Why do you recommend gypsum when I have high sodium in my soils?

Gypsum (CaSO4) is considered both a soil amendment and a source of plant nutrients.

When soils have been exposed to too much sodium (usually from irrigation water containing high sodium ), two concerns arise. One is that sodium on the exchange sites of clays and organic matter tends to make them disperse and the soil becomes impermeable as the clays clog up the pore spaces. This is a very big problem in heavy clays soils, especially black cotton soils found in many parts of Kenya. The second concern with high sodium in the soil is that it reduces the uptake of other nutrients such as calcium and magnesium. Too much uptake of sodium by a plant can cause toxicity problems usually manifest by necrosis (browning) of leaf edges.

An application of gypsum (calcium sulphate) to the soil will increase calcium levels in the soils and therefore flocculates the soil, which improves soil structure, water infiltration and drainage. Gypsum will also help to exclude the uptake of so much sodium by the roots just by the fact that the calcium ions will vastly out-number the sodium ions.

Whereas lime is used to increase the soil pH, gypsum can be added to the soil to supply the needed calcium without altering the soil pH value.