No matter how much sodium one puts into a sand rootzone, the soil structure cannot be affected, so gypsum won't be required
I received this question about leaching salts from the rootzone:
"I remember talking to you once before regarding flushing excess salts from the root zone and the application of gypsum or other calcium products before the flush and you telling me it was not necessary. I have since discovered that same conclusion for myself. I remember you sent me an article or a link to one of your blogs but I can't seem to find the email or article. Could you please send it to me again?"
I wrote back:
I don't recall that I've written anything specifically about that. I have written about Ca not being required in sand rootzones for the purposes of dealing with sodicity issues, because no matter how much sodium one puts into a sand rootzone, the soil structure cannot be affected, so gypsum won't be required. Relevant blog post:
Also, this: water and soil handout.
I have made a note to write a blog post [and here it is] about leaching salt from sand rootzones and Ca not being required. I'll do that sometime.
Real quick, water problems are divided into 3 main categories, and each has a different solution.
Salinity -- this is the total salt. The solution to salinity problems is to add extra water to leach the salts below the rootzone. No Ca is required for this. The water does the leaching.
Sodicity -- this is a soil structural problem that occurs in soils when the sodium gets too high. It is defined as exchangeable sodium percentage > 15%. This is irrelevant in sand rootzones because the sodium does not cause any structural problems in sand. This is a problem in clay soils. The solution to this problem is to add gypsum. The Ca in the gypsum then replaces some of the sodium and restores the soil structure.
Saline-Sodic -- in this case, the sodicity occurs and is combined with high total salts. Also irrelevant in sand rootzones because of reason mentioned above. The solution to this problem is to add gypsum, to restore soil structure, and then to add extra water to leach the salts.