| Summary: | One low salt tolerant alfalfa (Medicago sativa L.) cultivar and two germination salt tolerant alfalfa selections were compared for growth and N fixation at four salinity levels (0, -0.3, -0.6 and -1.2 Mpa). In the first experiment a Hoagland's solution at 5 ppm-N was used; in the second experiment the solution had a 1 ppm-N concentration and supplemental light was used. No significant differences were found among the cultivars. This provides additional support that germination salt tolerance is not necessarily related to salt tolerance for growth. Nitrogen fixed to the first harvest was 61, 48, 49, and 27% of the total shoot N for plants in the control, -0.3, -0.6, and -1.2 Mpa solutions, respectively. At the second harvest, N fixation percentages were 94, 89, 80, and 57% for the corresponding salinity levels which showed significant reduction in N fixation at -0.3 Mpa. The evaluation of N fixation was by 15N techniques.
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