Effect of Rhizobium Inoculation on Herbage Yield, Quality and Nitrogen Fixation of Annual Forage Legumes on Nitisols in Central Highlands of Ethiopia

The study was conducted with the objectives to evaluate the effect of Rhizobium leguminosarum biovar. viciae strain V6005 inoculation on yield, feed quality and nitrogen fixation of hairy vetch (Vicia villosa Roth.), woolly-pod vetch (Vicia dasycarpa Roth.), common vetch (Vicia sativa L.) and narbon vetch (Vicia narbonensis L.) on Nitisols at Holeta in the central highlands of Ethiopia. The experimental design was a randomized complete block design with three replicates. Analysis of variance (ANOVA) indicated that Rhizobium inoculation significantly (p < 0.05) affected vigor, root length, Root Dry Matter (RDM) accumulation, number of nodules per plant, crude protein (CP) and nitrogen fixation of these legumes. However, inoculation did not significantly (p > 0.05) influence days to emergence, stand count, plant height, fresh biomass yield, nodule fresh weight, nodulation rate, Neutral Detergent Fiber (NDF), Acid Detergent Fiber (ADF), ash, Organic Matter Digestibility (OMD) and Dry Matter (DM). Under low temperature characteristics of the study site woolly-pod vetch and hairy vetch showed a more promising agronomic performance and nitrogen fixation than common vetch and narbon vetch. The order of nitrogen fixation potential was woolly-pod vetch > hairy vetch > common vetch > narbon vetch as inoculated treatments of the respective species fixed 197.94, 165.80, 41.63 and 35.56 when compared to uninoculated control where these rates were 126.57, 127.64, 23.46 and 27.25 kg N ha-1. Improvement in nitrogen fixation of 22.40%, 34.85%, 74.78% and 39.69% was recorded due to inoculation for hairy vetch, woolly-pod, common vetch and narbon vetch respectively. Crude protein content of inoculated species was also improved following the same trend as for nitrogen fixation. This study indicate that the higher nitrogen yield obtained from tested Vicia species due to Rhizobium inoculation, especially from woolly-pod and hairy vetches depicts potential contribution of effective rhizobial strains to improve soil fertility and feed quality under subsistent mixed crop-livestock farming systems of the Ethiopian highlands.

کلیدواژه ها:

Forage legumes ، Rhizobia ، Inoculation ، Nitisols