Cultivar effects on oat-berseem clover intercrops

Oat (A vena sativa L.) intercropped with berseem clover (Trifolium alexandr inum L.), an annual forage legume, has economic and biological advantages f or use as a rotation crop in the north-central USA. To investigate the effe cts of different oat and berseem clover cultivars on the productivity of th e intercrop and its components, and to test for interspecific cultivar inte ractions, 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 interc rop biomass. Berseem clover cultivars varied for forage yield, stand, matur ity, damage due to disease and insects, and effects on intercrop biomass. I n one environment, only one of seven berseem clover cultivars survived afte r the first forage harvest. Adding oat to berseem clover reduced total fora ge and weed yields, clover stands, and relative maturity of clover, but inc reased 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 oa t test weight. Cultivar rankings of each species differed in monoculture vs . intercrop. Interspecific cultivar interactions were not significant for m ost traits. Greater genetic improvement in the productivity of the oat-bers eem clover intercrop will more likely be achieved by improvement of general agronomic productivity of berseem clover than by trying to enhance specifi c ecological combining ability of particular oat and berseem clover cultiva r combinations.