So I picked up a few bags of compost to help my clay soil. I did some investigation and settled on a place that has a pretty good reputation in the area. They make a compost out of horse manure (from hay) and wood shavings / saw dust.
So, I get it home, haul it out to the back yard and spread it out (about 3-4" thick) in one of my planting beds.
Now what??? I was told NOT to work it into the soil because it breaks down the "something-rather" and it's best to just lay it over the soil and let it "soak" into the soil below. Is it ok to water it? Will watering help break it down faster?

Just how thick should I spread it?

Rain and soil organisms can take it from here, Mike. Just plant it or mulch it (or both) to keep any weed sprouts down to a controllable level. If you aren't getting rain you can apply some water, but I'd mulch it first. If you don't mulch it, keep an eye on it so that you can get any weed sprouts early enough that they don't become firmly rooted plants.

Thanks Chelle, but what do you mean by "plant it"? I wasn't intending on putting any mulch on it though. We're up a little high on the hill here and when the Santa Ana Winds start blowing, look out! Whatever mulch I laid down would be down the street!
My plan was to just cover all the beds now and hopefully by spring it will have broken down enough to do some planting and a second round of compost. What do you think? Will it breakdown that quickly?
Thanks for the help. I'm just not that experienced.

Usually, by the time you buy a product labeled as compost it's broken down enough that it's safe and ready to plant. If you don't have anything that needs to be planted now, then you're done.
Think of the material you've just applied as food and shelter for your soil organisms; they'll take care of things below the surface so all you really need to worry about is what's going on above-ground. As long as these organisms have what they need to survive, they'll stick around and be your unseen helpers. Once these materials are gone, however, they'll be forced to leave and find food elsewhere, so replenish your compost once you no longer notice its presence in your beds. Since you're in an especially windy area, moistening your composted beds would probably be an excellent idea. Once again, though, to save yourself a big hassle later on, keep in mind that damp compost exposed to light is where seeds sprout best. Any seed that is already in the top layer of the compost now, or gets dropped into it later will want to sprout -weeds included.

Many or most gardeners agree with Chelle. You don't have to turn it under. I would agree this far: you don't need to turn it under if your soil is already half-decent and you are just maintaining its organic content and fertility.

Also, maybe there is no need if you are patient and don't want to do a lot of pick-and-hoe work.

But I think the compost will break down much faster if covered with soil, and the soil will improve overnight instead of over a year or three, if you turn it and break up the clods and mix it.

My own practice, when breaking up heavy clay that lacks worms and lacks aeration and lacks drainage, is to break up the clay while slightly moist, using a pick or mattock. I go at least 6" deep, usually 12" or more. Than I spread the compost, manure or mulch-like product. (For me, shredded conifer bark.)

Then I turn the compost under the clay I just broke up, to get it down there a s soon as possible and aerate the clay so that something can push roots into the clay and hopefully keep it aerated.

Almost everyone says that you can "just wait" and worms will do the heavy work for you. In my yard, I'm still waiting for the worms to come. The only things that keep the clay from reverting to clay is what I turn under and any roots that follow it.

I've found that they are pretty right, even in moderately heavy clay soil, once the initial improvement has occurred and the soil is light enough that at least weeds can thrive in it.

Maintaining soil capable of supporting weeds and some other plants does seem to work by the "top-down" or "trickle-down" method.

Lot's of people have said that they can get good growth by "lasagna layering" lots of compost on top of what they call "heavy clay" and growing plants in the compost. After a few years (or less?) they say that the underlying "clay" has become great loam.

I haven't experienced that, partly because I've never had a 4" layer of compost to put anywhere. And maybe people call soil "clay" even when it is only 40% or 50% clay. Lots of methods would probably wok on clay soil that is getting to be close to "clay loam soil".

I'm guessing that I have somewhere around 60-80% clay in most of my yard, and 90% in one nasty bed.

I used to always start by double digging my beds, then adding tons of organic matter, maybe finished compost, maybe just leaves and grass clippings. but lots of it. It still took two years of adding stuff pretty heavily before I could tell the soil was actually changing the way I had expected it to in a month or so. It just takes nature a lot of time to improve the soil, sure the clay was much more porous but it still looked like and acted like clay, after a couple of years I could actually see soil improvement, still a lot of my deeper clay still looks like clay. I don't know how many years it would take just by putting stuff on top. But that is all I do now, unless I am starting a new bed, just keep adding stuff on top and letting it decay, it forms a thin layer of very fertile looking very soft viable soil when the worms work it over a period of time. But when first starting out, I had no worms.

Planting what you just amended is good for several reasons. The cover crop will compete with weeds and suppress some of them.

The cover crop roots will continue to break up your clay without you swinging a pick and raking out clods.

The cover crop roots will help maintain open soil structure after the compost is digested and the clay tries to revert to airless, rock-hard clay.

When they die and decay, the cover crop roots and tops will add more organic matter to the soil than you bought and hauled in bags.

The cover crop roots will prevent erosion from rain and wind.

The cover crop tops will shade the soil.

That said, I usually forget to, or I;'m too lazy to, plant cover crops. usually I try to go straight to growing vegetables or flowers. I need to listen to Dave's podcast, something like "Why don't we do what we KNOW we should do?"

My theoretical compromise between what most people agree on and what I seem to have found necessary in my yard, would be to scratch up just the top few inches and mix with an affordable amount of compost and bark, but not go deep and not screen the clay balls laboriously through 1/4" screen. Hopefully that would create enough aerated "almost-soil" for hardy roots to grab hold and let the plants survive long enough to drill down into the clay over a few years. Plant cover crops for the first two years! Then try digging down 12-18" and see how much the solid clay has improved.

There are cover crops that tolerate heavy clay soil and no drainage. Here are some notes I took once. The short form would be: clover, oats, rye, vetch, alfalfa, Buckwheat and some cowpeas.

Actually, the best choice is whatever your local fed store stocks in big bags and is recommended LOCALLY for breaking up clay. Stress that it is not "clay soil" already in cultivation that you want to improve. If it is really bad, it is "clay" that you want to convert to arable "soil".

Annuals that tolerate and loosen heavy soils, cool weather:

Austrian Winter Pea
Barley, Awnless
Barley, Bearded
Bell Bean
Clover, Alsike
Clover, Berseem
Clover, Hykon Rose
Clover, Nitro Persian
Clover, Subterranean Mix
Clover, Sweet-Biennial Yellow
Daikon Radiash (??)
Legume / Oat Mixes
some Mustards
Oats, California Red
Oats, Cayuse White
Oats, Montezuma Red
Oregon Annual Ryegrass
Rye, Cereal
Rye, Merced
Tetraploid Annual Ryegrass
Triticale, Trios
Vetch, Common
Vetch, Hairy
Vetch, Lana Woolypod
Vetch, Namoi Woolypod
Vetch, Purple
Zorro Fescue

Perennials that Tolerate and loosen heavy soils:
Alfalfa [P]
Clover, Strawberry [P]
Clover, White [P]
Creeping Red Fescue [P]
Ryegrass, Perennial [P]
Sheep Fescue (Covar) [P]
Timothy Grass [P]

warm weather + heavy soil:

Buckwheat
Cowpea, Red 50
Crotolaria
Lablab
Sesame
Sesbania
Soybean


tolerates poor drainage:

Wheat, Red Winter
Clover, Alsike
Clover, Berseem
Clover, Nitro Persian
Clover, Sweet-Biennial Yellow
Miranda Pea
Rape, Canola
Rye, Cereal
Rye, Merced

Yes that was a good pod cast, and planting a cover crop is something I have always intended to do and have never ever done! If I plan a rose bed, double dig, add amendments and get it all raked out and looking beautiful, I just cannot force myself to plant a cover crop and wait till later to plant what ever I had planned for that particular bed. The roses, or the hostas, or marigolds go right in, but I someday will plant something with a cover crop. I think in my mind planting the cover crop would not be hard, but the idea of turning it under later always seems like too much work.

I agree with Seedfork, if I can add emphasis to one phrase:

>> But that is all I do now, unless I am starting a new bed, just keep adding stuff on top and letting it decay, it forms a thin layer of very fertile looking very soft viable soil when the worms work it over a period of time. But when first starting out, I had no worms.

>> sure the clay was much more porous but it still looked like and acted like clay, after a couple of years I could actually see soil improvement, still a lot of my deeper clay still looks like clay.

That initial right-away improved porosity is what I was chasing with my deep turning and finely breaking up clay balls and mixing with compost and sand/grit/bark fibers. It improved the soil to the point where anything would grow. I should have stressed "and break up the clay and mix it finely". That IS a huge amount of work even for small beds.

It seems to me that the next big change that occurs over the first two years is that microbes and roots penetrate the soil. Once they have drainage and oxygen, they can improve and maintain soil structure and tilth.

>> still a lot of my deeper clay still looks like clay.

Maybe I'm over-ambitious in wanting root zones that go 18" deep. Or crazy!

Seedfork said: ... planting a cover crop is something I have always intended to do and have never ever done! If I plan a rose bed, double dig, add amendments and get it all raked out and looking beautiful, I just cannot force myself to plant a cover crop and wait till later to plant what ever I had planned for that particular bed.

YES! Thank you for saying that. I thought I was being very stupid, lazy and impatient for never doing what I KNOW would have been a good idea. But if you don't, either, then I COULD still be a great gardener without overcoming that particular impatience!

Seedfork said: ... I think in my mind planting the cover crop would not be hard, but the idea of turning it under later always seems like too much work.

For me, anything that involves enriching the soil seems totally worth the work. I would rather cultivate the soil than the plants!

It might be easier if you first mow the tops, and then cover the roots with cardboard or plastic long enough for them to rot just a little. Then literally "turn" the rootballs upside down and let them finish rotting.

Or, easier yet, grow an annual cover crop, mow the tops and compost them or use them as green manure. LEAVE the roots in place over winter to maintain soil structure and drainage. Scratch the surface just before sowing next spring. The roots have already "turned themselves under" and mixed themselves well into the soil, and probably died.

It is SO easy to give advice without taking it myself!

Some day ... maybe when I retire ... if I;'m not totally feeble by then.

"I would rather cultivate the soil than the plants!"

The reality of gardening (other than hydroponics) is that you feed the soil and the soil feeds the plants. Bacteria and fungi break down any amendments you add and make them available to the plants.

Check out John Jeavons and his BioDynamic French Intensive method of gardening and building beds. He starts with large amounts of compost and fertilizers and tapers off over the years. Here's a link to his book.
http://www.amazon.com/John-Jea...
I have to admit that I have cut a few corners over the years, but the basics of feeding the soil have remained.

So true, Carl.

Application and reapplication of a blend of decomposable matter is the key to easy gardening. Not topsoil, not potting mix, but a good thick layer of organic matter.

This is counter to everything I have read about improving clay soil and comes from observation in my garden in the mountains of northern California.

My "soil" is what we call "glacier slurry". It is tightly compressed rocks with clay and silt in the crevices. None of the rocks are bigger than my fist. When I started this garden, I could not dig in the soil with a pick or a shovel. I didn't know enough to prepare whole beds.

One of the things I had noticed is that I have perfect drainage. It can rain hard for days and days and there are no puddles. Since the soil particles between the rocks is clay, it does hold moisture ... except during extreme drought.

When I made my first planting holes for my roses, I added a whole lot of compost to the back fill because I knew there wasn't any organic material in the planting area because the previous owners had covered the whole back yard with weed barrier and decorative rocks ... which I had scraped away. Long story short ... the compost decomposed and the roses sank.

When I planted the next batch of roses, I back filled with the "native soil" and mounded up the plant so that when the soil around the root mass decomposed and the plant sank, it would be at the desired level.

Over the years as I created a garden where nothing should be able to grow, I just put the compost and mulch on top. I did not dig anything into the soil. Within a couple of years I had lots and lots of worms and all of the plants were thriving. I did have to add nutrients, but I figured it was a whole lot easier to add nutrients than it was to correct drainage problems.

I can now dig in the garden beds where I have been planting and mulching with a trowel for about two feet down. I discovered, the hard way, that digging in organic matter destroys the structure of the glacier slurry, but just adding things on top will still improve the soil.

Nowadays, when I want to raise a bed or back fill an area where I have removed a plant, I include plenty of cinder rock in my back fill simply because it does not decompose. I like the cinder rock because it is porous and has rough edges. I put all of my OM on top of the soil and it seems to work very well in this garden.

Smiles,
Lyn

I think that's actually perfect, Lyn. We learned the exact same thing here.

One of the only exceptions I've found is with raised hugelkultur beds. In those beds the bottom of the root ball can sit at or about log level and be just fine. The same principal applies, and the logs will break down so slowly that any settling that occurs will be at a rate for which the plants can easily compensate. These are just my thoughts on the matter; my hugel beds are still fairly new, but all are doing enormously well. I'm actually having rather astounding success now with plants I've tried many times to grow in the past, but which ultimately failed.

Thanks for the feedback, Chelle. I hadn't made the connection to the hugelkultur beds.

It's just that every time I read the advice to improve clay soil with OM, I find myself wanting to shout, "Add lots of rocks, too."

Smiles,
Lyn

That, or, if adding is difficult, don't subtract as much. Digging the planting hole only as deep (or not quite as deep) as the root ball that's going in will help to combat overly deep settling. I like to do mine three times the width, though; that allows for replacing native soil directly against the root ball, with room left over near the edges for adding compost. Settling near the edges is a good thing; a slight reservoir develops to catch and hold a bit of extra water.

I think that is wise advice for gardens with much better soil than mine.

I have a lot to learn about gardening beyond the growing of good roses, but I think the most important thing I've learned over the years is to observe how your soil works with your plants.

Gardening in glacier slurry is what I consider to be an adventure. The water doesn't always go where you put it ... It can go down or it can flow sideways, depending upon the density of the rock below the surface. That's why it is best to place anything that might decompose on top of the the soil.

Smiles,
Lyn

>> John Jeavons and his BioDynamic French Intensive

"French Intensive" is pretty much my goal, but I haven't been able to produce as much compost as I need. I resist buying "enough" compost, because I'm cheap. So I try to get by as best I can while buying as much compost as I absolutely need. For the initial change from "pure clay" to "very heavy clay loam", probably 50% or more compost is needed (a 9" layer, mixed to 18" depth). After that, I think 4" per year on top would work better than 1-2" per year.

As a result, my soil is always just a few years away from reverting to clay.

I think the sand, grit and bark that I added at the beginning and again after 1-2 years are what save me from having "clay pudding". I think of my soil as being like a perpetual souffle: prone to "falling". A lot more compost and a little more sand and bark would be very good for it.

HI, Rick.

I have also started to add rock to my soil. I can buy compost from the green waste program for $20 a yard. I think I may have reached the point where I am actually adding too much compost. I have been adding the red lava rock for $65 a yard. It's 5/16" or 3/8" in size for the largest particles.

I grow bearded iris and also Louisiana iris in large raised beds that are lined with pond liner. The Louisiana beds are kept wet and I have no problem with cracking and shrinking of the soil. Not so with the bearded iris. But adding rock seems to help the problem. The soil is to the point where I am going to have to back off on the amount of compost I add. I have been thinking about adding sand to help break up the clay. Maybe I should look at bark instead?

Sand and grit are forever, but bark breaks down in 1-3 years dependence on size and probably climate.

>> I have been adding the red lava rock for $65 a yard. It's 5/16" or 3/8" in size for the largest particles.

Hmm, 8 to 9.5 mm for the largest particles. That's pretty coarse.

You might be getting more benefit from the gritty fraction (1 mm - 3 mm) than from the gravelly fraction (over 4 mm). I think 1/10" is great (2.5 mm) and really 3 mm and 4 mm particles probably do create some air spaces that don't flood easily.

But grains above 4-5 mm might give you more aeration per dollar if they were ground down to 2-3 mm. How easy would it be to crush some of the bigger lava pebbles?

P.S. Technically, by some standards, the dividing line between very coarse sand and very fine gravel is 2 mm. That doesn't leave any category for "grit", the most useful gardening size!

I think of sand as smaller than 1 mm grain size, and gravel as larger then 4 mm. That way, I can call anything from 1-4 mm "grit". 4 mm is 0.157 inches, around 1/6".