Establishment and summer survival of the perennial legumes, Dorycnium hirsutum and D. rectum in Mediterranean environments

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The genus Dorycnium has been identified for its potential use as a forage plant for southern Australia, but little is known about factors affecting establishment and survival. This investigation examined some factors affecting the establishment of D. hirsutum and D. rectum in Mediterranean environments of south-west Western Australia. The population dynamics of D. hirsutum and D. rectum seedlings were investigated during the summer drought in 4 environments. The effect of time of sowing on establishment and survival of D. hirsutum was tested as a management option for improving establishment of these species. Poor seedling performance was observed in both Dorycnium species. Less than 20% of D. rectum plants survived the summer drought at all locations, compared with >50% for D. hirsutum seedlings. Poor seedling vigour coupled with weed competition resulted in low plant numbers at 2 sites. Compared with autumn sowings, populations of D. hirsutum sown in August and September had lower plant densities before summer due to poorer seedling emergence. Plant numbers declined during the summer in all plots, but losses were greatest in those sown in September. In both experiments, small D. hirsutum plants survived in plots where little competition was present. Improvements in seedling vigour may be possible with plant breeding but establishment methods that reduce weed competition are valuable. Spring sowing may enable effective weed control before seeding, but later sowings run the risk of reducing seedling emergence and survival.