The 'Perfect' Gardening Soil Structure?

ssmdgardener(7)February 6, 2012

I'm really interested in learning more about the science behind soils. I'd like to start a discussion about the best way to amend any ordinary yard dirt to make it the perfect growing medium.

Please let me know if I have the basics correct:

* There are inorganic and organic matter in soil.

* Inorganic matter consists of sand, silt, and clay.

* Sand is the largest in particle size, then silt, with clay being the smallest.

* There is an optimal ratio of the 3 inorganic materials.

* Organic matter, such as compost, leaf mold, or bark can be added to the inorganic matter.

* Some organic matter are preferred over others as an amendment.

* There is an optimal ratio of inorganic to organic matter.

* The ratio of amendments differs in the ground vs in a raised bed.

* The method of amending is important, as you don't want to disturb the creatures in the soil food web.

Please add any information that is missing, or if you disagree with something. I'm particularly interested in the best method for adding amendments.

FYI, this all started because I started out with not enough organic matter (rocky clay) and now I think some of my beds have too much organic matter, which I didn't realize could be a bad thing. I'm sick of trial and error, as that has only cost me money and time, so I'd like to learn the science behind it first.


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tropical_thought(San Francisco)

You will find a lot of disagreement on the finer points of soil science here. For example I don't worry about disturbing the soil creatures. If I want to dig in some compost, I did it in because, the soil and the creature will right themselves. If you never dig the compost you won't improve the over all structure long term. Compost can be added to the top layer, but will be subject to being washed away by run off. It will take 10 years of adding to the top or so to reach lower levels. That is too long to wait.
There is an optimal ratio for hot composting which is 50 50, but for the actually soil, it really depends on your native soil and what you are trying to grow or plant. If I have a bed, I want that to have more OM, but if this is just an an area for a ground cover, I won't dig use as much OM, I won't dig as deep. There no hard and fast rules. Trial and error is the best way to learn what is working for you. I had a lemon tree, but the drainage was bad. I dug it up and noticed the roots were an unhealthy color so I knew I could not put the lemon there. I move it to another area. If you are growing water saving plants, they like less OM. You you will want to reach what kind of soil the plant likes online. Don't take information for just one place. Look for multiple sources of information. I don't have clay so I can't be of much help there, but clay is pretty tricky. Sandy soil is easy, just add a lot of OM.

    Bookmark   February 6, 2012 at 9:04AM
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I'm actually interested in hearing the disagreements on the finer points. I appreciate your point of view on digging in the organic matter.

I disagree about trial and error, though. Last year, I was blindly doing trial and error, and it didn't help me learn, except what *not* to do again. I'd like my next round of trial and error to be based on knowledge.

Also, what I learned from Al's posts about container gardening is that sometimes, the answer is so counterintuitive to a casual gardener that I never would have come across it on my own.

    Bookmark   February 6, 2012 at 9:49AM
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ralleia(z5 Omaha, NE)

I would have to tend to disagree on the statement that "if you never dig in the compost, you won't improve the soil structure."

The soils in my area (eastern Nebraska) have a lot of heavy clay. It is fertile, but very prone to compaction, and if overtilled one can destroy a lot of the drainage holes that were put there by plant roots and earthworms, insects, and digging mammals.

The tack that I plan to sail with my soil (particularly in my grow-intensive hoophouse) is to assist the soil life to create that "perfect" garden soil structure. The plan is still being formulated, but short-term it is to:

1) eliminate worm carnivores in the hoophouse (I had trouble with shrews in there)--last year we installed aluminum flashing around the perimeter, so now it just comes to killing any that are still living there.

2) plant deep-rooted cover crops to help create spaces in the soil

3) mulch around plants to keep the soil cooler in summer and retain moisture, making it a more hospitable environment for earthworms.

4) perhaps order in some additional soil-dwelling worms to kick-start the process (especially since I've now ringed out potential immigrants).

Also, I don't know if I would describe an "optimal" ratio between sand, clay, and silt. What is "optimal" is going to vary a lot with what you are growing! :) And then, trying to achieve "optimal" may result in a lot of unnecessary self-flagellation.

What is achievable varies with what you have been given. I am beginning to learn not to curse my clay but instead work within its limitations and advantages. And to enlist the help of little minions!

(Lloyd is not to read the next paragraph :)

Regarding a preference for one type of organic matter over another, the book "Teaming with Microbes" suggests a preference for fungally-dominant soils for trees and perennials versus bacterially-dominant soils for annuals and vegetables. The "browns" of composting and mulching--dried leaves, wood and bark mulch are more fungally-dominated, while the greens are the converse.

There's a lot more to say, but I'm sure that there will be more opportunity later. Thank you for bringing up a very interesting discussion!

    Bookmark   February 6, 2012 at 10:17AM
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I'll second tropical thought that this will lead to some disagreement among posts, but that's how people,come to new understandings, so let's jump on this pony and give it a few kicks...

Standard preface - the following statements apply to me and my experience in the limited soil types I've worked in -

-Regarding your original list of basics, the first three points are correct, but don't discount the presence of stones. Rocks and stones have a gradual influence on soil chemistry, but an immediate effect on texture. The presence of stones in garden soil can greatly hinder workability and root growth - your purported perfect soil may be well balanced in regard to particle size and the blend of soil types, but the stone walls that lace New England will attest to some of the problems rocks are considered to contribute.

- It is commonly accepted that there is an optimal ratio of sand, silt, clay, and organic matter - you'll see a lot of numbers thrown around here - but that ratio will vary by location - affected by the characteristics of particular native soils - and by crop. What's considered ideal for cultivating orchids may be disastrous for cucumbers.

- Organic matter can be added to improve soil, and often is a good method to do so, but it is not so simple as to just dig in whatever is at hand. The composition and texture and degree of decomposition, in addition to the source matter itself, can all have varying effects on the end result. It is not the panacea some make it out to be. Preferences of which organic matter to add will vary. Additionally, there are many inorganic amendments that are used that have similar effects on nutrient levels and availability, and may be used for a longer-term effect on soils than organic materials provide.

- Gardening methods will have some effect on deciding what constitutes an ideal soil. For raised beds, it may be better to alter drainage or texture, and the decision to use raised bed techniques might be influenced by native soils, but in general, for similar crops, the composition of the soil in regard to nutrient availability and texture will most be determined by the crop, and may not coincide with the preferences of the gardener.

- Methods of application of amendment materials will vary, depending on the material, existing soil type and structure, solubility, soil food web activity, and a host of other variables.

End result - there will likely be no consensus or hard-and-fast rules at the end of this discussion. There are too many considerations that come in to play for anything but generalized guidelines - so by extrapolation, no single definition of perfect soil is possible.

    Bookmark   February 6, 2012 at 10:20AM
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Bill, my clay is very rocky... There are pebbles and stones of all size, and occasionally boulders big enough to fill up the wheelbarrow. This is one of the reasons I've had to dig pretty deep when preparing the beds, even though I'd prefer to sheet mulch. How do you deal with the stones?

This spring, I have the opportunity to mix my own soil for vegetables in raised beds. Is there more of a consensus for the optimal soil structure in raised beds, and specifically for growing summer vegetables?

Ralleia, I never would have thought of eliminating worm carnivores. I think I like bird watching too much... Also, don't they eat unwanted pests as well?

    Bookmark   February 6, 2012 at 11:07AM
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This looks like your gettIng much better responses than on the container foum. As long as you make an actual soil in your raised beds, and not jus fill it with topsoil, and it has good aeration, drainage, water retention, and a good CEC, most plant wil thrive. Yes some plants prefer a more sandy soil and some more silt, but all will do well in a loamy soil, from there you can add more sand or compost to section to cater more specifically to the species' needs.

    Bookmark   February 6, 2012 at 11:20AM
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Bob, if I'm starting from scratch, how exactly do I make my soil "loamy"? I have on hand play sand, granite grit, clay from my own backyard, compost that I've made, shredded leaves, bark fines, and leaf mold. Is there a recommended ratio of these (or other) items?

I'm interested in having 1 raised bed or "sandy" loam for Mediterranean herbs and veggies that prefer faster draining soils, and 1 raised bed of "regular" loam for other common summer veggies.

    Bookmark   February 6, 2012 at 11:31AM
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ralleia(z5 Omaha, NE)

Sorry, I meant eliminating worm carnivores in the hoophouse. I wrote that rather ambiguously. The birds don't go into the hoophouse with the netting all around, and I *do* enjoy and feed the birdies (and trap the non-indigenous starlings and English house sparrows for raptor food, but that's another subject).

No, the worm-eating birds are welcome, and their feet as they go skipping across the ground are supposed to be great microbe "taxicabs."

But the shrews are not welcome, particularly in my hoophouse. Their burrowing has killed a number of my plants by drying out the roots, and I think one of them got my hoophouse-resident praying mantis last fall.

Regarding mixes in raised beds, I don't know what the "optimal" mix is, but I'll put out Mel Bartholomew's recipe for "How to Mix The Perfect Soil for the Perfect Garden." Then we can all tweak it from there for your specific conditions. I had good success with this mix for raised bed veggie gardens both in Massachusetts and here in Nebraska.

Mix thoroughly:

1 bale of peat moss: 6 cu ft
1 large bag of coarse vermiculite: 4 cu ft
10 pails (2 1/2 gallon size) of sand: 3 cu ft
2 pails wood ash and charcoal
10 pails compost 3 cu ft
1 coffee can full of lime
1 coffee can full of organic fertilizers
Makes 16 cu ft

Alternatively, there are also pre-mixed bales that you can buy; I have read some rave reviews on Gardenweb about Pro-Mix.

No matter what mix you go with, perhaps the most critical thing will be keeping the mix adequately moist. A lot of mixes tend to become hydrophobic and shed water once they get dry, so making sure they don't completely dry out in the summer will be important. Soaker hoses or other drip irrigation hoses (like T-tape) work very well with these mixes.

    Bookmark   February 6, 2012 at 11:35AM
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wayne_5 zone 6a Central Indiana

I am mostly a sheet composter when it comes to the residues after the crop is harvested. I like to chop them up with a mower. They rot more quickly when chopped up. I them mix in OM such as half rotted horse manure, leaf compost, and some mulched leaves. I believe a light mixing in the top inches of soil helps to balance out the distribution and speeds utilization. I don't have framed beds so I can do these chores more easily. I am not afraid to walk a bit on the soil and really good soil does not compact.

ssmdgardener, You have a daunting task with those rocks.I think it would be necessary to do some deep tilling to remove the worst of them. I have done some major soil amending on about half my garden areas. To my clay loam I added about 3 inches of sand [fine to coarse]. I also added about 4 inches of local peat moss. These make a wonder pair...both loosening the soil and the sand helps warmth and early drying while the peat helps hold moisture and loosens clay's tightness. I have mixed them [sand, peat moss, and original topsoil] all together deeply. Now the only need shallow working.

    Bookmark   February 6, 2012 at 1:03PM
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Okay, here I'll confess to what has been considered an aberration possibly worthy of professional help. My native soils are New England marine clay. The property I work was, some 180 years ago, the town poor farm, which to me is something of an indicator of exactly how unsuitable it probably was in an area known at that time for soft-wood lumber. sheep, and fishing. My initial efforts at gardening started with clearing brush, soil testing, and lots of digging. The first year, my garden was 25' x 70', consisting of 5 rows of raised beds that were 3' wide, 12' long, and framed in untreated lumber that I collected from local renovation projects. My paths were wide enough to accommodate a large wheelbarrow. This gave me enough ground to grow edible flowers, European and Asian salad greens, short season root crops, and cut flowers, which I sold to one chef at a small (48 seats) high-end restaurant. After a few years, I had modified my beds - no framing, lower height, only 30" wide, and as much as 180' long - and greatly expanded my growing area. I now have over 4 acres of gardens, comprised of about 65% annual vegetable production, 20% fruit and perennial food crops, 10% cut flowers and other ornamental, and 5% other horticultural products, such as basket-making materials, dye plants, and medicinal plants. My vegetable beds, because the crops are rotated annually, require a fairly homogenized soil mix, which I have eventually achieved. The thing that allows me to work this much ground is that I start each new bed by double-digging, amending with compost and leaf mold and rock powders, and planting peas followed by potatoes the first year. With marginal, soil, peas are a good crop, and provide a lot of quickly available N and a reasonable financial return. Potatoes are relatively tolerant of the acidic nature of my native soils, but more importantly, harvesting them means digging. During the initial bed preparation, I remove the larger stones, roots, perennial weeds, etc. When I harvest the potatoes, I re-dig the entire bed, and the soil gets sifted through a 1/2" mesh sifter that I built. The sifter is 30" wide and 10' long attached to an eccentric wheel on a horizontal shaft motor. The sifting bed has a slight tilt to one side, the soil falls back into the bed and the potatoes, rocks, roots, etc, collect in the path. I walk down the path collecting the potatoes, walk it again collecting the largest stones that could be used for building projects, then shovel the rest into my garden cart. The cart gets dumped into a large trough filled with water. Everything that floats gets skimmed off and added to the compost or shredder piles. I use a heavy rake to pull out the larger stones (2" or greater). What's left gets sifted a final time through 1/4 " mesh, giving me a pile of pea stone, which is handy for drainage and roadways and permanent paths. What gets through the 1/4" mesh is added back to my annual vegetable beds as a top dressing, which I finally dress with a metal-tined leaf rake. The rake will catch most of the larger bits, and they go into the path again. Finally, I go over the beds with a perforated roller I fabricated from an old commercial clothes dryer drum, which compacts the soil lightly and creates a level, uniform surface that my mechanical seeders perform well on.

Obviously, this requires an inordinate amount of time and labor. Sometimes I haven't gotten around to the sifting part for 2 or 3 years, because of other time pressures. Sifting is, for many crops, completely unnecessary. But for my root crops, and particularly things like oyster root, skirret, scorzonera, carrots, and parsnips, it is ideal. With the rotation I have in place, eventually all of my annual vegetable beds see root crops. My market is chefs, who want uniform, clean product. My carrots, as an example, grow straight, so they're easy to clean or peel, are very uniform in size, grow quickly because the soil is loose, and will easily lift out of the ground, often requiring no digging if the moisture levels are right. Eventually the enormous amount of labor that goes into bed preperation is rewarded with better quality crops, reduced production time, and higher prices and profits. It may not make sense for smaller home gardeners to sift an entire garden, but attention to soil tilth is one of the most effective ways to quickly build a productive and easily worked, and therefor easily amended, soil. That being said, my competitors often pronounce me a good candidate for extensive psychotherapy, so take it for what it's worth.

By the way, most of my beds get a bi-annual topdressing with compost, whatever amendments a soil test or the succeeding crop might recommend, and a simple working with a broadfork. Because I almost never till anymore, if I want any tilling I rent or borrow a machine. My fossil fuel use is limited to my mower, chipper-shredder, sifter, and transportation. At 53 years old, I am able to dig as much as 6 hours a day, but not every day, as I did when I was first starting.

Rather a long digression, but a partial explanation of what I consider an element of perfect gardening soil and what I've done to achieve it.

    Bookmark   February 6, 2012 at 1:19PM
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Thank you everyone for your input! This is very helpful.

I think I will actually cultivate the clay for the perennial beds, instead of relying purely on sheet mulching. The sheet mulched bed I started in the fall has done a good job of loosening up the clay underneath. I had read that tilling was anathema to good soil health, but now I feel more comfortable about digging in the organic matter, removing the stones, and mulching with more organic manner.

Any other raised bed recipes that you'd like to share? ralleia, are all of those specific ingredients necessary? Also, I like Pro-Mix quite a bit for starting seeds, but it would be *very* expensive to fill a raised bed with it.

    Bookmark   February 6, 2012 at 3:37PM
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ralleia(z5 Omaha, NE)

There's no need to follow the "formula" precisely--plants are pretty forgiving as long as their basic needs are met.

I don't bother with sand any more and instead use perlite if I want better drainage. The wood ash should be freely available from anyone who uses wood for heat (great time to get it now). Mel might recommend it as a way to balance the acidity in the peat moss, though it also provides a little potassium (0-1.7-7.0) I usually skip the lime since I have plenty of wood ash. For my organic fertilizers I use blood meal, bone meal, and a little bit of greensand.

Depending on what type of agriculture goes on in your area you might have other options available, too. Rice hulls for instance are supposed to be a good amendment for clay soil. I scoured the web trying to find a source a couple years ago, but I live in corn county and would likely have to truck in a tractor-trailer load to make it worth the freight. Alas.

You still want to be wary of tilling, particularly since you have significant clay in the soil. Though the mulch has loosened the clay now, if you try to work it while it is wet you can compact it again. Clay loves to adhere when wet!

But certainly you WILL need to remove those rocks before you can get to really growing, so just try to choose times when the soil is on the dry side. Sticks less to your boots, too. :)

    Bookmark   February 6, 2012 at 4:04PM
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1-2 part(s) backyard clay, 1 part perlite, 1 part fine charcoal (you can buy the all natural hardwood stuff at Walmart or homedepot, then crush it until nothing is bigger than 1/8"), 1 part coarse silica sand (trust me you can get this stuff a lot of places, it might take some scouring, but it's possible; don't use play sand, you want builders sand), 1/2 part bark (between 1/16" and 1/4"), 1/2 part peat. Mix it all in carefully, add CRF or organics (greensand, bone meal, blood meal, ash, etc.), and you will have a very good soil for your beds.

    Bookmark   February 6, 2012 at 6:10PM
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tropical_thought(San Francisco)

By trail and error, I did not mean blind trails. I mean after you research every point, then trail and error. If you are about to take a racial step that cost a lot of money, you can post it as a question first.

    Bookmark   February 6, 2012 at 6:19PM
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wayne 5, there are about a thousand threads/posting saying
not to do what you did (mix sand in clay), glad it worked for you.
My plan is roughly to put in
1 part bentonite clay
1 part coffee waste
1 part charcoal
1 part Bed soil(sand)
1 part Leaves,Dried Grass,Straw.
1/8 part bone meal, cotton seed mill,gypsum & lime.
No lime near Blueberries.
I will do this to one bed for a test first.

    Bookmark   February 6, 2012 at 9:17PM
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Loam, is considered by many to be the "perfect" garden soil. Loam is comprised of about 45 percent sand, 25 percent silt, 25 percent clay, and about 5 percent organic matter. there are pockets of Loam all over the USA, Canada, Europe, and Asia (so I am told) but not enough to meet our needs. Many soil scientists will tell you that you cannot make loam, although you could closely approximate it.
Most all plants will grow best in soils that are well endowed (5 to 8 percent) with organic matter that are evenly moist but well drained.
I have seen some clay soils that will not allow the necessary interactivity with OM piled on them to incorporate that OM into the soil, although most will. If you have such a clay soil it will be necessary to till OM into the soil, initially, and then more can be piled on the soil and the Soil Food Web will work on moving it into the soil.
The "perfect" soil is the one the plants you are growing need to grow in. Some plants need a leaner, meaner soil then do others. Some plants grow better in soils with a lower pHs then can others. There is no one perfect soil to grow plants in because it depends on where and what kind of soil the plants you want to grow evolved in.

    Bookmark   February 7, 2012 at 7:34AM
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tropical_thought(San Francisco)

kimmsr why would that be the perfect garden soil when they keep telling you not to add sand and clay together at the same time. I would think the perfect soil would be starting with sand clay or silt and then adding the right amount of OM, but those amounts I don't know what they would be. This would of course depend on the plants you were growing, as you said. But, I think the perfect soil would be one that would appeal to the most average of plants such as rose. I am just suggesting roses because they have middle of the road needs not too much OM not too little.

    Bookmark   February 7, 2012 at 9:17AM
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Kimm, you said: "I have seen some clay soils that will not allow the necessary interactivity with OM piled on them to incorporate that OM into the soil, although most will."

I just recently learned about hardpan/claypan, and that's probably what I have. I can't dig more than a couple of inches without hitting what feels like cement. In fact, I often worry that I've hit some sort of a metal pipe. I've given up on the shovel and need a mattock to break up the hardpan.

(Tropical, sorry about that, the trial-and-error rant was really aimed towards myself, because I'm frustrated at some of the egregious mistakes I've made, like turning the soil when it was soaking wet.)

So here is what I'm going to use in my test raised bed:
1 part backyard clay
1 part builder's sand
1 part Turface fines that were sifted out
1 part composted coffee grounds/filter
1 part composted leaves/grass cuttings
1 part pine bark fines

Slow release fertilizer like Osmocote
Lime or ash to counteract the acidity

I'm going to do some more research on biochar and rock powders, since I don't know much about them.

This will be for tomatoes and garden veggies. Is this too much organic matter?

    Bookmark   February 7, 2012 at 11:35AM
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tropical_thought(San Francisco)

Don't add sand to clay, I did that once in a raised veg box. I got clay cat litter and I got horticultural sand. I added OM. It worked out, but often I try to dig it and it feels too hard considering how much OM I added, it should be softer then that. If you are just doing one bed you could omit the clay, because sand is better really it has better drainage. I think sandy with OM is the best you can get if you tend to over water like me.

    Bookmark   February 7, 2012 at 11:53AM
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The whole don't add sand to clay issue is a way of warning people to be careful when adding sand to clay. If you add clay and small grained sand, you get cement. If you add clay to builders size or larger (preferably 1mm), you get a water and nutrient retentive, yet well drained medium that works wonders. If starting from scratch in a bed, you most certainly can add clay and sand, just get large grained sand! I think the wording is bad, if you amend clay with sand, it won't work, if you amend sand with clay, it will most definitely work.
Your mix looks good, but the turface is not necessary. Clay will retain water and hold nutrients, as will bark, turface too. I would go with perlite instead just because you don't want to retain too much water. The OM portion looks good, the greens and coffee will breakdown within the season releasing N and making the structure nice, while the bark will take a very long time to breakdown making the structure last longer.

    Bookmark   February 7, 2012 at 1:28PM
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A search on the net says from 5% to 45% on some sites in OM.
I say you can not have to much organic matter as long as you can still see the soil & the soil structure in the mix.
But before anyone told me, it would not work, I planted crops in 6 inches of rotten cow & horse manure for one of the best gardens, I have had in 30 years.
But I have to much sand so this may not work for poor loom or red clay.

    Bookmark   February 7, 2012 at 1:36PM
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wayne_5 zone 6a Central Indiana

Loam is a mixture of sand, silt, and clay. If your clayey loam soil already has some sand in it, How can adding some more sand of the right kind hurt it? Perhaps only western adobe clay might have trouble, but I would expect even that to work if sufficient OM like peat moss is added at the same time. I tell mix of different size sand particles and local peat moss to my clay loam is wonderfully scrumptiously a delight in all ways.

    Bookmark   February 7, 2012 at 2:04PM
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wayne_5 zone 6a Central Indiana

Loam is a mixture of sand, silt, and clay. If your clayey loam soil already has some sand in it, How can adding some more sand of the right kind hurt it? Perhaps only western adobe clay might have trouble, but I would expect even that to work if sufficient OM like peat moss is added at the same time. I tell mix of different size sand particles and local peat moss to my clay loam is wonderfully scrumptiously a delight in all ways.

ssmdgardener, The eastern soils have been tilled for a long time and likely are leached of many minerals.....Leonardtown loam and Norfolk sandy loam might be examples of that. These soils probably need lime and micro minerals and lots of OM.

I hope I am not double posting this, but don't want to chance losing this if not double posting.

    Bookmark   February 7, 2012 at 2:12PM
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The is no such thing as a 'perfect' soil structure, because we have so many different uses for soil.

What works to support a building would not necessarily be good for a road, or a bridge, or agriculture. The soils that grow great sugar beets would not be good for potatoes. So there is no one "right" answer.

So you want to learn about soils...

First, soil science is an exercise in engineering. Second, it's a practice in planning. It's much farther down the road that we get into agronomics.

As far as when it comes to growing things in soils...

Soils are by far the most complex part of the equation of growing plants. They are by far the least understood.

And to a certain extent, how much you know or what you know isn't that important.

Take your question, for example. To a soil scientist, the structure of a soil is more about it's engineering capacities than how to get a decent flower garden to grow. One question, two entirely different answers, each based on the perception of the person providing the answer or asking the question.

So what is the perfect garden soil? How much organic matter is to much? If there such a thing as too much organic matter, all the fans of lasagna/layer gardening would be up the proverbial creek, and that's before we get to hydroponics. It's less about the growing media, and more about how you manage it.

You've got perhaps the most difficult situation of all. A layer that is virtually impenetrable and relatively shallow. The "easy" answer is raised beds. The adventurous answer is explosives. The practical answer? There are far too many questions to be asked and answered before we can even get there.

    Bookmark   February 7, 2012 at 2:47PM
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toxcrusadr Clay Soil(Zone 6a - MO)

Adding sand to clay is all about the amounts (as well as the particle size of the sand as was mentioned earlier). A tiny amount won't be noticed. A little more, concrete ensues. Beyond that, after a certain point, the sand grains are numerous enough to begin touching each other amongst the clay matrix, which begins to hold the structure open. So it's not "don't add sand" but rather "beware when adding sand."

One suggestion...nothing wrong with starting this thread, but I hope you are also *reading* many of the others here in which these issues have been discussed by these and other smart people. [I do not include myself :-]

    Bookmark   February 7, 2012 at 3:13PM
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tropical_thought(San Francisco)

I knew my native sand was too fine to add it, and so I bought special horticulture sand that was at at the perfect size grains. They even sell these little bags anymore, I bought out all they had at osh, so even with the right size sand, it still did not work out as I would like it. The soil is ok, but it is much harder then it should be. Now, I can't actually take out the clay, so I am just dealing with it. If I could do it again, I would have omitted the clay. It a good soil, but its a bit heavy on some plants vegetables that would be better off in a lighter soil.

    Bookmark   February 7, 2012 at 5:05PM
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tropical thought, have you considered adding crushed bark or perlite? I grow sunchokes, which are in the sunflower family. The shredded stalks are a great soil conditioner, but they don't last much more than a year.

    Bookmark   February 7, 2012 at 5:56PM
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Dear ssmdgardner, please visit the first two threads, The mystery of HUMUS and Soil testing - why do it? I posted on there extensively and we are having a lively discussion. I use an integrated system emphasizing humus production, adding mycorrhizal fungi to my soil and complete soil testing. The results are phenomenal. I don't till anymore and my soil structure has improved so well that at first I couldn't believe it. I am using new organic technology that has happened within the last 10 years and especially the last 5. Current research is rewriting the textbooks. Also, I cordially invite you to check out my educational website, Best to ya and good growing. Your statement that you don't like trial and error really got my attention. I hate guessing - I generally research anything that I want to use thoroughly before trying it.

    Bookmark   February 8, 2012 at 3:17AM
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Organic_popeye, I've been following the other posts with interest. It's great to learn about recent research, but I'm still unclear on practical applications.

-How do I incorporate mycorrhizal fungi into my rocky, hardpan clay without tilling (and digging out the rocks/boulders) at least once?

-You said in the other post that we can't talk about products. But is that true? I've seen discussions of products here before. What are the products/methods you use to incorporate mycorrhizal fungi?

-What is the effect of using these fungi in the ground vs raised beds vs containers?

    Bookmark   February 8, 2012 at 6:52AM
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Popeye, I have one more question.

Isn't the soil structure still important? You could have all the mycorrhizal fungi you want, but if the soil structure (pure sand, not enough organic matter, etc.) isn't good enough to support plant life, then you still have dead plants. Right?

    Bookmark   February 8, 2012 at 7:56AM
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tropical_thought(San Francisco)

I used to have pure sand, but somehow before I started to use OM, I did have some limited success with a few plants. It is amazing that plants can live without any soil amending, but won't be at their best. I had some bushes that did ok. Re mycorrhizal fungi if you use wood product in your composting system or even a mulch of mircobark will encourage fungi.

Yes, I did add a lot of perlite, you can even see it there but still it is a bit on the hard side. I think over time with more OM, I will improve it. I can only add so much OM at one time as I have reached the top of the box. Or I could remove some of it and distribute it around my garden were it will not be so concentrated. I can bear to discard it, because that sand was hard to get.

    Bookmark   February 8, 2012 at 9:46AM
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Tropical, I wonder if that's why hugelkultur is supposed to work so well... does all that decaying wood invite mycorrhizal fungal action? What if I buried tree trunks/woody materials in my raised beds?

    Bookmark   February 8, 2012 at 10:25AM
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ralleia(z5 Omaha, NE)

To get the mycorrhizal fungi into the soil, the usual technique is to dust your transplants' roots with the fungi in dust form and then plant out as you normally do.

I've read some techniques dealing with drilling a hole in the ground and pouring in, but in your type of soil I wouldn't do it. They need somewhere hospitable to live first.

And it's not just about micorrhizal fungus, either, nor is it just about fungi. It's about bacteria, and a whole range of insects and arthopods, and about plants, and especially about earthworms!

If I had a lot of compressed, cracked, unworkable clay with big rocks mixed in I would probably do the following. (I do have quite a bit of compressed, sometimes cracked and unworkable clay in one area of the gardens).

1) Plant a taprooted annual cover crop to "drill" holes in my clay. The deeper-rooted the better. I've been thinking about trying to rent a seed drill to help get the seed situated in the compressed clay. (If that will even help).

2) Once it reaches maturity, kill it and mulch it. The roots slowly decompose, leaving holes in the ground for improved drainage & infiltration. The mulch helps support all the types of soil life that are required to improve the structure and composition of your soil.

3) Repeat steps 1-2 as many times as necessary to start to feel the structure of your soil improve, and it will. You can also rotate different types of cover crop.

For the winters I would be sure to have that soil covered with a dense cover crop that will perish over the winter to protect the soil from erosion and shelter soil life.

When I was preparing the soil in my hoophouse (it had originally been bad sod and weeds) I did three successions of buckwheat, mainly because it was a warm weather crop that I could grow quickly during summer in the hoophouse.

Peaceful Valley had a really good matrix for choosing cover crops for different goals, but I can't find it online at the moment. I've got soils homework to finish now, but once I'm all done I'll either find an electronic copy or upload a scan.

    Bookmark   February 8, 2012 at 12:06PM
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ralleia makes some excellent points, to which I would only add this - mixed cover crops, such as a blend of radish, clover, and alfalfa, will have a much faster beneficial effect on improving the tilth of clay soils. Successive cover crops, incorporated by mowing and leaving the residue as a mulch, will accelerate the biotic activity in the upper soil layers. A final shallow tillage will be all that is needed to easily start your crops in highly productive soils.

    Bookmark   February 8, 2012 at 1:34PM
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tropical_thought(San Francisco)

I have never done hugelkultur but since I use a wood mulch instead of a lawn, and it's microbark I get a lot of mushroom growing. I can see the white lines of the fungal bodies if I start to dig in the areas in which I have wood clips as mulch. However on the downside wood ties up the nitrogen and some people don't think plants are as healthy when placed in a wood mulch to keep weeds down. But, the nitrogen is only tied up briefly then it is returned. If you listen to a radio show called "you bet your garden" the host only uses peat moss and no wood. So, each expert has thier own opinion.

I think what people are talking about are extra fancy things you can do with your soil once you have your basic soil composition worked out to your satisfaction. There is no magic bullet to make a bad soil perfect other then time and work and OM. Some people just look at clay and give up. It is a lot of work and digging. Eucalyptus wood has oils that impede the growth of other plants. Foreign woods that one bring to thier garden may host diseases. Someone here on this forum mulched with some wood that made all his trees die.

Some people don't even like to add organic matter to clay. There is a case for this position also and a thread about it called The Myth of Soil Amendments. The theory is it is a bad to add OM to clay for trees. I think OM it would be ok for small little plants like pansies in clay. But, since I never tired it out, I don't really know. I have a cut down stump from a tree that I am letting decay slowly. It does seem to help the nearby soil a bit. Is wood good for clay? This would be the question to ask and have answered before trying hugelkultur.

    Bookmark   February 8, 2012 at 3:26PM
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ralleia(z5 Omaha, NE)

This youtube video shows a mixed cover crop field of "groundhog" radish, chickling vetch (nitrogen fixer), and Austrian winter peas (nitrogen fixer) similar to what Bill is suggesting. It shows some of the difference in soil compaction that can result from using cover crops.

Radish +vetch & peas cover crop result

I found the Peaceful Valley Cover Crop chart, but on closer inspection it doesn't speak very well to drilling holes in heavy clay. It's a decent resource for a lot of other cover crop applications though: PVFS cover crop matrix

Take a look-see at this marketing document on "Tillage Radish." Tillage Radish doc with great photos

Take it with a big grain of salt of course, since it *is* designed for marketing, but it has some excellent photographs explaining the concepts of why some of us with compacted soil might want to use taprooted plants to drill into heavy soils.

I've never tried tillage radish, but in my compacted clay soils, taprooted perennial weeds like curly dock, dandelion, and common mallow flourish. I've been trying to beat them back for years, but since I've not replaced them with anything taprooted to do the soil work, I think that my soil structure is deteriorating. The tomatoes didn't do well at all last year. So this year I'm going to obtain some form of freeze-killed radish cover crop to start regular planting in that area.

    Bookmark   February 8, 2012 at 3:33PM
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ralleia(z5 Omaha, NE)

Oops. Got carried away with quotation marks on the radish document link.

I'll let gardenweb handle it:

Here is a link that might be useful: Tillage Radish

    Bookmark   February 8, 2012 at 3:37PM
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ssmdgardeber, good to here from you again.
Have you tried trench composting?

    Bookmark   February 8, 2012 at 7:30PM
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Hi Jolj, it's just so darn hard to dig in this clay to do trench composting. I think it took me 3 hours to plant about 15-20 bulbs. They were muscari bulbs, only needed to be a few inches deep, but I had to dig out all the hardpan and all the rocks and amend the soil a few more inches. It was exhausting.

And the squirrels/cats LOVE the amended beds, because it's less work for them. :/ I can imagine they'll have a field day if I buried anything worth composting.

I don't have it in me to dig in this dirt anymore, unless I do some sheet mulching first to soften the clay. Whew, I'm tired just thinking about it.

    Bookmark   February 8, 2012 at 9:10PM
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ralleia(z5 Omaha, NE)

ssmdgardener--let the radishes and the earthworms do all your digging for you!

A human can be pretty strong, but compared to a thousands of radishes and a million earthworms? Psaw. We're puny.

Let the plants and the critters soften and work your soil for you. Become the benevolent master of your own little kingdom of millions of busy organisms. :)

That's my plan for the acre and a half of compressed clay that I have. It's slippery and sticky when wet--cracked and cement-like when dry. My hands and wrists have chronic overuse injury from swinging a mattock too many months. Now I'm going to enlist help.

    Bookmark   February 8, 2012 at 9:45PM
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wayne_5 zone 6a Central Indiana

That is quite a download on tillage radishes. I was going to link the video by Steve Groff also, but it may have been removed.
I liked the larger size I got from some planted about August 1st, but that isn't always feasible with many crops.

    Bookmark   February 8, 2012 at 10:06PM
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Hi ssmdgardener,
You have a lot of good info here, and instead of repeating all of the normal disclaimers... lets just say they all still apply ;-)

Anyway... FWIW and YMMV :-) This is what I did, and it really works for me....Yada Yada Yada !

As you have said "Hand Digging in Clay sucks" (I paraphrased your remarks ;-)

For a couple hundred bucks you could rent an excavator and add enough Decomposed Granite to comprise 35% of your Medium, Pumice 20% Finished Compost 20% Clay 25%

Decomposed granite is a rock powder and is an excellent amendment for clay soils. All rock powders are great sources of minerals and micronutrients. All growing soils need them. As the microbes and macrobes like earthworms, digest the insoluble minerals, they break down into the various soluble micronutrients that all forms of plants need.

For example, limestone rocks are rich in calcium. Granite rocks are rich in potassium, etc. Seaweeds of course are the king of micronutrient fertilizers and soil amendments. There can be up to 70+ trace elements in seaweed. In locations where seaweed is not readily available; rock powders is one answer to the problem.

Research continues to reveal that insoluble tiny particles like rock powder minerals, can be easily digested or absorbed via microbial activity, over time, into the anatomy of growing plants, thriving in the presence of rich organic compost, and other forms of powerful biostimulants like aerobic compost teas.

Obviously a heavy clay soil is very difficult to initially dig, whereas a sandy loam is much easier. Heavy clay soils can be improved considerably by adding a lot of mason's sand. DO NOT use beach or river sand! Mason's sand, being crushed granite, has sharp edges and actually loosens the soil.

One of the least understood aspects of gardening is that of capillary action of the garden soil. It is a proven fact that compressed earth has a better capillary action than undisturbed soil. That is why gardening books tell you never to walk between rows in a regular garden, as that encourages weed growth. And of course people are told never to step in a French Intensive bed and thus compress the soil.
But the capillary action is absolutely necessary to bring water up to the roots of growing plants to promote good and deep root growth. In regular garden rows, it is easy to roll a heavy 2 or 3 inch wide weighted wheel (mounted on an axle and handle) down the row directly over the freshly planted seeds, which will then promote deep root growth along that line. The spaces between the rows are than rototilled to eliminate footprints prior to the initial watering.
The basic concept of French Intensive gardening is that raised beds are created which have humus added, and the whole bed is light and fluffy to a depth of two feet to promote fantastic root growth. The beds are typically 4 feet wide and 12 or more feet long, with 3 foot paths between the beds.

Here is a link that might be useful: How to build a raised bed that will last forever.

    Bookmark   February 9, 2012 at 12:27AM
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Wow John, that's pretty incredible. Now I'm craving a salad in the middle of the night. I'm assuming builders sand, mason's sand, and crushed granite refer to the same/similar things? I just have a small back yard and couldn't justify renting a tool to excavate, even though I b!t@# about hand-digging. ;-)

ralleia, thanks for the pdf link. I already sheet mulched most of the areas that will be turned into perennial beds, but there is one last area, about 10x3, that still need to be prepped for next year. However, it's very shady. Would the radishes still work? Also, this area will be for perennials, not food crops. Would the radishes still be cost effective, compared to sheet mulching, which is pretty much free?

Last year, I tried planting seeds of clay-friendly natives that are supposed to break up the soil, but they had incredibly shallow roots in the unamended clay. Those pictures of those radishes were pretty awesome.

I haven't even started on the raised beds, but I'll just be placing cardboard on top of the grass and filling it with the soil mix, which I'm working on...

    Bookmark   February 9, 2012 at 5:30AM
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Cornell, the University of Wisconsin, and several others will tell you that you should not add sand to clay unless you can add 75 percent sand to that clay. Purdue, Michigan State, North Carolina State, and several others will tell you that you need to add 45 percent sand to clay. Anything much less then 45 percent can create more problems than that would solve.
Tropical, loam is one type of soil. It is about 45 percent san, 25 percent silt, 25 percent clay and 5 percent organic matter. The only really changeable part of that is the organic matter which is digested by the Soil Food Web to feed the plants growing in that soil. Plants can grow in soils lacking organic matter but most will not grow very well. Without sufficient amounts of organic matter in soil the Soil Food Web, including mycorrhizal fungi, will not function well. Dumping some "stuff" that contains fungi into soils lacking sufficient levels of organic matter will,largely, be a waste of money since those fungi, that need some organic matter to live on, will not have a nutrient source to pass on to the plants they extablish that symbiotic relationship with.
The "perfect" garden soil is the one that your plants grow srong and healthy in.

    Bookmark   February 9, 2012 at 7:44AM
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tropical_thought(San Francisco)

kimmsr is right about everything he said. I just wanted to add, I think the perfect soil is one that is easy to weed. When I was first starting out I had hard packed fine grained sand. It was not possible to weed it. If you pulled the weed the top part would break off and the root would stay in. It was too hard to use a tool to dig out the root and there were too many weeds. I got hand pain from weeding. Now that I have lots of OM, I can pull a weed and it will come right up with the root provided it has not be allowed to mature. My soil no longer has tons of weeds seeds because I got right on top of each weed and removed it before it went to seed. I used to hate weeding before I solved this problem. I let it go on for years with weeds making seeds. Now all I do is take a daily quick look to remove any new weeds, it takes less then 5 minutes.

    Bookmark   February 9, 2012 at 12:39PM
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I am not in full agreement regarding the practicality or advisability of the addition of sand to clay. In bordered raised beds, or in gardens of limited size, it is not unreasonable to amend clays with sufficient sand of the proper consistency. It is when one begins contemplating large areas that the physical and financial obstacles become prohibitive and impractical. In a series of raised beds, incorporating coarse crushed granite to clay-based mother soils is unlikely to cause any harm, and would, over time, have a noticeable effect on tilth and drainage and compaction without being too onerous a task.

    Bookmark   February 9, 2012 at 1:29PM
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wayne_5 zone 6a Central Indiana

Good point about capillary action. I am not afraid to walk some on good amended soil as it does not really compact....bad soils, not so much.

Kimm, I think you should amend your recommendation on adding sand. It should read: Add sand until it reaches 45% sand content, not add 45% any loamish soil already has some sand in it. I would not want that 75% either that you mentioned.

    Bookmark   February 9, 2012 at 1:31PM
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My friends succulents are planted in stones and sands then he feed with compost teas here and there. The rest of his garden is in soil that is clay/rich matter.

    Bookmark   February 9, 2012 at 1:37PM
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Hi ssmdgardener,
KIMM's % is probably fine, but I use 35% Decomposed Granite and 20% Pumice, so that's 55% and my soil is a literal dream, I can simply use my hand (no tool) and dig down to my elbow. previously posted percentages work very well.
With the addition of my awesome compost, I am totally blessed.

    Bookmark   February 9, 2012 at 5:21PM
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Jon, the pictures you post and the purpose of your gardens are truly an inspiration. It would be a privilege to visit and work in your gardens, to observe your practices and to support the work that you do.

    Bookmark   February 9, 2012 at 6:00PM
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That's funny Bill, Because I was thinking about visiting your site. After the clear and concise replies you have made to several posts, I feel I have come to understand a little of what you do......though ( you wrote to one person recently that they will have to "wait and buy the retirement book" . I hate waiting... I want to see now ;-)

    Bookmark   February 9, 2012 at 7:28PM
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tropical_thought(San Francisco)

I looked up Decomposed granite on wikipedia and it seems that it turns into sand clay or silt over time, but it does not say how much or which one it will turn into.

DG, is granitic rock that has weathered to the point that it readily fractures into smaller pieces or chunks of weak rock. Further weathering produces rock that easily crumbles into mixtures of gravel, sand, and silt-sized particles with some clay. Eventually, the gravel-sized particles may break down to produce a mixture of silica sand or silt particles and clay.

    Bookmark   February 9, 2012 at 8:36PM
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wayne_5 zone 6a Central Indiana

Jon, What is the texture of your Decomposed Granite? Is is gritty or fine? Where do you get calcium and magnesium from?

I too like a loose garden soil for most things. I have one part of one wide bed that is sandier than the others. I do not see it as any more productive than the others.

I can only take a rough guess on what my amended beds are....40% sand, 45% clay, and 15% silt for the mineral percentages......20% OM

    Bookmark   February 9, 2012 at 9:55PM
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Hi Wayne,
I watch them scoop it right off of the ground, it is literally mountains (1000' high) and they are sticking in sticks of Dynamite and shearing off 1' wall at a time and then they scoop it up and load it on trucks, because of that, it is every size ...1/8" to dust
PS...I'll go snap a picture...Be back in a minute ;-)

    Bookmark   February 10, 2012 at 11:46AM
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Wayne wrote: Where do you get calcium and magnesium from?
I have no idea !
I've never used any "fertilizer", but I keep hearing that it could really boost my production, so I am contemplating it. The only reason's I hesitate at all is :
1. I am relatively lazy (if it ain't broke,don't fix it...mentality).
2. It is expensive, and since I donate all of my veggies to the Food Bank, I just don't want to spend extra money, on something that I am not convinced will far outweigh the cost of implementing the procedure. I have 1379 square feet of garden beds and donated 9173 lbs last year (not counting what we ate) probably close to 7 lbs per foot , could I really get more by fertilizing... I just don't know... Maybe I will try a bed or two and see if they produce more, I may be pleasantly surprised and it will be worth the extra cash outlay.

PS. The Rock Quarry wasn't open... I'll go back later ;-)

    Bookmark   February 10, 2012 at 12:49PM
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wayne_5 zone 6a Central Indiana

Jon, You are doing a beautiful job there and God bless.
With the Decomposed Granite and Pumice you are getting a lot of micro and macro minerals. I am thinking that granite doesn't have much calcium or magnesium? Pumice might?

    Bookmark   February 10, 2012 at 2:24PM
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tropical_thought(San Francisco)

I am also interested in your Decomposed Granite and Pumice, so post us photos. I may get a little bit to experiment with, but it may be hard to find in san francisco. The only feed store is out in half moon bay.

    Bookmark   February 10, 2012 at 3:04PM
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A mountain of DG (Decomposed Granite)

    Bookmark   February 10, 2012 at 5:21PM
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Processed pumice is today used in horticulture, but unlike a superficially similar material, perlite. But extensive research conducted in Hungary in recent years has demonstrated that it can optimize moisture content in farm land, provide trace elements and boost the immune systems of plants, whilst reducing potentially harmful nitrate levels in the soil. If applied along with an organic nutrient, processed pumice can increase yields significantly compared to chemical fertilizers - and at a lower price.

Agricultural Pumice 3/8" to 1/4"

    Bookmark   February 10, 2012 at 5:46PM
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My area has several defunct granite quarries where people can shovel as much as they want, and screen it to a suitable size. There are also commercial operations that do this. You don't want to pay to have it shipped, it is very heavy.

Wish we had some pumice nearby.

    Bookmark   February 10, 2012 at 10:40PM
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No doubt Bill, It wouldn't pay to ship it,,,Yeah , I count my blessings each and every day, and try not to take it for granted !

    Bookmark   February 10, 2012 at 10:58PM
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Hey ssmd, Boy, its all here. Posts with opinions from everyone.

Observations from my chair - adding sand to clay soils is labor intensive, not necessary and further, by itself doesn't work. Humus, Humus, Humus - Mycorrhizae, Mycorrhizae, Mycorrhizae - soil test, soil test, soil test.

Products - Soil Secrets Terrapro, 94% REAL HUMUS + helper bacteria and mycorrhizae. Protein Crumblies, balanced food for the Terrapro helper bacteria. Liquid Earth Nectar and Earth Ambrosia once a month during the growing season, which gave more humus and biologics. All wild plants (I hate the term weeds) were pulled and dropped creating my own mulch. That has been my program for my 2010 and 2011 start up gardens on two separate locations here in Cochise, Arizona. I put these materials on top on my ph 8.8 and ph 7.3 concrete soils, watered them in, shallow planted and applied a 1" mulch. I did no tillage of any kind and no raised beds! All beds were at ground level. Virtually all of the foods grown had flavor that I can't remember tasting in any of my gardens since 1977. Some were close, but not as good. In 2010 a professional documentary film crew spent a day in the garden and we shot a how to and demonstration film titled, "The Double Victory Garden". You can get it on the web but I decided not to market it myself because it did have some minor errors that I wanted to correct. I am anal about these things.

The 94% humus (confirmed by lab analysis) in Terrapro primes the soil pump providing a powerful negative charged energy field which attracts and holds the positive charged nutrients, Ca, Mg, K. etc. mentioned in the "Soil test - Why do it? and the Humus (OOW) threads". One molecule of "Supramolecular" Humus can attract and hold for plant use over 10,000 water molecules! The negative charge (CEC)of sand(least), silt (more), and clay (most) on the CEC (Cation Exchange Capacity) scale rarely is over 30. Compost generally runs 25 to 75 (if well made) and Supramolecular Humus is up to 250! The compost provides slow steady release plant food and that is its value. It only provides a max of 5% humus, that is what the new research proves. If you doubt this, have your compost tested and I don't mean an organic matter test, I mean a HUMUS test! The more alkaline the soil is, the higher the CEC of the humus - No need to try to change the ph, the humus adjusts to it whatever it is. Humus is the great fixer - It adds body to sandy soils and with Ca and Mg will aggregate and open up heavy clay soils so they can breathe. Universal fix-all! Nature can make ideal soil as mentioned but we have to provide the right inputs. When I started, I had to stand on my soil probe to get in an inch. 3 months into the season I could sink it in over a foot but this was in the beds which had received drip irrigation. A month ago when the soil in the beds was dry, the probe still easily went in over a foot! That impressed me.

Jon, awesome garden! It obviously reflects your dedication and your hard work. I am not a market gardener, I am a researcher, experimenter and grow for the family I live with though I have sold some excess.

Please visit my website, and for the full story. On my site I have a before and after soil analysis for the 2011 garden. You might want to take a look. Blessings to us all.

    Bookmark   February 11, 2012 at 1:12AM
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I know money doesn't grow on trees, but I'd sure like to know what variety of broccoli you're growing.

    Bookmark   February 11, 2012 at 3:13AM
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The "perfect soil structure" ... for what plants? You can kill some plants with the same soil in which others thrive.

So first you need to figure out what kind of dirt you have, then decide what you want to grow, then decide if it's worth the hassle to make the dirt fit the plant.

There are many plants that would grow here based on the temperatures - but they need extremely organic, acidic soils. I have alluvial desert dirt ... lacking organic matter, extremely alkaline, and on the clay side. It would require extreme measures to make the soil "perfect" for them. So I don't. I grow things that prefer my dirt, or that prefer the kind of dirt that is within my reach with limited amounts of fertilizing and amending.

    Bookmark   February 11, 2012 at 6:16AM
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Thanks to everyone for this wonderful learning experience!

Wayne and Jon, it's interesting how your gardens have responded so positively to locally sourced ingredients (Wayne's peat moss and John's pumice and decomposed granite).

Leaf mold, coffee grounds, compost, and pine bark fines are "perfect" organic materials for me, partly because they're so readily available and cheap and/or free. I do wish there was a local source for inorganic materials besides clay. I'm still leaning towards adding coarse builder's sand to the new raised beds, being careful of the right sand/clay mix. I'd love to try those clay busting radishes, but the area that needs it the most gets very little sun.

Thank you all for teaching me about mycorrhizal fungus and humus. I'll be doing experiments this summer using MF and will post the results here!

    Bookmark   February 11, 2012 at 9:33AM
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wayne_5 zone 6a Central Indiana

I don't think that it is the variety of broccoli that Jon raises so much as the soil and such. My late fall crop of broccoli this past fall had heads 11 inches across right down the row...and they were extra delicious...commented on. I like Emerald Crown and Imperial best of the large number of varieties trialed [Stokes Seeds].

ssmd, I added sand to clay loam but also added local sphagnum peat moss at the same time in equal amounts. Both amendments are basically making the texture and structure better and they are very very long lasting. Even though the peat is nearly all OM, I add other OM ....definitely as the peat OM is not a very active OM. I just love the results and the plants do too.

    Bookmark   February 11, 2012 at 3:39PM
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macthayer(z9a NV)

I was in despair of growing anything in this one garden bed. It was lovely, surrounded by retaining walls, nice placement. But nothing grew, and I had a soil test done. Basically I had alkaline sand, with poor nutrients, that was the leftovers from excavating the house. It looked like hardpan. Sure didn't look like it had any clay --- just impossible to dig hardpan. I'm only 5'2", 108 lb, and under no illusion that I was going to dig it out myself. So I hired my landscaping company to take a foot off the top, and then loosen up what was underneath by another 12 inches. I couldn't do raised beds, but by digging down, essentially I created my own form of enclosed bed. I had them stockpile some of the sand, nice coarse stuff. Then I started layering, I worked as much compost into the loose sand as I could. Then I got "planting dirt" which you're supposed to mix 2 parts sand with 1 part planting dirt, but I mixed 3 parts sand to 1 part planting dirt because I had so much else to add. I mixed this up on a BIG tarp, and when that was mixed, added compost, kelp meal, bone meal, blood meal, mineral fertilizer especially for desert gardens, iron supplement (test showed a significant lack of iron in the soil), a bit of epson salts and a bit of phosphate to help with uptake of iron, That was spread out, and more and more mixed until I had about 24" of the stuff, (plus the 12 inches of loosened harpan mixed with compost) with room to add more on top. I'll want to add shredded bark once it's planted, and next year, another layer of compost.

This is my own composition, based on decades of gardening, careful observation, lots of research, a soil test, and abounding hope.

Just want to point out that I was VERY careful about the amounts of additives I put in (bone meal, blood meal, iron supplement, etc. etc.) and never exceeded recommended amounts, and in most cases, actually went under a bit. I can always add fertilizer, but once there, I can't take it out.

The new soil test isn't back yet, but I want to make sure I haven't messed up the pH before I plant anything.

Does anyone think I did good? What would you have done differently?

I have another bed to go, so now is the time to correct me!



    Bookmark   February 18, 2012 at 12:46AM
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art_1(10 CA)

Around here we have two varieties of decomposed granite available - blue and gold. Which is preferred for soil?

    Bookmark   February 18, 2012 at 1:11PM
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Humus produces superior soil structure and its absence or low levels in our soils is the reason why soil structure is so poor. Humus is the universal fixer - it opens up clay soils and gives sandy soils more body so everything doesn't leach down and away. It also provides the strongest negative magnetic energy charge to prime the soil nutrient pump. Getting more humic substances into our soils as rapidly as possible is the answer. I have already mentioned the benefits of well made effective humus products, good soil testing and mycorrhizal fungi. Roughly 98% of the humus in our soils is the result of mycorrhizae, not compost or mulch. As stated before, compost and mulch are food for the soil Food Web so will be consumed and must be periodically re-applied. In decades past I used to wonder where my compost went in only a month or two after applying it heavily to my soil. The answer is that the Soil Food Web ate it all up! Except for some coarse OM, I couldn't find it and my soils didn't get any darker. Bottom line? I wasn't building humus rich topsoil.

Inputs on top are effective and this is how I do it now. Nature has been doing it that way for roughly 450 million years, so why should I try to one-up this marvelous system? With the new humus products I keep referring to, my soil has opened up and gotten good structure in months, not years.

Success for all growers is paramount and is especially so for NEW GROWERS. I feel that they need to have good results from the opening gun so that they don't get discouraged, give up and quit growing.

Many of the suggestions listed above about blending sand with clay, creating various soil mixes, etc. are, from my chair, labor intensive, expensive and not necessary. Work with what you have. By the way, the only reasons that I would make raised beds is for convenience, low poor drainage soils or if a gardener can't get down to the soil level because of poor health. Nature doesn't make raised beds so why should we? I have had excellent success working at natural ground level.

Here is a link that might be useful: The Double Victory Garden

    Bookmark   February 19, 2012 at 5:27AM
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