well its not always that easy, as many CRP programs make the owner sigh an agreement they will not plant for "X" amount of yrs, so they cannot legally do anything with the lands till the contracty expires
its been many yrs since i knew prices but like 8-15 bucks an acre is what I recall a few yrs back, its not a lot, but out west when they have such HUGE acreage it adds up
next time I see my buddy I will ask, as he has some lands in CRP for the next 2 yrs, and just had one expire, and he didn't resign due to high corn and bean prices, he is regretting right now doing CRP on what all he did cause of current economy and crop prices/value's
but good luck
and not telling you to do this, but you can try just seeding a section with a turnip seeds or what ever in a rain in the spring time?? and some will grow,
can even do so right now!, and make that one section more attractive to deer then??
as long as its not a crop that has to be harvested, or the field is being cut for hay(which most CROP contracts don't allow) it will not be a problem really, but weeds will out grow what ever more or less, but it can sweeten one section over a whole field