Аннотация:Annual medic ( Medicago truncatula Gaertn.) and berseem clover ( Trifolium alexandrinum L.) have potential to fix atmospheric N 2 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 NO 3 –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.
