Opportunistic Mediterranean agriculture - Using ephemeral pasture legumes to utilize summer rainfall

The wet winters and summer droughts of dry Mediterranean-type climates create a highly seasonal supply of feed for livestock. Much of the forage value of winter-active annual pastures and crop residues is realized as dry feed during summer-autumn. Sporadic summer-autumn rainfall rapidly degrades the quality of dry plant residues. In low rainfall areas of the southern Australian wheatbelt, there are no well-adapted crops or pastures to convert summer rainfall into high-quality green feed and supplementary feeding is required to maintain livestock condition. We therefore investigated two undomesticated ephemeral legumes (Cullen cinereum and Cullen graveolens). In a field experiment, the ephemerals were dormant in winter-spring and responded strongly to summer rainfall, with 0.45-0.82 t ha-1 of shoot dry weight produced over summer. Extrapolation of regional historic rainfall records showed similar or greater summer-autumn rainfall in 40% of years and also suggested that conditions will probably be too dry for perennial pastures such as Medicago sativa (lucerne) to persist in up to 60% of years. An analysis using MIDAS, a bio-economic model, suggested that ephemerals could increase total farm profit and stocking rates (10.3% and 7.7%, respectively), and decrease supplementary feeding of grain by >50% by providing high quality feed in years that summer-autumn rainfall occurs. We suggest there is considerable potential for ephemeral legumes to contribute to the sustainability of mixed agriculture in dry Mediterranean-type climates by utilizing sporadic summer rainfall whilst complementing existing annual pasture and cropping systems.