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Clay dirt

 
                                  
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Can clay dirt be converted to good soil if you're patient?  If so, how?  We just moved to a new house, with new sod, and I don't want to start all over with top soil and seeding.

 
paul wheaton
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We have a half inch of soil under our sod at best.  After that, we've dug through 3 feet of clay by shovel to plant a tree, but could probably go further.  There was not a lot of rock.  We used a 12-inch auger once to dig a hole, but it kept getting stuck in the clay, so that didn't work too well.  Sorry, I don't have a picture to attach.
 
rachael hamblin
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I haven't done this myself, but from what I've read it is doable.  It would take a lot of effort though.  The main thing you're going to have to do is mix in a LOT of organic matter to lighten up the clay.  Clay also absorbs plant nutrients until it reaches a saturation point so you'll need to add more nutrients than you would usually. 

One drawback to this approach is that all that organic matter gets to be expensive.  The organic matter breaks down rapidly and has to be replaced yearly.  The first year you may need to mix in a layer 3-4 inches thick to open up the clay, after that you might only need half of that but it's still significant.  And after all that work it will still not grow plants as well as a light soil.
 
paul wheaton
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The previous suggestion is a damn good one.

With clay soils come lots of worries about lots of things.  Like drainage.    Are you having trouble with puddles?

How is your earthworm population?

Are you patient? 

Supposing you are patient and have earthworms, I would like to advocate the cheap and lazy approach of just mow high and get a good organic fertilizer program rolling.  Lots of clipped grass blades will end up on the soil surface as worm food.  The worms will drag it down deep to eat it.  Of course, it could take years to see significant change. 

This makes me think about the crazy idea of the posthole digger worm homes I mention at the bottom of the article.



 
                                  
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Thank you for taking the time to help...I really appreciate it.

We are not having trouble with puddles- but we have a really nice slope on our lawn.
We don't have very many- if any earthworms.  At least when we dug the holes, I didn't see any.  And when it rains, we don't have any on the sidewalk.
I'm not a very patient person, but I can be for a nice lawn.
Will mowing and fertilizer help me get more earthworms, or should I import them somehow?

In the other post, when she mentions "mixing a lot of organic matter to lighten up the clay", what does she mean?  I can't mix the organic matter into the soil, b/c we have the sod on top.  Should I just lay the organic matter right over the top of the sod?  Can this be done in the fall so that my kids don't have to play through it all summer?  And what kind of organic matter would be best for clay?

Thanks!

 
                                  
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Also- I'm sending a soil sample in to be tested.  When I get the results back, should I go ahead and do the sulfur/lime that is suggested?  Does this help clay?

Thanks.
 
paul wheaton
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No worms is a bad sign.  Kinda creepy really. 

How cold does it get there?

If you wanna go first class, bring in about four to six inches of compost and work it in to a depth of 18 inches, then seed on top of that.  But you will find that this is an enormous task.  Not for the cheap and lazy. 

Put some thought into making earthworm habitat. 

Let us know what the soil tests say.
 
                                  
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I'm in central Iowa...it get's pretty cold here.  Usually not below zero, but it sticks in the 20-30s for a long time.

When you say "work the 4-6 inches of compost in to a depth of 18 inches"- how do I do that?  I'm new to this, so sorry if it's obvious.

Would I make an earthworm habitat by using your posthole digger idea?

Thanks!
 
paul wheaton
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adwhite0704 wrote:
When you say "work the 4-6 inches of compost in to a depth of 18 inches"- how do I do that?  I'm new to this, so sorry if it's obvious.


That's the really hard, time consuming, expensive part.  You would probably want to use a bulldozer or a trackhoe or both. 


adwhite0704 wrote:
Would I make an earthworm habitat by using your posthole digger idea?


Yup!

 
                                  
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Thanks again for all your help.
 
rachael hamblin
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So to clarify, you have clay dirt under your lawn, and want to improve the soil without redoing your lawn?  Is the clay causing problems?  What are they?

And Paul, what is this posthole digger worm home you're referring to?  Sounds intriguing.
 
paul wheaton
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rachael hamblin wrote:

And Paul, what is this posthole digger worm home you're referring to?  Sounds intriguing.


Take a look at this:  http://www.richsoil.com/lawn-care.jsp and search for "post hole".  This is the article with which I started this whole site.  I got so many emails, I started these forums so that I could answer questions just once instead of over and over.




 
                                  
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Rachael- that's exactly right.  I have clay dirt under my lawn, and I want to improve my soil without redoing the lawn.  The clay isn't causing problems, except that my lawn is not green yet, even though all the other lawns in the area are.  I wouls also like to minimize weeds without using any products.

Paul- where do you get your Ringer fertilizer?  I've looked at Ace and True Value and neither carry it.  I found it online, but I'd rather find somewhere local.  Thanks!
 
paul wheaton
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I suggest you let your fingers do the walking - call around. 

I used to get it from the home depot, but it seems that HD has dropped ringers in favor of some "organic" product from scott's.  I'm terribly suspicious of this deal. 

 
Jeremy Bunag
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Ringer can be bought online at doitbest.com and shipped to store for free.  If you have a location near you then you'll be all set!

Hope this helps,

-Jeremy
 
                    
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Here's another option - upgrade soil per individual plantings. Combined with careful irrigation could solve problem w/ less "whole yard hassle"

Amending clay soil:

Dig your hole, make it generous in size
Put a liberal amount of Doctor Earth organic starter fertilizer in the hole first (organic fertilizer is great because it can go next to the roots and it's almost impossible to burn a plant with a good organic starter fertilizer)
Mix the native clay soil 50-50 with a quality amendment bagged soil before putting it into the hole
Place the plant and back-fill with your local/amended soil
Just a few plants that can work very well in dry and clay soil (and there are hundreds of others):

Phormium
California Lilac (shiny, evergreen, nice and tight, blooms, 4-5'
Rugosa (wild) or Juniper Roses (low-lying)
Pampas Grass (grows big)
-from www.greghughes.net
 
                                  
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Thank you all for your suggestions!

I just received my soil test back from the extension office, and my pH is 8.0.  So I know I need to add gardener's sulfur... do I just lay it on top of my sod?  And should I do this just once a year until the pH level is correct?

Also, the organic matter came back at 2.4%.  What does this mean exactly?
 
paul wheaton
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You could add gardener's sulfur twice a year. 

OM of 2.4% is okay.  5% is quite good.  10% is super fantastic.

So 2.4% of your soil is organic matter:  decomposing stuff.  Old grass blades, dead tree roots, dead insect bodies, etc.  OM is the closest thing to the magic bullet for gardening.  The more OM you have, everything else manages to be more forgiving.  OM stores nutrients and water, houses microbial life, buffers almost everything!

 
                                  
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Do you just lay the gardener's sulfur on top of the sod, or do you have to work it in somehow?
 
paul wheaton
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This would be a case where aerating your lawn would be wise.  Aerate and then put down the gardeners sulfur.  That way, some of it goes down those holes. 

The thing is that this is going to take a long time.  Years. 

If you can add lots of organic matter, that will help too. 

 
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