Cultivar Effects on Oat–Berseem Clover Intercrops

Oat ( Avena sativa L.) intercropped with berseem clover ( Trifolium alexandrinum L.), an annual forage legume, has economic and biological advantages for use as a rotation crop in the north‐central USA. To investigate the effects of different oat and berseem clover cultivars on the productivity of the intercrop and its components, and to test for interspecific cultivar interactions, we evaluated binary combinations and monocultures of a sample of oat and berseem clover cultivars in three Iowa environments. Oat cultivars varied for oat traits, effects on clover stands and yield, and total intercrop biomass. Berseem clover cultivars varied for forage yield, stand, maturity, damage due to disease and insects, and effects on intercrop biomass. In one environment, only one of seven berseem clover cultivars survived after the first forage harvest. Adding oat to berseem clover reduced total forage and weed yields, clover stands, and relative maturity of clover, but increased total crop biomass and forage plant health. Adding berseem clover to oat did not reduce oat grain or straw yields, and in one year increased oat test weight. Cultivar rankings of each species differed in monoculture vs. intercrop. Interspecific cultivar interactions were not significant for most traits. Greater genetic improvement in the productivity of the oat‐berseem clover intercrop will more likely be achieved by improvement of general agronomic productivity of berseem clover than by trying to enhance specific ecological combining ability of particular oat and berseem clover cultivar combinations.