Clay soil

My son-in-law recently rototilled his back yard to start a garden. He says the soil is quite clayy in nature and he's talking about adding sand to the plot. I think I read somewhere that adding sand to a clay soil does more harm than good. Any of you soil experts want to enlighten us?

Clay is made up of tiny plates - that's why it feels slippery or greasy when wet. The trouble with sand is the plates fill in around the grains of sand and sort of makes "concrete" IF not enough sand is used. But, you have to use tons of sand - I think at least a 50/50 ratio of sand to soil by volume - or the soil will be worse than before.

Perlite is another way to go. Perlite is a vulcanic rock. For horticultural purposes, it's heated and expands and is very lightweight. It has a relitively low water holding capacity which is what you want if you are amending clay. Since it's inorganic, it would not break down very much in the soil and so would be a permanent solution. But, it may be way too expensive in a big garden. I read one place the rate of application is 60/40 perlite to soil (by volume). (Don't use vermiculite because it holds too much water.)

A better way to go from my experience is to use organic matter: Till or dig in wood chips, hardwood bark, grass clippings, straw, compost, composted manure, or shredded newspapers (no color pages). You could also plant a cover crop and till in. Although we live far from you, we have clay too. We have tilled in garden wastes, compost, grass clipping and straw for only a few seasons and it has made a huge difference. We have used all of these organic materials as mulch around our plants, then dug it in at the end of the season. Our garden soil is now darker brown and very fluffly.

Easier would be to just put a thick (a good 4" or more) top dressing of any of the organic items above - or a combination. Just this heavy mulch will help a lot after a season as it decomposes.

If you can till in organic matter AND use mulch that is the ultimate. I guess what you use will depend on what's available, the expense, and how much time you have.

This message was edited Mar 14, 2008 10:47 AM

Amen, CompostR. The more organic matter the better. Sand + clay = concrete. LOL

I cannot argue with the above. ...all good advice

However, if you have a decent clay/silt/loam like me, sand added in about 40% plus 20% local peat moss [probably not shaghnum but likely reed sedge] and 40% original topsoil with added maure, mulched leaves, and such does not equal concrete, but rather such a nice , loose, aerated yet moist soil that you can dig by hand through it.

You can cheat a bit with builders sand which is much coarser, but it really depends on the type of clay you're trying to work with. I have good old VA red clay or rather I had. But DH and I have been working this ground for over 20 years, so there aren't many clay type spots left. LOL

And I can't argue with you Indy, or doccat.

Fluffly soil is a pleasure to plant in, isn't it? I use a hoe a lot in the garden and it's treat to hoe up too. I don't what it is about playing in the dirt ... : )

I really appreciate the valuable information you posted in response to my request for help in this clay soil matter, compostR. I think digging in the dirt is genetic to human beings...
Once again, many thanks for your expertise.

I'm about to tackle a similar situation in a month or so, Lettuceman. http://davesgarden.com/community/forums/t/795239/

Lettuceman, I am a newbie to clay soil, having moved from Orlando, where it was all sand. I bought the book Lasagne Gardening years ago, but didn't believe it would work here on my clay soil. I assumed that my soil was far worse than any encountered by the author and the DG folks who use the method. It was like concrete last summer when we moved in. DH and I started adding whatever material we could, laying down several sheets of newspaper as a base, then wood chips, grass, leaf mulch, kitchen scraps, partially broken down compost, potting soil from our 2007 containers. I didn't think we had enough organic material to make a difference over a four or five month period, but the area we put it on looks great. I went out today and dug into that previously impervious clay soil. I didn't use sand because I had read, as CompostR said, clay plus sand equal concrete. Already had that, didn't need more LOL.