Increased plant density with reduced nitrogen input can improve nitrogen use efficiency in winter wheat while maintaining grain yield

Abstract

Plant density and nitrogen (N) input level have notable effects on root development, distribution in the soil profile, and in turn, N-uptake of winter wheat. Our study objectives were to identify whether a high yield can be maintained with a reduced N input by increasing plant density. Field studies were conducted during four successive seasons (2014–2015, 2015–2016, 2016–2017, and 2017–2018) using a widely planted cultivar, Tainong18. Two regimes of N fertilization (180 kg ha⁻¹ and 240 kg ha⁻¹) and three planting densities (135, 270, and 405 plants per m²) were used. Higher plant density led to increased root length density (RLD) and enhanced N uptake from the whole soil profile. The RLD in the soil profile at 0–1.2 m, 0–0.4 m, and 0.4–0.8 m decreased while in the 0.8–1.2 m layer it increased in response to reduced N input. The combined effects of higher plant density and lower N input resulted in reduced N uptake, a lower nitrogen nutrition index (NNI), unchanged grain yield, and improved N use efficiency. In conclusion, it is possible and sustainable to maintain a high wheat yield with reduced N input by increasing plant density.