Effects of nitrogen application on yield and nitrogen use efficiency of summer maize under super-high yield conditions

The effects of nitrogen application rates on grain yield, nitrogen translocation and use efficiency under super-high yield conditions were studied in fields. Two cultivars of summer maize (Zea mays L.), Denghai 661 (DH661) and Zhengdan 958 (ZD958) were selected as experimental materials. The results show that the grain yield, amount of total nitrogen accumulation in plant and nitrogen recovery efficiency are increased at first, and then decreased with the increase of nitrogen application rates. The grain yields of DH661 and ZD958 reach to 1217215080 kg/ha and 1201115360 kg/ha under nitrogen fertilizer application rate of N 240360 kg/ha. Under those nitrogen fertilizer application rates, nitrogen recovery efficiency and nitrogen agronomic efficiency of DH661 are 10.623.1% and 11.513.6%, and are 24.128.6% and 9.511.4% for ZD958. For the two summer maize cultivars total nitrogen accumulation and nitrogen recovery efficiency are the highest under nitrogen fertilizer application rates of N 240360 kg/ha. Under those nitrogen fertilizer application rates, translocation efficiency and nitrogen contribution proportion of DH661 and ZD958 after the anthesis stage could be regulated effectively. As a result, nitrogen in grain and grain yield are improved. In conclusion, under this field experiment conditions, as far as grain yield and nitrogen use efficiency are concerned, the most optimal nitrogen fertilizer rates are N 240360 kg/ha.