Nitrogen Fertilization and Inoculation Effects on Dry Bean
Dry bean (Phaseolus vulgaris L.) has the ability to form symbiotic relationships with N2-fixing bacteria. The research objectives were to evaluate yield and growth differences between dry bean cultivars from black, navy, and pinto market classes, with different N management combinations utilizing urea fertilizer, and two rhizobacteria inoculants. Research was conducted near Park River and Prosper, ND, during 2010, 2012, 2013. The experiment was a RCBD 3 × 2 × 3 factorial with four replicates with three dry bean cultivars, two N fertility levels, and two rhizobacteria inoculum sources plus a non-inoculated treatment. The pinto cultivar was also evaluated in 2014. Results showed significant cultivar main effect differences for nodules per plant, vigor, height, and 1000 seed weight. The pinto cultivar had significantly more nodules per root (19) compared with the black (13) and navy cultivars (9). There were not significant differences between inoculant treatments. The fertilizer main effect indicated significant differences for vigor and 1000 seed weight. No significant interactions were detected among factors. Addition of 56 kg N ha-1 resulted in more vigorous plants, but had no effect on seed yield, and reduced 1000 seed weight at harvest at Park River in 2013. Root nodule number was higher with the inoculant treatments with 16.2 and 15.8 nodules per plant compared to the non-inoculated treatment with 10.7 nodules per plant at Park River in 2013. The pinto variety Lariat with an application of 56 kg ha-1 had visually greener plants in 2013 and 2014, except Park River in 2013, but SPAD readings were not following the same trend. Inoculation and application of N fertilizer on dry bean may not be necessary if rhizobacteria are present and soil N levels are sufficiently high but future research on rates, timing, and N source and appropriate strains of Rhizobia inoculant on other pinto varieties is suggested.