ALBERT

Description: For the C4 perennial grasses, Miscanthus  ×  giganteus and Panicum virgatum (switchgrass) to be successful for bioenergy production they must maintain high yields over the long term. Previous studies under the less conducive climate for productivity in N.W. Europe found little or no yield decline in M . ×  giganteus in the long term. This study provides the first analysis of whether yield decline occurs in M . ×  giganteus under United States. Midwest conditions in side-by-side trials with P. virgatum over 8–10 years at seven locations across Illinois. The effect of stand age was determined by using a linear regression model that included effects of weather. Miscanthus  ×  giganteus produced yields more than twice that of P. virgatum averaging 23.4 ± 1.2 Mg ha −1  yr −1 and 10.0 ± 0.9 Mg ha −1  yr −1 , respectively, averaged over 8–10 years. Relationships of yield with precipitation and growing degree days were established and used to estimate yields corrected for the stochastic effects of weather. Across all locations and in both species, yield initially increased until it reached a maximum during the fifth growing season and then declined to a stable, but lower level in the eighth. This pattern was more pronounced in M . ×  giganteus . The mean yields observed over this longer term period of 8–10 years were lower than the yields of the first 5 years. However, this decline was proportionately greater in M . ×  giganteus than in P. virgatum, suggesting a stronger effect of stand age on M . ×  giganteus . Based on the average yield over the period of this study, meeting the United States Renewable Fuel Standard mandate of 60 billion liters of cellulosic ethanol by 2022, would require 6.8 Mha of M . ×  giganteus or 15.8 Mha of P. virgatum . These appear manageable numbers for the United States, given the 16.0 Mha in the farmland Conservation Reserve Program in addition to another 13.0 Mha abandoned from agriculture in the last decade.

Description: Chemical Reviews DOI: 10.1021/acs.chemrev.6b00180

Description: Chemical Reviews DOI: 10.1021/acs.chemrev.5b00669

Description: Bacterial assemblages, especially diazotroph assemblages residing in the rhizomes and the rhizosphere soil of Miscanthus ×giganteus contribute to plant growth and nitrogen use efficiency. However, the composition of these microbial communities has not been adequately explored, nor have the potential ecological drivers for these communities been sufficiently studied. This knowledge is needed for understanding and potentially improving M. ×giganteus - microbe interactions, and further enhancing sustainability of M. ×giganteus production. In this study, cultivated M. ×giganteus from four sites in Illinois, Kentucky, Nebraska, and New Jersey were collected to examine the relative influences of soil conditions and plant compartments on assembly of the M. ×giganteus -associated microbiome. Automated ribosomal intergenic spacer (ARISA) and terminal restriction fragment length polymorphism (T-RFLP) targeting the nifH gene were applied to examine the total bacterial communities and diazotroph assemblages that reside in the rhizomes and the rhizosphere. Distinct microbial assemblages were detected in the endophytic and rhizosphere compartments. Site soil conditions had strong correlation with both total bacterial and diazotroph assemblages, but in different ways. Nitrogen treatments showed no significant effect on the composition of diazotroph assemblages in most sites. Endophytic compartments of different M . × giganteus plants tended to harbor similar microbial communities across all sites, whereas, the rhizosphere soil of different plant tended to harbor diverse microbial assemblages that were distinct among sites. These observations offer insight into better understanding of the associative interactions between M. ×giganteus and diazotrophs, and how this relationship is influenced by agronomic and edaphic factors. This article is protected by copyright. All rights reserved.

Description: The U.S. Department of Energy has mandated the production of 16 billion gallons (60.6 billion liters) of renewable biofuel from cellulosic feedstocks by 2022. The perennial grass, Miscanthus x giganteus , is a potential candidate for cellulosic biofuel production because of high productivity with minimal inputs. This study determined the effect of three different spring fertilizer treatments (0, 60, and 120 kg N ha −1 yr −1 as urea) on biomass production, soil organic matter (SOM), and inorganic N leaching in Illinois, Kentucky, Nebraska, New Jersey, and Virginia, along with N 2 O and CO 2 emissions at the IL site. There were no significant yield responses to fertilizer treatments, except at the IL site in 2012 (yields in 2012, year 4, varied from 10 to 23.7 Mg ha −1 across all sites). Potentially mineralizable N increased across all fertilizer treatments and sites in the 0 – 10 cm soil depth. An increase in permanganate oxidizable carbon (POX-C, labile C) in surface soils occurred at the IL and NJ sites, which were regularly tilled before planting. Decreases in POX-C were observed in the 0 – 10 cm soil depth at the KY and NE sites where highly managed turfgrass was grown prior to planting. Growing M . x giganteus altered SOM composition in only four years of production by increasing the amount of potentially mineralizable N at every site, regardless of fertilization amount. Nitrogen applications increased N leaching and N 2 O emission without increasing biomass production. This suggests that for the initial period (4 yr) of M . x giganteus production, N application has a detrimental environmental impact without any yield benefits and thus should not be recommended. Further research is needed to define a time when N application to M . x giganteus results in increased biomass production. This article is protected by copyright. All rights reserved.

Description: To meet U.S. renewable fuel mandates, perennial grasses have been identified as important potential feedstocks for processing into biofuels. Triploid Miscanthus × giganteus , a sterile, rhizomatous grass, has proven to be a high-yielding biomass crop over the past few decades in the European Union and, more recently, in the U.S. However, high establishment costs from rhizomes are a limitation to more widespread plantings without government subsidies. A recently developed tetraploid cultivar of M . × giganteus producing viable seeds (seeded miscanthus) shows promise in producing high yields with reduced establishment costs. Field experiments were conducted in Urbana, Illinois from 2011 to 2013 to optimize seeded miscanthus establishment by comparing seeding rates (10, 20 and 40 seeds m −2 ) and planting methods (drilling seeds at 38 and 76 cm row spacing versus hydroseeding with and without pre-moistened seeds) under irrigated and rainfed conditions. Drought conditions in 2011 and 2012 coincided with stand establishment failure under rainfed conditions, suggesting that seeded miscanthus may not establish well in water-stressed environments. In irrigated plots, hydroseeding without pre-moistening was significantly better than hydroseeding with pre-moistening, drilling at 38 cm and drilling at 76 cm with respect to plant number (18, 54 and 59% higher, respectively), plant frequency (13, 30 and 40% better, respectively), and the rate of canopy closure (18, 33 and 43% faster, respectively) when averaged across seeding rates. However, differences in second-year biomass yields among treatments were less pronounced, as plant size partially compensated for plant density. Both hydroseeding and drilling at rates of 20 or 40 seeds m −2 appear to be viable planting options for establishing seeded miscanthus provided sufficient soil moisture, but additional strategies are required for this new biomass production system under rain-fed conditions. This article is protected by copyright. All rights reserved.

Description: Concerns about invasions by novel bioenergy feedstocks are valid, given the parallels between the traits of energy crops and those of many common invasive plants. As the bioenergy industry is poised to introduce nonnative bioenergy crops to large acreages in the United States under state and federal mandates, it is important to consider these concerns – and not simply in an academic sense. Instead, the prevention of invasions should be codified in statutes and regulations pertaining to bioenergy production on both the state and federal level. Unfortunately, this is not occurring regularly or consistently at this time. The few existing regulations that do consider invasiveness in bioenergy systems suffer from vague terminology that could have major economic, environmental, and legal consequences. Here, we discuss existing regulatory challenges and provide solutions to address invasion potential of bioenergy crops. We provide model definitions and provisions to be included in revised or new state and federal regulations, including an invasion risk assessment process, a permit and bond system for high-risk crops, and a risk mitigation provision for all novel crops. Our proposal provides a consistent and transparent system that will allow the industry to move forward with minimal risk of invasion by novel feedstocks.

Description: Chemical Reviews DOI: 10.1021/cr300463y