Soil inoculants for alfalfa grown on moderately acid soil

Abstract

Field experiments were conducted with alfalfa (Medicago sativa L. var Peace) planted on a soil with pH 5.8. Granular inoculant was applied with the seed, below the seed or beside the row, or liquid inoculant was applied beside the row. The inoculants were prepared with Rhizobium meliloti NRG‐61 which had been selected for low‐pH tolerance. Forage yield, nodule numbers and weight, and inoculant strain occupancy of nodules were measured. Granular inoculant applied with or below the seed resulted in greater than 87% of the nodules occupied by strain NRG‐61 and increased nodule numbers and weight and forage yield when the moisture conditions for germination and plant establishment were favorable. Under moisture limiting conditions, the inoculant had little effect. The use of granular or liquid inoculant banded beside the row after crop establishment was not effective in improving nodulation nor increasing forage yield.