Abstract The adaptation of a number of grain legume species is being investigated for fine‐textured, neutral to alkaline soils that are unsuitable for narrow‐leafed lupin production. Canopy development and light absorption are important characteristics influencing crop adaptation. In short season, Mediterranean‐type environments, crops with rapid early canopy development minimize evaporation from the bare soil and maximize transpiration and light absorption, leading to rapid dry matter accumulation. In this study, the canopy development and light absorption of faba bean, field pea, narbon bean and chickpea were compared on a fine‐textured, neutral to alkaline soil in a dryland Mediterranean‐type environment at Merredin, Western Australia. The principle factors determining early canopy development of the above grain legumes were investigated. Among the species studied, high rates of leaf expansion and large leaves resulted in a high percentage of absorbed photosynthetically active radiation (PAR) and rapid ground cover as measured by the sunfleck. Faba bean had high leaf expansion rates (mean of 1.33 cm 2 d −1 ) and a large maximum leaf size (59.4cm 2 ), and hence, absorbed a large percentage of PAR (77% at 74 DAS). In contrast to faba bean, the mean leaf expansion rate of chickpea was only 0.11 cm 2 d −1 , its maximum leaf size was 6.9 cm 2 and it absorbed 43% of the PAR by 74 DAS. The rates of leaf expansion for narbon bean and field pea were similar to that of faba bean, but their leaves were significantly smaller than faba bean and greater than chickpea. Both field pea and narbon bean absorbed 58% of the PAR at 74 DAS. Rates of leaf appearance did not seem to have a large influence on rate of canopy development due to compensation between the number of branches and leaf size. In general, species with few branches developed their canopy faster than species such as chickpea, which had many branches.
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