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

Rhizobium inoculant products in North America are often prepared using non- sterile peat and may contain more contaminants than rhizobia. The effective ness of sterile and nonsterile peat-based inoculants applied to alfalfa (Me dicago sativa) seed using either traditional seed inoculation just before p lanting, or pre-inoculated and commercially coated, were evaluated for thre e years (eight harvests) at two sites in northwestern Alberta. Seeds inocul ated just before planting had more rhizobia at planting time than pre-inocu lated seed. When results from all the three years were combined, inoculatio n with Rhizobium, either seed-applied or pre-inoculated, significantly (P < 0.05) increased nodule dry matter (DM) at both sites. However, the respons e of forage N and DM yields to inoculation were significantly higher with s eed application than with seed coating at one site, and vice-versa at the o ther site. Differences resulting from the use of nonsterile peat or sterile peat were not significant.