Mix it into the Mulch ,no problem.
You did not say anything about checking for Nematode?.
Dig some roots out and you will see little round balls,hanging on the roots,if it is infested.
This is very important,more important than anything else you might be able to do.
You need to know this ,first.
Lowes got all kind of limestone:Powder,granulated,dolomitic,etc.
It is called :lawn(or, loan) doctor,Not sure how to spell this one, it is used,for to neutralise acidic soil,in suburban lawns (loan)and gardens.
PS:If you can't find limestone in your area,it may be that the soil in Arizona is alkaline,and do not need any Limestone,so if so,forget about it.