The experiment was carried out in Shandong Agriculture University experimental farm, Wenkou town of Taian city, Daan town of Yanzhou city and the State Key Laboratory of Crop Biology from 2008 to 2009. The analysis included field and ~(15)N isotopic dilutions for pot experiments. Two maize cultivars, DH661 and ZD958 were used as experimental materials. The effects of nitrogen application rates on yield, quality and physiological characteristics were studied in order to find out the most optimal nitrogen fer...