Do I need to carry an ID while I'm out doing yard work?

Of course you don't need to carry your ID; In you car, yes you do but anything else other then that and out buying items you don't need it. If a officer asks for your ID when your out doing yard work just tell him your name and he'll have all the information he needs (he has a laptop built in his car) all policemen do. Therefore you do not need an ID.