Well as you have found covering it with mulch eventually makes it more compliant. So it seems like the thing to do would be to keep up the mulching, as much as possible.

Years ago Sunset magazine had an article about a guy living in an L.A. neighborhood that had turned his lot into an oasis by taking unwanted fallen leaves etc. off of the hands of people around him, dumping them on his beds. So if you got the same kind of interaction and process going you could improve your soil without buying, housing and spreading bulk purchased mulches.

By the way as I remember it the L.A. guy's lush yard wasn't having to be watered. In nature bare soil is only something you see in deserts or other places like bedrock outcroppings where there aren't enough plants present to produce a lingering, uniform litter layer.

Here the garbage company rents us yard waste totes that are emptied twice per month, their contents then taken to a compost production business that turns it into compost - and then sells it back to the public. If the same kind of system is in place there maybe some of your neighbors would happily have you take all or part of their yard waste off their hands for free.

Check subsurface drainage and install drainage lines if needed (and there is a place to have the lines drain into). Or limit your gardening in that part of the property to berms of purchased soil or raised beds filled with it. The mulch wouldn't have had any effect on the soil being airless other than stopping the sun from baking it. Cold and stinky would be due to how the soil already was before mulching.

I love your descriptions and pictures, Tristan.

In the 'dry' picture, to my eyes the texture looks sandy. But if it's sandy, why would it hold together when dry? (I ask myself.) And I am sure it's clay because you've described it that way, but...

Can you do an experiment? Put some into a glass jar with straight sides, add water, and let it separate into all of its components. I'd be interested to know the amounts of each of sand, silt and clay.

Ha ha. Okay I am convinced.

I just stole that so I hope you do not have it copyrighted! I have the same problem, but our clay is a iron oxide red. I bet your soil test never settles. I have had the best long term success with FINE woodchips in a thin layer. But I have a chipper to make my own. Compost is usually going only into my garden. Also I will use a very thin sawdust. You can buy compressed sawdust pellets in 50lb bags for about 5 dollars at the local Tractor Supply Co. I apply No more than 2 inches for aeration reasons even on really bad areas and really 1/4 most of the time. I use a wheelbarrow and do some here there and everywhere over the course of the year. But it is hot and humid here, and the soil bio cranks up phenomenally in summer to eat all food offered. I would like to know your soil type and climate, so where exactly are you? Here is the link I will be using. I would then be interested to see how the climate effects the behavior of that type of soil. For example what makes it black?

http://www.arcgis.com/home/webmap/viewer.html?webmap=0edea1c7bbb84ba5842d20483af11679

They say that growing a crop of potatoes helps to break up clay. How do you feel about that?

What is this obsession with shovels? Shovels are the absolute worst tool for heavy, clay based soil. Digging forks, pry bars, pickaxes - pointy things work much better.

The best solution to clay soil is organic material, up to 6 to 8 percent organic matter in that soil mix. It takes about 20 tons of organic material per acre to raise the level of organic matter in soil 1 percent so you will need a lot of organic material.

Perhaps these simple soil tests may be of some help.

1) Soil test for organic
material. 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, to a point. Too much organic matter
can be bad as well.

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.

>>>In nature bare soil is only something you see in deserts or other places like bedrock outcroppings

Not that anyone asked but much of the time in the desert you are NOT seeing "bare soil," but what's called a biological soil crust or cryptobiotic soil crust. http://soilcrust.org/

Now to the soil. If it smells "like a sewer" you'd better check for a sewer, or other serious drainage problem underneath the garden. Nothing about mulching the top of the soil creates this condition; it's coming from beneath.

To break up your hardpan, obviously a cover crop is not going to be enough. You might consider decompacting with a broadfork before planting again: http://www.motherearthnews.com/organic-gardening/breaking-down-the-broadfork-zbcz1601

I'm just taking a swing at something...

You said you live in California. What region? And could you describe that small better?

I've never lived in around it, but I know that in some areas of California there are places where oil is very close to the surface. It doesn't help that years ago the oil booms in such areas made a mess of certain tracts of land. The are even places like La Brea in Los Angeles with tar.

And again, this is just a guess based on the look of that soil, and your report of a foul smell, but tar/oil could make a soil malleable, and the smell would be foul and perhaps sewery.

this is a textbook case of roots hitting a harder layer. You don't show it in your pics, but I wonder if they grow sideways all at the same depth, and if they do, you have your answer. But regardless, you have to break it.

You are doing everything right, but if I may offer my suggestions, the longer roots stay in the ground, the higher the probability that they break through. keep in mind that once a channel is made it lasts essentially forever and once channels are there your soil will improve on its own.

So, I suggest you keep using the same CC, but add also alfalfa, forage chicory, red clover (red, not sweet), beet or perhaps sugarbeet, canola, and if you are willing to try, horseradish. Now the important thing is that these crops stay in ground for more than one year, two ideally, or as long as possible for sugarbeet. I would even go as far as trying anything deep rooted or fast breaking, which may include also sorghum, buckwheat and fava. If you want a shorter list try alfalfa, chicory and horseradish. you have to be prepared to lose a growing season, and you can try in parts before going whole hog.

The nuclear option would be going with something woody, but that would lose you several growing seasons, I would not go that route without having exhausted all possibilities.

PS. a couple of considerations. First, the root you show has broken through in three places. If you gave it more time it would have broken through in many more places. You have to think in terms of forces. To exert more pressure, the plant can only brace itself with the superficial roots, and use that bracing to push down. Those take time to develop. Once the plant is mature, it will be able to push harder and break tougher spots.

Second, what is happening with the earthworms there? do you have periods of drought when they are forced down to moister layers? do you see earthworms channels?

If mallow grows there, it is probably able to break it. Have you excavated some plants to see what their roots look like? same for nightshade. I think you need to rent a jack hammer and dig large holes where you can inspect the roots of many plants. At any rate, I disagree with others who say OM on top is the solution for everything. It is not the solution for you and you will just waste time and effort. The only solution is root channels, many and deep.

Consider also that in winter the soil is softer due to the rain, and so plants living through the winter will go deeper than equivalent summer crops. I gardened in Portola Valley and Redwood City in my youth and i am familiar with your soil. it is not something you will fix in one winter. If you believe it you will keep on doing it and you will succeed. I used modern soil science in my garden in Michigan, but it was three years to the first tangible results. Now I am planting cover crops in July because I have too many vegetables and there is no need to plant a fall garden. But I believed the concepts and kept on trying. You may have to try different techniques of giving and withholding water (useful for summer only of course) to push various organisms down in search of moisture.

You may get initial indirect info by planting everything, watering, and seeing which plants predominate. Those would tend to be those which can reach farther down, but you still need to jack hammer it and see for yourself.

BTW, red clover and crimson clover are very different plants.

I have two questions first.

Do you know any of the history of the site?

what kind of soils exist around you? are you the only one with this problem, or do others have much the same plate forming soil and poor drainage?

You gots a problem with soil biology (the smell comes from an anaerobic condition, which leads to bad smells where ever such a condition occurs). What's the cause? compaction, poor drainage, (both of which may be related) but there's this little tickle in the back of my mind that wants to know more technical data on your location. Have access to one of the old USGS soil survey books? there's a website that has much of the same info, but I keep forgetting what is.

how to dig through it? king of spades. a.m. leonard. steel handle. get the bumpers, your feet will thank you.

In the past, when I've run across situations such as yours, I've had two possible answers. one is power equipment...from your descriptions of actions, I'm guessing this is off the table. the other way has been by mulching and managing the water. for what it's worth, such situations were construction, dealing less with topsoil and more with subsoil, and compacted (seriously, the contractor actually used a roller compacter to level the yard before laying sod). By mulching and managing water applications (irrigation, sometimes less and sometimes more), I was able to grow anything I wanted to and solve whatever issues arose.

Wood chip mulch:
Landscape boon or bane?

https://puyallup.wsu.edu/wp-content/uploads/sites/403/2015/03/wood-chips.pdf

the smell Wayne discusses is just another by-product of compaction. No channels leads to anaerobic conditions. but, hey, determination and long lived plants can fix this site.

what I was really looking for was buried in of the above posts.

entisols - orthents.

you don't actually have topsoil, and that's part of your problem. nearly all of your issues come from that. Most places I have lived, this has been an issue in newer developments, where the topsoil was removed and sold off by the developer. not exactly your problem, but you may have similarities.

So...what are you trying to do? landscape? vegetables? lawn?

Shovel

Check out that shovel...i use mine like a prybar if needed. Mine has lasted me...over ten years, now that I think about it.

Access to compostables is going to be your limitation. so things will take time. Or you drop a huge sum of money at the problem...I'm going to guess things in the bay area are priced a little ridiculous?

Essentially, you have to focus on soil building. Which is ironic, because soil building practices aren't actually soil building at all...soil is decomposed rock, and essentially, in your lifetime, or any person's lifetime not named Methuselah (and perhaps even his), you aren't going to build any soil...what you do is build (create) compost, and incorporate it with the top layers of soil, and grow in that. So what was it you said about giving up and doing raised beds? and why phrase it that way?

out of curiosity, what kind of results do you get from a basic soil test? specifically, fertilizer recommendations and CEC levels? **

So far, unless I've missed something, your stated complaints are hard, brick like clay, and where you can dig, aromas and temperature. Are there any other complaints I missed? have you tried to do certain things and you got results that you didn't anticipate or were otherwise less than hoped for?

what I've learned about soil is that at a very basic level, you have to learn how to manage it. It means you have to pay attention and adapt your approaches to what you have to work with...and based on your descriptions, you have the observations, you're really more at a lose how to proceed.

If there's one thing I've learned about soil and growing plants, it's that soil is the most complex part of growing things, and even more misunderstood.

** this forum is littered with lengthy threads where people endlessly try to interpret soil test results. I'm not suggesting you go that route. I'm going to guess the fertility results are off the charts, but little in plant available forms...which would make managing fertility something to consider as part of your strategy. and some things would be low...but that's just a guess. What we know is you have a soil type that generally lacks topsoil, not necessarily why or what the parent material was. which has the potential to make your soil test results interesting.

Tristan, it has been an interesting thread to read and I was especially curious when wikipedia described a sulfer clay common to your soil which is a remnant of its origins from the bottom of a large body of water. It is probably chock full of goodness locked into an acidic clay. It described a young soil with no layers. It decribed also a hilly terrain? Is that you? The topsoils would slough off from what I read, but construction has probably impacted your condition. I would be thrilled to have learned the knowledge of how to unlock it, liming being a common recipe but in your case is the soil acidic? Do you have success with acid surviving plants and failures with those that like a higher ph? It bodes well for a garden to be slightly low for the Old #7 ph.

As an aside, the only only time I have been able to penetrate my clay beyond 5 feet deep with a metal rod by hand was when I fed fungi for a season. Wood was involved but so was molasses. There is a cost of course because nothing is free. The cost would be the fungal attack on plants that do not do well with high levels of fungus, most grasses and veggies. The fungal hyphae will have no problem dividing the clay particles in search of water, which will be brought up to the top 2 inches where heat and oxygen and nitrogen are available in abundance.

The SF peninsula has lots of hills running for miles and miles to the coast, and then the inner 2-3 miles alongside the bay are all flat. I live right at the bottom of the hills, right inside the flat area. When you get within half a mile of the bay itself, 1.5 miles from my house, everything (even the air) smells like sulfur. I wonder if that has anything to do with it.....

What grows basically wild here: figs, citrus (mostly oranges), blackberries, oak and redwoods. My city is called redwood city, for reasons you might guess! A lot of people xeriscape.

The goal of the garden is fruit trees. I planted 18 in various spots. Fruit grows well here, at least many people have one or several trees, including my mom and sister who live a couple cities over. So I know they can survive here! I have one or 2 of every kind of fruit (except tropical fruits) and picked particular varieties I knew someone nearby had success growing. As long as I can keep my trees alive and healthy, that's all I care about. But flower borders and a clover lawn in between trees would be my ideal.

The bay area is ridiculously expensive. I went through my yearly gardening budget around early April. The area I'm trying to improve is 50x70sft.

I want to spend a while doing the best I can to improve my soil. I'm planning on doing *something* when fall starts. I'm not sure what, just yet. More cover crops? More mulch? Tilling woodchips in? (aka the nuclear option!) Extensive trench composting? A massive composting effort using coffee grounds, leaves and woodchips and anything else I can get free? Acquiring chickens or bunnies or some other animal to use as a poop farm? Is there a next step at all or should I let it sit as is? Is there a better plan I haven't thought of?

It sounds like your plate is quite full of ideas. I would caution about any suggestion that decomposition- and that does mean oxidation, which is the primary function- could be improved under such a fine grain sediment and oxygen deprived soil as is clay. The way I understand clay currently is that the oxygen particle being roughly 30 percent larger than that of the Hydrogen particle in a smidge of water is simply screened off as a filtering effect of the fineness of the clay. The preservation of the stink attests to that. It should also mean that you should get a test to prove that it is acidic soil as I suspect it would be with all the excess hydrogen which is what is measured on the ph test.

I don't think mulch is the answer. I think plants and their roots are the answer. Digging stuff in sometimes. Later, some chickens would be fun and they would have greenery, and they can help themselves to any fallen fruit.

My old boss told me of someone who had an orchard and chickens. He divided the orchard into four sections and built the hen's sleeping and laying quarters in the middle. The chickens were rotated when required. I've always liked the sound of that.

Mulch is to the same end. Put food on top of the soil and creatures from the deep dirt will come up for it, loosening and changing the clay as they establish a biozone. The time frame is the problem. Force it and it imbalance follows. Terra Preta took thousands of years to be formed. I really like the concept of biochar and my kind of clay. Ultisol that is, but would it be right on the left coast? I would not know without a little more digging...so to speak.

Wood chips are a good source of organic matter but they can take quite some time to be digested even in a soil with a very active Soil Food Web.

What the soil, where that putrid odor is, is saying is it is holding water too well and that is excluding the air soils also need . That anaerobic condition also limits what you might have in the way of that Soil Food Web.

Are you watering the area where the wood chips is, too? I can't quite figure out the stink there. Obvious guess is that you are over-watering there, and since the water is not draining away, you're getting that stink. I find areas with wood chips and similar dry, woody mulch don't get that way - the water gets absorbed and/or evaporates. (Mind, it's possible there is a small thin layer during rainy/wet periods, I've never checked that closely.) I'd tend to think the answer - or at least easiest thing to try - is more mulch, less water.

Amending more than small areas of a hostile-appearing soil is too much work and is not a suitable approach for growing long term plants like trees, shrubs and perennials. It's more natural to apply new material to the surface of the existing soil, either mulching and waiting until the existing soil is improved by that or making berms, mounds or raised beds with purchased soil, on top of the existing soil, and planting in those - without blending the two layers together.

Amended soils are still the same soils after the amending - there is no such thing as building a soil - and will constantly be in a process of returning to their previous condition, unless amending continues indefinitely. Feasible for small rooted, frequently replaced plants like annual vegetables and flowering annuals - and not much else. It is also quite possible to quickly overdo additions of amendments and create adverse situations such as excessive drainage (from applications of sand for instance) or excesses of particular soil nutrients.

Roots will have the carbonic acid and point pressure to break that thing. Micro organisms will not. The picture below is a phenomenon generated by roots, not bacteria. Bacteria will have a role but physics is what it is. add mulch to that rock and nothing happens.

cover crops make mulch, but really your figure of merit is organic matter injected, not organic matter. if you put down enough seed even less productive crops will form a jungle. buy a scythe to make mulch but remember that plants need time to break that thing. large seeded crops are not the same as deep rooted crops, and in fact they often have small seeds.

Lucerne (alfalfa) has small seeds and

l

o

n

g

roots. The chooks will like it too.

If you buy some alfalfa seed, get some of the rhizobial inocculent that it needs for a good germination.

There is no one really good way to increase the amount of organic mater in soil and many of us have used a combination of methods over the years. Mulches can work, and contrary to what some think a thick layer of mulch does not inhibit the exchange of air in soil, although plastic (or other impervious types of sheeting) will.

The roots of some cover crops will help provide some organic matter mass while the top growth will provide more. The top growth of cover crops can be crimped, knocked over so the stems at ground level are broken, and will, eventually, be digested and incorporated into the soil, a scythe is not necessary. One person I know uses a length of 2 x 4 to crimp the cover crops that he grows in his 4 foot wide planting beds.

The speediest way to get organic material worked into the soil is to till it in, if that is possible, but it still takes a few years for the soil to fix its problems because the Soil Food Web needs that organic matter to live on and increase in numbers.

Lots of intelligent thoughts here (as usual!). I used a combination of methods on my clay. At first, a lot of tilling of compost. Mulches and top dressings of compost. As the top layer (one shovel deep) got pretty good, even some double digging in the vegetable gardens. As time went on, less and less tilling and more reliance on gently digging in compost, amending planting holes for peppers and tomatoes rather than digging up the whole bed, and continued use of nutritious mulches. After 25 years the beds have 'fluffed' several inches and the texture is much improved. Nutrient levels are high. Now the only problem is tree roots, which heard the music and came to the party. I must be doing something right.

TaT, yes that is true. Alfalfa penetration over 2 years is unparalleled. One can look at it here

http://soilandhealth.org/wp-content/uploads/01aglibrary/010139fieldcroproots/010139toc.html

Note that in the soil under discussion those 10 ft will turn into maybe 5. But nothing else will do 5 over the same time frame. That is why those who want to go no-till are advised to start with a 2-years planting of alfalfa, so that the compaction layer just under the plowing depth is destroyed. For deep branching, beet (same site) is unbeatable. Radish does a single taproot, like alfalfa. The interest of deep rooted plants is that the following crop, if medium rooted, can reach its normal depth even if it does not have the penetration pressure needed.