There are different type clays, clay soils, and soil chemistries. Some clays are very expansive: swelling when wet, shrinking/cracking when dry. Other clays are more stable and often less sticky. Some points:
Adding sand and coarse organic material can create adobe (bricks). The volume of coarse, *angular* sand needed to ease brickness is so high as to be prohibitive. Fine organic matter (humus-rich) binds with clay particles and causes clay to aggregate together into larger particles (called peds). These peds are somewhat stable in the presence of water so that drainage improves and stickiness is decreased. The soil is here described as having good structure.
If your clay is neutral to alkaline (pH above 7), you can add gypsum (calcium sulfate) which will help aggregate clay into peds and improve drainage. Fertilizers with high salt index (look at bag label) are BAD for clay soil, causing the clay to "puddle", or lose structure.
Adding organic material to the surface and in the upper soil horizon (say upper foot) will work wonders -- reduced wet-dry, improved air and water movement, feeding soil organisms (especially worms), and improved nutrients.
This is probably more than you wanted to know but at least you have a few guidelines.
Marsh I've been looking for you :-) Needed to ask you a question regarding termites which I've posted now on another forum. However, the info you provided is excellent and I can't thank you enough. Two questions though - I have lots of quartz rocks in the red clay and wondered what your opinions were of this. And what are your opinions regarding horse versus cow manure. I was thinking of adding lots of it to the soil!! Thanks poppysue for thinking about me and for the hyperlink. I will check it out now :-) Poppysue I have just read the info you provided for me and it is very good except it does contradict the idea from Marshseed regarding the coarse sand additive. Perhaps this is OK with the addition of humous. I have also considered vetch as a green manure.
Thanks for thinking of me ;>) Quartz rock? Is it crystalline or amorphous like flint or chert? Quartz is common with granitic type rocks, weathering down to acid soils but usually not especially clayey. Limestones and marly shales will break down to clays and might have small to large pieces of chert or flint. Soils are usually alkaline to neutral. So which is yours? or another?
Manures ought to be composted first. Or at least a delay of several months from time of soil application. If you are applying to an existing orchard, that's another matter. I have access to lots of (polo) horse manure but harder to compost. Cown manure is messier but makes a fine compost.
I feel pretty strongly about not adding "some" sand to very sticky clay. Bricks are make from clay and sand, adobe from clay, sand and straw.
Marsh thanks so much. We have the crystalline quartz here and lots of it must have been removed when the builders bulldozed their way in - I couldn't bear to watch the trees felled - however there is an abundant supply to uncover no doubt! But the soil looks clayey after all the rain we had.(red clay!!) We have a mixture of hardwood and pine on the land which to me would indicate a pretty neautral ph - yes? We have only been in this new house for a week so haven't done the soil test yet I'm ashamed to say. This area was once used as a timber business. Many tulip poplars and dogwoods, maples and pine. I will have access to horse manure and yes I realize it has to be well rotted -I've always used it back home. I again note your comments about adding sand and as far as I'm concerned you are the expert. Thanks again Marsh. Now to look for my post re termites. Have a great Sunday!!
I suspect you have acid soil with mostly non-expansive clays. Go ahead with adding lots of organic material if drainage is okay (dig a hole about 18-24 inches deep and fill with water. If it drains away in a day, you are okay. If not, time for some raised beds!
Hi again Marsh and thanks. Sorry it took me so long to get back to you. I've had some soul-searching to do!! Now if I had dug that hole you suggested I would not have had to fill it up with water because it has rained quite a bit! The land is sloped gently away from the house to accommodate the septic drain field and leach field! Surely this will help to drain the 'clay' - or maybe not? Great site for the 'lasagna' method Terri - thanks!
Poppysue and louisa I assume you have read the other threads in the soil forum where use of sawdust is mentioned. If you don't have a sawmill nearby a good source for wood chips is the power company. They have to pay money to the dump to haul their woodchips away. They will provide you as many truckloads as you would like. I rerun them through my shredder to get them a bit finer. As mentioned elswhere in the soil forum amend the chips with green material. I piled mine in a problem area - a sloping bank that had been a trash heap. When I started the area was full of concrete chunks 3-4 feet across, bedsprings, bricks, plastic and large pieces of tree trunks. Much sledgehammering, trunk burning, and judicious hauling of the worst trash and 18 months of letting the woodchip material decay and I had a flower bed. I planted flowers in it and now the remaining trash is buried under lovely flowers never to be seen again. I like to take a blighted area and make it beautiful. It sure does take time though.
Oh - I almost forgot. Do not use walnut sawdust. It contains material that can keep some plants from growing and will take forever to break down. I am learning what will grow under a walnut tree as I go so I have some experience with this.
What I did for a clayey area of my yard was a mixture of chopped leaves, gypsum, lime and composted manure. It has taken several years but it is beginning to support life at a reasonable rate.
I have another area which is essentially a mound of plaster removed from an old house. Organic material works for that too. It is hard to call it soil yet but we are getting there!
So don't feel bad about clay because anything can be fixed with organic material, manure, patience and hard work. Good luck on your efforts.
for a great idea while you are working on the clay issue...why not do raised beds with good dirt? this can help until your soil is where u need it to be...just a thought...Kelly
PS. I do have red clay...it is very hard, and slow to drain in places. I have used gypsum..try granule...it seems better to me than the powder which makes a mess...
I would first use organic matter...sand will make it even worse I think.
>> Adding sand and coarse organic material can create adobe (bricks). The volume of coarse, *angular* sand needed to ease brickness is so high as to be prohibitive. Fine organic matter (humus-rich) binds with clay particles and causes clay to aggregate together into larger particles (called peds).
So far, I agree completely. Sticky clay needs compost. I would say that 33-50% compost is needed if compost is all you add, and the clay started out with no organic matter. (One part compost plus 1-2 parts of clay). Even then, you have to keep adding compost every year since it will be digested by soil microbes.
>> I feel pretty strongly about not adding "some" sand to very sticky clay.
Most people will agree with you, but I've started to think a variation on that is more accurate. If the clay is really sticky, like it has almost no organic matter at all, sand won't help it unless you have around 2 parts of sand per one part of clay.
If you add plenty of organic matter to clay, it may not need sand to drain well.
But I usually have a lot more clay than compost. I might have 1 or at most 2 inches of finished compost to mix into 12" of clay. That's only 8-16% compost, and after digesting for a few months, it might be as little as 5% compost!
Clearly, not enough to improve the clay greatly.
In that situation, I find that clay is still sticky and malleable. It tends to slump into one big pudding, and it's too sticky to mix new amendments into it.
I find, in that situation, that "some" sand, like 10-20%, seems to make the sticky clay less sticky, or at least more friable. I can break it up with a fork or rake.
And since I'm not trying to use sand to create air channels, it can be medium or even fine sand, which is easier to find than grit-sized crushed rock. Fine sand seems to "go further" in this application than grit.
I think of it as "dusting" tiny clay balls, like sprinkling sugar crystals or powdered sugar on gumdrops. Now the sticky gum drops don't stick together (as much).
However, it might not be this "powder" mechanism that makes the clay more friable. It might be that when the sand is well mixed into the clay, it gives the tiny clayballs a bit of stiffness (less malleability) so that, when two are adjacent, they don't slump into each other and squeeze out the air gaps. If very tiny peds are stiffer, they only touch in a few points, and don't slump together in intimate contact and then stick along a whole surface.
Using a little sand this way seems to make my beds easier to "fluff up" while I'm still building up their organic matter reserves. Without any sand at all, it seems to revert faster to airless mud pudding.
P.S. Since i discovered The Wonders Of Pine Bark (or fir or hemlock), I use that in preference to sand. Cheaper, lighter, coarser and it's organic.
Pine bark lasts 2-4 years in the ground. By the time it has digested, the soil has amended itself with roots and accumlated layers of compost and mulch.