Interactive Effects of Water Management and Controlled Release Nitrogen Fertilizer on Dry Matter and Nitrogen Accumulation and Distribution in Summer Maize (Zea mays L.).

Summer maize production in China typically follows winter wheat and is frequently challenged by both drought stress and low nitrogen (N) use efficiency in its short growing season. In an experiment, treatments of three water levels (normal water W3 which the soil moisture keeps 75%±5% of the field capacity, mild water stress W2 which is 55%±5%, severe water stress W1 which is 35%±5%) and four levels of controlled release urea fertilizer (N3 was 315 kgN ha^-1, N2 was 210 kgN ha^-1, N1 was 105 kgN ha^-1 and N0) were compared in a rainout shelter system with soil. The water stress in W1 and W2 was imposed at growth season and urea was applied at sowing. Water treatments, N treatments and their interactions affected grain yield, dry matter, N accumulation, and N translocation and distribution after silking. Maize grain yield increases in response to N treatments, relative to the control N0, ranged from 13.17%–20.96% under severe water stress (W1), by 13.93%–32.48% under mild water stress (W2), and by 14.37%–21.83% under normal water (W3). As anticipated, maize grain yields at a consistent N rate were also higher with more water supplying. Highest overall dry matter, nitrogen accumulation and grain yields were observed with W2N3, W3N2, and W3N3 treatments, but significant interactions occurred in plant N efficiencies among these 3 treatments despite the fact that their yields were not significantly different. The REN of W2N3 was significantly higher than these of W2N2 and W3N3. Under normal water conditions (W3), the REN of N2 was 34.93% higher than that of N3. In this experiment, the N rate of 210 kg ha^-1 was optimal when the soil moisture was 75%±5% of field capacity but the N rate of 315 kg ha^-1 was superior when soil moisture was 55%±5% of field capacity.