Technical Abstract: A biological nitrogen fixation (BNF) experiment was conducted in the field in Paterson, Washington in 2010. The objective was to survey bean genotypes for biological nitrogen response under low soil N conditions. Twenty-eight genotypes were screened from all major U.S. market classes and include checks P-152, a high nitrogen fixer, and a non-nod check R99 (Park and Buttery, 2006). However, data for P-152 is not included in this report due to late maturity.The non-nodulating genotypic check R99 had 43% more seed yield in the N (3460 kgha-1) than the NT (1966 kgha-1) which suggests that response to supplemental N in the absence of nodulation was detectable in this field trial. Across the Andean genotypes tested there was a significant treatment effect on yield resulting in a 10% reduction between N and BS treatments, and 4% between N and NT, though insignificant. For Durango genotypes there was no significant difference between NT and N treatments and a 9% reduction for yield between N and BS treatments. Mesoamerican genotypes had no significant differences among all three treatments. Across all genotypes there was a consistent significant effect for the BS inoculant treatment which unexpectedly resulted in 7 and 8% less yield than the NT & N treatments, respectively (data not shown). Perhaps the added Rhizobia were less effective, in part, by inhibiting root colonization by the endemic strains.