Abstract: With field experiment and under low-density condition,this paper studied the individual grain yield (GY) and nitrogen utilization efficiency (NUE) of fifty Zea mays cultivars widely planted in North China since 1990s.Exploring analyses and normality tests showed that the 1000kernal weight (KW),above-ground biomass per plant (AB),grain harvest index (HI_G), NUE,and nitrogen harvest index (HI_N) were all conformed to normal distribution,with N(265.1,44.50²),N(322.3,36.91²),N(515.8,64.73²),N(0.514,0.06²),N(43.0,5.37²),and N(0.643,0.06²),respectively.The GY ranged from 198.35 to 345.22 g·plant^-1,KW from 241.50 to 391.82 g·1000 kernal^-1,AB from 402.34 to 712.84 g·plant^-1,HI_G from 0.39 to 0.63,NUE from 31.18 to 57.35 g grain·g N^-1,and HI_N from 0.47 to 0.74.Correlation analyses indicated that GY positively and significantly correlated with NUE (partial correlation coefficient was 0.471**,P=0.001),while KW negatively and significantly correlated with NUE (Pearson correlation coefficient was -0.427**,P=0.002).Through hierarchical cluster analyses for GY and NUE,the test Zea maysvarieties could be sorted into 3 types,i.e.,high-GY with high-NEU,low-GY with low-NEU,and mediate type.Currently,only 24 percent of Zea mays cultivars in North China were of high-GY with high-NEU type,and thus,its breeding should be strengthened in the future.

Key words: Phenanthrene, Soybean, SOD activities, Biomarkers, Recovery