I'll be a kill-joy and say it's not worth it. Not UNLESS something were there, going on, before the orchard/cultivation. Because random fumble fingers losses from those workers (harvester, planter, passerbys, etc...) is not worth the effort. Sure there will be a random wheatie or something from an apple-picker in 1955 (if you knock yourself silly canvassing acre after acre). But the places to hunt are where commerce/travel-campers/recreation, etc.... occurred. Like a stage stop, park, camping-spot, etc.... Not just random orchard or row-crop land.
Perhaps in a place like Britain, where fields and orchards have had 1000 to 2000 yrs. of continuous cultivation, can you go out to just "any random field" and find metal. But the history of the USA is too new for that level of accumulation to have occurred. So your best bet here, is if you have isolated that some structure or gathering spot had been. Esp. if where $$ changed hands, like stage stop, saloon, etc.... had been.