Trifolium spumosum L. (bladder clover) is an aerial seeding annual legume that is adapted to fine-textured soils throughout the Mediterranean Basin. This article is the first of two papers that describe the process of domestication of T. spumosum as a new species to commercial agriculture. This paper describes a broad range of investigations into the ecology, agronomy and rhizobiology of this new species. Through a series of five experiments, we have tested the general hypothesis that T. spumosum accessions demonstrate a range of sought-after agronomic traits and offer an alternative to annual Medicago spp. for ley farming systems in the medium to low rainfall areas of the mixed crop/livestock zone of southern Australia.
T. spumosum presents seeds at the top of the canopy in heads that do not readily shatter, so seed can be harvested using conventional cereal harvesters instead of the specialist suction equipment required for harvest of seed from annual T. subterraneum and Medicago spp. T. spumosum was found to be relatively fecund and had high levels of biomass production in comparison to the other annual legumes that were tested. The species also demonstrated high levels of within-season hardseededness (remaining hard in summer and softening in autumn) so seedbanks would be protected from summer rainfall events. In addition, T. spumosum showed high levels of between-season dormancy, which allows the species to carry a seedbank through a cropping phase or series of poor seasons. A herbicide experiment showed that clover species varied in tolerances, with T. spumosum the least sensitive of all of the legumes tested to Flumetsulam. A cross-inoculation experiment to measure symbiotic effectiveness revealed that WSM1325 (current clover strain) surpasses WSM409 (previous strain) in its relationship with the annual clovers of contemporary interest, while being highly effective at nitrogen fixation with T. spumosum.
The results of this study and an associated investigation into feeding value indicate that T. spumosum offers a productive alternative to annual Medicago spp. on fine-textured soils. Of the T. spumosum accessions tested, the most promising has been released under the cultivar name of AGWEST Bartolo.