Effect of planting density and nitrogen application rate on quinoa yield and nitrogen agronomic use efficiency

Quinoa ( Chenopodium quinoa Willd.) is a high‐value crop that requires region‐specific management. For emerging production areas like the North China Plain, the combined effects of planting density and nitrogen (N) application on growth, yield, and nitrogen agronomic efficiency (AEN) remain unclear. A 2‐year (2024–2025) split‐plot experiment in Jinxiang, Shandong, tested three densities (9.0, 12.0, and 15.0 plants m − 2 ) and four N rates (0, 120, 180, and 240 kg N ha − 1 ). Increased N application prolonged the growth period (from sowing to maturity), while increased density shortened it; N application mitigated this density‐induced shortening. A significant density and N interaction affected plant height. Increasing density increased plant height but decreased stem diameter, productive branches per plant, and individual plant biomass. Increasing N enhanced plant height, stem diameter, and biomass, with benefits plateauing beyond 180 kg N ha − 1 . Note that 12 plants m − 2 combined with 180 kg N ha − 1 consistently achieved the highest grain yield (3612.1 and 3872.7 kg ha − 1 in 2024 and 2025, respectively). Under 180 kg N ha − 1 , AEN peaked at 12 plants m − 2 and then declined with further increases in planting density. Yield was positively correlated with 1000‐kernel weight, total aboveground biomass, and panicle length. The combination of 12 plants m − 2 and 180 kg N ha − 1 optimally balanced population structure and individual plant performance, synchronizing high grain yield with improved N use efficiency. This configuration is recommended as a key cultivation strategy for quinoa production in the North China Plain and similar ecological regions.