Effect of Rhizobium Numbers on Nodulation and Dinitrogen Fixation in Groundnut

In greenhouse studies, shoot and nodule wt./plant of groundnut cv. Kadiri 71-1 increased with increase in inoculum density from 6.1 × 10² to 3.2 × 109 rhizobia/seed. In a 2nd experiment with cv. Robut 33-1 and TMV2 inoculated with 2 Rhizobium strains, number of nodules/plant increased from 6-11 at 2.7 × 10² to 143-243 at 2.7 × 108 rhizobia/seed but N2 fixation at 106 rhizobia/seed was close to that at 108. Strain 5a/70 fixed more N2 at a given inoculum density than strain NC92.ADDITIONAL ABSTRACT:In greenhouse studies, seedlings of three cultivars were inoculated with Rhizobium at four inoculum densities (102-109 rhizobia/seed). Robut 33-1 and TMV2 required 106 rhizobia/seed for maximum nodulation and nitrogen fixation, while Kadiri 71-1 required larger numbers