The general nitrogen recommendation ranges from 1 to 1.2 lbs of nitrogen for every bushel in your yield goal depending on your soil type. If you believe your farm and management style has the capacity to produce 250 bushels per acre then it would take 300+ lbs of N per acre. Yes, corn is and can be more efficient and produce a bushel for every 1.0 pound or less of nitrogen per acre however in sandier, coarse soils with low CEC, it is better to error on the high side. If you have the capability to apply N though your pivot, divide your total N supply into increments and apply every 10 to 14 days, finishing up at tassel.