Really want to know why gypsum doesn’t work here? In arid parts of the country, sodium occupies many of the cation exchange sites in the soil. And since it is only a +1 charge, soil colloids tend to disperse and can be easily compacted together causing a poor soil structure. Adding gypsum (CaSO4) allows the Ca++ to release and replace the soil-bound Na+. The released Na+ is leached out as Na2SO4, and the soil tends to granulate due to flocculation (fluffing up and colloidally glued together on the microscopic level) with more Ca++ on the exchange sites. This granulated condition improves soil structure, and soil is then less prone to compaction. Since there is far more calcium than sodium on exchange sites in our Louisiana soils, adding calcium via gypsum has little or no effect on most of our soils.
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