Nitrogen distribution in four grain legumes

The partitioning of above ground nitrogen (N) in chickpea (Cicer arietinum), lentil (Lens culinaris), lupin (Lupinus angustifolius) and pea (Pisum sativum) at crop maturity was investigated. The plants were grown at different plant populations and sowing depths in 1998/99 and 1999/2000 in Canterbury, New Zealand. In all four legumes the N concentration was highest in seed (29-36 mg/g N) followed by senescent leaves. The lowest N concentration was in stems. Lupin had the highest seed N yield at 16.82 and 19.29 g/m(2) followed by chickpea at 10.26 and 13.10 g/m(2), in 1998/99 and 1999/2000, respectively. Lentil had the lowest N concentrations and yield. The distribution of N to all legume plant parts increased as population increased up to twice the optimum and 400 plants/m(2) in 1998/99 and 1999/2000, respectively. Over all plant populations, the nitrogen harvest index (NHI) was stable in each of the four species across the two seasons. However, the NHI changed with changes in plant population and sowing depth. The N accumulation efficiency (E-N) was highest in lentil at 0.024 and 0.027 g N/g DM and lowest in chickpea at 0.018 and 0.021 g N/g DM in 1998/99 and 1999/2000, respectively. The NHI and the crop harvest index (CHI) were correlated and both were strongly associated with seed yield. Thus, NHI might be useful as a selection criterion to improve seed yield in grain legumes.