Effect of Nitrogen Fertilizer on Yield and Nodulation of Dry Bean (Phaseolus vulgaris L.) in Southern Manitoba

Dry bean (Phaseolus vulgaris L.) production practices in Canada include application of nitrogen (N) fertilizer to overcome historically low biological N fixation. This is the first investigation of yield, nodulation, and economic response of modern cultivars to N fertilizer rates in Manitoba. The response of one pinto and one navy bean cultivar to five rates of N fertilizer (0, 39, 78, 118, and 157 kg N ha-1) without inoculation was evaluated across 5 site-years in southern Manitoba. Nitrogen treatment had no interactive effect with bean type on nodulation or seed yield. Nodulation of dry bean was not affected with 39 kg N ha-1 but was reduced with rates of 78 kg N ha-1 or higher. Seed yield increased linearly with N rate and was significantly greater than the 0 N rate at the highest rate of N (157 kg N ha-1) only. Application of N fertilizer at any rate did not increase economic return compared to the non-inoculated, non-fertilized control. The relatively high yields achieved in this study and the non-economical yield response to N fertilizer suggests that N rates may be reduced in dry bean production if future work can confirm that native soil rhizobia are compatible with widely grown dry bean cultivars for biological N fixation.