AGRONOMIC PERFORMANCE OF QUACKGRASS AND HYBRID WHEATGRASS POPULATIONS

Quackgrass [Elytrigia repens (L.) Nevski] is a troublesome weed that h as found recent use as a parent in interspecific hybrids with other Tr iticeae grasses. The objective of this research was to determine the p otential of quackgrass and interspecific hybrid populations, involving quackgrass as a parent, for use as forage crops in the northcentral U SA. Field experiments were conducted between 1988 and 1995 at Arlingto n and Marshfield, WI to compare six quackgrass and four hybrid wheatgr ass populations to check cultivars of orchardgrass (Dactylis glomerata L.), smooth bromegrass (Bromus inermis Leysser), timothy (Phleum prat ense L.), tall fescue (Festuca arundinacea Schreber), and reed canaryg rass (Phalaris arundinacea L.). Under relatively normal to dry conditi ons, both quackgrass and hybrid wheatgrass had forage yields (7.56-7.7 7 Mg ha(-1)) in the middle of the range of most other species (5.03-8. 94 Mg ha(-1)). However, on wetter soils, both quackgrass and hybrid wh eatgrass had forage yields (6.28-6.39 Mg ha(-1)) similar to the means of the lowest fielding cultivars of the cultivated species (5.51-6.81 Mg ha(-1)). While quackgrass was reasonably adapted to mixtures with l egumes, showing a mean grass concentration (492 g kg(-1)) within the r ange of cultivars (355-563 g kg(-1)), hybrid wheatgrass was unadapted to mixtures with legumes, with grass concentration seldom greater than natural levels (43-75 g kg(-1)) and decreasing with age. Large genoty pe x environment interactions and differential adaptation of strains w ill limit the effectiveness of programs to recommend the use of either quackgrass or hybrid wheatgrass as cultivated forage crops in the nor th-central USA.