High root vigor contributes to high yield formation of summer maize in the North China Plain

The root is a key organ influencing water and nutrient absorption, which ultimately affects maize yield formation. Quantifying the differences in root traits among maize cultivars with distinct yield levels is critical for guiding high-yield breeding and cultivation practices. A two-year field experiment was conducted with eleven widely cultivated summer maize cultivars in the North China Plain. Based on cluster analysis of grain yield, the cultivars were classified into three yield levels: high-yielding (L1), medium-yielding (L2), and low-yielding (L3). The results indicated that the total root number (0-30cm) of L1 increased by 10.0%–12.3% and 20.0%–41.4% compared to L2 and L3, respectively. Root length density of L1 was 25.9%–42.8% higher than L2 and 44.7%–52.6% higher than L3. During the grain-filling stage, root vigor (0-20cm) of L1 was 11.9% and 31.0% higher than that of L2 and L3, respectively. In addition, antioxidant enzyme activities (superoxide dismutase, peroxidase, and catalase) were significantly higher in L1, indicating delayed root senescence in high-yielding maize. Correlation analysis and random forest modeling further identified root vigor as the most influential physiological trait contributing to grain yield. This study revealed that optimized root architecture and sustained physiological activity underpinned high-yield formation, providing new insights into maize yield determination and a theoretical basis for future high-yield breeding and cultivation strategies.