Research note: The use of Lolium multiflorum and uninoculated Trofolium subterraneum as reference crops in nitrogen fixation studies

Abstract

The ¹⁵N natural abundance and¹⁵ N dilutions methods were used to determine the viability of using either Lolium Multiflorum (annual ryegrass) or uninoculated Trifolium subterraneum (subterrenean clover), as non-fixing reference crops in N₂-fixation studies. The δ¹⁵ N values for the¹⁵ N natural abundance method and atom% ¹⁵N values for the ¹⁵N dilution method for plant and soil samples are presented. The ryegrass pastures showed the least variation in δ¹⁵N and atom%¹⁵N values between experimental plots. This crop appeared to be a more appropriate choice in such studies, but further investigation is needed to confirm this observation. The use of uninoculated subterranean clover as a reference crop seemed problematic, since inoculation with effective rhizobia could not be prevented. Relatively high variation in δ¹⁵N values for inoculated for subterranean clover was obtained compared to the atom% ¹⁵N values. This result indicated that the use of the ¹⁵N natural abundance method should be evaluated for other pasture legume species.

Keywords: botany; crops; Lolium multiflorum; nitrogen fixation; nodulation; Roodeplaat Research Station; ryegrass; South Africa; subterraneum clover; Trifolium subterraneum; Woogenellup; ¹⁵N

African Journal of Range and Forage Science 1995, 12 (1):46–48