How many gallons a day? How many plants etc? I got 2 x 400gpd RO filters running on mine for doing potted plants and misting. I don't use that much but can if needed. Could easily water a couple dozen trees with it.
Really no other way to remove hardness from the water. You can filter out the dirt but to remove disolved solids RO is going to be the best (maybe only) option. I sent Mark in TX the links to make the RO system, can repost here if you want it. It's about 100$ for every 400gpd filter. And that will probably use about 1200gpd or more of well water input and leave you 800gpd of harder waste water you need to do something with.
I put the waste water on an oak tree and holy cow the oak tree is growing out of control!
You can get TDS (total disolved solids) meters on amazon or ebay for around 10$. That will give you a good idea how hard the water is. Mine is 600ppm out of the ground and around 20ppm after RO treatment.
RO is not the only way to remove hard water. Far from it. Most home water softeners, for example, work by swapping out the calcium and magnesium in solution for sodium and potassium, using sodium or potassium chloride that you replace regularly. In the case of watering plants, you'd obviously want potassium, which is a nutrient you need to give your plants regardless. NOTE: given the reaction, I wouldn't expect it to add chlorine, but you might want to check to be sure.
Another type of water softener is a slaked lime softener. Which sounds weird because you're adding calcium/magnesium compounds to reduce calcium and magnesium
But when it dissolves, it raises the pH, causing dissolved CO2 to convert to carbonate, precipitating out both the added ions and those already in the water as carbonates. It also flocculates your water (removes particulates) and other less soluble ions (iron, arsenic, etc)
Lastly, if your only real problem is pH (after all, plants need calcium and magnesium), you could just add sulfur. A little bit goes a long way (although it takes a year or so for bacteria to break it down to lower the pH). If you want a faster change, you can use (VERY diluted) sulfuric acid.