Soft water has many benefits indoors, including reducing soap scum, maintaining softer skin and improving the taste of ice cubes, just to name a few. However, the sodium in soft water builds up outdoors and over time causes flaky soil that is unable to retain water. It thereby can starve a lawn that is regularly watered with soft water, especially in areas where rainfall is not reliable. Fortunately, with two applications of gypsum, you can reduce the damage soft water causes and successfully water your grass lawn with it.
Irrigate your lawn the same way you would if you had regular water. Most grasses need about an inch of water a week from spring until fall. Supplement rain with your soft water so it gets a total of 1 inch of water per week. Water in the morning when less water evaporates.
Apply 2.5 lb. of agricultural gypsum (calcium sulphate dihydroxide) for every 100 square feet of lawn. Purchase gypsum at your local nursery or landscaping company. Apply it two times a year--once in the the late spring or early summer and then again in late summer or early fall. Repeat every year as long as you are still using soft water to irrigate your grass.
Water the area with about 1 to 2 inches of water afterward to water in the gypsum. Continue to water your lawn as normal to dissolve the gypsum, which takes approximately a month to counteract the sodium buildup and restore the soil.