How long’s a piece of string! Without ducking the issue, this really is a very difficult question to answer because so many factors need to be taken into account when arriving at a decision.
The first thing you need to consider is how much feed’s available on the ground and how many birds, locally, are likely to be drawn to it.
Do other pigeon shooters have access to the land?
If you’re in competition with someone else you can guarantee he will jump in ahead of you and pop away at what does come to the field. Remember, too, to think about the farmer.
It’s all well and good you trying to get as good a bag as possible, but the landowner isn’t going to take kindly to watching a growing number of birds hammering a newly drilled field or patch of laid wheat.