Can I prune the bottom of a fir tree that is to say spreading over my pasture to receive mowing easier? I do not want to damage the tree.

I do not want to damage the tree.
Nice prairie hedge/bush?
Answers:    Sure - I've see large evergreens pruned up to allow access underneath for shade gardens and whatnot. Won't hurt the tree.
And if the branches are dragging on the ground - they're going to win beat up anyway. Cutting them stale is fine. The practice is called "limbing up".
Where do i find philosophy for my landscape...
Sure you can. I would not de-nude more than 1/3rd of the total tree altitude, though, so be sure the tree will have plenty of limb left. But if this is an elder tree that has lately never had the bottom limbed up, you are fine doing it. Just wear a head covering when mowing - fir trees tend to harbor spiders and you want a moment to notice them beforehand they surprise you if you pick up a rider while mowing, as it were. You do not obligation to use that patching stuff when you cut the limb, any, it has be proven not to help the health-giving after the removal.
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