Water use and water use efficiency of cool season grain legumes in low rainfall Mediterranean-type environments

The water use (E_t) and water use efficiency (WUE) of a range of cool season grain legume species (field pea Pisum sativum L.], faba bean Vicia faba L.], chickpea Cicer arietinum L.], lentil Lens culinaris Med.], albus lupin Lupinus albus L.], dwarf chickling Lathyrus cicera L.], ochrus chickling Lathyrus ochrus L.], grass pea Lathyrus sativus L.], narbon bean Vicia narbonensis L.], common vetch Vicia sativa L.], and purple vetch Vicia benghalensis L.]) were examined on fine textured neutral to alkaline soils in the low to medium rainfall Mediterranean-type environments in south-western Australia at Merredin and Mullewa in two seasons. There was no difference in the total E_t between grain legumes at either site in either year. There was also no variation in soil water extraction between species on the shallow sandy loam soil at Merredin. However, C. arietinum, L. sativus and L. cicera had greater water extraction and P. sativum the least water extraction at Mullewa where soil conditions were less hostile and root penetration was not restricted. The pattern of water use varied markedly between the grain legume species examined. Grain yield was positively correlated with post-flowering water use (E_tpa) in both erect (r=0.59) and prostrate (r=0.54) grain legume species. Water use efficiencies for dry matter production (WUE_dm) of up to 30 kg ha^?1 mm^?1 for V. faba and V. narbonensis at Merredin, and water use efficiencies for grain yield (WUE_gr) of up to 16 kg ha^?1 mm^?1 for P. sativum and 13 kg ha^?1 mm^?1 for V. faba at Mullewa, were comparable to those reported for cereals and other grain legumes in previous studies in this and other environments. Potential transpiration efficiencies (TE) of 15 kg ha^?1 mm^?1 together with soil evaporation (E_s) values of 100–125 mm were estimated in this and associated studies, and can be used as benchmark values to assess the yield potential of cool season grain legume crops in low rainfall Mediterranean-type environments. The major traits of adaptation for grain legume species producing large yields in this short season environment are early flowering, and pod and seed set before the onset of terminal drought. Early phenology together with rapid ground cover and dry matter production allows greater water use in the post flowering period. This leads to greater partitioning of dry matter into seed, which is reflected in greater harvest index (HI) and WUE_gr, as was observed for V. faba and P. sativum. Improvement in the adaptation of other grain legume species to short season Mediterranean-type environments requires increased early growth for rapid ground cover and improved tolerance to low temperatures (especially for C. arietinum) during flowering and podding.