Pecan nuts on tree (Wikimedia Commons)
In our neighborhood, the orchards are much smaller and unfenced. The trees around us hang over our fence, so we find handfuls of pecan hulls in our yard, just there for the picking. We strip off the hulls and bring in the pecans to age a bit before cracking them.
We've been watching our neighbor across the street to see how he deals with his dozen or so pecan trees. First, he raked up all the fallen leaves in the yard, leaving them in rows along the fence line. Then, to our surprise, one clear and calm afternoon he sprayed the piles with kerosene and set them all on fire. The low fires didn't seem to hurt the trees, gave his grandchildren a great deal to be excited about, and were soon out, leaving clean ground behind and all ready for the next step.
My neighbor's leaf fire
This morning, a group of strong young men arrived and began beating the tree branches with long poles. Now they are crawling along the ground (how I admire their knees!) and gathering the nuts by hand.
In larger orchards, large machines that shake the trees are used. I hope to get photos of that happening soon.