Studies On Nitrogen Utilization Efficiency Of Different Maize Inbred Lines

The improvement of nitrogen use efficiency in maize can be achieved through two main strategies: by adopting more efficient crop nutrient management practices and breeding more nitrogen use efficiency cultivars. Selecting and breeding nutrient stress-resistant crop genotypes and digging their genetic potential is an efficient way to improve nutrient efficiency, solve the shortage of fertilizer resources and help to agricultural sustainable development. This paper focused on improving nitrogen use efficiency through screening high N use efficiency maize varieties. We collected 19 maize inbred lines and analyzed their nitrogen efficiency at different N levels both in pot and field experiments. The correlations of some related morphological, physiological and biochemical parameters with biomass and yield were studied, provided some scientific basis, practical experience and a rapid, efficient method and path for screening nitrogen efficient maize.The main results are as follows.(1) Response to N fertilizer among different maize inbred lines was studied in the field experiment. It showed that there were significant differences in biomass, grain yield, total N uptake of plant and N use efficiency at the same N level. Based on the analysis in N use efficiency and N response at two N levels, 19 maize inbred lines were classified into four types of nitrogen efficiency:(a)Efficient–Efficient(EE), high nitrogen efficiency at low N and high N level, such as Ji818, Tie7922, oh43, Huangzaosi, Mo17, 444 and Chang7-2;(b) Efficient-Nonefficient(EN), high nitrogen efficiency at low N level but low nitrogen efficiency at high N level, such as Huangyesi and 340;(c) Nonefficient–Nonefficient(NN), low nitrogen efficiency at low N or high N level, such as Pa91, 9046, Lv9, Zhong451, L105, 7884-7Ht, 360, Dong46 and Za C546;(d) Nonefficient–Efficient(NE), high nitrogen efficiency at high N level but low efficiency at low N level, such as Ji842.(2) In the field experiment, the correlations of SPAD value of ear leaf, N content of ear leaf, leaf area of ear leaf,height of ear leaf,height of the plant and biomass of the plant at teaseling stage with field yield were analyzed. It indicated that there were significant positive correlations between these indicators with yield. Not only relying solely on the yield to select low nitrogen tolerance varieties but also using some morphological and physiological indicators to assist selection would significantly improve the efficiency of selection and simplify the selection method.(3) The pot experiment with two N levels showed that there were significant differences in amino acids, nitrate and ammonium nitrogen concentration in different inbred lines. The correlation of these indicators with total N uptake, biomass were studied and the result showed that there were significant positive correlation between these indicators with total N uptake and biomass. It indicated that the change of the concentration of amino acids, nitrate and ammonium nitrogen in the xylem sap was related with the absorption and assimilation of inorganic nitrogen in plant.(4) The correlation of some morphological, physiological and biochemical indicators at jointing stage in pot experiment with field yield were analyzed. The results showed that the height, biomass, N uptake of plant, RGR, amino acids and nitrate had significant correlation with field yield. However, the possibility and accuracy of using the biomass and other indicators of jointing stage to screen nitrogen efficient maize material need further research and discussion as the correlation coefficients were not high enough and there were some differences when the types of nitrogen efficiency of the inbred lines were divided by the results at field experiment and pot experiment.