Add gypsum to break up heavy clay??

I've been reading a couple of gardening/landscaping/horticultural books written for the texas gulf coast area (& coastal south), and naturally, our compacted clay soil ("black gumbo" here in Houston) is frequently discussed. Agricultural gypsum was listed as a way to help break down some of the soil's toughness. I did a forum search for "gypsum" here on DG, and noticed that there are some different views about the efficacy of this stuff... We just moved into this house a few months ago, so I'm starting my garden from scratch (fyi) - here's what I've got, if it gives you a better frame of reference:

• hard, black clay - practically solid clay - soil... there's not really any layers of loam, sand, or much else for that matter - just grass, fallen pine needles/leaves, then clay!
• Coop extension soil test came back with 6.0 pH (located in a pine wooded area)
• Only nutrient shown significantly lacking is KO2 [potassium oxide, or something like that?] (N, Mg, P levels are fine)

I don't expect that the gypsum would be a solution to my soil problems, but would it at least make the ground easier for me to work with? My back needs a break!

For flower beds, incorporate compost (about 15-20% by volume) to loosen soil. Mix it into the top 6-8".

For lawn areas, core aerating seems to help in clay soil. If you are redoing your lawn now, then maybe gypsum will help, but it requires sodium to be high in your soil for it to work. It also require you to mix it thoroughly in large quantities into the top soil profile. E.g. topdressing a lawn with a small amount of gypsum wont work. Mixing it well into the soil at time of planting may.

Lack of potassium is not uncommon in clay soils. When planting, use some sulfate of potash (0-0-60) in the planting hole.

For lawns, use the so-called "winterizers" to fertilize your soil (they will have numbers such as 29-3-14 as opposed to 29-3-4). The last number of the 3 is potassium and a relatively high number (compared to the 3 others) indiciate that there is relatively high amounts of potassium in the bag. "Winterizers" is formulated with high levels of potassium based on old belief that it was especially useful in winter (now it is known that it should be used regularily through the growing season). Therefore, you can buy so-called "Winterizer" lawn fertilizers and use them on regular basis as they have elevated levels of potassium.

FYI - potassium is one of the elements which is flushed through the root zone fastest, which is why it is often deficient in soils.

Concise and helpful, Kdj. I would add a "topdress" comment to start adding organic matter to areas that will be worked more in the future.

I'm in one of those desert clays that is pretty rich in Potassium.
K, James

If you've got the time, do some lasagna gardening on top of the clay and let it sit and make sure you include coffee grinds (go by Starbucks, they are very generous). The coffee grinds attract the earth worms which will help aerate your soil without you needing to be involved. I've also heard that corrugated cardboard attracts earthworms too so if you have weeds in your clay, just lay some corrugated cardboard down on top and then add your grass clippings, shredded paper and leaves and kitchen scraps. Top off with a relatiively thin layer of clay and mulch it with the coffee grinds. Let it sit for 6 months or so. You can keep adding the coffee grinds as a mulch on top to keep weeds to a minimum. I find the dark brown of the coffee grinds makes a rather attractive appearance even if it is bare. Bet you will be able to dig much more easily after 6 months. Keep it watered in the mean time. (6 months is just a guess, maybe more or less...)

My montana clay gets 1 part clay to 3 to 5 parts compost to make it work. Not the other way. Then the worms go up and down and make it happen. If you soil tests low in potassium and it is acidic you can use wood ash. Not too much but high in potassium.

Thanks for the helpful advice all!

I will topdress with copious amounts of compost/organic matter right now - I don't own a tiller, so I'll have to go rent one, have a free weekend to work the ground, etc., etc... I might just try that coffee grinds thing too - I drink it like a fiend, I'm afraid, so no shortage of grinds here!

Kelly

Kelly,

We gardened in Fort Worth from 1963 to 1983. Our builder hauled in black gumbo to cover our otherwise native caliche lot. Black gumbo on top of caliche is not a good combination, because it made the black gumbo very alkaline.

I used a lot of a local product called "Sulfa-Soil" (a combination of iron sulfide with some other trace elements) and a lot of gypsum and a lot of triple superphosphate (that stuff was practically dripping with sulfuric acid).

Over a period of a few years I had over 20 loads (6-yard and 7-yard loads) of sand delivered. That sounds like a lot, but it raised the lot only a few inches, more in the back garden area than in the front lawn area.

I built compost piles and recycled all of our lawn clippings, of which there were a lot. You could see our Bermuda grass and St. Augustine grow in the hot Texas sun. And watch our water meter spin. I didn't use herbicides or insecticides on the lawn to make the clippings safer for use in our vegetable garden.

Early on I purchased a Merry Tiller and used it frequently to mix soil amendments into the soil. I got the biggest Merry Tiller available (it was called the "Exporter" model back then) and its mid-tined design let it till very, very deep, eventually over 16 inches deep with its tines completely submerged and its Briggs & Stratton engine down near the soil surface. It was continually making the topsoil layer deeper and chipping away at the caliche subsoil layer, converting it to topsoil.

Its unstoppable high-torque tines pulled out tons of caliche rocks that I eventually incorporated in a long concrete retaining wall. The limestone in the caliche was already pretty rotten and my acidification program made it even more so, so my Merry Tiller could really rip it apart with its triple-reduction transmission and very high torque tines. It was common to see a piece of caliche that the tiller had cut cleanly through.

I had the standard slasher tines that came with the tiller and I subsequently purchased optional pick tines, self-sharpening bolo tines, finger tines, and aerator tines. I used the aerator tines to "till" the lawn while we were still using it. With repeated use, the aerator tines did a decent job of mixing the top sand layer into the black gumbo while letting the grass grow and be mowed and giving us full use of the lawn. The aerator tines only went about 3 inches deep into the lawn soil, but we also got considerable help from a bountiful crop of earthworms.

That big Merry Tiller was probably the best purchase I ever made. I used it several times a year and with its help (and the sand truck drivers) my original black gumbo and caliche garden became a luscious deep, dark sandy loam that let you skip the trowel and just dig with your hand. You could see the garden grow in the Texas heat and I had Silver Queen corn 10 feet tall (counting the tassels) with ears like firewood logs. That was Texas corn. I couldn't come close to that here in Maine.

MM

Well done MM! I is good to see someone hard at work to make the garden happy. I know because my garden is happy doing much of the same thing. One thing though how do you make you tiller "merry" mine is just mean and aggressive. LOL

Soferdig,

I named my tiller "Tillie" and gave it lots of tender loving care. I later lost that tiller and all of its accessories in the "Great Flood of 93" in the St. Louis area, but here in Maine I purchased a replacement Merry Tiller. It's very similar to my original and it "inherited" the name of Tillie. It's also good at dealing with our rocky soil here in Maine. The attached picture shows it with a homemade dozer blade that I was using to help level our garden. You know its "merry" because it says that right on it. (grin)

MM

Does it leap ahead when it hits rocks? I always see tillers in perfectly tilled soil. When I till I'm jumping from one log, rock, or bedrock to the other. I have a rear tined tiller. Troy bilt. And it is a good thing it has a dead man's bar to stop it because it will leap 5' down a hill. You in Maine should have similar problems.

Both lime and gypsum can chemically aggregate soil and help improve it's structure. I remember having a discussion with my soils instructor in college. Some golf course superintendents apply the technology too.

But, organic matter can accomplish the process too, because it supplies polysaccharides and glomalin which improve soil condition and structure.

You could also use a small amount of lime / gypsum with organic matter.

Compost / mulch is the common means for me when cultivating.

I prefer lime to aggregate soil when it's a lawn situation where the grass is remaining in place.

Tracy DiSabato-Aust in The Well-Tended Perennial Garden" says that gypsum only helps the type of soil in certain types of west coast gardens that have a lot of clay (see page 34). Does anyone know if that is true, and if so, why?

Soferdig,

"Does it leap ahead when it hits rocks? I always see tillers in perfectly tilled soil. When I till I'm jumping from one log, rock, or bedrock to the other. I have a rear tined tiller. Troy bilt."

That's the problem with rear-tined tillers. They have very fast tine speeds, in the range from 200 rpm to 300 rpm. They're bound to leap ahead or worse when they encounter a rock. The high tine speed doesn't give the rock a chance to move. The triple-reduction transmission and dual V-belt clutch on my Merry Tiller give me a very controllable slow tine speed in the range of 40 to 60 rpm and very high, nearly unstoppable, tine torque.

I encounter a lot of rocks, and my Merry Tiller simply picks most of them up and rolls them out onto the surface, where I can pick them up. It has rolled out some surprisingly large rocks. The smaller rocks I put in a "rock bucket" to empty in a rock disposal area later. For big rocks that won't fit in the bucket, I move them to a temporary spot, to be carried to the rock pile after I finish the tilling job. Rocks one inch or smaller remain as a part of the soil, since they don't cause a problem.

For really large rocks or submerged boulders, my Merry Tiller just "finds" them and scratches on them, a little bit like a dog scratching on a door. When that occurs, I shut off my tiller and dig the rock out by hand using a spading fork, a railroad pick, and a big iron pry bar. I have dug out rocks that weighed over a hundred pounds that way.

So, when my tiller encounters a rock, it normally doesn't jump at all. It usually just rocks from side to side as it pulls the rock out onto the surface. I have learned to hold the handles loosely to allow the rocking motion and not try to "fight" it. The more I till, the fewer rocks I have to deal with. I have dug out tons of rocks with my tiller. If I had been using a rear-tined tiller, I would have broken it, or myself, several times over. But I actually encounter more rocks than I would with a rear-tined tiller, because I am tilling at least twice as deep.

My Merry Tiller's dual V-belt clutch is also a big help. When I suspect that the going will be "rough" in an area, I can hold a little less pressure on the clutch lever so that it will slip rather than kill the engine if it encounters something pretty immovable. Slipping the clutch is a good way to make things more controllable. If need be, I can control each individual plunge of the tines. That comes in handy when I let the tiller "climb" up onto the concrete floor of the garage from the gravel driveway. I slip the clutch to move the tines very slowly, a quarter turn at a time.

Since the tines move so deliberately, the tiller never throws dirt, even at a high throttle, so there is no dirt shield, or need for it, and I have a full unobstructed view of the tilling zone. I have saved the life of many a toad, baby snake, and such by quickly stopping the already slowly moving tines. A full view of the tilling zone has also let me find a lot of things that were unearthed before they got reburied by the tines.

The slow tine speed is also much less hazardous to the earthworms. Occasionally one might get cut in two, but the high tine speed of a rear-tined tiller tends to make mince meat of them. The tiller is gently blending the soil, not "puréeing" it. That leaves the soil crumb structure in good shape. I really like the slow tine speed, high torque, fully visible and controllable way of tilling.

MM

Sounds good MM. All I need to do is to get a smaller pulley and slow down the tines. I had a front mount and all the rocks got stuck at the top of the tines between the motor and tine. That is why I got a rear tine. I had to use a breaker bar to get them out. It was a pain. So "merry" doesn't do that? I like the earthworm thought cause with my slower tiller I had little worm dammage and with the rear tine it is awfull. Whole families shredded beyound reconition. I have a hard time placing them together in graves. LOL

Soferdig,

"I had a front mount and all the rocks got stuck at the top of the tines between the motor and tine. That is why I got a rear tine. I had to use a breaker bar to get them out. It was a pain. So "merry" doesn't do that?"

Once in a blue moon a rock just happens to wedge between a tine and the transmission case. That usually kills the engine unless I happen to have the twin V-belt clutch slipping. It happens very seldom and when it does I merely raise the handle bars a little to release the rock. Usually it is a fairly small rock with an elongated shape.

So the occasional rock hangups aren't a problem. The Merry Tiller transmission case has a very slim design to let it "cut" through the soil.

MM

Good machine with good engineering. Mine didn't have an engineer. Every rock over 2" in diameter would lodge in the same space you describe. Next time a merry tiller. Not a rear tine toro.

Devon, I have used gypsum to loosen clay soil with some success. Sometimes I think adding anything will help. I happened to read something Thomas Jefferson wrote about its use in Virginia. I had a bunch of sheetrock dust and scraps and tried it next to my bro's house. It sure didn't hurt anything. I dig up the rotting leaves all my neighbors dump in the woods near our houses, and mix that in. I'm through remodeling for now

Claypa: I agree that gypsum seems to help -- that's why I didn't understand DiSabato-Aust's comments that it wouldn't help "Eastern" clay.

This is why DiSabato-Aust's visage will never appear on U.S. currency! (typo)

This message was edited Jul 21, 2006 12:37 PM