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What does liquid gypsum do?

By Joe, Founder of Dr Forest · June 2026

What does liquid gypsum do?

Liquid gypsum does two jobs. It supplies calcium and sulphur, two nutrients plants need, without changing soil pH the way lime does. And on clay that disperses and caps, the calcium helps soil particles clump together, which improves surface drainage and reduces crusting.

Calcium is a building block for plant cell walls, and a steady supply matters most to fast-fruiting crops such as tomatoes, peppers and apples. Sulphur is needed for proteins and for the flavour compounds in alliums and brassicas, and many gardens are shorter of it than they used to be. Because gypsum carries both in a plant-available form and does not move pH, you can use it on a soil that is already at the right pH without nudging it more alkaline.

The structural side is where honesty matters. Gypsum can improve the structure of clay, but the evidence for that is strongest on sodic or dispersive clay, the sort that slumps into a sticky skin and seals over after rain. There the calcium and the extra salts in solution make dispersed clay flocculate, so water soaks in instead of sitting on top. On ordinary, well-behaved clay that does not disperse, that structural change is small, and the dependable benefit is the calcium and sulphur it feeds.