The evaluation of effectiveness of Rhizobium lupini strains

Biologically fixed nitrogen plays an important role in crop rotation of green agriculture. Significant increase of legumes yields are obtained by seed treatment with active nitrogen fixing bacteria strains before sowing. The possibility of the improvement of plant biomass yields through the use of more efficient combinations of Rhizobia and legumes was explored. Experiments were carried out the at the Institute of Plant and Soil Sciences Latvian University of Agriculture to investigate the effectiveness of two Rhizobium lupini strains- a commercial preparation, nitragin, marketed by the company 'Bioefekts' and the strain Rhizobium lupini from the collection of the Institute of Soil and Plant Sciences. The test samples were placed in 5 L pots with washed river sand, mixed with Kemira GrowHow NPK 0-5-20 and microelements fertilizer. Nitrogen was added as ammonium nitrate, 0.024 g per 1 kg of sand for inoculated plants and ten times more (0.24 g kg-1) for the control variant, where plants were not inoculated. In the vegetation pot experiments three lupines species, L. luteus variety 'Juno', L. angustifolius variety 'Sonet' and L. albus variety 'Wat' were used. Before sowing the lupine seeds were inoculated with Rhizobium lupini strains. The results showed that plants receiving increased nitrogen dosages sprout later and lag in height in the period of active growth. The plant length depends on plant species. The smallest length was observed of the species L. angustifolius variety 'Sonet', the largest are plants of the species L. luteus variety 'Juno'. The inoculation of plant seeds promotes increase in plant length till the phase of bud formation. There are no significant differences between Rhizobium lupini strains. The largest fresh and dry weights were observed for L. albus variety 'Wat', but species L. angustifolius had the smallest fresh and dry weight. The largest dry matter content in plants till the stage of bud formation was observed for inoculated plants. After the phase of flowering it was found that symbiotic systems are not sufficient in providing nitrogen. The effectiveness of Rhizobium lupini strains are species dependent.