Influence of Rhizobium inoculation on dry bean yield and symbiotic nitrogen fixation potential

Inoculation of dry bean (Phaseolus vulgaris L.) might have potential to increase symbiotic nitrogen fixation (SNF) and to reduce dependency on chemical fertilizers. Peat based inoculant can cause clogging of air seeder and therefore, the potential of liquid inoculant was compared to peat based- and without inoculant during 2016 and 2017 growing seasons in the Red River Valley of ND and MN. Seed yield and SNF, using 15N isotope enrichment, response to inoculation were studied for four pinto and four kidney bean cultivars. Inoculation did not increase seed yield; moreover, both liquid and peat inoculation reduced kidney cultivars' seed yield by 47% and 62% over control (without inoculation) treatment, respectively in 2016. In 2017, percent N derived from the atmosphere (%Ndfa) was significantly reduced by peat inoculation (61.2%) over control (76.7%). On average, pinto cultivars fixed 90.5 and 73.7 kg N ha−1 and kidney cultivars fixed 73.8 and 65.1 kg N ha−1, respectively in 2016 and 2017. The interaction between inoculation and cultivar influenced the quantity of SNF, specifically for kidney cultivars in 2017. Rather than inoculation, selection of cultivars had a more pronounced effect on seed yield and SNF.