SD treats turkeys like big game, you must apply and can earn preference if unsucessful draw. I am unsure if you can take a turkey with a bow if you are in possession of a gun tag. Personally I would take a shotgun and a rifle due to the expanse of some of the areas down there. Also there is some reservation lands in Gregory Co. so be sure you know where you are or risk a hefty fine from the tribe.
I have had good success in that area of SD but not so much hunting the river breaks on the state land. Better off asking private land owners, especially ones who have corn or grain stockpiles that these turkeys love to ravage.
My best luck has been using calls that imitate 2 jakes fighting. Really brings the dominate tom a runnin.
As far as the time to come is all dependent on the weather. Drier is better and it seems the warmer it gets the more frisky they are out there. There typically is not as much pressure during the weekdays so if you can plan to hunt a couple days during the week if possible. A lot of the guys I know will hunt the opener due to fact of stupid birds but that is not always the best time based on cooler wetter weather. Also first weekend is kind of irrelevant if you are interested in shooting them with a .223 or such from 300 yards!!! Have done that and is quite challenging out on the open prairie to even get that close. Check out the GFP website SDGFP.info for more information. Good luck.

huntnfish,
Thank you for the awesome reply. That does help alot!!! the way it looks we are going the weekend of the 19th of April and hunting for 3-5 days. We have access to 160 acres of private ground and the landowner also lesses some tribal ground that we can gain access to if we have an indian guide or something. We are just going to try our luck on the 160 and see what happens. From what the landowner is telling us it sounds like there is alot birds there!!!!!

huntnfish,
Have you ever hunted whitetails in that part of the state???? I have also heard that there are some mullies running around?????

Yes I have hunted whitetail in and around Gregory Co. Pretty good hunts. Not too much for mulies from what I saw. I am sure there are some around but the whitetail usually run em off. I think I have talked to the guy you are hunting on and he sounds genuine. Are you hunting around the Ponca creek area south of Burke? If you hunt the tribal land you will need a tribal license also. Not worth it in my opinion.
The whitetail usually are pretty decent in size out there with 130-140 class pretty normal. Lots and lots of does also. Worth the extra $50 for the meat. There typically is a lot of pressure for deer so they will usually be on the move. In fact the best buck I shot in Gregory Co. (136 inch 4x5) was spooked to me in the early morning by some guys shooting at it before opening time from the road (poachers) Scared that poor devil right to me where I was sitting about 2 miles away.
As far as the turkeys, there are bunches of them. The ranches I hunted one county west (Tripp) of you it was not uncommon to see 100-150 birds a day. And Gregory Co. is no different. That is no exaggeration just the facts. Lots of different toms to choose from. But they can be harder to hunt with so many eyes and ears out there. You should hear and see turkeys every day without any problem. Set up on their roosting spots in the a.m. and you should be in the money. Don't forget your varmit rifles, lots of coyotes, free to hunt with any state issued license. Also, soft point bullets only, no FMJ if you plan on shooting your turkey with a centerfire rifle. Have fun looking at all the pheasants also as it is breeding time for them and they will be everywhere on the roads.
Let me know how you do and have a fun hunt. Let me know if you have any more questions.

Leasing tribal land in SD doesnt mean you can hunt it without a tribal license and the "indian guide" thing is nonesense. you must have a license from the tribe to hunt tribal land period. Just thought id give you a heads up.

Actually Romey the tribal land area in Gregory County is under the Rosebud Sioux Tribe and they require all hunters to have a tribal license and a tribal guide. They changed the regs on that a few years back due to all the tresspassing from what I heard. Kinda crazy in my opinion due to the good maps that are out there to see which is deeded land and which is tribal. Easier to hunt the private land to stay away from the chance of tresspassing in my opinion.

Interesting thats for the heads up, though is somewhat what i ment , i dont beleive I exspressed myself correctly, i didnt know that land was rosebud tribe though, I have land in lower tripp county that I hunt grouse ,pheasant and whitetails but thats like gregory and tripp counties are ttwo different worlds and side by side!