Effect of base-N to dress-N ratio on water and nitrogen utilization,growth of summer maize in North China Plain.Ⅰ.Growth,development and water use efficiency of summer maize

Under low N application rate［180 kg(N)/ha］,maize (Zhengdan958) was used to study the effect of base-N to dress-N ratios (RBTD) at 1∶2，1∶1 and 2∶1 on growth,development and water use efficiency (WUE) of summer maize in North China Plain.Results show increased leaf number,plant height and yield of summer maize under N fertilization,and that the increment gets larger with increased dress-N to total-N ratio (RDTT).Base-N has beneficial effects on leaf area expansion,while dress-N has beneficial effects on leaf area maintenance in filling stage.Coarse protein and free amino acid contents in maize grains increase with N fertilization and increased RDTT.The starch content of 1∶2 RBTD treatment increases,while those of the other two treatments drop.WUE heightens with increasing N application,and higher percentages of dress-N are proved to be advantageous to heightened WUE.Because precipitation mainly occurs in the sowing to jointing stage of summer maize in the North China Plain,it is concluded that less base-N application and RBTD ratio of 1∶2 are the best dosage for agronomic and quality traits amelioration,heightening yield and WUE of summer maize.