If you're going the cover crop route, I'd suggest clover or alfalfa, not beans. Winter rye for now, if its not too late to plant it. The problem being - if this is an urban or suburban situation, you could find yourself besieged by lawn nazis.

If you're rich, sure, remove the existing soil and have something better trucked in. But this honestly isn't your best option and I'm willing to bet it's too expensive anyway.

I honestly would not try to improve the soil of my entire yard - unless your yard is fairly small, I wouldn't suggest that to you either. How much space are we talking about?

To get good garden going, I would cover the area you intend to plant now with collapsed corrugated cardboard boxes. Wet the area down first so it's damp down to 16" to 18" (if its bare soil) or at least 8" (if its currently covered with sod). A foot'll do but more is better. Assuming you're not in Arizona or Las Vegas or something like that, that is. That's a different set of problems.

Lay down a layer of damp flattened cardboard. Put your compost down on that to keep it from blowing away. Come the spring you should be able to till that all in fairly easily and now you will have excellent planting beds for your summer garden.

There is little point in worrying about trees, you cannot possibly amend/"improve" the soil deeply enough to matter for a tree. What you CAN do is dig as big a hole as possible when you plant your tree. Break up the dirt you took out of the hole and remove any really big rocks, but don't worry too much about rocks etc. Mix a small amount of peat moss into the same dirt you took out of the hole, and put this back INTO the hole to plant the tree into. It doesn't need to be real deep, but if possible make it at least 3' around. This will break up the soil enough so that the tree can get a good start, but won't change it so much that the tree's roots start circling the original hole and essentially become "root bound" IN THE GROUND.

A shovel full or so of compost is OK, but I do not use compost when planting trees, nor do I fertilize unless there is some specific problem with the soil until the tree has been established for several months. Just water well, let it get over its transplant shock.

Of course I assume we are talking typical bare root or small nursery stock, and not something that it takes a team and/or heavy equipment to plant.

Take your time improving the rest of your lawn or yard. Sheet compost with the cardboard and some kind of mulch - whatever you can lay your hands on, straw, livestock bedding, even chopped up trees and leaves from a municipal yard recycling operation or the like. Leave that for a year or at least over winter, then work it up in the spring and plant that section - to lawn, ornamentals, whatever you want. Just do it a section at a time, and before you know it, you'll have a great bloomin' yard.

I have found, after years of double-digging and "working in" compost, humus, and "organic matter", that a heavy clay soil will just eat all that and ask for more.

But if you sheet compost and let the worms do the work for you, it will improve and continue to improve with little additional work from you after the first time over the ground with the tiller (after sheet composting for a year first). As long as you don't do worm-unfriendly things - like soil drenches and what not - things will continue to improve on their own. Just one round of this will help, but depending on what you are aiming for, 2 or 3 years would be even better.

I basically sheet compost into my garden every year and I don't have to do anything else to it, other than stick the plants in there and make sure it gets watered once in awhile. I don't even "work in" the cardboard underlayment or the mulch - the worms will pull that down into the soil over time.

So I have a no-till and practically hands-off garden. Raised beds and square foot gardening and drip irrigation lend themselves very very well to this approach. (I do not fill up a raised bed with "good soil", I just start sheet mulching it and before you know it, it is ALL "good soil".)

Lawns are a different matter. I admit to being somewhat cavalier about lawns. I don't think a good lawn necessarily requires the same level of soil work as a garden bed, but it DOES need to not be compacted and full of junk. Like sheets, and fiberglass insulation, and other odds and ends of construction detritus. Yes, I have pulled all of that junk, and more, out of lawns I have renovated.

So working on one section at a time, for me just one year of sheet composting, then working up that area and pulling out any junk, then putting down sod or seed, whichever - and move on to another section, this has been sufficient for me.

I do not use lawn services or any chemicals, including fertilizer, on my lawn. I do cut the grass middlin' high and often enough that I can just let the clippings fall back to the ground to be worm-food and fertilizer. I like to overseed with dutch clover because it fixes nitrogen, does NOT kill the grass, but will fill in any bare spots that may be caused by, say, Fido having his Special Spot in the yard for when he wants to water the grass. In my long-lost youth, any grass seed mix that did NOT include some dutch clover was a pretty poor seed mix.

But then along came lawn "services" dumping gallons of chemicals all over everything, and it was sayanara, butterflies, bees, and lightning bugs. And suddenly white dutch clover was a weed instead of a highly desired component of your lawn.

Granted my lawn does not remotely resemble a golf course - but I don't want it to. I want it to be low maintenance, drought tolerant, and healthy with as little intervention as possible.

But what are YOUR goals? Will any part of this work for you?

This post was edited by zensojourner on Wed, Oct 8, 14 at 23:04

sensojo gave you alot of soil improvment info that works. Is this new construction? Your concurn about drainage is somthing to make a grand plan of from the begaining. Amendments don't actually raise grade as much as it would appear. If your lot isn't well drained,you might create swales to handle drainage while placing soil on top of composted and uncomposted material in other areas. While moving soil,don't overlook properly backfilling foundation if needed. Before you start digging,search "hugelkultur" and decide if you want to do some while moving soil.

HAH! We had a huge pile of cardboard from moving, renovation, etc, and last week I spent a long time tearing it up into little pieces, and piling it up into a corner, layered with manure. To make cardboard compost. I guess I should dig it out and layer it around the backyard.

Anyway thanks for the detailed advice. This answers a lot of questions.

In Los Angeles right now lawns are actually frowned upon because they take so much water. I'll let my lawn earn its' water with some clippings for compost for a while but eventually it will go to make way for trees and succulents and maybe vegetables. When I want to kill the lawn, do you recommend simply covering it with cardboard and compost? And then when it's been in the dark for many months, plant something else?

There's something like 800 or 1000 ft^2 of dirt in the back and front combined. Not a lot.

Thanks again.

Agree about the alfalfa as a cover crop - it has a deeply penetrating root system and is excellent for loosening clay soil.

Berms/mounds are great ways to plant immediately in heavy/clay or poorly draining soils. They are essentially raised beds but informal ones that can be made to any size or shape you want. They add valuable dimension to what is often a flat landscape and they provide excellent drainage. As long as you do not over-water - likely not an issue in SoCal these days :-) - there is little chance of run-off causing drainage issues elsewhere in the yard. The soil you need to import to build the mounds tends to be absorbent without being excessively moisture retentive. Don't construct the berms or mounds of just organic matter (compost) - use a mineral based soil mix. Compost shrinks with time, so that the mounds will diminish to almost nothing if that's all they are and you do not want that a severe a disparity between the two soil types. In fact, roughing up the base soil as best you can before constructing the berms is recommended.

And amending individual planting holes has been shown to have detrimental effects on the successful establishment of plants - especially trees - and is not longer advised by those with a horticultural background. This is even more so the case with clay soils. Dig a very wide but shallow planting hole with sloped sides and plant high - with the rootball several inches above grade. Fill with removed soil only, mounding it up to the top of the rootball (creating a mini-berm or mound). Any amendments you think you may need should be applied as a mulch or topdressing only. The reason for this is something called soil interface, or the movement of water (or lack thereof) between two distinctly different soil types. If you fill a planting hole in clay soil with amended soil, water does not drain easily......sometimes hardly at all. This is commonly known as the bathtub effect :-)) And the plant roots wind up rotting in perpetually damp muck. Also an enriched planting hole, clay soil or not, does not encourage the plants to spread their roots out into the surrounding soil as they would naturally.

FWIW, raised beds make a lot of sense if you are considering vegetables. Vegetable gardens tend to be less than attractive for a good part of the year and raised beds will keep the growing confined plus offer ease of soil management, maintenance, fertilizing and watering - all issues with edibles that supercede those of landscape ornamentals.

Ben, here's one way to kill your lawn without killing the soil.

I love OG magazine, but this is one of my long-standing beefs with them - an awful lot of their advice is only applicable if you live on a farm. In LA, just where are you going to get a truckload of manure to dump on your lawn? And how long do you think the neighbors will tolerate having poop and dead grass piled on top of cardboard in your yard before they have the Lawn Nazis out after you?

But that's the basic method, adjusted for the materials available to you.

DO NOT dump your kitchen waste on this, whatever else you are using. That's just dumb advice. Set up an actual compost bin, that's where your kitchen waste belongs.

So where DID you get a pile of manure in LA? Just wondering ...

Anyway if that is pretty well rotted - so it doesn't look or smell like manure - you can use that to pile up on the cardboard and keep it from blowing away. But I would use your "best stuff" for your veggie garden first, and if you can get recycled city yard waste in LA, I'd use that to cover up the cardboard where you are killing the lawn. Wet it down first so it's good and damp, then the cardboard + mulch will help to preserve that and attract and support a large workforce - errr, I mean earthworm population.

Just a thought about planting the tree slightly above the level of the ground - this is perhaps not the best choice in dry areas such as where we live. Instead, make a wide shallow dish-shaped slope, at the bottom of which you will plant your tree. This is a water catchment to help your tree get enough water in a dry environment. And in fact, you should try to build this catchment out to the expected mature drip line.

It should be a shallow slope, but definitely there. I don't know how much rain LA gets - not much recently, that's for sure - but here we get 7 inches a YEAR. A tree planted higher than ground level here, or in a similarly dry area, simply would not survive.

If you want to get fancy-schmancy about it, you can partially line the catchment - starting about a foot from the edge and extending about a foot into the sloped area - with concrete pavers (the small ones, not the stepping stones) or brick. This will help to direct water into the catchment area, cut down on weeds and dust, and will still allow a heavy rain some chance to soak in around the bricks and not just run off the way it would if it were solid concrete or pavement.

It doesn't have to just be a big bowl for a single tree, either. With a little planning, you can plant other plants and even some small shrubs around the edges.

And MULCH. And plant drought tolerant ground covers. There are native species that you can use. Creeping thyme is a good drought tolerant ground cover that will grow between pavers and will even tolerate mowing and light traffic. Not that you should need to mow, it only gets a couple inches high.

Here are several ideas for designing landscapes to make the most of whatever rain you get:

Rain collection
planting on a slope to catch rain
Rain Garden Zones - about 1/4th of the way down there's a diagram of a multi-plant catchment zone, with a tree at the center of it all.
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More on rain collection for landscaping

Look for information on xeriscaping as well. Truth is most of CA is and always has been desert or near desert, but the water banquet is over. I tell my son the next great shortage is not going to be gasoline - it's water. And its already started.

BTW - Alfalfa can grow roots penetrating up to 20'. But it is a multi-year crop. If you can grow it without triggering a visit from the lawn police, it needs to go 3 to 5 years to have enough time and growth to break up and aerate the soil. Just FYI. Great cover crop for hard compact soil, but it does need time to do its work.

There is no good reason to remove that clay soil, just add organic matter to it. Removing, say, 6 inches of that clay and putting down 6 inches of something called "topsoil" will simply create on large bathtub. Water will flow in and not be able to flow out because of the surrounding clay soil. Same thing as amending a planting hole and not the rest of the area.
Raised beds may be an option for a while as the rest of the soil is worked into a good healthy soil. Until your base soil begins to drain fairly well raised beds can provide that for what you grow.
Cover/green manure crops might be an option for you, but any organic matter you can get into that soil will be of help.

Wow, lots of advice! I was clueless about the trees, so this was definitely a lot of help.

It looks like the consensus is that top dressing is better than digging compost in with heavy clay soil, and that alfalfa is a great, and that I don't need to remove any clay.

If I cover a layer with manure, cardboard, and mature compost, how long should I wait until I plant the alfalfa?

If you do it now - in the spring? I can't remember when alfalfa is normally planted off the top of my head. Some cover crops are fall planted, some are spring planted.

It looks like alfalfa can be sown in the fall in LA, CA. But I'd need to let the compost sit for a while before sowing it, right? Planting straight into the current bad soil, or into compost is a bad idea?

How soon after laying manure on that soil you could seed the Alfalfa will depend on the age of the manure. Fresh manure would most likely cook the seed while well aged would be more like soil. No reason you could not seed compost right away, unless it was not finished.

I think it depends on what type of tree in a clay area!
I've got a Chinese elm, many oaks, a Japanese maple, a Mimosa, a black locust, cypress growing with vigor!
For some reason, in the front yard we have lost a fruitless mulberry, a Fuji apple and some weeping evergreen.
The three that were lost, we made large holes and amended them with tons of compost, but when pulling them found the "bathtub effect" and that the roots were just curled up in that little tub!
OTOH, when I moved my compost pile of many years, I was able to dig down a couple of feet, when in other areas of the yard, I couldn't even pierce the soil! Nancy

Alfalfa is good, but there are better options for the biological drilling you are trying to do (inject OM without digging). In particular fava beans produce far more biomass and root mass, and go deeper. But the best are daikon type crops, which have a large, penetrating root that will decay in place. You can find them at any gardening web site that sells cover crops.

Fava beans and daikon are not necessarily "better" than alfalfa for a green manure cover crop.

Neither fava nor daikon will put roots down 15' into the soil. Neither actually produces nearly the total biomass when alfalfa is not cut for hay but is left to go back into the soil.

Daikon only grows down to about 18" while fava may put roots down between 1' and 3' at maximum in depth. And it will be nearer the minimum than maximum in heavy compacted clay soil for the first several years.

There may be some short term benefits from either of these 2 cover crops, but overall - alfalfa is the better choice IF you have the time to let it do its work. The depth of the roots loosens not only the top 12" or so, but brings root mass and breaks up hardpan much deeper - which improves drainage and aeration for the upper levels of soil where you want to grow crops. If hardpan is left unaltered, you will still have (lack of) drainage issues and other problems.

Daikon actually can be a good companion to alfalfa - but in and of itself it is not a better cover crop.

Daikon cover crop root

http://www.territorialseed.com/product/Groundhog_Daikon_Radish_Cover_Crop_Seed

Fava roots and cover (scroll down to March 2011)

http://rootsofnourishment.blogspot.com

I have seen 5 ft fava stands. I have not dug them, but I am fairly sure at least the biomass (and nitrogen/acre) is hard to beat.

Whats the earthworm situation?

You need organic matter and sufficient moisture to build a significant worm population, but once they're there, they do a wonderful job of loosening the soil.

So I already planted a couple beds of alfalfa. One bed is doing quite well, in section which already had decent soil which I double dug for good measure.

The other bed is just a big layer of compost on top of a layer of cardboard straight on top of the undisturbed clay soil. This one isn't doing as well, because a creature, I'm guessing a possum, is digging it up for compost grubs! So much of the alfalfa sprouts were killed. The remaining ones aren't growing as fast, I think because the alfalfa roots prefer denser soil. I guess I should have dug up some clay soil with a grub ax and mixed it with the compost.

That's what I'll do with the next bed. And maybe use a combination of daikon, fava, and alfalfa, and see which one does best!

As far as earthworms, I haven't seen any yet. I've got plenty of food and good habitat for them, so nature will bring them along eventually, but I'm wondering if I should speed up the process and buy some worms?

Amended beds are for short-lived plants with small root systems like flowering annuals and vegetables. Otherwise you should choose plants suited to the existing soil or provide a different soil for them to grow in, either through excavation and replacement (of a large enough area) or through berming/mounding. Even in the case of amended beds for plants with small root systems it is a lot quicker and more direct to bring in suitable soil and plant in that than to dig amendments into an existing soil thought to not be suitable in its current condition.

No real need to buy worms. If the habitat is good, they will show up eventually in most places. Usually the worms for sale are red wigglers, which are good in worm bins eating food scrap but not so much in compost or the ground.

The rule of thumb is, if the conditions are not right, purchased worms will leave or die. If they are right, native ones will flourish. It may take a season to start seeing them. If you've been at this awhile, consider getting a few from a friend who has a lot in their garden. Even a scoop of soil will probably have eggs in it.

The soil a plant grows in is the single most important part of the whole process and each gardener should look at and know the soil each plant needs to grow up strong and healthy. However, the vast majority of plants, for food or visual pleasure, need a soil that is well amended with organic matter so it is evenly moist but well drained with a pH in the 6.2 to 6.8 range and balanced nutrient levels.
The problem with most soils is simply that they lack adequate amounts of organic matter.

One other thing: worms are just one part of the complex biological web that lives in soil. All kinds of microbes and other insects do a huge amount of work breaking down organic matter, transferring nutrients, etc. So worms are not the whole deal, and don't freak if you don't see a lot of them right away.

I'm more a fan of finding plants that thrive in you type of soil then modifying the soil to fit the plants. If you live in a draught prone area, there are advantages to clay soil...it holds water.

If you want to modify the soil of you whole lawn, the best solution I can think of is renting a plow. Cover you soil with cardboard and compost, let the cardboard rot, then plow it under. Wouldn't it mix the top layer with soil a few inches beneath? Then plant a legume and plow it under.

If you are planting legumes on lot that had new construction,be sue to use the right inoculum fo that legume, o you won't get the benefit of the nitrogen fixation.

I did not bother to read the whole thread. But do not fight the nature.

If you have a small garden, do whatever you like. But for a large yard, it is impossible to change the soil....

One deep root thing to consider if you live in an arid area that has soil moisture only when you supply it: deep growing roots don't automatically grow deep. They will grow if there's moisture they can reach to, but if you have a nine inches of damp soil on top of a few thousand miles of aridity, the plant roots will remain shallow. This sort of thing can affect everything from okra to trees.

That's a rule of thumb and (of course) all such rules of thumb have exceptions, but it's possibly a waste of time and money as a remedy with expensive water and low ground moisture.

YMMV

The Bottom Line
•
Ideal soils, from a fertility standpoint, are generally
defined as containing no more than 5% OM
by weight or 10% by volume
•
Before you add organic amendments to your gard
en, have your soil tested to determine its OM
content and nutrient levels
•
Be conservative with organic amendments; add onl
y what is necessary to correct deficiencies and
maintain OM at ideal levels
•
Do not incorporate organic amendments into
landscapes destined for permanent installations;
topdress with mulch instead
•
Abnormally high levels of nutrients can have
negative effects on plant and soil health
•
Any nutrients not immediately utilized by micr
obes or plants contribute to non-point source
pollution

Here is a link that might be useful: The Myth of Soil Amendments, Part III “Healthy soil has high organic content”

These simple soil tests have helped many people over the years get the soil they have into a good healthy soil. Working on getting the soil into a good healthy condition does not, as Prof. Chalker-Scott states, imply the soil you have now is unhealthy. Soils lacking adequate amounts of organic matter just are not as healthy as they could be.
1) Soil test for organic matter. From that soil sample put enough of the rest to make a 4 inch level in a clear 1 quart jar, with a tight fitting lid. Fill that jar with water and replace the lid, tightly. Shake the jar vigorously and then let it stand for 24 hours. Your soil will settle out according to soil particle size and weight. For example, a good loam will have about 1-3/4 inch (about 45%) of sand on the bottom. about 1 inch (about 25%) of silt next, about 1 inch (25%) of clay above that, and about 1/4 inch (about 5%) of organic matter on the top.

2) Drainage. Dig a hole 1 foot square and 1 foot deep and fill that with water. After that water drains away refill the hole with more water and time how long it takes that to drain away. Anything less than 2 hours and your soil drains’ too quickly and needs more organic matter to slow that drainage down. Anything over 6 hours and the soil drains too slowly and needs lots of organic matter to speed it up.

3) Tilth. Take a handful of your slightly damp soil and squeeze it tightly. When the pressure is released the soil should hold together in that clump, but when poked with a finger that clump should fall apart.

4) Smell. What does your soil smell like? A pleasant, rich earthy odor? Putrid, offensive, repugnant odor? The more organic matter in your soil the more active the soil bacteria will be and the nicer your soil will smell.

5) Life. How many earthworms per shovel full were there? 5 or more indicates a pretty healthy soil. Fewer than 5, according to the Natural Resources Conservation Service, indicates a soil that is not healthy.

>The more organic matter in your soil the more active the soil bacteria will be and the nicer your soil will smellThis is simply false, there is a point of diminishing returns that is reached at much lower amounts of organic content than what is usually present after piling the amendments on. Some of the most infertile, smelly soils are those composed primarily of decomposed organic material and very low in mineral content.