How Much Zinc is Needed for Pecan Trees?

One of our long-time members, @Owl asked me to post this question below.

"I’m trying to find some resource that will help me figure out how much zinc my pecan trees need? I have soil testing for several places around the farm but my trees haven’t produced in several years and an expert told me that they need lots of zinc, in addition to a lot more water than we’ve been giving them."

Can you help Owl find out?