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ARS Home » Southeast Area » Booneville, Arkansas » Dale Bumpers Small Farms Research Center » Research » Publications at this Location » Publication #325000

Title: Switchgrass compositional variations arising from spatial distribution and legume intercropping

item ASHWORTH, AMANDA - Orise Fellow
item ALLEN, FRED - University Of Tennessee
item GODDARD, KEN - University Of Tennessee
item WARWICK, KARA - University Of Tennessee
item YEAMAN, DUNCAN - University Of Tennessee
item Pote, Daniel

Submitted to: Communications in Soil Science and Plant Analysis
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/5/2017
Publication Date: 9/5/2017
Citation: Ashworth, A.J., Allen, F.L., Goddard, K., Warwick, K.S., Yeaman, D., Pote, D.H. 2017. Switchgrass compositional variations arising from spatial distribution and legume intercropping. Communications in Soil Science and Plant Analysis. 48:1473-1485.

Interpretive Summary: Switchgrass is a native North American bunchgrass that requires minimal inputs, can be grown on marginal lands, and produces high biomass yields for cellulosic ethanol production. However, the conversion efficiency and enzymes required for producing ethanol from switchgrass biomass are dependent on quality and consistency of switchgrass. A research team investigated the effects of fertilization practices, legume intercropping, switchgrass farm location and harvest timing on quality and consistency of the biomass produced. The researchers found that legume intercropping had little effect, but switchgrass quality sometimes varied significantly with farm location and nitrogen fertilization. This study is of interest to scientists, extension personnel, agricultural producers, and the biofuel industry because it shows that switchgrass can be successfully intercropped with some legume species, and that switchgrass biorefinery facilities should expect variations in switchgrass feedstock composition that may require adjustments in enzyme requirements for the conversion to ethanol.

Technical Abstract: Switchgrass (Panicum virgatum) is a high–yielding, second-generation feedstock that can be grown on marginal land with minimal inputs. Due to the high genetic diversity within and among cultivars of this species, there may be a great amount of genotype x environment-induced differences among secondary cell wall constituents. In addition, management practices (e.g., fertilization and legume intercropping) may further affect homogeneity of feedstocks. Consequently, two separate experiments were conducted to determine factors influencing secondary cell wall constituents using near infrared spectrometry (NIR) of biomass. One experiment included testing influences from legume intercrops [alfalfa (Medicago sativa), red clover (Trifolium pretense), crimson clover (Trifolium incarnatum), hairy vetch (Vicia villosa), Illinois bundle flower (Desmanthus illinoensis), and partridge pea (Chamaechrista fasciculata)], fertilization [67 and 135 kg inorganic-nitrogen ha-1 (60 and 120 lbs ac-1, respectively)], and location impacts on feedstock components. The second experiment was aimed at determining feedstock compositional responses on producer farms by testing bale variance within and across locations. Clustering of NIR spectral data indicated differences in switchgrass chemical signatures among locations and nitrogen treatments, but less so among legume intercrops. Results from producer farms further suggested ‘Alamo’ switchgrass cell wall composition may vary across locations responsible for supplying biomass to a biorefinery, indicating switchgrass fermentability may vary across regions. Thus, conversion efficiencies and enzymatic requirements for ethanol production may be affected. Consequently, switchgrass can be intercropped with legumes for inorganic nitrogen displacement with minimal compositional changes, whereas location and nitrogen levels may influence feedstock quality and recalcitrance level.