Field comparison of pre-inoculated alfalfa seed and traditional seed inoculation with inoculant prepared in sterile or non-sterile peat

Abstract

Rhizobium inoculant products in North America are often prepared using non-sterile peat and may contain more contaminants than rhizobia. The effectiveness of sterile and non-sterile peat-based inoculants applied to alfalfa (Medicago sativa) seed using either traditional seed inoculation just before planting, or pre-inoculated and commercially coated, were evaluated for three years (eight harvests) at two sites in northwestern Alberta. Seeds inoculated just before planting had more rhizobia at planting time than pre-inoculated seed. When results from all the three years were combined, inoculation with Rhizobium, either seed-applied or pre-inoculated, significantly (P<0.05) increased nodule dry matter (DM) at both sites. However, the response of forage N and DM yields to inoculation were significantly higher with seed application than with seed coating at one site, and vice–versa at the other site. Differences resulting from the use of non-sterile peat or sterile peat were not significant.