Interactive effects of field pea genotypes and Rhizobium Leguminosarum strains on nodulation, yield, and nitrogen fixation in Sinana district, Ethiopia

Field pea (Pisum sativum L.) is one of the most important food legumes in the highlands of Ethiopia, but its productivity in Sinana District is limited by poor soil fertility and inefficient biological nitrogen fixation (BNF). This study examined the joint effects of field pea genotypes and Rhizobium leguminosarum strains on nodulation, yield, nutrient uptake, and nitrogen fixation in greenhouse and field experiments. Two strains (EAL 300 and EAL 302), their mixture, and a control were compared for three varieties (local, 'Wayitu', and 'Dadimos') in a factorial randomized complete block design (RCBD) with three replications. Greenhouse experiments showed that EAL 302 had better survival ability on seeds, competitiveness, and symbiotic efficiency than EAL 300. In the field experiment, significant interactions between genotypes and strains were found for nodulation and straw yield. Inoculation with EAL 302 increased nodule dry weight, plant dry matter, grain yield (2900 kg ha⁻¹), straw yield (5633 kg ha⁻¹), total Nitrogen (TN) uptake (169.7 kg N ha⁻¹), and total nitrogen fixed (242 kg N ha⁻¹) significantly compared with the uninoculated control. Among varieties, 'Wayitu' had the highest grain yield (2876 kg ha⁻¹) and better nodulation and nutrient uptake. The combination of 'Wayitu' and EAL 302 was found to be the most effective symbiotic combination. The results clearly show that genotype-strain interaction is an important factor in improving BNF and yield. Inoculation with EAL 302, especially 'Wayitu', is recommended as a promising inoculation strategy to improve field pea yield, nitrogen fixation, and soil nitrogen status in Sinana District.