Planting around a septic field

We got a septic field underground on our property that's on top of a hill. We are NOT planning to put anything ON the septic field directly. But there's a nice area downhill from it, and I'm wondering how far away from the septic we need to be for ogranic gardening or fruit trees? I'm mainly worried about the chemicals. We try to use toxin-free stuff for cleaning and washing, but occasionally we do use chemicals, and I don't want them in my food.

Would 50 ft be safe? 100?

Our soil is deep solid caliche with a thin layer of rocky top soil with barely any grass. The caliche can absorb some moisture, but it's slower draining.

100 feet is the minimum distance that my county allows between a septic field and a well, so I am thinking that 100 feet is most likely safe for your situation.

I would say 3x the MATURE height of the tree, and if it is a tree that suckers, then dont even plant it.

So pecan trees get to 100ft tall so the spacing for that would be 300ft, but elderberry only gets to 10ft so 30ft would be more than good enough.