Alamo Switchgrass Research Articles

Octoploids Show Enhanced Salt Tolerance through Chromosome Doubling in Switchgrass (Panicum virgatum L.).

Polyploid plants often exhibit enhanced stress tolerance. Switchgrass is a perennial rhizomatous bunchgrass that is considered ideal for cultivation in marginal lands, including sites with saline soil. In this study, we investigated the physiological responses and transcriptome changes in the octoploid and tetraploid of switchgrass (Panicum virgatum L. 'Alamo') under salt stress. We found that autoploid 8× switchgrass had enhanced salt tolerance compared with the amphidiploid 4× precursor, as indicated by physiological and phenotypic traits. Octoploids had increased salt tolerance by significant changes to the osmoregulatory and antioxidant systems. The salt-treated 8× Alamo plants showed greater potassium (K+) accumulation and an increase in the K+/Na+ ratio. Root transcriptome analysis for octoploid and tetraploid plants with or without salt stress revealed that 302 upregulated and 546 downregulated differentially expressed genes were enriched in genes involved in plant hormone signal transduction pathways and were specifically associated with the auxin, cytokinin, abscisic acid, and ethylene pathways. Weighted gene co-expression network analysis (WGCNA) detected four significant salt stress-related modules. This study explored the changes in the osmoregulatory system, inorganic ions, antioxidant enzyme system, and the root transcriptome in response to salt stress in 8× and 4× Alamo switchgrass. The results enhance knowledge of the salt tolerance of artificially induced homologous polyploid plants and provide experimental and sequencing data to aid research on the short-term adaptability and breeding of salt-tolerant biofuel plants.

Comparative transcriptome study of switchgrass (Panicum virgatum L.) homologous autopolyploid and its parental amphidiploid responding to consistent drought stress

BackgroundNewly formed polyploids may experience short-term adaptative changes in their genome that may enhance the resistance of plants to stress. Considering the increasingly serious effects of drought on biofuel plants, whole genome duplication (WGD) may be an efficient way to proceed with drought resistant breeding. However, the molecular mechanism of drought response before/after WGD remains largely unclear.ResultWe found that autoploid switchgrass (Panicum virgatum L.) 8X Alamo had higher drought tolerance than its parent amphidiploid 4X Alamo using physiological tests. RNA and microRNA sequencing at different time points during drought were then conducted on 8X Alamo and 4X Alamo switchgrass. The specific differentially expressed transcripts (DETs) that related to drought stress (DS) in 8X Alamo were enriched in ribonucleoside and ribonucleotide binding, while the drought-related DETs in 4X Alamo were enriched in structural molecule activity. Ploidy-related DETs were primarily associated with signal transduction mechanisms. Weighted gene co-expression network analysis (WGCNA) detected three significant DS-related modules, and their DETs were primarily enriched in biosynthesis process and photosynthesis. A total of 26 differentially expressed microRNAs (DEmiRs) were detected, and among them, sbi-microRNA 399b was only expressed in 8X Alamo. The targets of microRNAs that were responded to polyploidization and drought stress all contained cytochrome P450 and superoxide dismutase genes.ConclusionsThis study explored the drought response of 8X and 4X Alamo switchgrass on both physiological and transcriptional levels, and provided experimental and sequencing data basis for a short-term adaptability study and drought-resistant biofuel plant breeding.

CELF significantly reduces milling requirements and improves soaking effectiveness for maximum sugar recovery of Alamo switchgrass over dilute sulfuric acid pretreatment

BackgroundPretreatment is effective in reducing the natural recalcitrance of plant biomass so polysaccharides in cell walls can be accessed for conversion to sugars. Furthermore, lignocellulosic biomass must typically be reduced in size to increase the pretreatment effectiveness and realize high sugar yields. However, biomass size reduction is a very energy-intensive operation and contributes significantly to the overall capital cost.ResultsIn this study, the effect of particle size reduction and biomass presoaking on the deconstruction of Alamo switchgrass was examined prior to pretreatment by dilute sulfuric acid (DSA) and Co-solvent Enhanced Lignocellulosic Fractionation (CELF) at pretreatment conditions optimized for maximum sugar release by each pretreatment coupled with subsequent enzymatic hydrolysis. Sugar yields by enzymatic hydrolysis were measured over a range of enzyme loadings. In general, DSA successfully solubilized hemicellulose, while CELF removed nearly 80% of Klason lignin from switchgrass in addition to the majority of hemicellulose. Presoaking and particle size reduction did not have a significant impact on biomass compositions after pretreatment for both DSA and CELF. However, presoaking for 4 h slightly increased sugar yields by enzymatic hydrolysis of DSA-pretreated switchgrass compared to unsoaked samples, whereas sugar yields from enzymatic hydrolysis of CELF solids continued to increase substantially for up to 18 h of presoaking time. Of particular importance, DSA required particle size reduction by knife milling to < 2 mm in order to achieve adequate sugar yields by subsequent enzymatic hydrolysis. CELF solids, on the other hand, realized nearly identical sugar yields from unmilled and milled switchgrass even at very low enzyme loadings.ConclusionsCELF was capable of achieving nearly theoretical sugar yields from enzymatic hydrolysis of pretreated switchgrass solids without size reduction, unlike DSA. These results indicate that CELF may be able to eliminate particle size reduction prior to pretreatment and thereby reduce overall costs of biological processing of biomass to fuels. In addition, presoaking proved much more effective for CELF than for DSA, particularly at low enzyme loadings.

Silvopasture Switchgrass Fertilized with Poultry Litter: Nutrient Removal, Soil Fertility, and Runoff Water Quality

ABSTRACTAlternative use of poultry litter (PL) for forest rather than pasture fertilization would improve forest soil fertility and reduce nutrient build-up in pasture. Yield and nutrient uptake of Alamo switchgrass (Panicum virgatum L.) in a loblolly pine (Pinus taeda L.) silvopasture annually fertilized with PL or urea at 80 and 160 kg N ha−1 for four years, and without fertilization were compared. Treatment effects on soil fertility and effect of PL on runoff water quality were also determined. Fertilization with N increased yields 120% to an average of 3.8 Mg ha−1 yr−1. Since nutrient removal was small, P, base cations and pH increased in the ≤30 cm depth soil with PL. Total P in edge-of-plot runoff was increased by 0.31 kg ha−1 y−1 at the higher PL rate. Two applications at this rate per tree rotation might be justified based on increased soil fertility and infrequently increased P load.

Morpho-Physiological Responses of Alamo Switchgrass During Germination and Early Seedling Stage Under Salinity or Water Stress Conditions

Switchgrass (Panicum virgatum L.) is a warm perennial grass with valuable characteristics as a biofuel crop. To avoid competition with food crops, biofuel crops will be likely relegated to less productive soils such as marginal lands. Consequently, the salinity and water scarcity problems that commonly affect marginal lands compromise biofuel crop germination, emergence, and seedling establishment. The aims of this study were to study the germination and seedling growth of switchgrass under salinity and water stress and to describe the morpho-anatomical responses of the roots and leaves in the seedlings to these stress conditions. The effect of salt and water stress was assessed using sodium chloride (NaCl) and polyethylene glycol (PEG) 8000 at the same water potentials of − 0.8, − 1.0, and − 1.2 MPa. Seeds were moist prechilled for 7 days at 5 °C and germinated at 30/15 °C (8 h light/16 h dark). NaCl treatments (− 0.8 and − 1.0 MPa) delayed germination rates but did not reduce the final germination percentage, whereas at a lower potential (− 1.2 MPa), the final germination percentage was diminished. The effects of PEG (− 1.0 and − 1.2 MPa) on the germination rate and final percentage were more detrimental than those induced by isosmotic concentrations of NaCl. PEG and NaCl reduced significantly the vigor index of − 0.8 to − 1.2 MPa. The morpho-anatomical changes such as the reduction in the root cross-sectional area and the thickening of the endodermis walls for both stress conditions and aerenchyma formation in the cortex under salinity could significantly contribute in the survival and tolerance during the early seedling stages.

Implications of biofuel-induced changes in land use and crop management on sustainability of agriculture in the Texas High Plains

Texas High Plains (THP), which is an important cotton (Gossypium hirsutum L.) growing region in the United States faces challenges from declining/deteriorating groundwater levels/quality, recurring droughts and severe wind erosion. Growing cover crops after harvesting cotton and/or changing land use from cotton to perennial bioenergy crops could not only address above challenges, but also assist in meeting the national biofuel target. The objective of this study is to assess the implications of changes in land use (replacing cotton with Alamo switchgrass (Panicum virgatum L.) and Miscanthus×giganteus) and crop management (growing winter wheat (Triticum aestivum L.) cover crop) on hydrology and wind erosion in the Double Mountain Fork Brazos Watershed using the Agricultural Policy/Environmental eXtender (APEX) model. Simulated average annual wind erosion, total nitrogen (TN) loss to surface water and nitrate-nitrogen (NO3-N) leaching to groundwater reduced by more than 37%, 43% and 73%, respectively, when winter wheat was grown as a cover crop under the 457 mm (18-inch) annual groundwater pumping limit setup by the High Plains Water District. In addition, winter wheat produced about 0.20–0.26 kg m−2 of biomass for biofuel purposes. Land use change from irrigated cotton to switchgrass and rainfed cotton to Miscanthus decreased the TN load, NO3-N leaching and soil loss by wind erosion by > 89% relative to the baseline scenario. Under the groundwater pumping restrictions, multiple harvests of perennial grasses were found to be better in terms of biomass production (>2 kg m−2), and protection of groundwater and soil.

Organic carbon, nutrient, and salt dynamics in saline soil and switchgrass (Panicum virgatum L.) irrigated with treated municipal wastewater

AbstractThis study was conducted to evaluate the effects of treated municipal wastewater irrigation on soil organic carbon (SOC), soil macronutrients, Na, Cl, and SO4 dynamics in soil as well as switchgrass (Panicum virgatum L.) shoots under greenhouse conditions. Average SOC concentrations in upper 60 cm increased significantly from the prestudy level of 18 Mg ha−1 to between 21 and 23 Mg ha−1 at the end of the study (2009–2015) under different treatments. Annual average rate of increase for all four depths (upper 60 cm) ranged from 0.6 to 0.8 Mg ha−1 y−1. Nutrient concentration in soil samples was positively influenced by fertilizer application. N, P, and K concentrations in soil and switchgrass shoots were significantly positively correlated. On average, Alamo switchgrass cultivar under irrigated conditions removed 28.5 to 35.7 g N m−2, 2.52 to 3.48 g P m−2, and 29.6 to 38.4 g K m−2, and differences between freshwater and wastewater treatments were not significant. This indicated that wastewater irrigation did not result in excessive accumulation of nutrients in switchgrass tissue. Although salt constituents such as Na, Cl, and SO4 concentrations in soil increased over time as a result of wastewater irrigation, their concentration did not increase in switchgrass shoots, indicating a salt exclusion mechanism. The results of this greenhouse study indicated that the use treated municipal wastewater for irrigation can improve SOC contents of salt affected lands and extend the availability of freshwater in arid regions.

Hydrologic cost-effectiveness ratio favors switchgrass production on marginal croplands over existing grasslands.

Switchgrass (Panicum virgatum L.) has attracted attention as a promising second generation biofuel feedstock. Both existing grasslands and marginal croplands have been suggested as targets for conversion to switchgrass, but the resulting production potentials and hydrologic impacts are not clear. The objectives of this study were to model switchgrass production on existing grasslands (scenario-I) and on marginal croplands that have severe to very severe limitations for crop production (scenario-II) and to evaluate the effects on evapotranspiration (ET) and streamflow. The Soil and Water Assessment Tool (SWAT) was applied to the 1063 km2 Skeleton Creek watershed in north-central Oklahoma, a watershed dominated by grasslands (35%) and winter wheat cropland (47%). The simulated average annual yield (2002–2011) for rainfed Alamo switchgrass for both scenarios was 12 Mg ha-1. Yield varied spatially under scenario-I from 6.1 to 15.3 Mg ha-1, while under scenario-II the range was from 8.2 to 13.8 Mg ha-1. Comparison of average annual ET and streamflow between the baseline simulation (existing land use) and scenario-I showed that scenario-I had 5.6% (37 mm) higher average annual ET and 27.7% lower streamflow, representing a 40.7 million m3 yr-1 streamflow reduction. Compared to the baseline, scenario-II had only 0.5% higher ET and 3.2% lower streamflow, but some monthly impacts were larger. In this watershed, the water yield reduction per ton of biomass production (i.e. hydrologic cost-effectiveness ratio) was more than 5X greater under scenario-I than under scenario-II. These results suggest that, from a hydrologic perspective, it may be preferable to convert marginal cropland to switchgrass production rather than converting existing grasslands.

Improving Processing and Performance of Pure Lignin Carbon Fibers through Hardwood and Herbaceous Lignin Blends.

Lignin/lignin blends were used to improve fiber spinning, stabilization rates, and properties of lignin-based carbon fibers. Organosolv lignin from Alamo switchgrass (Panicum virgatum) and yellow poplar (Liriodendron tulipifera) were used as blends for making lignin-based carbon fibers. Different ratios of yellow poplar:switchgrass lignin blends were prepared (50:50, 75:25, and 85:15 w/w). Chemical composition and thermal properties of lignin samples were determined. Thermal properties of lignins were analyzed using thermogravimetric analysis and differential scanning calorimetry. Thermal analysis confirmed switchgrass and yellow poplar lignin form miscible blends, as a single glass transition was observed. Lignin fibers were produced via melt-spinning by twin-screw extrusion. Lignin fibers were thermostabilized at different rates and subsequently carbonized. Spinnability of switchgrass lignin markedly improved by blending with yellow poplar lignin. On the other hand, switchgrass lignin significantly improved thermostabilization performance of yellow poplar fibers, preventing fusion of fibers during fast stabilization and improving mechanical properties of fibers. These results suggest a route towards a 100% renewable carbon fiber with significant decrease in production time and improved mechanical performance.

Assessing the hydrologic and water quality impacts of biofuel‐induced changes in land use and management

AbstractThe Southern High Plains (SHP) of Texas, where cotton (Gossypium hirsutum L.) is grown in vast acreage, and the Texas Rolling Plains (TRP), which is dominated by an invasive brush, honey mesquite (Prosopis glandulosa) have the potential for biofuel production for meeting the U.S. bioenergy target of 2022. However, a shift in land use from cotton to perennial grasses and a change in land management such as the harvesting of mesquite for biofuel production can significantly affect regional hydrology and water quality. In this study, APEX and SWAT models were integrated to assess the impacts of replacing cotton with Alamo switchgrass (Panicum virgatum L.) and Miscanthus × giganteus in the upstream subwatershed and harvesting mesquite in the downstream subwatershed on water and nitrogen balances in the Double Mountain Fork Brazos watershed in the SHP and TRP regions. Simulated average (1994–2009) annual surface runoff from the baseline cotton areas decreased significantly (P &lt; 0.05) by 88%, and percolation increased by 28% under the perennial grasses scenario compared to the baseline cotton scenario. The soil water content enhanced significantly under the irrigated switchgrass scenario compared to the baseline irrigated cotton scenario from January to April and August to October. However, the soil water content was depleted significantly under the dryland Miscanthus scenario from April to July relative to the baseline dryland cotton scenario. The nitrate‐nitrogen (NO3‐N) and organic‐N loads in surface runoff and NO3‐N leaching to groundwater reduced significantly by 86%, 98%, and 100%, respectively, under the perennial grasses scenario. Similarly, surface runoff, and NO3‐N and organic‐N loads through surface runoff reduced significantly by 98.9%, 99.9%, and 99.5%, respectively, under the post‐mesquite‐harvest scenario. Perennial grasses exhibited superior ethanol production potential compared to mesquite. However, mesquite is an appropriate supplementary bioenergy source in the TRP region because of its standing biomass and rapid regrowth characteristics.

Role of Physicochemical Structure of Organosolv Hardwood and Herbaceous Lignins on Carbon Fiber Performance

Lignin was extracted from Alamo switchgrass (Panicum virgatum) and yellow polar (Liriodendron tulipifera) by organosolv fractionation at different pretreatment temperatures, and its chemical structure was studied by means of elemental analysis and spectroscopy. Thermal properties of lignins were investigated using thermogravimetric analysis and differential scanning calorimetry. Lignin fibers were produced via melt-spinning by a twin-screw extruder with a custom spinneret. Fibers were thermostabilized at different rates and finally carbonized. In both species, lignin obtained from higher severity organosolv fractionation had fewer impurities, higher content of phenolic hydroxyl groups, and more condensed structures as a result of extensive cleavage of aryl ether linkages. Higher organosolv severity improved the ability to spin fibers; in the case of switchgrass, only the high severity sample was spinnable. High severity also decreased thermostabilization time and increased tensile strength and modulus of ...

Spatial Variability of Biofuel Production Potential and Hydrologic Fluxes of Land Use Change from Cotton (Gossypium hirsutum L.) to Alamo Switchgrass (Panicum virgatum L.) in the Texas High Plains

Bioenergy crop production has the potential to protect marginal crop lands that generate high surface runoff and produce poor crop yields. Long-term evaluation of the impacts of such land use change on hydrologic fluxes and biofuel production potential is necessary before adopting such strategies on a large scale. In this study, the hydrologic impacts of replacing cotton (Gossypium hirsutum L.) on marginal lands in an intensive agricultural watershed in the Texas High Plains with Alamo switchgrass (Panicum virgatum L.) as a bioenergy crop were evaluated using the Agricultural Policy/Environmental eXtender (APEX) model. The surface runoff to cotton yield ratio was used as a criterion to identify marginal cotton subareas (homogenous spatial units delineated by APEX) in the study watershed, and three replacement scenarios (low (9 %), medium (33 %), and high (57 %) extents of cotton acreage replaced by switchgrass) were implemented in the scenario analysis. The average (1994–2009) annual surface runoff decreased by about 84 and 66 %, and the percolation increased by 106 and 57 % in the irrigated and dryland subareas, respectively, when cotton was replaced by switchgrass under the high replacement scenario. Spatial analysis showed that switchgrass was a feasible bioenergy crop for replacing cotton, especially in the western part of the study watershed, due to its higher water use efficiency and better water conservation effects compared to cotton. It is estimated that 193 and 381 million liters of ethanol could be produced from the dryland and irrigated subareas of the study watershed, respectively, under the high replacement scenario.

Development and evaluation of targeted marginal land mapping approach in SWAT model for simulating water quality impacts of selected second generation biofeedstock

Information about location of marginal lands in a watershed is of interest to those who view these areas as potential land for producing biofuel crops. However, representing marginal lands into a distributed model such as the Soil and Water Assessment Tool (SWAT) is a challenge due to a rigid framework used for watershed sub-division. In this study, we developed a Geographic Information System (GIS) based approach for implementing targeted land use i.e. marginal lands into the SWAT model and evaluated the applicability of the approach on a 8-digit Hydrologic Unit Code (HUC) watershed scale. Comparative results showed that conventional targeting approach overestimates the benefit of targeting marginal lands for Alamo switchgrass (Panicum virgatum, L) and giant miscanthus (Miscanthus × giganteus) production due to simulation of larger area under marginal land category. Compared to baseline condition, which corresponds to no biofuel crop production on marginal lands, the pollutant losses under new targeting approach with simulation of Alamo switchgrass and giant miscanthus on marginal lands were substantially lower. The new targeting approach advances the science behind landscape representation in the SWAT model – that has potential to be used in future targeting studies.

Hydrological responses of land use change from cotton (Gossypium hirsutum L.) to cellulosic bioenergy crops in the Southern High Plains of Texas,USA

AbstractThe Southern High Plains (SHP) region of Texas in the United States, where cotton is grown in a vast acreage, has the potential to grow cellulosic bioenergy crops such as perennial grasses and biomass sorghum (Sorghum bicolor). Evaluation of hydrological responses and biofuel production potential of hypothetical land use change from cotton (Gossypium hirsutum L.) to cellulosic bioenergy crops enables better understanding of the associated key agroecosystem processes and provides for the feasibility assessment of the targeted land use change in theSHP. The Soil and Water Assessment Tool (SWAT) was used to assess the impacts of replacing cotton with perennial Alamo switchgrass (Panicum virgatum L.),Miscanthus × giganteus(Miscanthus sinensisAnderss. [Poaceae]), big bluestem (Andropogon gerardii) and annual biomass sorghum on water balances, water use efficiency and biofuel production potential in the Double Mountain Fork Brazos watershed. Under perennial grass scenarios, the average (1994–2009) annual surface runoff from the entire watershed decreased by 6–8% relative to the baseline cotton scenario. In contrast, surface runoff increased by about 5% under the biomass sorghum scenario. Perennial grass land use change scenarios suggested an increase in average annual percolation within a range of 3–22% and maintenance of a higher soil water content during August to April compared to the baseline cotton scenario. About 19.1, 11.1, 3.2 and 8.8 Mg ha−1of biomass could potentially be produced if cotton area in the watershed would hypothetically be replaced byMiscanthus, switchgrass, big bluestem and biomass sorghum, respectively. Finally,Miscanthusand switchgrass were found to be ideal bioenergy crops for the dryland and irrigated systems, respectively, in the study watershed due to their higher water use efficiency, better water conservation effects, greater biomass and biofuel production potential, and minimum crop management requirements.

Coupling effects of water availability and pH on switchgrass and the optimization of these variables for switchgrass productivity determined by response surface methodology

Perennial grasses can be planted in marginal lands, and the perennial grass species switchgrass (Panicum virgatum) has emerged as an ideal candidate for bioethanol production. To choose the optimal soil water content and pH value for bioethanol production using switchgrass, a greenhouse experiment was conducted with five pH levels (4.9, 6.3, 7.0, 7.7, and 9.1) and five soil water contents (8%, 16%, 20%, 24%, and 32%). The coupling effects of water and pH stresses on switchgrass were investigated by evaluating fresh weight and dry weight, biomass composition (acid detergent fiber, neutral detergent fiber, acid detergent lignin, cellulose, hemi-cellulose, and lignin) and physiological response (soluble sugar content, proline content, MDA content, chlorophyll content and relative conductivity) in Alamo switchgrass. The results demonstrate a significant and positive correlation between the cellulose and acid detergent fiber content in switchgrass biomass (R2 = 0.959). The results of the variance analyses demonstrate that water and pH stress yielded a coupling effect on switchgrass, and this finding was significant for fresh weight and neutral detergent fiber and proline content. By response surface methodology, the optimal combination of soil water content (SWC) and pH was SWC = 31.968%–44.424% and pH = 6.328–8.123. These results provide basic evidence for planting switchgrass in marginal lands.

Cool temperature effects on photosynthetic parameters of two biomass fuel feedstocks in a low light intensity environment

The ability to attain the feedstock production goal in the USA for biofuel production is limited by available arable land, cool temperatures, and periods of low light intensity. This study investigates the effects of warm and cool temperatures growth conditions in a low light regime on the photosynthesis and growth of switchgrass (Panicum virgatum cv. Alamo) and giant miscanthus (Miscanthus giganteus). Alamo switchgrass did not acclimate to low light conditions and had a 47% lower growth and significantly lower mean light saturated photosynthetic rate (Asat = 10.3 μmol m−2s−1) at 14/12°C day/night, compared with 28/25°C (Asat = 18.8 μmol m−2s−1). In contrast, photosynthesis of giant miscanthus acclimated to low light conditions, but there was no significant decrease in quantum requirement or light saturated photosynthetic rates in cool growing conditions (Asat = 8.2 μmol m−2s−1 and 7.0 μmol m−2s−1 for warm and cool conditions, respectively). In summary, giant miscanthus growth and photosynthesis is relatively more tolerant of cool temperature than switchgrass, but is severely limited by low radiation. In contrast, Alamo switchgrass growth and photosynthesis is very sensitive to cool conditions, but is able to maintain higher growth than miscanthus at low radiation conditions.

Evaluating the impacts of climate change and switchgrass production on a semiarid basin

AbstractClimate and land use changes greatly modify hydrologic regimes. In this paper, we modelled the impacts of biofuel cultivation in the US Great Plains on a 1061‐km2 watershed using the Soil and Water Assessment Tool (SWAT) hydrologic model. The model was calibrated to monthly discharges spanning 2002–2010 and for the winter, spring, and summer seasons. SWAT was then run for a climate‐change‐only scenario using downscaled precipitation and a projected temperature for 16 general circulation model (GCM) runs associated with the Intergovernmental Panel on Climate Change Special Report on Emission Scenarios A2 scenario spanning 2040–2050. SWAT was also run on a climate change plus land use change scenario in which Alamo switchgrass (Panicum virgatum L.) replaced native range grasses, winter wheat, and rye (89% of the basin). For the climate‐change‐only scenario, the GCMs agreed on a monthly temperature increase of 1–2 °C by the 2042–2050 period, but they disagreed on the direction of change in precipitation. For this scenario, decreases in surface runoff during all three seasons and increases in spring and summer evapotranspiration (eT) were driven predominantly by precipitation. Increased summer temperatures also significantly contributed to changes in eT. With the addition of switchgrass, changes in surface runoff are amplified during the winter and summer, and changes in eT are amplified during all three seasons. Depending on the GCM utilized, either climate change or land use change (switchgrass cultivation) was the dominant driver of change in surface runoff while switchgrass cultivation was the major driver of changes in eT. Copyright © 2014 John Wiley &amp; Sons, Ltd.

Niobium oxide catalyst for delignification of switchgrass for fermentable sugar production

In this research, niobium oxide, a solid acid catalyst was evaluated as a pretreatment agent for delignification of Alamo switchgrass. The objectives were to determine the effects of temperature, catalyst loading, and pretreatment time on delignification and enzymatic hydrolysis of switchgrass and evaluate reusability of the catalyst. Batch experiments were performed using a Box–Behnken statistical model to study the effects of temperature, pretreatment time, and catalyst loading followed by hydrolysis using Cellic®Ctec2 (Novozymes). Niobium oxide was able to reduce total lignin concentrations up to 44.6±0.97%. Hydrolysis experiments performed for 72 and 168h (7% enzyme loading) indicated that a maximum glucose yield of 0.169gg−1 (59.94% conversion)–0.196gg−1 (77.51% conversion) was obtained. Catalyst reusability studies suggested that niobium oxide was able to pretreat four separate batches of switchgrass without losing activity. Niobium oxide is expected to serve as a reusable pretreatment catalyst and make ethanol production inexpensive and environmentally friendly.

Rapid Assessment of Bioenergy Feedstock Quality by Near Infrared Reflectance Spectroscopy

The portability, quick turnaround time, and low long‐term maintenance costs of near infrared reflectance spectroscopy (NIRS) offers rapid determination of feedstock quality. The objective of this study was to estimate biomass composition (total N [TN], acid detergent fiber [ADF], neutral detergent fiber [NDF], and acid detergent lignin [ADL]) with NIRS. Linear regression of simple ratios (SRs), and partial least square (PLS) regression models with all wavebands (WBs) and selected waveband (SB) approaches were used. Laboratory analysis was conducted for TN, ADF, NDF, and ADL. Samples from 13 switchgrass (Panicum virgatum L.) cultivars, ES5200 high‐biomass sorghum [Sorghum bicolor (L.) Moench], and mixed grasses composed of Alamo switchgrass, Cheyenne Indian grass [Sorghastrum nutans (L.) Nash] and Kaw big bluestem (Andropogon gerardii Vitman) fertilized at different rates of N ranging from 0 to 252 kg N ha–1 yr–1 were collected from two locations in Oklahoma. Spectral reflectance between 1000 and 2500 nm was collected with an ASD Fieldspec spectroradiometer from all samples. Results showed that TN can be estimated using a SR of R2080/R2190 (r2 = 0.84), while a SR of R2190/R2230 (r2 = 0.65) was able to estimate ADF (r2 = 0.70), NDF (r2 = 0.65), and ADL (r2 = 0.67). In comparison with SRs, a SB PLS model gave better prediction accuracy with nine wavebands for TN (r2 = 0.93) and seven wavebands for ADF (r2 = 0.78), NDF (r2 = 0.78), and ADL (r2 = 0.65). In conclusion, the success of both SR and SB PLS for estimating bioenergy feedstock composition indicates opportunities for instrument development for practical purposes.

Perennial Biomass Grasses and the Mason–Dixon Line: Comparative Productivity across Latitudes in the Southern Great Plains

Understanding latitudinal adaptation of switchgrass (Panicum virgatum L.) and Miscanthus (Miscanthus × giganteus J. M. Greef & Deuter ex Hodk. & Renvoize) to the southern Great Plains is key to maximizing productivity by matching each grass variety to its optimal production environment. The objectives of this study were: (1) to quantify latitudinal variation in production of representative upland switchgrass ecotypes (Blackwell, Cave-in-Rock, and Shawnee), lowland switchgrass ecotypes (Alamo, Kanlow), and Miscanthus in the southern half of the US Great Plains and (2) to investigate the environmental factors affecting yield variation. Leaf area and yield were measured on plots at 10 locations in Missouri, Arkansas, Oklahoma, and Texas. More cold winter days led to decreased subsequent Alamo switchgrass yields and increased subsequent upland switchgrass yields. More hot-growing season days led to decreased Kanlow and Miscanthus yields. Increased drought intensity also contributed to decreased Miscanthus yields. Alamo switchgrass had the greatest radiation use efficiency (RUE) with a mean of 4.3 g per megajoule intercepted PAR and water use efficiency (WUE) with a mean of 4.5 mg of dry weight per gram of water transpired. The representative RUE values for other varieties ranged from 67 to 80 % of Alamo’s RUE value and 67 to 87 % of Alamo’s WUE. These results will provide valuable inputs to process-based models to realistically simulate these important perennial grasses in this region and to assess the environmental impacts of production on water use and nutrient demands. In addition, it will also be useful for landowners and companies choosing the most productive perennial grasses for biofuel production.