Interaction between genotypic difference and nitrogen management strategy in determining nitrogen use efficiency of summer maize

Best nitrogen (N) management and N-efficient cultivars were two main strategies used to add N capture from soil, environment and fertilizer N sources, and increase grain yield and N use efficiency (NUE). This study aimed to evaluate the interaction between genotypic difference and nitrogen management strategy and to determine optimal N management strategy for summer maize hybrids (Zea mays L.) in China. Two on-farm experiments with six N levels and two maize hybrids (NE and ND) were conducted in HM County of the North China plain (NCP) in 2005 and 2006. The maize hybrid of NE has proved to have higher grain yield potential with lower N applications, compared to ND of the major commercial hybrid in the NCP. Calculated maximum grain yield of NE reached 9.3 and 7.7 t ha(-1) using grain response curve, compared to 6.4 and 6.4 t ha(-1) for ND in 2005 and 2006, respectively. No N fertilizer and only 79 kg N ha(-1) for NE were required to achieve the maximum grain yield of ND, which required 150 and 116 kg N ha(-1) in 2005 and 2006, respectively. Compared with those of ND, high N stress tolerance, low N demand with low straw N concentration and high growing capacity after ten-leaf stage were main reasons to achieve higher grain yield with lower N fertilizer application for NE. Although calculated optimal N rates for NE by grain yield response curve were significantly higher than these for ND, no differences were observed before the ten-leaf stage. Therefore, we conclude that more N fertilizer should be applied after ten-leaf stage for higher grain yield potential hybrid of NE in comparison to common hybrid of ND.