Clay Soil and Gypsum

Ron Vanderhoff
Sat, 23 Jan 2010 19:59:23 PST
Not sure if this is necessarily a bulb question, but .  .  .
Aaron makes a great point that a physical addition of large quantities of organics to clay soil is far more effective that any "simple fix", such as gypsum, concentrated humic acids, surfactants, etc.

Gypsum is not a miracle, but I do suggest it if the conditions are right and used correctly:
	* Gypsum is only effective on sodic (saline) soils. If the soil is not saline, no effect will likely be seen. A soil test first, would be very useful.
	* Gypsum contains calcium and and sulfur and should not be applied in excess. The 50lbs per 10 sq. ft. is likely to do more damage than good. Agriculturally gypsum (SO4) is applied at a rate of about 300-400 lbs per acre, so Aaron you are way over the suggested application rate.
	* When applied, gypsum should be thoroughly blended with the soil to a reasonable depth. Adding gypsum to the soil surface has little, if any value (although there is lots of debate about this).
	* Gypsum will eventually be washed out of the soil profile. Depending upon the soil structure, amount of water applied, etc. this usually means 6 to 12 months of value, which may be enough for the initial establishment of the plants.
Gypsum is inexpensive. If the soil is saline and the user understands what gypsum can and cannot do, it is a worthwhile consideration in clay soils. As Aaron found out, there is no substitute for lots of composted organic material, way more than most people assume. But even with lots of organic matter added to the soil, you're still not done, at least not for long. The organics will be consumed fairly quickly by the biologicals in the soil and in a short while the soil will return to clay unless organics continue to be added on a regular basis. That's where top mulching becomes essential in a garden. It is through the constant maintenance of a thick organic surface mulch that keeps the soil "alive" and keeps it friable, aerated and prevents it from turning once again to sticky clay. Just maintain an abundance of organic material on the surface of the soil and you'll eventually change the entire soil soil profile - that's natures way.
Ron Vanderhoff in California


From: aaron floden <>
To: Pacific Bulb Society <>
Sent: Sat, January 23, 2010 7:12:50 PM
Subject: Re: [pbs] Clay Soil and Gypsum

 Gypsum never did a thing for the clay I had in Kansas, even when added in large quantities (50lbs/10 sq ft). The only thing that helped was collecting 100+ bags of leaves each fall in addition to what fell naturally in the yard and adding them as mulch after being chopped. After three years of this the soil improved immensely.
 Aaron Floden

--- On Sun, 1/24/10, <> wrote:

Of those of you with clay soil, do you really feel that adding gypsum  
helped your clay?

If so, how much did gypsum did it take to produce a difference?
(I'm asking this because I've seen several references to gypsum NOT  
working as well as gypsum producing miracles.)

Anita Clyburn


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