Gypsum will boost calcium and sulfur levels but will not appreciably change pH (acidity). Limestone, on the other hand, will boost calcium and reduce acidity. A deep sandy soil generally lacks the storage capacity for minerals. This can be improved through the repeated application of organic matter such as manure or compost, or by using cover crops. The organic content of the soil is critical to retain nutrients, otherwise any minerals you add will quickly leach out.
You might try going the opposite way, adding first magnesium and then adding calcium mixed with compost.
The other factor is the lack of organic material in sandy soils that needs to be addressed by adding a lot of organic material.
But really you should start out with a CEC soil test to have some idea of where to move, nutrient-wise. It's not a good idea to add nutrients haphazardly (and I am to blame for this too, so do as I say not as I do!!).
Good luck and test that soil!
The Cover Crops page ( http://edis.ifas.ufl.edu/aa217) from the UF Extension Service lists several plants that work well for green manuring in Florida and sandy soil.
"...Even after 16 yr, the gypsum effects were still clearly visible. Exchangeable Ca and SO4 were higher down the soil profile in the gypsum than in the control treatment. A complementary reduction in exchangeable Al was observed in the gypsum treatment to the 80-cm depth. However, pH was not greatly altered down the profile. This amelioration of the effects of subsoil acidity was reflected in improved crop yields of both corn (29–50%) and alfalfa (≈50%) on the gypsum treatments. Because the gypsum effect is so long-lasting, its use as a subsoil acidity ameliorant becomes highly economic because the initially high cost can be amortized over an extended period of time."
"Highly statistically significant and economically profitable yield responses were obtained for all crops."
I'm very interested in this aspect of gypsum. It's too bad nobody seems to have experiences with it in this regard.
He then goes on to describe adding limestone to raise Ph, clay to counter the sandy soil, greensand and phosphate rock for minerals, and compost to bring fertility.
When I began gardening on my place in Maine, the soil test showed a Ph of 4.3(very acidic) and a note from the soil scientist warned that the ground did not seem suitable for agriculture. Well, every soil can be made suitable
There is a lot of information on using gypsum in agriculture, and there are examples of its use on sandy soils. But I wonder if those instances ( weathered or depleted agricultural soils, land reclamation, etc) translates well to a virgin tract of pure sand being changed into a working home garden.
Are you looking more at Albrecht's (et al) work on mineraliztion / Ca cation, perhaps? His work may have several aspects that might not match to the needs of 'pure sand' type soil. If you want to pursue that research, you might want to read Steve Solomon's work; he is an active proponent of that practice and has several books and a forum to help with the more extensive soil testing it seems to require.
But it would be pretty easy to set up a small experiment; Divide a patch into 3 or 4 sections, add gypsum to one, compost to another, maybe something like Coleman's approach to a 3rd, and perhaps a Albrechtian approach to a 4th, and a selection of probable crops to each. Note in a journal how seeds germinate, grow, yields, etc. To me, it seems trying 3 or 4 methods in one year and getting good results from one patch would be preferable to putting all the effort into a single one without a solid base of evidence that it will work.
And I'd note that Coleman, who has a fair amount of gardening experience, started out with a soil test. I'd augment that by spending some time reading what the local Uni or county extension service and/or Master Gardeners advices about local conditions.
This might also be of interest:
Likewise, applying gypsum won’t help if the crop doesn’t have enough nitrogen,
added UW-Madison emeritus extension soil scientist Richard Wolkowski.
In research plots at Arlington, WI, his group found that grain yield
didn’t respond to the sulfur in FGD gypsum until adequate nitrogen was
provided. In fact, gypsum actually lowered yields when nitrogen was
applied at sub-optimal rates.
And that article is largely 'pro-gypsum'.
Bryan Jasons wrote:I'm wondering if an area of pure sand next to my field would benefit from gypsum. Most people talk about gypsum for clay soil, sodic soil, mineral deficient soil etc. but what about acidic sand? This soil is very deep, I dug down 3-4 feet and it only changed from brown sand to tan sand. Isn't this an advantage in that the roots can grow deeper than in a typical soil? This is where the gypsum comes in; studies show it can get into subsoils and alleviate Al toxicity, allowing roots to grow deeper and yields to increase. I'm hoping for a fertility boost, as the soil definitely needs one. I've never met or heard from anyone who has tried this though.
How do we know that anything added will be leached in a sandy soil? Isn't calcium relatively insoluble? Wouldn't dealing with sub soil problems require some leaching? Is a high CEC bad is this context? How do we know it's harmful to oceans or watersheds? Maybe there is clay in the subsoil, who knows.. There are clearly conflicting claims out there, even just regarding Al specifically :
"Gypsum can increase leaching of aluminum, which can detoxify soils but also contaminates
"The application of gypsum or lime + gypsum lowered the levels of exchangeable Al; also, the low proportion of Al in outflow solutions suggests the immobilization of Al as a solid phase. Except for exchangeable Al, the gypsum amendment increases the proportion of all forms of Al extracted (bound to organic matter, sorbed to, oxalate and citrate) with various selected reagents relative to unamended samples. The amount of Al extracted increases with increase of gypsum added. The gypsum or lime + gypsum amendments increased soil productivity."
Also, the importance of being holistic and thorough - like Coleman or Soloman are - isn't lost on me. But I never planned on using this area for vegetables; I was thinking cover crops, sweet potatoes, millet or some other easy to grow crop that I have experience with. I already have vegetables gardens with mulch and cover crops being used in other places.
Bryan Jasons wrote:Do we know that gypsum when added will do nothing useful in sandy soil?
Bryan Jasons wrote:How do we know that anything added will be leached in a sandy soil?
I think the literature (both science and general garden info) has pretty well established that sandy soils don't hold minerals, water, fertilizer well. That's the domain of humus. And the literature is pretty clear that water is the medium which allows the cations to work with the bacteria and roots. (http://extension.psu.edu/business/start-farming/soils-and-soil-management/soil-quality-introduction-to-soils-fact-sheet-1) is a pretty good overview; FAO's The importance of soil organic matter:Key to drought-resistant soil and sustained food production (http://www.fao.org/docrep/009/a0100e/a0100e00.htm) is another resource and it goes into more detail. I'm sure others could bring other resources they've found worthy.
Clay particles are much smaller than sand. They significantly increase the available surface area for nutrients to hang onto and create micropores to slow down the flow of water. Both are good things; at least until there is too much..... But that is another topic.
Bryan Jasons wrote:Also, the importance of being holistic and thorough - like Coleman or Soloman are - isn't lost on me. But I never planned on using this area for vegetables; I was thinking cover crops, sweet potatoes, millet or some other easy to grow crop that I have experience with. I already have vegetables gardens with mulch and cover crops being used in other places.
Even a cover crop needs organic material in the soil. An advantage of cover-cropping is it is generating green manure, but it needs some nutrients to grow. And we seem to back to how much fertilizer will be available to the roots. Success by light and frequent amendments of organic material and equally light and possibly more frequent watering to have a crop that can be turned under might work.
In any case, knowing where whatever amendments we put into soil ultimately goes is a good thing. Saves $$$, saves water, saves time and effort, being aware of water and soil / subsoil ecology are important.
At this point, it might be best to ask if a $20 home garden soil kit test has been run? Or an Albrechtian lab soil test? What sort of fertilizer / mineralization / Cation level amendments have been recommended? Is there evidence that Al levels need to be addressed?