The size like statedin the other postdepends on your deer densities.....Here in Ohio I planted a 5 acre field of sunflowers for dove and the deer ate the entire field before it could get knee high, I tried 2 different soybean plots of 1/2 acre and 1 acre, The deer ate them as soon as they sprouted. You might try spring oats and just keep replanting if the deer eat it down, I also use grain sorghum the deer leave it alone all summer then afterit froststhey hit it very hard eating the seed heads......Again these are just my experiences..