I've got 13 acres in the Piedmont area of NC. Zone 8b and somewhere around 42 inches of rain per year, elevation 400', south facing slope, 5 acres of trees on the western and southern sides of the land. Toward the front of my property (north side), i have clay right at the surface that i've been covering with horse manure to add humus (while building our house, the builders scalped the ground to the subbase soil). On the south side of the house, i have deep sand with about 4-8" of humus with a lot of broom sedge and blackberries. I'm looking to get a bulldozer out here for some other work that needs to be done, but while it's here, i'm also going to install some swales that i can begin planting a food forest on. The question is--how deep and wide should those swales be, and how far spread apart? I've seen a number of different answers for one particular type of soil, but when i get these swales installed, there are going to be places where i transition from sandy to clay soil.
Also, I've worked out deals with a tree trimming service to start getting wood chips dropped off for free whenever they have a job in the area. Should i fill up my swales with wood chips, or should i mulch the trees which are planted on the backside of the swale? or both? Thanks for the help!