More questions:
1) Have you determined where your turkeys are roosting by listening for them at first light in the morning, not only on your fifty acres, but also listening where possible on the surrounding properties? (public roads, for example)
2) Assuming they are roosting somewhere nearby, but not on your property, have you contacted the property owner where they are roosting and sought permission to hunt there? ….And if not, why not?
Knowing where the turkeys are roosting is a key ingredient to success. Even if you can't hunt there, knowing that location gives you lots of information that is applicable to your hunting tactics and set-ups. Examples:
If they are roosted far off of your property, you will know to focus your efforts later in the day, rather than trying to hunt them early.
If they are close enough to your property that they could hear you from the roost, setting up on the property line and calling loudly might get them headed in your direction (I called two gobblers off the roost from an adjacent property from 400-500 yards away a couple of weeks ago by doing just that).
If they are roosted way off of your property and only show up on occasion, it could be they are just randomly coming on your place once in a while. In that case, I believe you should be putting more effort into finding a more productive place to hunt (i.e....doing more talking to your neighbors and relying less on those birds showing up on your land)
"Real" turkey hunting is not a "guess or by gosh" proposition. Most consistently successful turkey hunters take a proactive approach to finding birds and establishing a carefully-thought-out plan to maximize their chances of success. From your descriptions of what you are doing, it sounds to me like you need to be "thinking outside the box" (the "box" being your fifty-acre parcel) a little more in your approach to killing a gobbler.
Again,...just trying to help you be successful....