Regulation of Second Basal Internode Characteristics by Nitrogen Fertilizer Enhances Lodging Resistance and Yield in Winter Wheat (Triticum aestivum L.)

Key findings from this study

This research indicates that:

• A 3:7 basal-to-topdressing nitrogen ratio increased both lodging resistance index and grain yield by 12.2% relative to balanced nitrogen application at 270 kg ha-1 total.
• Culm lodging resistance index declined 41.8% from flowering to milk stage, with structural characteristics of the second basal internode mediating this vulnerability.
• Structural equation modeling revealed that nitrogen timing influences I2 chemical composition and anatomy, which in turn determine mechanical properties and lodging susceptibility.

Overview

Winter wheat lodging in the North China Plain reduces yield during grain-filling periods when wind and rain occur. The second basal internode (I2) functions as the primary load-bearing structure determining yield stability. This study examined how nitrogen basal-to-topdressing ratios at constant total nitrogen (270 kg ha-1) regulate I2 characteristics to optimize both lodging resistance and yield. Field experiments across two seasons tested three cultivars under three split ratios (5:5, 3:7, and 7:3). Dynamic measurements quantified I2 mechanical properties, morphology, anatomy, and chemical composition. Structural equation modeling identified mechanistic pathways linking composition to lodging resistance and yield.

Methods and approach

Field experiments were conducted across two seasons with three winter wheat cultivars and three nitrogen split treatments at constant total nitrogen application of 270 kg ha-1. The split ratios tested were 5:5 (CK control), 3:7 (N1), and 7:3 (N2) for basal-to-topdressing nitrogen. The authors measured I2 mechanical properties, morphological traits, anatomical characteristics, and chemical composition at multiple phenological stages. Culm lodging resistance index (CLRI) was calculated as a composite measure. Structural equation modeling was applied to elucidate relationships among composition, structure, lodging resistance, and yield.

Results

The culm lodging resistance index declined 41.8% from flowering to milk stage across all treatments, with CLRI at milk stage ranging from 0.11 to 0.15 in lodging-affected plots. Structural equation modeling confirmed a composition-structure-lodging resistance-yield pathway, with CLRI functioning as the primary mediator between I2 characteristics and grain yield. The N1 treatment (3:7 basal-to-topdressing ratio) significantly enhanced CLRI at all developmental stages relative to the control treatment. Grain yield increased by 12.2% in N1 compared to the control, demonstrating simultaneous gains in both lodging resistance and productivity.

Implications

Nitrogen fertilizer timing substantially influences I2 structural integrity and mechanical competence in winter wheat. The concentration of nitrogen topdressing (3:7 ratio) outperformed both balanced and basal-heavy ratios in maintaining stem strength through grain-filling. These results establish a mechanistic basis for optimizing nitrogen application schedules in high-yield wheat systems where environmental stress coincides with critical development stages. The identified composition-structure-function chain provides a quantitative framework for predicting lodging risk under different management scenarios.

Scope and limitations

This summary is based on the study abstract and available metadata. It does not include a full analysis of the complete paper, supplementary materials, or underlying datasets unless explicitly stated. Findings should be interpreted in the context of the original publication.