Optimizing water and nitrogen management improves maize productivity by regulating root development in the cold...

Water constraints and excessive nitrogen (N) application hinder root development in spring maize in cold semi-arid regions (CSR), limiting growth and yield. In this study, we focused on the CSR where water scarcity and high fertilizer use are major challenges. Optimizing water-N interactions can enhance root distribution and nutrient uptake, offering a key strategy for improving crop productivity.

To determine the optimal water-N management strategy under local climatic conditions and evaluate its effects on root physiology and yield performance of spring maize. A two-year field experiment (2020-2021) tested four N application rates (N0: 0 kg ha^-1, N100: 100 kg ha^-1, N200: 200kg ha^-1, N300: 300 kg ha^-1) and three soil moisture levels (S1: 40%, S2: 60%, S3: 80% field capacity). Water was managed by maintaining target soil moisture using TDR-based measurements and supplemental irrigation.

Compared with S3-N300, S3-N200 increased plant height (7.89%), stalk thickness (10.48%), and spike position height (5.14%), while substantially boosting root antioxidant enzymes (7.72%), lowering reactive oxygen species (11.81%) and raising K⁺ (18.22%), Ca²⁺ (16.35%), Mg²⁺ (20.01%), and reduced Na⁺ (3.83%) levels. It also elevated Indole-3-acetic acid (IAA), Gibberellins (GAs), and Zeatin + Zeatin Riboside (Z+ZR) by 45%, 43%, and 30%, respectively. Biomass accumulation rose in spike (11.98%), leaf (23.21%), stalk (16.63%), and grain (6.95%), resulting in 8.01% yield improvement. Structural equation modeling (SEM) showed that water-N interactions explained 94% of the variation in yield, 89% in ion content, 94% in hormones, and 91% in ROS levels.

These findings confirm that S3-N200 (80% field capacity + 200 kg N ha^-1) treatment improved root function, stress resilience, and nutrient uptake, thereby enhancing growth and yield compared to conventional local practice (>250-300 Kg N ha^-1) without optimized water management. Optimizing water-N strategies in North China's CSR supports sustainable maize production and strengthens agricultural resilience under water-limited conditions.