I am posting in this forum because it seems to have a good number of Master Gardeners. I keep reading a "fact" in various forums cautioning about the use of sand in clay soils because it will turn the soil into cement.

I think this is nonsense. I admit that I have done most of my growing in good black Iowa soil that was measured in feet, not inches. However, the last three years I have turned a homesite( which wouldn't grow crabgrass) that had nasty yellow clay into a productive and pretty yard. I attribute a lot of this success to the use of sand. So far, the only cement I have found is limited to the sidewalk and driveways that I poured.

I have read in the new book, THE WELL TENDED PERENNIAL GARDEN, by Tracy DiSabato-Aust (an excellent read and reference book) that sand is of little value in clay soils because, "Most people are not willing to add that much sand to their soils." She refers to "30% or more by volume". These are the only well reasoned comments that I can find referring to the use of sand in clay soils. Nowhere does she attribute sand to making cement.

I personally use a rule of thumb to strive for an initial clay soil preparation of 1/3 soil, 1/3 sand and 1/3 compost. Excellent results have been achieved with this ratio and it is a delight to cultivate and work this soil even though it is not as black or as deep as the soil on my father's farm.

I say cautions of using sand are BALONEY. However, I also realize that things may be different in other areas of the country. What do you say?

IronBelly

It all depends on the amount of sand used.

Soils are drained and aerated due to the size and number of macro-pore spaces in the soil. Sand particles are large, clay particles are very small. If you put a lot of large sand particles together they will not fit together well and in between will be the macro-pores. If you put a lot of clay particles together they will fit closely and there will be few if any macro-pores.

If you have a clay soil and add only a small percentage of sand, the clay particles will surround the sand and there'll be no increase in macro-pore spaces. If you put in enough sand so that the sand particles begin touching each other, you'll improve the number of macro-pores and improve the structure of the soil.

How much sand do you need? If you had a clay soil with no sand and you wanted to add sand to the point where the texture became a sandy clay, or a sandy loam, you would need to have at least 60 percent of the soil be composed of sand. A loam soil is usually classified as 50 percent sand, 30 percent silt, and 20 percent clay.

A better way of improving a clay soil is through the addition of organic matter. The organic matter binds, or collects, clay particles together into larger aggregates; these aggregates for large size particles that improve soil macro-pore numbers. Calcium and magnesium also bind clay particles together in larger aggregates (the process is called flocculation) and creates more macro-pores. This is the bases for adding lime or gypsum to a clay soil to improve the structure.

So, adding large amounts of sand, 50 percent by volume, will improve the drainage and structure of a clay soil. (Actually how much sand is needed really depends on how much is already there). Adding small amounts will not improve it. Will adding small amounts of sand make it worse? No. But it might disappoint the heck out of you when you were expecting such good results.

Have a nice day. (IronBelly?) Significance?

Bob (in Maryland)

Bob,

Sounds like the old "soil triangle" that I studied about 25 years ago in agronomy class at Iowa State.

Thanks for the knowledgeable response.

IronBelly

Both of you have made some good points. My own personal feeling is that you don't grow plants, you grow healthy soils and you can't keep plants from growing.

When I was a kid, we moved onto a place where the garden (nearly half an acre) was almost pure clay covered with a huge crop of weeds. My Dad mowed off the weeds, and hauled several large loads of manure onto it. All the leaves we raked up from the yard (surrounded by trees) were put on top of the manure. All winter long, we heated with wood and coal, and all ashes were added to the menu of the garden. In the spring, It was all plowed under and disked. We had a good garden that year. Each year we continued with repeats of the leaves and ashes. The third year, I joined 4-H garden project and we had to keep track of the value of the produce. Dad, an excellent carpenter, earned $4000. The value of produce from the garden was over $1000.

I have often added sand to my clay soils, always an improvement. My mother is on pure clay and I am on pure silt, just a little coarser than clay. We continually haul buckets of soild from one place to the other, improving beds in each place.

Pottery clays are different from most ordinary clay, and I think this is where the sand added makes the hard coating.

IronBelly (totally ripped abs??), I think your original post contains the answer along with your question. Two points: As you pointed out in quoting DiSabato, it is the amount of sand one must use--"30% by volume" (or even 50%, according to Bob) would be necessary--while the average person probably goes to K-Mart or Lowe's and figures he's solved the problem with a 50-pound sack or two of play sand spread over his/her whole yard. And then you mention the real clincher: you "strive for... 1/3 soil, 1/3 sand, AND 1/3 COMPOST." (Emphasis mine.) As Bob and Barb both pointed out, and with which I wholeheartedly concur, the addition of organic matter is the deciding factor, the absolute necessary third part of your "soil triangle." I have personally seen the liberal use of mower-chopped leaves do wonders for both clay and sandy soils. Well, anyway, had to add my 2 cents. CK

Hi IronBelly,

This thing of not adding sand to clay has been quoted frequently and seems to be a standard concept. However, when you add lots of humus to the soil at the same time the soil does seems to get better. For example, one end of my garden area had a bunch of leftover sand thrown on it and the rest is heavy clay. I have added lots of humus such as leaves and shreaded plant material over the past four years. The end that had the sand is much softer and doesn't stick together like the end with clay and humus only. So sand does seem to be benefical if used with a lot of humus added. So I have to agree with you. Sand is fine for adding to clay, provided humus is also used.

Edd

Is it safe to say that just as there are many different
soil compositions there are many different clay
compositions? Could it have anything to do with what kind
of clay you are dealing with? The adobe clay of our area
is composed of fine clay particles, quartz and other
minerals. Adobe has great plasticity when moist, but when
dry tillage is impossible. When organic matter and sand
was added to adobe (in the 1/3--1/3--1/3 ratios) and it was
allowed to dry, the bricks for the construction of the
early California Missions became possible. The "recipe"
for adobe bricks is documented and is in our state's
archives. I don't have immediate access to the
information, but I know from personal experience that
adding organic material and sand measuring in quantities
less than tons per 100 square feet creates a conglomerate
worse than abobe clay alone. This doesn't happen when just organic material alone is added. Master gardeners and nursery personnel alike advise against adding sand to adobe, not because if enough added might not work, but because small amounts make things worse. To noticably change the quality of the adobe is totally impractical. To improve adobe using sand and organic matter you would need to raise the level of soil 6-10 FEET! Not something an urban gardener is capable of doing.

What about adding gypsum to clay soils? What does that do?

Steve,
Gypsy, calcium sulfate, improved clay soils through a process called, "flocculation." The problem with clay soils is that the individual clay particles are very small, so small that they fit together closely and there is little room in between the particles for open spaces. Open spaces in soil (called pore spaces) are important for air movement into and out of the soil. In clay soils, the tiny spaces between soil particles is usually filled with water instead of air. Roots need air and don't grow into soil without it.

The calcium in gypsum (the calcium in lime works the same way) attracts the clay particles into groups or aggregates, this is the flocculation process. These groups or aggregates are much larger and more irregular in shape than the individual clay particles, thus they don't fit nicely together, and they create bigger spaces between them. This allows excess water to drain out and air to move in.

The problem with using gypsum, or lime, to improve clay soils is that these materials have to be MIXED with the clay, not just dumped on the surface. Organic matter will also create clay aggregates. This all leads us back to the necessity of working clay soils and incorporating amendments, whether they be lime, gypsum or organic matter. It's the incorporation process (digging up the clay soil) that results in all the work. People are always looking for something to just sprinkle on the surface and make the clay soil better; there ain't no such thing; at least not yet.

By the way, the difference between gypsum and lime is related to changes in soil pH. Lime improves clay soils and raises the soil pH, makes it less acidic. Gypsum improves clay soil but doesn't change the pH.

Bob (in Maryland)

I absolutely agree with Barb and Carol. It is the addition of compost that makes the difference.

Sand will change soil texture but it will do nothing to change soil structure. Therein is where organic matter/compost/humus does the job.

You can add sand to clays but it will only give you something like grainy peanut butter. Sand has no electrical bonding capability, no nutrient holding ability. It is essentially, 'inert'. Just like a carrier on a herbicide is used to carry the active ingredient.

It will help with porosity, air space and thus drainage, but to actually improve the vitality and life of the soil it does nothing.

Fact. I've done it succesfully with some of the worst clay soils known. Clays which totally absorbed all organic matter of all kinds and quantities in one year were rendered essentially permanently workable by adding copious sand. It's back-breaking work and does require a hefty percentage (I wouldn't argue with the one given). And adding lime to such amended soil does NOT create concrete! After I sold that place, though, I swore I'd never buy on clay again. It's not worth it: you can fix the garden and aise shrub beds but what about the lawn and everything else (by the way, your HOUSE is still on clay). No thanks!

Bologna.

Just try applying all that mumbo jumbo to Texas alkaline (8.55PH) clay soils. We can add sharpe sand or poteet sand but not regular sand. But the real key to working our clay is organic material, water, a good mulch layer, and patience. Our clay is extremely expansive and I have actually watched it rise during rare periods of rain. But there is a point of dryness that it actually sheds water and doesn't absorb in. The water beads up. As an aside to this question, some kids in town are building a house from bricks they are making by adding sand to our clay mixing it with cactus juice and drying in our sun. Very nice adobe. It's the same recipe they used to build the missions.

Has anyone use EnviroMax (used to be called SoilMaster RX) for clay soil. Tobby Tobin on Kansas City radio station Saturday morning garden show is always talking about spraying this on clay soils.Suppose to work after 2 applications to loosen up the soil probably about 2 inches deep. Ingrediants are polmaleic anionic terpolymer 34.3%,maleic anhydride sulfonated copolymer 10.8% and inert ingredients 54.9%. It is about $75 a gallon. He says he has treated yards where water drains fast and yard dirt is soft after treating it. He talks about it so much I'm beginning to wonder if has some type of monetary interest in the company. Its by ChemCraft, INC. in Overland Park, Kansas.
I heard is was developed for the carrot industry to loosen up the soil. Is their anything out their cheaper then this stuff?

I know the original post was about adding sand, but then about adding gypsum. Here's the scoop on gypsum....

Here is a link that might be useful: Is Gypsum a Gyp?

Gypsum does not always appear to work on the heavy, locally compacted clay around my home, but when a gypsiferous clay is attacked by a diggin' iron it forms crumbs instead of powder, and does not readily revert to a cloddy or amorphous mass.

Calcium nitrate (15.5-0-0) is also good to use on clays and its aggregating effect is often noticeable at once when a solution is applied.

-Tony

Here is a link that might be useful: Head In the Sand