CONICET | Buscador de Institutos y Recursos Humanos

Increasing the area sown to Ornithopus spp. can reduce overall fertiliser requirements in Australian permanent pastures due to their greater nutrient acquisition efficiency compared with that of more widely used pasture legumes, such as Trifolium spp. However, uncertainty regarding their waterlogging tolerance may restrict their adoption in the high rainfall zone of southern Australia. The waterlogging tolerance of three species of Ornithopus (compressus, sativus and pinnatus) was determined by comparing the root and shoot growth of plants in deoxygenated stagnant agar nutrient solution (simulated waterlogging) with those in aerated nutrient solution. The responses were benchmarked against the known waterlogging-tolerant pasture legume Trifolium michelianum. All Ornithopus cultivars were highly impacted by the deoxygenated stagnant treatment, including the anecdotally waterlogging-tolerant O. pinnatus. The 14-d stagnant treatment reduced root dry mass by 32?62% and root relative growth rate (RGR) by 36?73%. At the same time, root porosity increased from 1.4 to 8.8%. Following a 14-d recovery period, where plants were returned to aerated nutrient solution, Ornithopus spp. failed to increase their shoot RGR (particularly for O. sativus cultivars) but root RGR returned to that of the aerated controls. The stagnant conditions inhibited the transport of K+ to the shoots in all species, as evidenced by lower shoot tissue K+ concentrations, with O. compressus and O. sativus most adversely impacted (45% and 48% of the tissue concentration of aerated control plants). We conclude that the suggested area for Ornithopus spp. adaptation should not preclude areas of high rainfall as they have root adaptations that would assist them in coping with transient water excess; however, soil types and surface profiles conducive to long-term waterlogging should be avoided to negate significant productivity losses.