Preliminary evaluation of the effectiveness of Rhizobium leguminosarum bv. viceae strains in nodulating hairy vetch (Vicia villosa) in the sandy soils of Zimbabwe

Abstract

Hairy vetch (Vicia villosa Roth) is an introduced temperate forage legume in Zimbabwe that has no locally available commercial inoculant. In this study, Rhizobium leguminosarum bv. viceae strains MAR 1504, MAR 833 and MAR 346 available in Zimbabwe's strain bank were evaluated for nodulation and N₂-fixing effectiveness in a sandy soil (Typic Kandiustalf). There was no significant difference in hairy vetch biomass (range: 3.4–4.5 g pot⁻¹) and nitrogen (N) content between plants in acidic and limed soil, showing that soil acidity was not a major problem for hairy vetch productivity in the short term. Inoculation with R. leguminosarum significantly increased (p < 0.05) biomass production (range: 0.37–3.11 t ha⁻¹) and enhanced N₂ fixation of hairy vetch compared to the uninoculated control, which had no nodules and significantly less biomass. Hairy vetch fixed up to 66.5 kg N ha⁻¹ in the field, and this amount may be made available for cereal crops as green manure. From the strains tested, MAR 833 and MAR1504 were more effective than MAR 346 in increasing the amount of N₂ fixed per unit area and are thus recommended for further multilocation field testing in farmer's fields to allow conclusive identification of strains to use in commercial inoculant production.