Efficiency of alfalfa seed priming and rhizobial-based liquid inoculants in an Eutric Cambisol

In the last few decades, peat-based bioinoculants have been proven as successful in alfalfa (Medicago sativa L.) seeds inoculation. However, the use of liquid inoculants or pre-inoculated seeds will greatly facilitate the sowing of alfalfa as a small seed legume. Therefore, this study evaluated the effect of four liquid formulations on the survival of Sinorhizobium (Ensifer) meliloti strain 218 during long-term storage. Sodium-alginate (SA) and polyvinylpyrrolidone (PVP) did not affect the growth of S. meliloti strain 218 and showed a significant positive effect on its survival in liquid bioinoculants up to 240 days of storage. The effect of seeds pre-inoculation on the efficiency of nitrogen (N) fixation in alfalfa plants in test tube and a two-year field experiment was measured. The field experiment was conducted in 2018 and 2019 in an Eutric Cambisol. The dry weight of alfalfa shoots and total N content significantly increased in pre-inoculated seeds with all media, compared to the control treatments without pre-inoculation and adding mineral N. In both years of cultivation, the highest total shoot dry weight was achieved by seeds pre-inoculation with SA and PVP 3 months before sowing. Furthermore, in these treatments, shoot dry weight significantly increased compared to the treatment with mineral N in the 2nd (2019) year. The results of the research showed that rhizobial bioinoculants with SA and PVP could be used as liquid bioinoculants as well as for successful pre-inoculation of alfalfa seeds.