Skip to main content
SLU publication database (SLUpub)

Research article2005Peer reviewed

Use of different plant parts to study N-2 fixation with N-15 techniques in field-grown red clover (Trifolium pratense)

Huss-Danell K, Chaia E


Red clover, Trifolium pratense L., is the dominant forage legume in Sweden and is usually harvested twice per year, once in June and once in August. Two N-15-based methods -N-15 isotopic dilution (ID) and N-15 natural abundance (NA) - were used to study N-2 fixation from spring until first harvest in late June, from first to second harvest in late August, and from second harvest until first frost in autumn in Umea, Sweden. The material studied comprized three neighbouring fields carrying a first year ley, a second year ley and a third year ley. For the N-15 ID method, small amounts of highly enriched N-15-nitrate were added to experimental plots. The non-legumes in the plots, essentially Phleum pratense L. together with Festuca pratensis L., served as reference plants for both the ID and N-15 NA measurements. Dry matter, N and N-15 were separately analysed in leaves (laminae), stems (including petioles), stubble and roots. The proportion of N derived from air (pNdfa) was then calculated for each plant part and for whole plants. Estimates of the proportion of N derived from N-2 fixation (pNdfa) were always very high, usually >= 0.8. Generally, estimates of pNdfa obtained by the ID and NA methods were similar, but the ID method gave higher estimates of pNdfa than the NA method when the highest N-2 fixation levels were recorded, at the August harvest. Regression analyses suggest that estimates of pNdfa in leaves could provide useful indications of pNdfa in shoots and whole T. pratense plants, thus avoiding the need for time-consuming root analyses

Published in

Physiologia Plantarum
2005, Volume: 125, number: 1, pages: 21-30

      SLU Authors

    • Huss-Danell, Kerstin

      • Department of Agricultural Research for Northern Sweden, Swedish University of Agricultural Sciences

    UKÄ Subject classification

    Agricultural Science

    Publication identifier


    Permanent link to this page (URI)