand in it. If your soil has those slate like flat layered rocks/stones, probably your soil has some sand in it already. but they are also red. So I wouln't be bothered with buying sand. If I have to buy it then I would rather buy compost in its place.

    Bookmark   April 14, 2009 at 5:04AM
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I guess then all the golf courses should stop adding sand to they're greens when they aerate.

I'm not saying to use sand alone. In fact in percentages it would be small. Not everyone has the time or $$$ to excavate out all the clay. If clay still exists the sand will reduce the binding. Then improving drainage. Some have access to free sand.

I have an area in my yard to my surprise that a shovel went in like a knife through butter. It was loaded with sand. So I redistributed it in areas I wanted to improve. Yes I still added organic materials. I feel it saved me a little $$$$.

    Bookmark   April 14, 2009 at 9:23AM
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satellitehead(z8 ATL Metro)

rb33 brings up a good point about leaf bags on the side of the road, but I want to share my experience with this after my former roommate did the same thing for a season or two.

basically, the leaf-grabbing, leaf-mulching deal had interesting side effects, some great, some terrible.

after a winter had come and gone and seeds had time to stratify in some cases, we found all kinds of interesting new plants coming up around the yard. NONE were native, but some were very welcome additions.

of particular note, we wound up with about a dozen Nandina bushes that i gladly hacked to bits after reaching suitable size.

we ended up with three unknown Japanese Maple trees. it's been about 14 months since they sprouted, one is 6" tall, another is 12" tall, and the last one is almost 18" tall at this point. i transplanted the smaller two into pots this weekend, and my rear deck's Oleander is looking rough right now, like it might croak, so the third may go in its gigantic pot.

finally, the one other thing that came up (which reseeds profusely) is purple Shiso. i transplanted it as well, and we still find little sprouts popping up here and there and everywhere - i have about two thousand seeds from just one plant.

anyway, just sharing the fun things that can happen when you grab bags off the street. be picky about the houses you take them from. if they have nasty invasives or lots of weeds, your 'free blessing' may end up a 'nasty curse' quick, depending on what seeds got swept in with the leaves.

    Bookmark   April 14, 2009 at 11:19AM
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Now, I'm not golf course manager, but I believe that they put sand on TOP of the ground to fill in low spots. The grass then levels itself up by growing through the fill.

This is not, in my opinion, the same as mixing soil and clay together to amend beds. And don't forget - those golf courses probably put down a nice layer of topsoil before they plant the greens.

By putting the sand on the top, it mixes a little bit with the thatch from the grass and perhaps is gradually worked into the top part of the soil (inch or less) by bugs/worms as they digest the thatch.

I agree that a small amount of sand could be worked into a mixture of original soil and organic material with sand definitely being on the small side. I have had, however, great success with a Daphne plant by following Walter Reeves's recommendation to excavate the planting hole and mix in 1/3 parts the original soil, nature's helper and sand. Obviously that does make superb drainage, but it is a lot of work. The rest of my yard just gets organic top dressing and mulch.

Anyway, just my opinion.

    Bookmark   April 14, 2009 at 12:36PM
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I am assuming you are referring to Daphne odora? when you described the planting method.
FWIW, I would NEVER plant Daphne odora IN the ground. Mine are planted above the ground, at least 6" above the existing soil level, which I do not disturb. I construct a large mound of Natures Helper or pine bark fines and compost and spread the roots over that. The roots are then covered with an inch or two of the same mixture. Watered in and staked to prevent the wind from blowing them away!
I have nine of them, planted using this method and the oldest one is 22+ years old.
I also planted Daphne x burkwoodii 'Carol Mackie' very high in a location that has very good drainage and it seems perfectly happy. Daphne genkwa is located in a raised bed, on a slope, also well drained.
I am starting Daphne caucasica from seed, obtained from a Russian botanist, since most of the one's available in this country and labeled as such, are really hybrids
(D. x transatlantica (D. caucasica x D. collina)).

I respect WR's opinions and advice about lawns, but that's about as far as I will go!

    Bookmark   April 14, 2009 at 3:41PM
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