Biomass Yield from Planted Mixtures and Monocultures of Native Prairie Vegetation Across a Heterogeneous Farm Landscape

Farms in the glaciated tallgrass prairie region of North America are topographically heterogeneous withwide-ranging soil quality. This environmental heterogeneity may affect choice and placement of species planted for biomass production. We designed replicated experiments and monitored farm-scale production to evaluate the effects of landscape position, vegetation type, and year on yields of monoculture sand mixtures. Research was conducted on a 262-ha South Dakota working farm where cropland had been replanted with a variety of native grassland types having biofuel feedstock potential. Vegetation type (diverse mixture or switchgrass [Panicum virgatum L.] monoculture) and year interacted to influenceyield in replicated experiments (p \u3c 0.10). Mean annual switchgrass yield above a stubble height of 10 cmwas 9.3 Mg ha−1 in two replicated experiments, and was greater than yield of mixtures (7.3 Mg ha−1) in 6 of 7 year × vegetation type combinations. Landscape position interacted with year and vegetation type to influence yield (p \u3c 0.10). Variability was generally greatest at the lowest landscape position. On thefarm’s larger fields (0.4–46 ha), three-year mean yields of switchgrass monocultures cut at ground level(12.7 Mg ha−1) were also greater than yields of mixtures (9.7 Mg ha−1) but both were less than prairie cordgrass (Spartina pectinata Link) monoculture yield (13.2 Mg ha−1) in a restored wetland. A combination of prairie monocultures and mixtures, strategically placed across a farm landscape, could offer a balance of productivity, ecosystem services, and income with potential as biofuel feedstock and other income streams (hay, seed, beef)