@Susan Williams good question, and honestly one that comes up a lot with this module.
The 50km figure is specifically the drone-to-drone spec — both modules elevated, ground reflections eliminated. For your sensor network where nodes are going to be at ground level or close to it, you're looking at the 5km ground-to-ground range as the more realistic baseline. That's still the tested figure, and flat open farmland is actually a decent environment for hitting close to it.
Tree lines and low hills will eat into that, but how much depends on density and height. A sparse tree line between nodes is more of a soft attenuator than a hard wall — you'll see some signal degradation but usually not a cliff-edge drop. A solid hill with meaningful elevation blocking your Fresnel zone is a different story and will hurt more than you'd expect even at low frequencies.
For a rural sensor mesh deployment I'd plan your node spacing assuming maybe 60-70% of the ground spec to give yourself margin, then test a node pair across your worst-case path before committing to the full layout. The module's receiver sensitivity is genuinely good, so it tends to hold a link longer than you'd expect before it dies — but having that buffer in your design is still the right call.
