Technical Abstract: Information is limited concerning how harvest date, storage method and duration of storage interact to influence switchgrass biomass loss and feedstock quality. Our objective was to compare the effect of harvest date and storage practice on switchgrass biomass loss for the biorefinery market. A 23-ha field of ‘Shawnee’ switchgrass was seeded at Mead, NE in 2006. Switchgrass was harvested with commercial haying equipment at anthesis (1 August) and 2-weeks after the first killing frost in 2007 and 2008. Switchgrass was baled in large round bales (net-wrapped 3 times and net-wrapped 4 times) and large square bales and stored (open, covered, or in a hay barn), and the effects of storage method on the feedstock was determined. Bales from each harvest and baling method were weighed and sampled immediately after harvest and at 4-month intervals for 12 months. Average field-scale yield for the seeding year and two production years was 9 Mg ha-1. Preliminary data indicate biomass loss could be as great as 24% after 12 months of outdoor storage with inadequate bale protection.. Changes in switchgrass biomass and feedstock quality will be important to understand as the biorefinery market develops.