For a typical plot size of 600 sq. ft., about 25 lbs. of gypsum per growing season is sufficient. Double this amount if you have high levels of salt in your soil. Gypsum needs to be mixed well into the soil to avoid clumping when wet. Granular form is usually easier to apply but is costlier. Gypsum (calcium sulfate) contains sulfur and breathing the dust may injure lungs. It is strongly recommended to wear a mask and gloves when applying.