The 15N natural abundance and15 N dilution methods were used to determine the viability of using either Lolium multiflorum (annual ryegrass) or uninoculated Trifolium subterraneum (subterranean clover), as non?fixing reference crops in N2?fixation studies. The δ13N 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% I5N 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 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.
Journal articles from the Grassland Society of Southern Africa (GSSA) African Journal of Range and Forage Science as well as related articles and reports from throughout the southern African region.