Abstract
This research investigates the influence of water-nitrogen coupling on soil water content, nitrogen dynamics, and root distribution in farmland, along with the interactions among soil water, nitrogen transport, root distribution, and crop yield. A field experiment was conducted under moderate drought stress (50-60% of field capacity) and three nitrogen application rates (100, 200, and 300 kg·ha(-1), split-applied at 50% during sowing and 50% at the jointing stage, labeled as N(1), N(2), and N(3)) at the two critical growth stages (jointing stage P(1) and tasseling-silking stage P(2)) of maize (Denghai 605). The results demonstrated that maize root morphological parameters exhibited the trend N(2) > N(1) > N(3) under different nitrogen treatments. Compared to N(2), low nitrogen (N(1)) decreased root morphological parameters by 35.01-49.60% on average, whereas high nitrogen (N(3)) led to a reduction of 49.93-61.37%. The N(2) treatment consistently maintained greater water uptake, with the highest yield of 13,336 kg·ha(-1) observed under the CKN(2) treatment, representing increases of 16.1% and 9.2% compared to the P(1)N(2) and P(2)N(2) treatments, respectively. Drought stress at the jointing stage (P(1)) inhibited root development more severely than at the tasseling-silking stage (P(2)), demonstrating a bidirectional adaptation strategy characterized by deeper vertical penetration under water stress and increased horizontal expansion under nitrogen imbalance. Correlation analysis revealed a positive correlation between soil nutrient content and maize yield indicators. At the same time, root characteristic values were significantly negatively correlated with yield (p < 0.05). Appropriate water-nitrogen management effectively stimulated root growth, mitigated nitrogen leaching risks, and improved yield. These findings offer a theoretical foundation for optimizing water and nitrogen management in maize production within the Yellow River Basin.