Effect of Azospirillum inoculation on nitrogen fixation and growth of several winter legumes

Inoculation of naturally nodulated Pisum sativum L. (garden pea) with Azospirillum in the greenhouse caused a significant increase in nodule numbers above controls. Field inoculation of garden peas in the winter 1981-1982 and Cicer arietinum L. (chick pea), in winter 1982-1983, with Azospirillum one week after plant emergence, produced a significant increase in seed yield, but did not affect plant dry matter yield. For Vicia sativa L. (vetch) grown in soil in the greenhouse and in the field for forage, winter 1980-1981, inoculation significantly increased dry matter yield, %N, N-content, and acetylene reduction (nitrogen fixation) activity. In Hedysarum coronarium L. (sulla clover), winter 1981-1982, inoculated with both its specific Rhizobium (by the slurry method) and Azospirillum, 7 days after emergence, there was an increase in acetylene reduction above controls inoculated with Rhizobium alone. These results suggest that it is possible, under conditions tested in this work, to increase nodulation, nitrogen fixation, and crop yields of winter legumes by inoculation with Azospirillum.