Hard water is more difficult for plants to absorb and break down than soft water. It tends to bind up soil nutrients, making it more difficult for plants to absorb what they need. To try and compensate, farmers will tend to increase their rate of irrigation, which leads to other problems.
As fields are irrigated and water either evaporates or is absorbed into plants and deep into the ground, the soil is left with all the dissolved mineral salts—calcium carbonate, sodium carbonate, various bicarbonates, etc.—carried by the water. In areas where there isn’t a lot of rain to flush out this excess salt, it accumulates, and the salinity of the soil steadily increases. Over time, this hardens the soil. If you’ve ever been out in a dry region and come across hardpan or caliche, this is the end result of soil that’s been exposed to large amounts of hard water over a long period of time. The buildup of salt causes the soil to bind together, becoming cement-like in extreme cases. When soil has become hardened, water and important nutrients can’t reach plant roots. Consequently, crops fail to thrive, become more susceptible to pests and disease, and have lower yields.
Before hard water ever hits the soil of a farmer’s field, it travels through the irrigation system, leaving behind hard water deposits, which eventually reduces the efficiency of water delivery to the plants. Over time, watering zones may become completely blocked, as is often the case with drip irrigation systems. Farmers must deal with this by continually unclogging emitters and other components of their delivery systems. Oftentimes they only realize there’s an issue after plants start to yellow and wither. With plants that are already weakened by reduced soil quality and difficulties with nutrient uptake, they may suffer irreversible damage by the time a grower realizes that a sprinkler or drip system isn’t working properly.