A survey of proportional dependence of subterranean clover [Trifolium subterraneum] and other pasture legumes on N2 fixation in south-west Australia utilizing 15N natural abundance
1994
Sanford, P. (Western Australian Dept. of Agriculture, Albany. Albany Regional Office) | Pate, J.S. | Unkovich, M.J. (Western Australia Univ., Nedlands. Dept. of Botany and Centre for Legumes in Mediterranean Agriculture)
In an attempt to understand why pasture production in southern Australia had declined markedly in recent years a survey of the symbiotic performance of the legume component of annual pastures on 81 farms (243 sites) was undertaken in the southern coastal region of Western Australia. The 15N natural abundance technique was used to determine the percentage of plant nitrogen derived from the atmosphere (NA) using capeweed (Arctotheca calendula) as principal non-fixing reference species. NA values were then related to edaphic and management information. The principal legume species encountered exhibited similar mean NA values but substantial variation in symbiotic performance was evident across the sites. Of the 24 edaphic and management factors evaluated, only one, percentage Al in shoot, DM showed a significant relationship with NA, with 40 percent of the pastures surveyed deemed at risk in terms of acidity related Al toxicity. High values NA for sub-clover were often associated with very low soil pH or high soil N, suggesting possible adaptation of symbiotic partnerships to acidity or high mineral N.
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