Field investigations were undertaken during the winters of 1971–6 to study the grain yield responses of lentil cultivars to seed inoculation with single and mixtures of Rhizobium strains. An effective symbiosis and consequent increase in the grain yield was associated with the efficacy of the strain. Inoculation with a superior strain produced 23–32 % more grain than no inoculation on loamy-sand soil and 46–90% more on sandy-loam soil.

In separate studies comprising inoculation and nitrogen treatments, the seed treated with an effective Rhizobium strain gave on average 43% more yield than no inoculation and the application of 25 kg N/ha alone gave the same yield as inoculation. Rhizobium inoculation plus 20 kg N/ha was the best combination for maximum yield under both loamy-sand and sandy-loam soils.