# Root–Canopy Coordination Drives High Yield and Nitrogen Use Efficiency in Dryland Winter Wheat

## TL;DR

This study shows that high-yield, high-efficiency dryland winter wheat cultivars achieve better performance through coordinated root and canopy traits that improve water and nitrogen use.

## Contribution

The study identifies coordinated root–canopy traits as key drivers of yield and nitrogen use efficiency in dryland wheat.

## Key findings

- HH cultivars increased yield by 41.5% and water-use efficiency by 24.1% compared to LH cultivars.
- HH cultivars had denser shallow roots, higher leaf area index, and better post-anthesis nitrogen remobilization.
- Positive correlations were found between root–canopy traits, water/nitrogen dynamics, and yield.

## Abstract

Improving yield and nitrogen-use efficiency (NUE) is essential for dryland winter wheat. We hypothesized that cultivars classified as high-yield and high-efficiency (HH) achieve superior performance through coordinated root–canopy traits that enhance water and nitrogen acquisition, sustain post-anthesis photosynthesis, and maintain assimilate and nitrogen remobilization. A two-year field experiment was conducted using ten regionally representative cultivars, which were grouped into HH, high-yield and low-efficiency (HL), low-yield and high-efficiency (LH), and low-yield and low-efficiency (LL) types based strictly on grain yield and NUE. Measurements included yield components, grain-filling, dry matter accumulation and partitioning, soil water use, nitrogen uptake and remobilization, and root–canopy structural traits. HH increased yield by 41.5% and water-use efficiency by 24.1% relative to LH, supported by denser shallow roots, moderate deeper-root development, higher leaf area index, and more compact canopies. HH also exhibited stronger post-anthesis dry matter and nitrogen translocation, resulting in a larger grain number per unit area and improved sink capacity. Correlation analyses further demonstrated positive associations among root–canopy traits, water and nitrogen dynamics, and yield formation. These results support the hypothesis that a coordinated root–canopy structure underlies the superior yield and NUE performance of HH cultivars in dryland systems, providing a physiological basis for cultivar improvement.