Establishment and yield of perennial grass monocultures and binary mixtures for bioenergy in North Dakota

To develop appropriate bioenergy production systems to match site-specific situations, establishment and yield were evaluated for switchgrass (Panicum virgatum L.), intermediate wheatgrass [Thinopyrum intermedium (Host) Barkworth and D.R. Dewey], tall wheatgrass [Thinopyrum ponticum (Podp.) Z.-W. Liu and R.-C. Wang], and three binary mixtures at four sites in North Dakota from 2006 to 2011. One year after seeding in 2007, intermediate wheatgrass, tall wheatgrass, a binary mixture of tall wheatgrass and intermediate wheatgrass, and a binary mixture of tall wheatgrass with ‘Sunburst’ switchgrass (dominated by tall wheatgrass) stand canopy cover was above 85% at all four sites. Sunburst switchgrass and its binary mixture with big bluestem (Andropogon gerardiiVitman) stand canopy cover reached 100% at Carrington, the most eastern site; and below 35% at Williston, the most western site, 1 yr after seeding. Meanwhile, their stand canopy cover was more than 70% at Minot and Streeter, the north central and south central sites, respectively, 2 to 3 yr after seeding. Sunburst switchgrass produced the highest biomass at Carrington (10.6 ± 1.8 Mg ha⁻¹), whereas intermediate wheatgrass was the highest at Williston (3.0 ± 1.0 Mg ha⁻¹). The binary mixture of tall wheatgrass with Sunburst switchgrass had the highest yield at Minot (8.5 ± 2.5 Mg ha⁻¹) and Streeter (6.7 ± 1.9 Mg ha⁻¹). Yields of binary mixtures were at least comparable to and sometimes higher than those of their compositional component monocultures. Binary mixtures with carefully selected species could have potential for bioenergy production systems in North Dakota.