It really all depends on the location, and what you're trying to accomplish with these food plots.
The best thing for you to do, is to get your hands on some good resources like the Dougherty's book "Grow 'Em Right, a guide to creating habitat and food plots". Also Ed Spinazola's book "Ultimate Deer Food Plots".
Ed's book is packed with all the info you'll need to create food plots, while the Dougherty's book covers much more about everything, including all aspects of property management for holding deer.
Do some research, then make an educated decision on what you want to do.