A side-by-side comparison of biological nitrogen fixation and yield of four legume crops

Aims Evaluate potential N benefit from chickpea (Cicer arietinum L.), faba bean (Vicia faba L.), lentil (Lens culinaris L.) and field pea (Pisum sativum L.). This is the first phase of a 2-year cropping sequence study quantifying above-ground and below-ground residue contributions to N uptake by subsequent crops. Methods The four legume crops were grown in field experiments. Biological N fixation (BNF) was quantified by N-15 isotope dilution. Results Faba bean fixed the most N (76%) and had the highest seed yield but because it exported >80% of N fixed to seed it had the second lowest residue N (39 kg ha(-1)). Chickpea and lentil fixed comparable amounts of N (62%) but had low seed yields and hence higher residue N (56 kg ha(-1) and 40 kg ha(-1), respectively). Field pea fixed the lowest amount of N (50%) but had the second highest seed yield and consequently the lowest residue N (24 kg ha(-1)). Conclusions High BNF does not reflect potential N benefit. Distribution of N to seed and residue were different among the legume crops, with chickpea and lentil being more sensitive than pea or faba bean to different climate conditions.