Symbiotic Effectiveness of Indigenous Rhizobial Strains on Biological Nitrogen Fixation of Lablab (Lablab purpureus) in the Derived Savanna of Nigeria

Field and pot experiments were conducted in the derived savanna of Nigeria to determine the effectiveness of three indigenous rhizobial strains on the Nitrogen (N) fixation of lablab (Lablab purpureus). Soils were collected from two locations, Idi Ayunre and University of Ibadan Teaching and Research Farm (UITRF) for pot experiment in a completely randomised design with a factorial arrangement of 2 × 2 × 6. The treatments were soil type (Idi Ayunre and UITRF soils), sterilisation (partially-sterile and unsterile) and six rhizobial strains inoculation {three indigenous strains, IDC8, OISa-6e and TRC; two exotic strains, IRj 2180A and R25B; and the control (resident native rhizobial strains)}. A field experiment was further conducted at UITRF using five rhizobial inoculations, the three indigenous strains, a combination of R25B and IRj 2180A (R25B+IRj 2180A) and control. Data were collected on biomass dry weight, a number of nodules, nodule dry weight, N derived from the atmosphere (Ndfa), N and P uptake and total N fixed. No significant difference was observed in the Ndfa (%) among the strains. However, indigenous strains IDC8 and OISa-6e performed better than the resident native rhizobia regarding N fixed, dry biomass weight, nodule formation and N uptake. N fixed by lablab inoculated with IDC8 was more than 200% higher than that fixed by resident native bacteria. Lablab N fixation efficiency can be improved using effective indigenous rhizobial strains. Further screening of indigenous strain for N fixation efficiency is recommended.