Environmental Engineering Reference
In-Depth Information
Switchgrass is adapted to a wide range of habitats, climatic conditions, and management
strategies. In North America, switchgrass can be found in hardiness zones 3-9, from southern
Canada (Manitoba to Newfoundland) to Baja California and the Gulf Coast (central Mexico to central
Florida) (Figure 22.1). Switchgrass tolerates drought, extreme heat and cold, and moderately acid
soils, and has relatively few major insect or disease pests. Switchgrass can be defoliated a number of
times during the growing season, as in a managed grazing system, or infrequently, as in a bioenergy
management system with only one or two harvests per season. Timing of harvests is moderately
critical, largely to ensure that the plant is allowed to translocate storage carbohydrates to roots for
regrowth after harvest and following overwintering. Grazing systems should incorporate adequate
rest periods, although hay or bioenergy management systems should avoid harvesting during the last
few weeks of the growing season to allow carbohydrate storage.
Switchgrass is a C
4
species with associated anatomical and physiological characteristics
(Waller and Lewis 1979). Switchgrass is very slow to establish, largely because establishment-
year development is oriented toward extensive root and crown development, often resulting in
intense above-ground competition between switchgrass shoots and annual weeds. Both pre- and
postemergence herbicides are valuable tools that aid in the establishment of switchgrass, shortening
the time required to reach successful establishment and maximal biomass yields.
Interest in switchgrass as a bioenergy feedstock began when the U.S. Department of Energy
(DOE) initiated its Bioenergy Feedstock Development Program (BFDP) by selecting switchgrass
as the herbaceous model species. The decision was made largely because of consistently high
biomass yields relative to other species across a broad geographic landscape, the relative simplicity
of switchgrass propagation by seed, and an existing seed industry (McLaughlin and Kzsos 2005;
Parrish and Fike 2005; Sanderson et al. 2007). Accomplishments of this program are credited
with the approximately 25% increase in biomass yields of switchgrass because of the improved
description and deployment of adapted cultivars, improved harvest and fertility management,
and the development of new cultivars with higher biomass yield and expanded adaptation ranges
(Sanderson et al. 2007).
60°
15°
FIGure 22.1
Historical range of switchgrass in North America.
