Which of the following is an example of a nitrogen-fixing cover crop?

Clover is recognized as a nitrogen-fixing cover crop because it belongs to a group of plants known as legumes. Legumes have a unique ability to form symbiotic relationships with nitrogen-fixing bacteria, such as Rhizobium, which inhabit nodules on their roots. This relationship allows legumes to convert atmospheric nitrogen into a form that can be utilized by plants, thus enriching the soil with this essential nutrient.

By incorporating clover as a cover crop, farmers can enhance soil fertility naturally, reducing the need for synthetic fertilizers. This practice not only improves the nutrient content of the soil but also benefits subsequent crops grown in the same field by providing them with readily available nitrogen.

Other cover crops listed, such as oats, rye, and barley, do not possess this nitrogen-fixing capability. While they can improve soil structure and moisture retention, they do not contribute to the nitrogen levels in the soil the way clover and other legumes do.