Testing soil with distilled water

Asked February 14, 2019, 3:23 AM EST

How come you have to “test” the ph of your soil with “distilled” water, but you mostly water your plants (in the garden) with tap water? Seems like it would change it astronomically, but for some reason it doesn't. I understand that distilled water is closer to neutral than tap water, and this is the reason why. Doesn't make any sense to me.

Washtenaw County Michigan

1 Response

The soil is a very highly buffered system. You could dump a concentrated acid into the soil and it would not change the pH as much as you might expect. The problem with using tap water to measure pH is that if the water had high salt content or high iron it could affect the pH by one or two tenths. This is not a large difference, but for consistency of readings it is best to use distilled water.