Cultivar × binary mixture interaction effect on agronomic traits in orchardgrass

A study was conducted from 2009 to 2012 to evaluate and characterize the agronomic value of seven agronomic traits, including dry matter yield and forage quality of 25 orchardgrass cultivars grown in monoculture and binary mixtures with alfalfa. The irrigated Millville, UT, USA (41 degrees 4124N, 111 degrees 4948W) field site was characterized by a semiarid climate and elevation over 1300m. The cultivarxmixture interaction was significant for all traits but flag leaf height, and contained a substantial crossover component among the cultivars. Differences among cultivar means were significant for all traits in both the monoculture and mixture settings. Yet, concordance for high cultivar performance in both monoculture and mixture was low. Thus, the strong underlying cultivarxmixture interaction found in this study complicates the identification of best cultivars in both settings. Yet, for each trait cultivars were identified that possessed statistically high phenotypic performance under the monoculture and mixed sward conditions. Thus, despite the substantial cultivarxenvironment effect, it should be possible to develop orchardgrass cultivars with improved agronomic performance under both management conditions.