When you struggle with clay soil or sodic (high sodium) soil, gypsum is an effective means of amending and improving the soil. Gypsum (calcium sulphate) is not a fertilizer, but rather it is a soil amendment that will attach to the particles in soil and loosen heavy soil over time. Because gypsum works slowly, expect that you will need to apply it once or twice per year for several years to begin to see the desired effects. With time and repeated applications, your soil will become lighter and will drain more effectively, and plants will be healthier.
Fill the broadcast spreader with an appropriate amount of granular gypsum. If you are spreading gypsum onto soil among existing plants, spread 40 lbs. of gypsum over every 1,000 square feet of soil area. If you are spreading gypsum onto soil to prepare a new planting area, spread between 20 and 30 lbs. of gypsum over every 1,000 square feet of soil area.
Apply the gypsum to the top of the soil using the hand or lawn spreader, applying the proper amount for the size of your area.
Water the soil thoroughly immediately after applying the gypsum. Use a garden hose with a spray attachment or set up a sprinkler to saturate the area. The water will activate the gypsum in the soil. Water until you have added approximately 1 inch of water to the soil area.