I'm a sucker. I think ya'll have left some dangling questions about CRP, hoping that all the wiggling will attract a fish. Yes, I'm a fool. Or, a fish. I don't know which. I know I'm not brief, but I'll do my best.
In a general sign-up, open only during a specifically announced time period, land is offered by owners or operators with sufficient control of the land. Those individuals can OFFER their land with certain conservation practices they can select. There are tons of different options. These practices earn points. Also, the environmental character of the land earns points. The more 'environmentally sensitive' the land, the more points it accumulates. Once all the OFFERS are in, they are ranked by points. If the general sign up can accept a million acres, then the OFFERS are accepted by accumulated ranking points until the acreage cap is met. The lesson here is nobody dictated what the landowners or producers offered.
A CP12 is short hand for a food plot. Food plots can only be installed as part of another conservation practice, like grass cover or planted pines. Depending on the sign up, and the policy in effect at the time, only 10% to 20% of the total enrolled acreage can be in food plots.
NRCS is the technical conservation planner. They create job sheets, and depending on where you, are and who you are dealing with there can be a lot of latitude, or not much. Human nature at work. FSA is the administrator. So, if you want to know if you can plant turnips, ask NRCS. If you want to know about the details of the contract from beginning to end, ask FSA.
Now, why do you suppose these food plots are to be planted by, basically, the final planting dates for most crops? And, why would one not be allowed to spray or mow? Think habitat. Wildlife habitat. Nesting season. It's debatable, but a clean food plot is not necessarily the best wildlife habitat. Maybe you want to remove your summer crop and plant a fall crop, but, in a general way, when you do that you destroy habitat. It might not be deer habitat, but it is wildlife habitat. And, in as much as this food plot is enrolled in CRP, it is generating a small but reliable income stream for 10 or 15 years.