Dear Derek,

The question you asked touches a very interesting and important issue.
Guess-estimating the plant available water (PAW) limits from texture and
bulk density has been addressed deeply by Arjan assuming drained upper limit
is the true upper limit for water uptake. Optimizing for PAW limits using
some limited soil water content measurements along with yield may not always
help fine tune these estimates because so many factors play a role in yield.
What makes it even more complicated is that you are trying to get an average
PAW limits for 2 different soil series. One thing you can be sure of is that
the soil porosity is higher than the highest of your soil water content
measurements. My suggestion is to use the PAW limits that are closest to the
PAW estimates from texture and bulk density.

Regards,

Ayman