A cover crop is great for your orchard floor and preventing bare spots. With a standard rake and harvester, you can harvest through knee high grass no problem. The grass not only provides ground cover, but keep the “trash” in place as extra cover. Your biggest challenge will in the tree row where the blowers on the sweeper can’t blow the nuts over because of the grass/crop hold them in place. So you have a few options. For years we used rakes and would hand rake the nuts in the tree row over. Our current solution was to buy a Lockwood pecan harvester and I’ll run it in a cross hatch pattern. No sweeper required, just shake and harvest. And trust me, with a couple of small modifications, it will harvest through 12 inch tall green cover and dry Bermuda grass.

As for the subsurface irrigation, I’ve been looking at N-drip. https://ndrip.com/. No filters, no pumps required. Just 17″ of head pressure. It was developed in Israel and is being tested in the US in California and Arizona. They also have a trial going in a new planting of pecans at the Leyendecker plant science center at NMSU.