One thing I am surprised has not been mentioned is to sit back and glass from a distance and formulate a plan based on what he does when he rises or returns... Simple, but effective. patience
It would certainly be dependent on a lot of variables like huntable land size, where the buck will likely go, field size, landscape, etc..
It might be that you slip to the field edge and shoot him when he gets there... Might take a pit, but if its close enough to the buck bed and done now, it will likely spook him digging...
I think if he were in the middle of open crp grass, he did not leave it in daylight and there were no trees close enough I would wait for high winds, or heavy rain, and belly crawl close to the bed and then try and get an arrow in him. If there is any roll to the landscape that would be used to my advantage, as would the position he faced while bedded.