That's usually a pretty accurate way. I was thinking what the hell? Compared what I've had to deal with on new fields that's a pretty low ph. Of course mine is a different type soil and other variables but generally starting for me is at worst usually about 5.2. Then I know some that have never been limed and run 7.0-7.2

I still think I'd use the 1.5 tons now and recheck and add a little more at planting next year. Good luck!