Drip irrigation coupled with appropriate N input increased maize ( Zea mays L.) yield and lodging resistance via optimizing root and stem trait

Irrigation practices are important agronomic measures that influence maize yield and lodging resistance. However, the impact of irrigation practices on the spatial distribution of maize roots and stem traits, as well as their interaction with nitrogen application, remains unclear. This study examined the combined and single-factor effects of irrigation and nitrogen fertilizer on the root distribution, stem traits, and grain yield of different lodging-resistant maize hybrids. Three irrigation practices, drip irrigation (DI), flood irrigation (FI), and rainfed (RF), along with three nitrogen application rates, 0 (N0), 180 (N180), and 360 kg hm-1 (N360), were employed. Irrigation and nitrogen optimized maize root distribution, leaf productivity, and grain biomass allocation, leading to increased maize yield. Irrigation and nitrogen increased root length density (RLD) and the proportion of coarse root length (CRP). Compared with FI and RF, DI enlarged the difference in RLD among nitrogen application rates. N180 and N360 did not differ in RLD regardless of irrigation practice except in interplant. The difference in RLD of interplant across treatments was smaller than that of interrow, especially at the 20-60 cm soil depth. Irrigation and nitrogen increased dry matter accumulation and yield by increasing leaf area and chlorophyll content. However, excessive nitrogen reduced the remobilization of nitrogen and dry matter to the grains. DI and FI increased grain yield by 70.9 % and 55.0 % in ZD958, and by 33.8 % and 20.3 % in FM985 regardless of nitrogen application rate, respectively, compared to RF. Consequently, the combination of DI and N180 significantly increased RLD, stem puncture strength, dry matter accumulation, and yield of maize. Moreover, root length at different soil layers was closely related to yield, while the proportion of coarse roots at the surface layer contributing the most to yield.