If you’ve ever wondered why and when a farmer may choose to add gypsum to soil, wonder no more.
Gypsum — also known as calcium sulphate — is a source of both calcium and sulphate, and can work as a nutrient source for both of these, except that it’s actually a pretty expensive way to add Ca and S. Where gypsum is likely a fit is in high magnesium soils.
As Peter Johnson, RealAgriculture resident agronomist explains, gypsum is best known for helping to stabilize heavy clay soils IF high levels of magnesium are causing issues.
In areas of Manitoba, and some isolated pockets of other provinces, high magnesium (over 20% saturation) can de-stabilize clay, meaning it doesn’t want to form good structure, which impedes the soil’s ability to dry. When you add calcium, it replaces the magnesium in the clay structure and adds that stability, Johnson explains.
As with all other inputs, if you’re going to try gypsum as a soil stability improver, make sure you leave a test strip (or better yet, block out the field in reps), and always, always, always, start with a current soil test.
Remember that sometimes a positive response in the crop is actually because of the sulphur, but there are less expensive sources of sulphur. Get your soil test done, leave a test plot, and run the numbers.
Listen below for more on this topic from Peter “Wheat Pete” Johnson: