Annual Medic and Berseem Clover Dry Matter and Nitrogen Production in Rotation with Corn

Abstract

Annual medic (Medicago truncatula Gaertn.) and berseem clover (Trifolium alexandrinum L.) have potential to fix atmospheric N2 for use by subsequent crops. Our objectives were to determine the dry matter and N production of annual barrel medic and berseem clover, and their effect on grain yield of a subsequent corn (Zea mays L.) crop. First‐year treatments included spring‐seeded annual medic–oat (Avena sativa L.) and berseem clover–oat intercrops; summer‐seeded annual medic following spring‐seeded oat; and a spring‐seeded oat monoculture. The second‐year corn crop was fertilized with four N rates. In three of four environments, berseem clover had greater average fall dry matter (4392 kg ha−1) and N yield (125 kg ha−1) than spring‐ or summer‐seeded barrel medic. Spring‐ and summer‐seeded medics had similar fall dry matter (1309 kg ha−1 avg.) and N yields (38 kg ha−1 avg.) in two environments, but spring‐seeded medics had greater dry matter and N yield than summer‐seeded medic in two environments (avg. dry matter yield of 5304 and 2428 kg ha−1, respectively, and N yield of 138 and 70 kg ha−1, respectively). Berseem clover and medic did not consistently differ in their effects on soil NO3–N or corn grain yield when no N fertilizer was applied. Legume treatments increased second‐year corn grain yields from 9% for the silt loam soil to 82% for the loamy sand soil compared with the no‐legume treatment when no fertilizer N was applied; however, this effect decreased as N fertilizer rate increased.