Effect of nitrogen fertilization on maize yield and nitrogenefficiency of different maize varieties

Efficient use of nitrogen (N) fertilizer is essential for increased economic returns of maize and minimum potential nega-tive effects of N on water and soil. Efforts at improving yield potential have focused on maize varieties with high N use efficiency (NUE). The effects of N fertilizer on yield and NUE were determined in a conducted field experiment in Xuchang County of Henan Province, China. A total of about 15 common maize varieties in China were used under 3 N doses (0 kg·hm^?2, 120 kg·hm^?2 and 240 kg·hm^?2). The results showed that “Zhengdan958”, “32D22”, “Huayu14”, “Yufeng335”, “Xindan29”, “Zhongke11” and “Luodan9” had the highest grain yield at 120 kg·hm^?2 N dose. Also “Xianyu335”, “Xundan18”, “Liyu13”, “Xundan20”, “Nongda108”, “NE8”, “Yuhe988” and “Luoyu4” had the highest yield at 240 kg·hm?2 N treatment. Based on yield difference, 15 maize varieties were classified as high-yield varieties, medium-yield varieties and low-yield varieties. At the three N doses, “Liyu13” was identified as a high-yieldvariety, “Xianyu335” as a medium-yield variety, and “Yufeng335” and “Yuhe988” as low-yield varieties. Based on nitrogen efficiency (NE), 15 maize varieties were classified into 4 NE grades under medium and high nitrogen treatments. “Zhengdan958”, “Xundan20”, “Liyu13”, “Xundan18” and “Luodan9” were classified as double high-efficient type; and “Nongda108”, “NE8”, “Yuhe988”, “Yufeng335” and “Luoyu4” as double low-efficient type. Cluster analysis on yield and N efficiency showed that “Liyu13” and “Xundan20” were high-yield and high-NE varieties under medium and high N application dose; “Zhengdan958” and “Luodan9” were high-yield and high-NE varieties under medium N application dose; “Yufeng335”, “Yuhe988”, “NE8” and “Luoyu4” were low-yield and low-NE varieties under both medium and high N application doses; “Nongda108” was low-yield and low-NE variety under high N application dose. Correlation analysis for grain yield and N content showed that N uptake efficiency little influenced yield. While NUE inhibited straw N accumulation, it synergized N harvest index. Path analysis indicated that yield was determined mainly by NUE and that for all the treatments, N uptake efficiency little influenced yield. NUE and grain N uptake significantly in-fluenced yield under low N conditions, but it was true form NUE under high N conditions.