Fig. 1

Effect of nitrogen dosages and irrigation regimes on the activities of nitrate reductase (NR), nitrite reductase (NiR), RubisCoRubisco, glutamine synthase (GS), glutamate dehydrogenase (GDH), and glutamate synthase (GOGAT). The bar represents the standard error. The nitrogen treatments control, N200, N250, N300 and N350 represent the application of nitrogen at the rate of 0, 200, 250, 300 and 350 kg N ha^− 1. HW and LW represent the irrigation water at the rate of 80 and 60% of field capacity. The V9, R1, R3, and R6 stages represent the maize with 9 leaves, silking, milking, and maturity stages, respectively