Iron Deficiency Chlorosis (IDC) and weedy Amaranthus species are two production challenges affecting soybean production in North Dakota. Field experiments were conducted to evaluate the effect of an oat companion crop on soybean and to evaluate soybean preemergence herbicides effect on an oat companion crop and Amaranthus. An oat companion crop reduced IDC symptoms in one environment, but did not reduce IDC in others. An oat companion crop reduced Amaranthus biomass, but in many site years this suppression did not occur until soybean yield loss was realized. Flumioxazin and sulfentrazone consistently provided the greatest control of Amaranthus, but was also the most injurious to an oat companion crop. Greenhouse research evaluated competitiveness of two Amaranthus species, and factors tested did not influence competitiveness. Other forms of IDC and Amaranthus suppression may be more consistent with suppression and stable yields than that of an oat companion crop.