Rebecca E. Haling1, Lawrie K. Brown2, Adam Stefanski1, Daniel R. Kidd3, Megan H. Ryan3, Graeme A. Sandral4, Phillip G.H. Nichols3,5, Timothy S. George2, Hans Lambers3, Richard J. Simpson1
1 CSIRO Agriculture, GPO Box 1700, Acton, ACT, 2601. email@example.com
2 The James Hutton Institute, Invergowrie, Dundee DD2 5DA, UK.
3 The University of Western Australia, School of Plant Biology & Institute of Agriculture, Crawley, WA, 6009.
4 Department of Primary Industries, Wagga Wagga Agricultural Institute, Pine Gully Road, Wagga Wagga, NSW, 2650.
5 Department of Agriculture and Food Western Australia, 3 Baron-Hay Court, South Perth, WA, 6151.
Subterranean clover has a requirement for relatively high soil P fertility to achieve high yields. However, some other pasture legumes can yield as well as subterranean clover with less applied P as a consequence of having roots that can explore soil more effectively. The aim of this work was: (i) to determine whether there is variation in yield among cultivars of subterranean clover when grown in low-P soil, and (ii) to determine the root morphology traits underpinning this variation. Thirty cultivars of subterranean clover were grown at an intermediate and high level of soil P availability in a pot experiment. The cultivars had similar shoot yields in the high-P soil, but varied two-fold in shoot yield at the intermediate level of P supply. In a further experiment, the root morphology acclimation of five of these cultivars was assessed in response to seven rates of soil P availability. Cultivars that had a combination of high root length density and high specific root length were able to maintain higher soil exploration at lower concentrations of available P. They acquired more P from low-P soil and yielded better than the cultivars with roots poorer at nutrient foraging. The results indicate that there is significant intra-specific variation in P-acquisition efficiency among subterranean clover cultivars and this is potentially useful for improving pasture yields in marginally P-deficient soils.