Nodulation and acetylene reduction by two legumes with Rhizobia indigenous to northern Great Basin soils

Medicago sativa L. and Hedysarum boreale Nutt. were grown in the greenhouse on soils representing 27 of the major soil associations of the northern Great Basin. Nodulation of Medicago sativa L. by indigenous rhizobia occurred with 25 of the soil associations and of Hedysarum boreale Nutt. with 21 of these soil associations. Nitrogen fixation, as indicated by acetylene reduction activity, was greater for Medicago sativa L. than for Hedysarum boreale Nutt. for most of the soil associations. Multiple regression functions incorporating 49 independent climatic, edaphic, and vegetation variables failed to predict acetylene reduction activity with satisfactory precision.