Growth, seed yield and water use of faba bean (Vicia faba L) in a short-season Mediterranean-type environment

A number of studies conducted in Western Australia have shown that faba bean has considerable potential as a pulse crop in the low to medium rainfall cropping regions (300-450 mm/year). However, its yield is variable and can be low in seasons when rainfall is less than average. Traits associated with the adaptation of 10 diverse faba bean genotypes to low rainfall, Mediterranean-type environments were evaluated at Merredin in south-western Australia over 2 contrasting seasons. Plant density was varied with seed size to ensure all genotypes achieved similar canopy development and dry matter production. Time to flowering appeared to be the most important trait influencing seed yield of faba bean in this environment. Seed yield was significantly correlated with time to 50% first flower in 1994 and 1995 (r(2) = 0.61 and 0.82 respectively, P < 0.01). In the dry 1994 season, rapid leaf area development in ACC286 allowed a greater absorption of photosynthetically active radiation resulting in more dry matter accumulation than other genotypes. ACC286 also had greater root length density at 20-30 cm depth compared with Icarus and the standard cultivar Fiord. There were no significant differences in total water use between the genotypes examined, although the pattern of water use varied markedly. The ratio of pre-to post-flowering water use was about 1:1 in the early flowering and high yielding ACC286 and 2.6:1 for the late maturing, low yielding Icarus. Seed yield and harvest index were positively correlated with post-flowering water use (r(2) = 0.75 and 0.71 respectively). Above-average rainfall in 1995 resulted in increased yield of all genotypes, particularly ACC286 which again produced the highest yields. Early flowering genotypes with rapid dry matter accumulation in the seedling stages (such as ACC286) could widen the adaptation of faba bean to low rainfall, Mediterranean-type environments and situations where sowing is delayed.