Soft water (like hard water) poses its own set of problems for garden plants.
Soft water has high salt (sodium chloride) content. While it may be fine for household use, it’s not meant to be used to irrigate your garden (or for any plant irrigation for that matter).
Soft water reduces the amount of soap, detergent, shampoo, or other cleaning agents needed to get things clean. Hard water makes it more difficult (or harder, if you’ll pardon the pun) to get things clean. Hard water will build scale on the inside of water pipes, and coats the heating element in your water heater, reducing efficiency and increasing the cost of hot water.
Soft water, however poses its own set of problems. Using soft water in overhead sprinklers can wash away calcium and magnesium carbonates, it replaces them with sodium salts that can retard plant growth and even kill lawns.
As with hard water, rainfall can dilute and wash accumulated salts from the soil. But in the arid and desert southwest, where rainfall is sparse, this process has a negligible effect on soils.
One way to help solve this problem is to either dilute the soft water with harvested rainwater or alternate rainwater and soft water when irrigating.
Ornamentals, fruits and vegetable plants are generally more susceptible to slats in soft water than lawn grass.
