Nontechnical Summary Zhu, Y., C. C. Sheaffer, M. P. Russelle, and C. P. Vance. Dry matter accumulation and dinitrogen fixation of annual Medicago species. Farmers and scientists are learning the benefits of diversifying cropping systems. Lower pest infestations, more stable and higher crop yields, and reduced commercial fertilizer requirements are a few of these benefits. Including legumes in crop rotations can significantly reduce the need for purchased nitrogen fertilizer, but many farmers are reluctant to sow long-lived legumes, like alfalfa, because perennial crops limit flexibility in cropping decisions.
Annual medics are closely related to alfalfa but grow only for one season.
We measured the growth and nitrogen contribution of several annual medics under Upper Midwest conditions and found that they can contribute as much nitrogen in 2 to 3 months as farmers usually apply to corn.