I have soft well water (high sodium), not hard water (high calcium), but the pH is high and the bicarbonates are high. I have not tried magnetic treatment but I have tried citric acid constant feed injection. It works ok to lower pH and bicarbonates, but it takes an awful lot of it to do so in my water and is not particularly cost-effective. There are also concerns about citric acid coming from gmo corn. You might try vinegar as an option, though I hear it takes a lot of that to adjust water too. I deal with high sodium now in my soil because the water is high sodium (now the soil is over 7% base saturation sodium), so I don’t really think a traditional water softener (that adds sodium chloride to soften) is the right approach unless you are in a high rainfall area with very low sodium soils.

Any ag lab will do an irrigation suitability test for water, and give you recommendations appropriate for growing crops (not taking showers or doing laundry which is what most softeners are aimed at).