Screening For Varieties With High Nitrogen Use Efficiency And Establishment Of Evaluation Index System In Maize(Zea Mays L.)

Maize is the most productive food crop in our country and the world. One of the important factors that made maize yield increased so fast is greater use of nitrogen fertilizer. However, in recent years, excessive application of nitrogen has resulted in serious water and air pollution and this problem is receiving more and more attention. So improving the nitrogen use efficiency in maize has become a problem we have to face with. Selection and planting of nitrogen efficient maize hybrids is a cost-effective way to improve the nitrogen use efficiency.Twenty maize varieties, which composed of the main varieties in corn production or the varieties that were authorized newly, were chosen as experimental materials in this research. The field experiments in two years were carried out to study the effects of different nitrogen application(0kg.hm-2,225 kg.hm-2,450 kg.hm-2) on the production performance. Then the yield and nitrogen efficiency type were classified, respectively. Meanwhile, the traits related to nitrogen efficiency were measured, such as biomass and nitrogen accumulation at different growth stage, the SPAD values of the ear leaf at silking stage. And the correlation analysis has made between yield and agronomic traits related to nitrogen efficiency or between nitrogen efficiency and agronomic traits. The results were as follows:1. According to the results of nitrogen efficiency classification in two years, Xundan 20 and Xundan 29 were screened as nitrogen efficient type under both medium and high nitrogen application rate, Weike 702 was screened as nitrogen efficiency type under high nitrogen application rate and Denghai 6702 was screened as nitrogen efficiency type under medium nitrogen application rate. Considering the nitrogen efficiency type and yield, Xundan 29 can be used as high efficient and high yield maize varieties in production.2. The physiological traits, such as the SPAD values of the ear leaf at silking stage, total nitrogen accumulation and crude protein yield, showed more significant difference than the phenotypic characters, such as grain yield, biomass, leaf area under different nitrogen application rate on the base of high soil fertility. Only the activity of glutamine synthetase showed significant difference under different nitrogen application rate in the hydroponic experiment.3. The correlation analysis between grain yield and N content showed that the grainyield has significantly positive correlation with nitrogen absorption of grain, nitrogen uptake efficiency and nitrogen accumulation after the silking stage under different nitrogen applied. Nitrogen accumulation after the silking stage inhibited the nitrogen translation in vegetative organs and nitrogen utilization efficiency synergized nitrogen harvest index under different nitrogen application rate.4. The SPAD values of the ear leaf at silking stage can be used as screening index for maize nitrogen efficiency under low nitrogen application rate; biomass and nitrogen accumulation at silking stage can be used as screening index both under low nitrogen and medium nitrogen application rate; biomass at mature stage can be used as screening index for maize under different nitrogen application rate.5. Path analysis indicated that nitrogen uptake efficiency had larger direct effect on nitrogen efficiency under the low nitrogen and medium nitrogen application rate, and nitrogen utilization efficiency had larger direct effect on nitrogen efficiency under the high nitrogen application rate,...