I doubt it will hurt them. Pines and other evergreens tend to create their own acid soil (because of the decomposition of the needles on the ground around them). What kind of pine? And are you going to pump a lot straight onto the same spot all of the time, or spread it around?
Trees like the Elderica or Afghan pine are a true desert tree and won't be happy if they get too much water. Others would like it better, but you might want to look up your specific trees to see their growth requirements.
_________________ Northwesterner
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