Screening of rice cultivars and diazotrophs combination for better n₂-fixing system

In a pot culture experiment three rice cultivars were inoculated with eight different N₂-fixing bacterial strains with the objective to find out effective nitrogen fixer and rice cultivar combination for better nitrogen nutrition. Dry weight of shoot and N-accumulation data showed that effect of diazotrophs was more in IR 50 than the other two varieties, MW 10 and CR 544-1-1. Among the ‘variety x diazotroph’ combinations, Azospirillum (Ap18) appeared to be the best followed by Pseudomonas (P12) and Azotobacter (A7) when inoculated to rice variety IR-50. In this study some isolates (D2, P3 and P4) failed to show any encouraging result although they had better acetylene reduction activity (ARA) under pure culture conditions.