Switchgrass Yield Research Articles

Valuing the Seed of an Improved Switchgrass Cultivar

ABSTRACTSwitchgrass (Panicum virgatum L.) has been identified as a model perennial grass species to compete with alternative sources for providing biomass to fulfill cellulosic biofuels provisions of the US Energy Independence and Security Act of 2007. The objective of this study is to determine the value of a more productive switchgrass variety relative to that of the best available alternative. Biomass data were produced in an experiment with four commercial switchgrass cultivars (Alamo, Blackwell, Kanlow, and Cave‐in‐Rock) and five experimental lines over 4 yr at Stillwater, OK. One of the experimental lines, Cimarron, was released as a cultivar in 2008 during the experiment. The remaining four experimental lines were NL93‐2, NSL 2001‐1, NL 94‐2001‐1, and NSU 95‐2001. An ANOVA model is used to test for differences in switchgrass yield. Enterprise budgets are used to calculate net returns and stochastic efficiency analysis is used to investigate yield risk. For a farm‐gate biomass price of $50 Mg−1, expected net returns were estimated to be $80 ha−1 yr−1 greater in postestablishment years for Cimarron than for Alamo. Assuming a year for establishment, nine postestablishment production years, a farm‐gate biomass price of $50 Mg−1, a discount rate of 6.5%, and environmental conditions similar to those that prevailed during the field experiment, the net present value of seeding a field in the region to Cimarron rather than Alamo would be $501 ha−1.

Switchgrass Stand Density and Yield as Influenced by Seedbed Preparation Methods in a Sandy Loam Soil

Successful establishment of switchgrass (Panicum virgatum L.) remains a challenge. It is reported that increasing seed-soil contact using a roller could improve switchgrass establishment in silt-loam soils. However, use of rollers is not common among growers and operating them could be difficult. The objective of this study was to assess whether rolling could improve switchgrass stand establishment in sandy-loam soils by increasing seed-soil contact through compacting the soil, and to evaluate the use of cultipacker as a more user-friendly alternative to roller. An experiment was conducted in 2012 and repeated in the 2013 growing season at the University of Massachusetts Agricultural Experiment Station farm in Deerfield. The soil type at the experimental site was Hadley fine sandy loam (nonacid, mesic Typic Udifluvent). The experimental design was a randomized complete block design with four replicates. There were eight treatments including disking-planting (D-P), disking-cultipacking-planting (D-C-P), disking-cultipacking-planting-cultipacking (D-C-P-C), disking-cultipacking-planting-cultipacking-cultipacking (D-C-P-C-C), disking-rolling-planting (D-R-P), disking-rolling-planting-rolling (D-R-P-R), disking-rolling-planting-rolling-rolling (D-R-P-R-R), and disking-rolling-planting-rolling-rolling-rolling (D-R-P-R-R-R). Tiller density was influenced rolling and cultipacking frequency but not by the compaction equipment. Tiller density increased by cultipacking or rolling the soil once (D-C-P-C; D-R-P-R) and two times after planting (D-C-P-C-C; D-R-P-R-R). Disking-planting had the lowest tiller density with 188 and 110 plants (m−2) in 2012 and 2013 growing seasons, respectively. Similar to tiller density, biomass yield was not influenced by compaction equipment but by compaction frequency. Higher biomass yield was obtained from soils that were firmed once before and at least once after planting (D-C-P-C; D-R-P-R) compared with seedbed firming only once before planting (D-C-P; D-R-P). In a dry season (2012), a twofold yield increase (1.06 Mg ha−1) was obtained from D-C-P-C compared with D-C-P (0.55 Mg ha−1). However, two times rolling (D-R-P-R-R-) or cultipacking (D-C-P-C-C) after planting was needed in 2013 to increase the yield compared with D-C-P by 41 %. Our results indicated that using cultipacker as an alternative to roller can be a solution to improve switchgrass establishment. We conclude that D-C-P-C-C could ensure switchgrass establishment and improve switchgrass biomass production in the establishment year in a sandy-loam soil.

Application of the Smith‐Hazel Selection Index for Improving Biomass Yield and Quality of Switchgrass

ABSTRACTApart from the importance of switchgrass (Panicum virgatum L.) as forage for livestock, it is useful as a high‐value cellulosic biofuel feedstock. Breeding for a biofuel crop is complicated by the existence of multiple platforms for conversion of biomass to energy. Our main objective was to investigate the relative merits of single‐trait selection, correlated response to selection, and Smith‐Hazel‐index‐based selection for the following traits: biomass dry matter yield (YLD), ethanol (ETOH), Klason lignin (KL), and high heating value (HHV). The genetic analysis was based on a 2‐yr data set generated from evaluation of 144 half‐sib (HS) families in sward‐plot trials at Arlington and Marshfield, WI. There was significant (P < 0.05) additive genetic variation among the families for all traits and for family × site interaction for the traits HHV and YLD. The estimates of narrow sense heritability on a HS family mean basis ranged from 0.37 for YLD to 0.51 for KL. Genetic correlation of YLD with ETOH, HHV, and KL were 0.38, 0.27, and 0.01, respectively. The index constructed to increase YLD and ETOH and reduce KL was most successful for a fermentation platform. This index enabled identification of families for enhancing ethanol production that would have been missed if selection was based solely on YLD. The index weighted to increase YLD and KL best suited a combustion platform. Both of these two indices had economic impacts superior to any other selection index evaluated.

PvTB1, a Teosinte Branched1 Gene Homolog, Negatively Regulates Tillering in Switchgrass

Switchgrass belongs to the family Poaceae and genus Panicum, and is a highly versatile grass used for soil and water conservation, livestock production, and biomass production for energy conversion. Tillering plays an important role in determining the morphology of the aboveground parts and the final biomass yield of switchgrass. In this study, we first cloned and identified PvTB1, a teosinte branched1 (TB1) gene homolog in switchgrass, based on its sequence similarity with the TB1 gene, which is involved in lateral branching in maize. Similar to other TB1 genes, the PvTB1 gene encoded putative transcription factors containing a basic helix-loop-helix type of DNA-binding motif called the TCP domain. Tiller emergence and development were obviously inhibited by overexpression of PvTB1 in transgenic plants, and the mutated phenotypes could be rescued using 6-benzylaminopurine. Overexpression or suppression of PvTB1 through a transgenic approach resulted in changes in tiller number, stem height, stem diameter, and biomass yield. Taken together, our results suggest that PvTB1 negatively regulates tillering in switchgrass, presumably via its expression in axillary buds.

Life Cycle Assessment of Switchgrass Cellulosic Ethanol Production in the Wisconsin and Michigan Agricultural Contexts

Spatial variability in yields and greenhouse gas emissions from soils has been identified as a key source of variability in life cycle assessments (LCAs) of agricultural products such as cellulosic ethanol. This study aims to conduct an LCA of cellulosic ethanol production from switchgrass in a way that captures this spatial variability and tests results for sensitivity to using spatially averaged results. The Environment Policy Integrated Climate (EPIC) model was used to calculate switchgrass yields, greenhouse gas (GHG) emissions, and nitrogen and phosphorus emissions from crop production in southern Wisconsin and Michigan at the watershed scale. These data were combined with cellulosic ethanol production data via ammonia fiber expansion and dilute acid pretreatment methods and region-specific electricity production data into an LCA model of eight ethanol production scenarios. Standard deviations from the spatial mean yields and soil emissions were used to test the sensitivity of net energy ratio, global warming potential intensity, and eutrophication and acidification potential metrics to spatial variability. Substantial variation in the eutrophication potential was also observed when nitrogen and phosphorus emissions from soils were varied. This work illustrates the need for spatially explicit agricultural production data in the LCA of biofuels and other agricultural products.

Switchgrass procurement strategies for managing yield variability: Estimating the cost-efficient D (downtime cost) L (land to lease) frontier

Lignocellulosic biorefineries that plan to use switchgrass (Panicum virgatum L.) biomass exclusively will encounter both temporal (across years) and spatial (across locations within a given year) variability in feedstock production. Long term land leases could be employed to facilitate feedstock availability for the expected life of the biorefinery. If the quantity of land leased is based on average yields, in some years more biomass will be produced than can be processed. In other years feedstock production on the leased land may be insufficient to prevent biorefinery downtime. An optimal strategy for identifying which land to lease and seed to switchgrass, while considering yield variability and the opportunity cost of biorefinery downtime, is the focus of the research. The objective is to determine for a given biorefinery location the least-cost quantity, quality, and location of land to lease for alternative estimates of biorefinery downtime cost due to variable switchgrass yields. Fifty years of weather data are used to simulate switchgrass yield distributions for a case study region. An innovative mathematical programming model is developed and used to reveal the cost-efficient D (Downtime Cost) L (Land to Lease) frontier for a 2 Gg d−1 biomass capacity biorefinery. If interyear storage is not permitted, 60,492 ha would be required to insure that the biorefinery run at full capacity every year given the estimated yield distributions. However, for some circumstances, it would be optimal to produce switchgrass on only 49,464 ha and idle the biorefinery for some days in low biomass production years.

Carbon dynamics in a biochar-amended loamy soil under switchgrass

Allaire, S. E., Baril, B., Vanasse, A., Lange, S. F., MacKay, J. and Smith, D. L. 2015. Carbon dynamics in a biochar-amended loamy soil under switchgrass. Can. J. Soil Sci. 95: 1–13. The environmental impacts of switchgrass production for bioenergy could be reduced through the use of biofertilizers rather than mineral fertilizers and through soil amendment with biochar. The objectives of this study were: (1) to assess the impact of biochar and biofertilizer on switchgrass (Panicum virgatum L.) yield and parameters related to carbon dynamics, (2) to correlate carbon parameters with soil physico-chemical properties over the first two growing seasons, and (3) to develop a C budget. A complete randomized block design was installed in a sandy loam with split plot treatment design, the main plots receiving 0 or 10 t ha−1of biochar and the sub − plots receiving no fertilization, mineral N fertilization, or biofertilizers. Biofertilizers had no significant impact on plant and soil. Biochar increased yield relative to the control treatment by about 10% during the first year and root biomass by up to 50% after 2 yr (P>0.1). Mineral N fertilization also increased yield resulting in higher plant C sequestration after 2 yr. Biochar increased CO2soil concentration (CO2-soil) by up to 50% but its impact on CO2emission flux (CO2-flux) changed over time. The impact of mineral fertilization on CO2-fluxalso varied with time. Soil CO2dynamics was mostly influenced by temperature, N and water content. Biochar and fertilization treatments showed interactions on some plant and soil parameters. The highest C sequestration budget was obtained with a combination of biochar and mineral N fertilization. The equivalent of about one-third of the increase in soil C content associated with biochar treatments was respired away by soil microorganisms. Nearly one-fourth of C sequestered by plants remained in or at the soil surface (root and crop residues).

Switchgrass Management Practice Effects on Near-Surface Soil Properties in West-Central Arkansas

Agronomic management practices that maximize monoculture switchgrass (Panicum virgatum L.) yield are generally well understood; however, little is known about corresponding effects of differing switchgrass management practices on near-surface soil properties and processes. The objective of the study was to evaluate the effects of cultivar (“Alamo” and “Cave-in-Rock”), harvest frequency (1- and 2-cuts per year), fertilizer source (poultry litter and commercial fertilizer), and irrigation management (irrigated and non-irrigated) on near-surface soil properties and surface infiltration in a Leadvale silt loam (fine-silty, siliceous, semiactive, thermic, Typic Fragiudult) after four years (2008 through 2011) of consistent management in west-central Arkansas. Irrigating switchgrass increased (P 0.05) and averaged 0.79 mm∙min−1. Results from this study indicate that management decisions to maximize switchgrass biomass production affect soil properties over relatively short periods of time, and further research is needed to develop local best management practices to maximize yield while maintaining or improving soil quality.

Harvest Date Effects on Biomass Yield, Moisture Content, Mineral Concentration, and Mineral Export in Switchgrass and Native Polycultures Managed for Bioenergy

Various local factors influence the decision of when to harvest grassland biomass for renewable energy including climate, plant composition, and phenological stage. However, research on biomass yield and quality related to a wide range of harvest timing from multiple environments and years is lacking. Our objective was to determine the effect of harvest timing on yield, moisture, and mineral concentration of switchgrass (Panicum virgatum L.) and native polyculture biomass. Biomass was harvested on 56 unique days ranging from late summer (2 September) to late spring (20 May) spanning 3 years (2009 to 2011) and seven sites in Minnesota, USA. Biomass yield varied considerably by location and year (range = 0.7–11.7 Mg ha−1) and was lowest during the winter. On average, there was no difference in biomass yield harvested in early fall compared to late spring. Biomass moisture content was lowest in late spring, averaging 156 g kg−1 across all locations and years when harvested after 1 April. Biomass N concentration did not change across harvest dates; however, P and K concentrations declined dramatically from late summer to late spring. Considering the economic costs of replacing exported minerals and changes in revenues from biomass yield through time, biomass harvest should be conducted in late summer–early fall or late spring and avoided in winter. However, biomass managed for gasification should be harvested in spring to reduce concentrations of minerals that lead to slagging and fouling. Changes in biomass yield and quality through time were similar for switchgrass and native polyculture biomass. These biomass harvest recommendations are made from data spanning multiple years and locations and should be applicable to various growing conditions across the Upper Midwest.

Cultural treatments for accelerated growth and flowering of Panicum virgatum

Background: Exploiting heterosis through hybrid breeding is essential to increase biomass yields of switchgrass (Panicum virgatum). However, life cycle timespan for clone evaluation for field evaluation is a major limitation to genetic selection. Methods & results: In an attempt to shorten the switchgrass life cycle timespan, we investigated the effect of four variables on the vegetative and reproductive morphology of the P. virgatum cultivar “Alamo”: day length, temperature, container size, and application of plant growth regulators. Seedlings grew fastest and reached flowering fastest under 18 hours of daylight with growth being severely and mildly inhibited at 8 h and 23 h, respectively. Under the optimum (18 h) photoperiod, day temperature of 25°C led to the fastest growth and flowering whereas a 5°C increase or decrease inhibited growth and flowering. Within the 18 h/25°C treatment, 44% of plants flowered after 90 d and >15% of plants reached full anthesis or post-anthesis seed set. Conclusions: Allowing 45 d for seed set and 30 d for cold stratification, generation time for the post-anthesis plants grown in 18 h/25°C conditions is approximately 165 days, allowing for the production of two generations of switchgrass per year for accelerating germplasm development for this perennial bioenergy crop.

Switchgrass Harvest Time Effects on Nutrient Use and Yield: An Economic Analysis

This article analyzes economic tradeoffs among harvest date, fertilizer applied, nutrient removal, and switchgrass yield as they vary with respect to input and output prices. Economic sensitivity analyses suggest that higher biomass prices lead to earlier harvest. Optimal harvest time occurs beyond time of maximum yield because nutrient removal in the biomass is an important economic consideration. Switchgrass price premia that reflect the cost of non-optimal harvest time are driven by standing crop yield loss, nutrient removal, storage loss, and opportunity cost. These price premia could provide a mechanism to compensate producers for alternative harvest times and aid with logistics management.

Environmental impact assessment of regional switchgrass feedstock production comparing nitrogen input scenarios and legume-intercropping systems

Abstract As the use of second-generation biofuel crops increases, so do questions about sustainability, particularly their potential to affect fossil energy consumption and greenhouse gas emissions. This study used a life-cycle approach to compare environmental impacts associated with three switchgrass (Panicum virgatum L.) production scenarios: i) regional production from a pool of Tennessee farmers based on in-field inputs and biomass yield; ii) varying nitrogen (N)-input levels from a replicated field study for 8-yrs i.e., a 100% and 9% decrease, and an 81% and 172% increase from 'baseline levels' of N inputs used under objective i; and, iii) a legume-intercrop system compared to baseline levels in order to determine effects of displacing synthetic-N with legumes. When compared across all agricultural inputs, nitrogen fertilizer production and breakdown resulted in the greatest environmental impacts. Although fertilization increased lignocellulosic yields, a 100% reduction in N-inputs from baseline levels reduced the formation of carbon, methane, and nitrous oxides per unit of production, (or dry tonne of biomass over 10-yrs) compared to a 172% increase. Switchgrass yield response indicated a 'less is more' scenario, as inputs beyond the current recommended input level (67 kg N ha−1) are not environmentally remunerating. During switchgrass biomass production, inputs with lesser impacts included phosphorus, herbicides, pesticides, and diesel fuel. Legume-intercropping reduced greenhouse gas emissions and groundwater acidification (5% and 27% reduction in global warming potential and formation of acidifying species, respectively) compared with the 67 kg N ha−1rate. Although N-fertilizers impact environmental sustainability of regional switchgrass feedstock production, environmental consequences can be reduced under proper N-management i.e., ≤67 kg N ha−1 or legume intercropping. However, given that the aim of second-generation feedstocks is to reduce the current reliance on fossil fuels, their production still requires fossil energy-based inputs. Consequently, greenhouse gas reductions and the extent of cleaner feedstock production during the agricultural biofuel supply chain is contingent upon input management and optimizing synthetic fertilizer usage.

Harvest Frequency and Nitrogen Effects on Yield, Chemical Characteristics, and Nutrient Removal of Switchgrass

Harvest frequency (HF) and fertilizer effects on biomass production, nutrient removal, and ethanol yield must be understood to help guide management decisions in switchgrass (Panicum virgatum L.) production. This 4‐yr study quantified yield and chemical composition responses of Alamo switchgrass to factorial combinations (4 × 2) of four HFs (harvesting one, two, three, or six times annually) and two N application rates (80 and 160 kg N ha−1) in a randomized complete block design experiment with three replications. In all years, yields decreased linearly with HF. In the one‐cut HF, yield increased from 8.8 in Year 1 to 14.7 Mg ha−1 in Year 3 and plateaued thereafter. For the two‐cut HF, yield was similar across years, averaging 10 Mg ha−1, but for the three‐ and six‐cut HFs, yield increased from Year 1 to Year 2 and declined by Year 4. Nutrient concentration increased with HF, while nutrient removal responses fluctuated among elements. Acid detergent fiber, neutral detergent fiber, hemicellulose, cellulose, and lignin concentrations decreased with increasing HF, but there was no effect of N rate. In Years 1 and 2, theoretical ethanol production (TEP) was similar between the one‐ (3.7 kL ha−1) and two‐cut HFs (4.2 kL ha−1) but decreased as the HF increased to three (2.6–3.4 kL ha−1) and six cuts (1.4– 2.5 kL ha−1). In Years 3 and 4, TEP decreased linearly with increasing HF. Greater HF resulted in reduced feedstock yield, quality, ethanol yield, and production, but N application rate did not have any effect.

Biomass Production of Switchgrass in Saline-Alkali Land

A field experiment was carried out to study the growth characteristics of switchgrass cultivated in saline-alkali lands. The results show that: the survival rate, plant height, tiller numbers per plant and biomass yield of switchgrass significantly reduce with the increasing magnitude of salinity-alkalinity stresses. Switchgrass can grow in saline-alkali environments, the survival rate is more than 85%, and the overwintering rate is more than 95%. Switchgrass plants grow better in mild and moderate saline-alkali lands, and it achieve the highest biomass yield and theoretical ethanol yield of 14.3 t/ha and 5958.8 l/ha respectively, in the third year. With saline-alkali stress, ash and lignin content of switchgrass biomass increase, calorific value, cellulose and hemicelluloses content of switchgrass biomass decrease, and fuel quality of switchgrass biomass reduce to a certain extent.

Switchgrass Establishment Influenced by Cover Crop, Tillage Systems, and Weed Control

Successful establishment of switchgrass (Panicum virgatum L.) is often challenging. The objective of this study was to improve switchgrass stand establishment through integrated management practices that included cover crops, tillage systems and herbicide application. The study was conducted at the University of Massachusetts Agricultural Experiment Station in Deerfield during the growing seasons of 2012 and 2013. A split split-plot design with three replications was used in both years. The main plots consisted of three cover crop treatments (fallow, oat [Avena sativa L.], and rye [Secale cereale L.]). The sub-plots were two seeding methods (no-till drill, and cultipacker seeder [Brillion]). The sub sub-plots were herbicide treatments that consisted (1) pre-emergence (PRE) application of atrazine (A) and quinclorac (Q) and (2) a Broad Spectrum application of PRE A + Q that was supplemented with post-emergence (POST) application of 2,4-D and dicamba. The no-till seeding method in both years resulted in higher stand density and biomass. Weed control was improved with the Broad Spectrum herbicide (0.90 Mg ha−1) compared with A + Q treatment (1.3 Mg ha−1). No-till seeding produced considerably higher tiller numbers (190 tiller m−2) than that of cultipacker seeder which in turn resulted in significant weed suppression. In general, when planted after rye, switchgrass produced fewer tillers than after oat or fallow. No-till seeding into oat mulch with the application of Broad Spectrum herbicides resulted in highest switchgrass yield (2,098 kg ha−1) in the establishment year.

A mixed-integer optimization model for the economic and environmental analysis of biomass production

Biofuel production from second-generation feedstock has become critical due to environmental concerns and the need for sustainable energy supply. This paper provides a unique optimization approach of quantifying and formulating the economic and environmental benefits of switchgrass production at the farm level. In particular, we propose a multi-objective mixed-integer programming model, which maximizes the revenue from harvested switchgrass biomass and the economic value obtained from the positive environmental impacts of switchgrass yield during a ten-year planning horizon. Environmental impacts include soil erosion prevention, sustainability of bird populations, carbon sequestration, and carbon emissions, while economic impacts are analyzed under various budget, yield, and sustainability scenarios. The proposed model is then applied to a case study in the state of Kansas. Results show that given the current market prices, switchgrass cultivation on grassland and cropland is highly profitable. The model results also suggest that if utilized by the government, conservation reserve program (CRP) incentives could make marginal land more favorable over cropland. We perform sensitivity analysis to address the uncertainty in budget, yield, and utilization of cropland, and present insights into the economic and environmental impacts of switchgrass production. This model can also be extended to biomass production from any other types of energy crops to identify the most efficient production planning strategies under various management scenarios.

Bioenergy crop greenhouse gas mitigation potential under a range of management practices

AbstractPerennial grasses have been proposed as viable bioenergy crops because of their potential to yield harvestable biomass on marginal lands annually without displacing food and to contribute to greenhouse gas (GHG) reduction by storing carbon in soil. Switchgrass, miscanthus, and restored native prairie are among the crops being considered in the corn and agricultural regions of the Midwest and eastern United States. In this study, we used an extensive dataset of site observations for each of these crops to evaluate and improve the DayCent biogeochemical model and make predictions about how both yield and GHG fluxes would respond to different management practices compared to a traditional corn‐soy rotation. Using this model‐data integration approach, we found 30–75% improvement in our predictions over previous studies and a subsequent evaluation with a synthesis of sites across the region revealed good model‐data agreement of harvested yields (r2 > 0.62 for all crops). We found that replacement of corn‐soy rotations would result in a net GHG reduction of 0.5, 1.0, and 2.0 Mg C ha−1 yr−1 with average annual yields of 3.6, 9.2, and 17.2 Mg of dry biomass per year for native prairie, switchgrass, and miscanthus respectively. Both the yield and GHG balance of switchgrass and miscanthus were affected by harvest date with highest yields occurring near onset of senescence and highest GHG reductions occurring in early spring before the new crops emergence. Addition of a moderate length rotation (10–15 years) caused less than a 15% change to yield and GHG balance. For policy incentives aimed at GHG reduction through onsite management practices and improvement of soil quality, post‐senescence harvests are a more effective means than maximizing yield potential.

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 with wide-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 monocultures and 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 influence yield in replicated experiments (p<0.10). Mean annual switchgrass yield above a stubble height of 10cm was 9.3Mgha−1 in two replicated experiments, and was greater than yield of mixtures (7.3Mgha−1) in 6 of 7 year×vegetation type combinations. Landscape position interacted with year and vegetation type to influence yield (p<0.10). Variability was generally greatest at the lowest landscape position. On the farm's larger fields (0.4–46ha), three-year mean yields of switchgrass monocultures cut at ground level (12.7Mgha−1) were also greater than yields of mixtures (9.7Mgha−1) but both were less than prairie cordgrass (Spartina pectinata Link) monoculture yield (13.2Mgha−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).

Soil Properties, Nitrogen Status, and Switchgrass Productivity in a Biochar‐Amended Silty Clay Loam

A 14‐wk greenhouse study was conducted to assess how varying application rates of biomass‐derived black carbon (biochar) and N fertilizer affect soil properties, plant N status, and switchgrass (Panicum virgatum L.) productivity. Biochar derived from a southern pine species was mixed with a silty clay loam at rates of 0, 0.4, 1.9, and 3.9% (w/w) and two rates of N fertilizer (0 and 56 kg ha−1 of N as urea) were applied in a randomized complete block design. Biochar provided increases in the volumetric water content (VWC, %) of the soil during the study period. At study completion, soil pH and total C were increased. Foliar N concentration and content did not differ among treatments despite significant increases in soil C/N ratios due to biochar. Switchgrass yields were reduced at the highest biochar application rate but were unaffected when rates were moderate. Nitrogen fertilization had few effects on measured soil and plant properties, and no interactive effects were found when applied in conjunction with biochar. Overall, moderate rates of biochar application increased soil pH, soil C content, and VWC but had negligible effects on plant N status or switchgrass yields. Our results demonstrate a potential function of biochar for improving temperate soil properties.

Impacts of Improved Switchgrass and Big Bluestem Selections on Yield, Morphological Characteristics, and Biomass Quality

Switchgrass (Panicum virgatumL.) and big bluestem (Andropogon gerardiiV.) are promising warm-season grasses for biomass production. Understanding the morphological and quality-related traits of these grasses can guide breeders in developing strategies to improve yield and quality for bioindustrial applications. Elite selections were made in Southern Quebec from four promising varieties of switchgrass and one of big bluestem. Biomass yield, morphological characteristics, and selected quality traits were evaluated at two sites in 2011 and 2012. Significant variation was detected for all measured characteristics, with differences varying by site and year. In some cases the selection process modified characteristics including increasing height and reducing tiller mortality. Switchgrasses reached a similar tiller equilibrium density in both years of 690 m−2and 379 m−2at a productive and marginal site, respectively. Differences in yield were pronounced at the marginal site, with some advanced selections having a higher yield than their parent varieties. Switchgrass yields were generally greater than those of big bluestem. A delayed spring harvest date greatly reduced yield but reduced moisture content and slightly increased cellulose concentration. Big bluestem had a higher cellulose content than switchgrass, likely due to greater stem content.