When a measure becomes a target, it ceases to be a good measure.
That’s a generalization of Goodhart’s law. I’m an advocate of measuring some surface performance, plant, and soil parameters.
The normal range of calcium (Ca) in irrigation water is 20 to 60 ppm. That comes right from Penn State’s Irrigation water quality guidelines for turfgrass sites.
Were you surprised by the previous post that worked out daily Ca use by the grass, and Ca added in irrigation water, to find that irrigation water was supplying 26 times more Ca than the grass was using?
Did you see where soil potassium (K) only went down by 1 ppm after 374 mm (14.7 inches) of rain?
In that same comparison of pre- and post-rain samples, the soil calcium (Ca) went down by 26 ppm.