Sparse-Flowering Orchardgrass Is Stable Across Temperate North America.

Three sparse-flowering orchardgrass populations were developed by selective breeding as a mechanism to reduce stem production during the early spring season in management-intensive grazing systems.  These populations and three check cultivars were evaluated under frequent- and infrequent-harvest systems at 21 locations in the USA and Canada in 2008-2010. The sparse-flowering trait, including its impact on forage yield and quality, was stably expressed across temperate North America with relatively subtle variations associated with climate and geography.  Sparse-flowering populations had 61% fewer culms and panicles compared to cultivars, resulting in a 24% reduction in first-cut forage yield under a 3-cut system and a 31% reduction in first-cut yield under a 5-cut system.  The sparse-flowering trait had little impact on regrowth forage yield, resulting in total annual forage yield reductions of 14% under both harvest systems.  As partial compensation for the forage-yield reductions, sparse-flowering populations were 2% lower in neutral detergent fiber (NDF), 3% higher in NDF digestibility, and 2% higher in in vitro dry matter digestibility compared to normal populations at first harvest.  These sparse flowering populations have significant potential to improve flexibility in grazing management of orchardgrass-based pastures, provided that the management advantages have sufficienit value to offset the reductions in forage yield and carrying capacity.