Nitrogen use efficiency is a complex trait involving many crop physiological mechanisms. Breeding for this trait has therefore not been challenged, despite its potential benefits. Scientists Lammerts van Bueren and Struik review breeding strategies for nitrogen use efficiency in vegetables and compare those with strategies in grain crops. They argue that some traits are generic across species, while other traits are crop-specific. They conclude that there is sufficient genetic variation available among modern cultivars to improve nitrogen use efficiency.