New Zealand Journal of Agricultural Research abstracts

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Effect of rhizobia from caucasian clover (Trifolium ambiguum) on nodulation and nitrogen fixation of white clover (Trifolium repens)

H. N. Pryor¹
R. M. Elliot²*
W. L. Lowther¹
C. W. Ronson²

¹AgResearch
Invermay Agricultural Centre
Private Bag 50 034
Mosgiel, New Zealand

²Department of Microbiology
University of Otago
P.O. Box 56
Dunedin, New Zealand

*Present address: Tatua R&D Laboratory, Centre for Innovation, University of Otago, P.O. Box 56, Dunedin, New Zealand.

Abstract  Three glasshouse trials investigated N2 fixation in white clover following inoculation with rhizobia from caucasian clover. We grew white clover in agar, vermiculite/perlite and soils low in available-N and with no detectable rhizobia. Media were subsequently treated with inoculum containing rhizobia effective on either (i) caucasian clover, (ii) white clover, or (iii) mixtures of the two. The percentage of ineffective nodules on white clover increased as the proportion of rhizobia from caucasian clover in the inoculant mix increased. However, the percentages of ineffective nodules on white clover were less than the proportion of ineffective rhizobia in the inoculant, indicating that the ineffective rhizobia were less competitive in nodule formation. Foliage yield and symbiotic N₂ fixation in white clover were not significantly affected when ineffective rhizobia from caucasian clover made up 67% or less of the inoculant. However, when ineffective rhizobia made up a high proportion of the inoculant mix (>92%), both foliage yield and N₂ fixation were significantly reduced compared with plants inoculated with only white clover rhizobia. Extrapolation of the present glasshouse results to the field is difficult and further field trials are required to determine if rhizobia from caucasian clover have any effect on symbiotic N₂ fixation of white clover in pastoral situations.

Keywords  caucasian clover; competition; nitrogen fixation; nodulation; rhizobia; Trifolium ambiguum; Trifolium repens; white clover

A03019; Received 3 April 2003; accepted 15 August 2003; online publication date 26 February 2004
New Zealand Journal of Agricultural Research, 2004, Vol. 47: 75-83
0028-8233/04/4701-0075 © The Royal Society of New Zealand 2004

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