Mitigating Soil Acidity with Gypsiferous Amendments.

Enter abstract here

The literature pertaining to the use of gypsum as a soil amendment to overcome subsoil acidity will be reviewed as a prelude to the remaining presentations in the symposium. Basically, gypsum was first used in South Africa for this purpose where it was shown that unlike lime that does not readily move in the soil profile, gypsum being much more soluble moves down in a relatively short time. On arrival in the subsoil, sulfate ions in the gypsum displaces OH- from sesquioxide surfaces that neutralize exchangeable Al³⁺ by the so-called “Self liming effect”. Together with the increased levels of soluble Ca²⁺, this neutralization allows roots to proliferate and access water previously beyond their reach resulting in increased yields. Subsequently a large amount of research was carried out in Brazil on the highly acidic Oxisols and Ultisols common throughout the country resulting in the cultivation of vast areas that were previously highly unproductive. Similar conditions are extant in the southeastern United States where similar responses have been obtained. This strategy has been greatly facilitated by the vast quantities of industrial gypsum materials that have become available at strategic locations making the cost economically attractive.