Effect of regulated deficit irrigation and nitrogen fertilization on maize leaf protective system

A pot experiment was conducted on spring maize to determine the effect of the water deficit period and nitrogen application rate on leaf protective system of malondialdehyde (MDA), soluble sugar (SS) contents as well as peroxidase (POD) and superoxide dismutase (SOD) activity. The study shows that while regulated deficit irrigation increases MDA and SS contents, it at the same time decreases POD and SOD activity. Nitrogen application ensures high levels of SS, SOD and POD before heading. MDA content is negatively correlated with nitrogen rate and irrigation level, reaching its peak in the late stage of jointing, and then decreasing. Nitrogen application in regulated deficit irrigation leads to a relatively high SS content from seedling to terminal jointing stage, whereas high nitrogen application rates in continuous water deficit decreases SS content. POD activity is maximum at terminal jointing stage, decreasing during heading stage. Water deficit significantly decreases POD activity, with a significant compensation effect after re-flood irrigation. Although nitrogen application enhances POD activity, but high nitrogen dose with water deficit in heading or during whole growing stage decreases POD activity at heading stage. SOD activity trend is consistent with that of POD. Compensation effect of re-flood irrigation is better for physiology and biochemistry under water deficit at seedling stage, and it takes the second place under water deficit at jointing stage. High nitrogen treatment is not suitable for water deficit irrigation at heading stage. The best treatment combination is water deficit at seedling stage with low nitrogen dose.