If you have irrigation, injecting N through the pivot is the most efficient and effective method of applying nitrogen in corn. Dribbling nitrogen (both liquid or dry) by the row is the next preferred method as it keeps the majority of N closet to the root system early in the growth phase and ear development phase. Broadcasting N is an efficient application but may not be the most effective as some N will be captured in the whorls of leaves causing some burning of tissue. It will require rainfall or irrigation to get that which does fall into the whorls dissolved in solution and ultimately in soil solution by washing off the plant and onto the soil. In addition, nitrogen in the middle of the row is far enough away that it takes time for roots to reach the area where the nitrogen is available.