Sainfoin (Onobrychis viciifolia Scop.) is a forage legume of growing interest in different agroecosystems due mainly to good palatability, drought tolerance and presence of polyphenols, including tannins. The effect of inoculation with two strains of Rhizobium on seed of a sainfoin ecotype 'Reznos' and the sowing date (spring and autumn) on forage yield and nutritive value was studied in Asturias during 2014‑2015. The largest production of dry matter per harvest was found in treatments with sainfoin inoculated compared to un‑inoculated sainfoin. Similarly, inoculated sainfoin treatments had higher crude protein content than un‑inoculated treatments. In both cases, there were no differences between the two Rhizobium strains. Spring sowing showed higher values of dry matter yield per harvest than autumn sowing. Nodulation of sainfoin was effective both in its influence on dry matter production and its higher crude protein values.