Biomass Yield and Stand Characteristics of Switchgrass in South Central U.S. Environments

Abstract

Optimizing feedstock production from switchgrass (Panicum virgatum L.) requires careful matching of genotype to environment, especially for southern U.S. regions. Nine genotypes from four combinations of ecotype and morphological type were harvested once yearly in autumn for 3 or 4 yr at five locations across Texas, Arkansas, and Louisiana that varied in latitude and precipitation. Genotypes were evaluated for dry matter yield (DMY), plant density, tiller density, lodging, and rust (caused by Puccinia spp.) infection. Genotype × environment (G×E) interactions were identified for most traits. Biomass yield of all genotypes tended to increase with latitude, but lowland morphological types may have been more sensitive than upland morphological types to differences in moisture availability. Yield (5.82 vs. 14.97 Mg ha−1, respectively) and persistence (final stand density, 3.99 vs. 5.96 plants m−2) were lower for upland than for lowland genotypes, particularly at higher rainfall and more southern sites. Lowland genotypes were often able to compensate for stand thinning by increasing individual plant size, but upland genotypes were not. Lodging and rust scores were higher for upland than for lowland genotypes. Yield (13.65 vs. 9.75 Mg ha−1) and final plant density (5.58 vs. 4.95 plants m−2) were higher for southern than northern ecotypes. The southern‐lowland combination exhibited the best yield and persistence over the study region, and genotypes within this group exhibited variability in yield among sites. Therefore, development of switchgrass cultivars for biomass production in the southern USA should focus on the southern‐lowland genotypes.

Switchgrass as a biofuels feedstock in the USA

“…The first phase, funded largely by DOE, has involved evaluation of existing germplasm across much of the historical range of switchgrass in the USA. Multi-location cultivar evaluations have helped to define adaptation zones of existing cultivars, identifying the importance of photoperiod, cold tolerance, and heat tolerance in limiting the breadth of adaptation of most switchgrass cultivars Casler et al 2004;Cassida et al 2005a, b;Fike et al 2006a, b). These studies have also illustrated the remarkably broad adaptation range of cultivars such as Cave-in-Rock, which has superior biomass production far north and east of its origin (Madakadze et al 1998;Casler and Boe 2003) but reduced performance in northern dryland environments (Jefferson et al 2002;Berdahl et al 2005).…”

Exploring Potential U.S. Switchgrass Production for Lignocellulosic Ethanol

“…Similarly, yield and winter survival declines at high latitude sites, more so for strains of more southern origin, whether of lowland (Casler et al 2004) or upland morphology (Berdahl et al 2005). Responses to precipitation are ambiguous; some research has found that yields were not strongly correlated with precipitation inputs (Cassida et al 2005b), whereas many investigators have found positive correlations between precipitation and yield, with sensitivity to soil moisture differing between ecotypes (Berdahl et al 2005, Cassida et al 2005b, Lee and Boe 2005, Fike et al 2006a. The high degree of phenotypic and ecotypic variation is not surprising, given the cytotypic diversity within switchgrass.…”

“…Management factors play a role as well; low rainfall in August-September reduced yields in a two-cut, but not in a one-cut system (Reynolds et al 2000). Soil texture and depth, topography (e.g., distance from a stream), supplemental irrigation, different cultivar requirements, or excess rainfall close to harvest could all confound an overall relationship between yield and annual or "growing season" precipitation (Cassida et al 2005b). Very high growing season precipitation could also correlate with extensive cloud cover and associated low levels of solar radiation, tending to reduce yield.…”

“…One variable that can be eliminated in this analysis, however, is irrigation. In some of the field trials located in Texas (Sanderson et al 1999b, Cassida et al 2005b, plots were irrigated during the establishment years because of severe drought. Other than that, supplemental water was not provided in the studies cited.…”

Switchgrass (Panicum virgatum L.) Cultivar Adaptation, Biomass Production, and Cellulose Concentration as Affected by Latitude of Origin

“…Cultivation of switchgrass in this region will require cultivars adapted to northern latitudes. Northern ecotypes have a longer winter dormant period with better winter survival than southern ecotypes when grown at the same latitude [3]. The attributes of switchgrass for a biomass crop include its yield potential, longevity, water use and nutrient use efficiency, and suitability for marginal land.…”