Which of the following crops primarily benefits from the addition of nitrogen-fixing bacteria in the seed?

The addition of nitrogen-fixing bacteria is particularly beneficial for soybeans due to their symbiotic relationship with Rhizobium species. Soybeans, being legumes, have special root nodules that house these bacteria. During this symbiosis, the bacteria convert atmospheric nitrogen into a form that the plant can use, thereby enriching the soil with nitrogen and reducing the need for synthetic fertilizers. This relationship not only aids in the growth and overall health of the soybean plants but also contributes to soil fertility for future crops, as the residual nitrogen benefits subsequent plantings.

In contrast, corn, wheat, and barley do not have the same type of symbiotic relationship with nitrogen-fixing bacteria. These crops primarily rely on external sources of nitrogen, such as soil nutrients or fertilizers, for their growth and development. This fundamental difference in nutrient acquisition highlights why soybean is the crop most associated with the benefit from nitrogen-fixing bacteria.