Effect of Gypsum in Reducing Aluminum Toxicity
Almost 50% of potentially arable lands in the world are faced with the acidification problem. Use of agricultural gypsum in soils with high aluminum concentration, such as the soils in lands under tea cultivation and those near dried up swamps used in agriculture, reduces aluminum toxicity and promotes growth of plant roots.
Al + SO4 AlSO4
This equation shows that toxic aluminum is replaced with aluminum sulfate, an ionic compound that has low toxicity. Moreover, the increase in soil calcium transfers aluminum adsorbed on the surface of clay particles into soil solution. It is noteworthy that gypsum does not have a very noticeable effect in the increase in pH values of acidic soils.
Application of gypsum to soils with high magnesium content
Use of gypsum in soils with high magnesium content
Soil-Mg + Ca2+ Soil-Ca + Mg2+
At equal concentrations of calcium and magnesium, calcium is more inclined to be adsorbed on clay than magnesium.
Research by scientists has shown that applying gypsum at the rate of 2 t/ha has no effect on magnesium concentrations in surface and deep soil. Consequently, in some soils that are not rich in magnesium, this gypsum application rate has no negative impact on soil magnesium content.
However, in soils with excessive magnesium content, applying gypsum at 20 t/ha reduces soil magnesium content to the desirable level.