Responses of Leaf Senescence, Shoot Biomass, and Grain Yield of Maize to Drought–Flood Abrupt Alternation

With global warming, both the frequency and intensity of drought–flood abrupt alternation (DFAA) have been increasing, posing a severe threat to the sustainability of crop production. This study involved a two-year rainproof-pond experiment on maize (Zea mays L.) to investigate the effects of varied DFAA combinations on leaf senescence characteristics and grain yield. The treatments consisted of well-watered conditions throughout the maize growing season (CK), maintaining soil moisture at 55–60% of field capacity (D), waterlogging for 6 days (W), and abrupt alternation between drought (D) and slight (3 days), moderate (6 days), and severe (9 days) waterlogging, denoted as D-LW, D-MW, and D-HW, respectively. The water stress was applied at the sixth leaf (V6) stage. Compared to CK, D, W, D-MW, and D-HW significantly decreased the leaf area index, soil and plant analyzer development (SPAD) value, net photosynthetic rate, superoxide dismutase, peroxidase, catalase activities, soluble protein content, shoot biomass, harvest index, ears per hectare, kernels per cob, and 1000-kernel weight, thus significantly lowering grain yield (reduced by 9.4–74.9%). D-LW, however, behaved in the opposite manner and achieved a high grain yield (reduced by 7.0%). Enhanced root growth contributed to the relatively stable grain yield under D-LW. Thus, drought–slight waterlogging abrupt alternation could sustain maize yield by stabilizing leaf size, photosynthesis, antioxidant defense system, shoot biomass, and harvest index.