Honestly, who, in their right mind, would buy ( or maybe rent from the Algarve) a sort of lawnmower and then walk around the sides of a very large field, three times, cutting the grass
Jan, why don't you hire a crop spraying drone and fill its tanks with that salt and vinegar concoction you make? Do it at night, they are quiet, and give it a chance to soak in - do it a few nights.