Steve,

I would think you, more than most would know about PT.
Having said that, I don't know that manure can ever harm trees planted in the ground. As far as fertilizing, cow manure is very good for citrus, chicken manure is a little too "hot" in terms of N; horse manure adds humous, but takes a long time to decompose, and at first can actually rob nutrients from the soil. Those are the most common, and the one thing they have in common... at least for heavy feeders like Meyer lemons, is that you have to use quite a lot to feed them adequately.

From

justfruitsandexotics bottom of second page

Do NOT add mushroom
compost or manure to the planting hole OR use it as mulch. Manure can make
citrus on trifoliate rootstock very sick and could even kill the tree

\.http://justfruitsandexotics.com/JF%20Citrus.pdf

Steve