Factors associated with variability in nitrogen use efficiency of winter wheat grown in Northwestern Europe

Nitrogen (N) availability largely determines winter wheat yield, with the efficiency of N capture and conversion into yield broadly described as nitrogen use efficiency (NUE). Within northwestern Europe, commercial winter wheat systems typically achieve high yields but show wide variation in NUE. Using a decade-long (2013–2022) dataset from the Yield Enhancement Network (YEN) comprising > 1000 winter wheat field observations across northwestern Europe, this study assessed the influences of 32 agronomic and environmental variables on five NUE metrics (yield:N fertiliser ratio or partial factor productivity (PFP), Yield-NUE, nitrogen uptake efficiency (NUpE), nitrogen utilisation efficiency (NUtE) and nitrogen harvest index (NHI)) using Bayesian regression and permutation-based importance analysis. PFP, Yield-NUE, NUpE and NUtE were strongly intercorrelated and positively associated with yield-related traits, whereas NHI showed weak relationships. Increased fertiliser N rate and soil N supply (SNS) were identified as primary negative determinants of PFP, Yield-NUE, NUpE and NUtE. Light sands and shallow soils were associated with reduced NUpE and Yield-NUE. Increased sulphur input, manuring frequency, beans and vegetables as previous crops, Group 4 feed-type varieties, plant growth regulator applications and foundation-phase thermal time, showed positive associations with Yield-NUE, whereas urea ammonium nitrate (UAN) fertiliser without sulphur, later sowing, Group 1&2 bread-making varieties and higher foundation-phase rainfall showed negative associations. This study demonstrates high yield and high NUE can be achieved concurrently with strategies supporting both outcomes. Improving NUE through reducing N input risks compromising yield and depleting SNS. Instead, NUE optimisation must coordinate yield-oriented fertiliser and crop management adapted to site-specific conditions.