Nitrogen fertilization, yield components, and species selection of perennial grass bioenergy cropping systems across eastern North America

Perennial grasses are being studied as a fuel source and potential replacement for fossil fuels. Perennial grasses are a versatile group of potential bioenergy crops that have the ability to produce large yields on relatively low-quality land or with lower inputs than traditional annual row crops such as maize. Grasses can be directly combusted to produce heat and/or electricity or can be processed to produce cellulosic ethanol similarly to corn grain ethanol that is combined with gasoline for use as a liquid transportation fuel. Miscanthus x giganteus (Miscanthus), Panicum virgatum (switchgrass), and recreated, multi-species tallgrass prairies are possible perennial systems for high-yield production in crop-growing regions of North America. However, past research has reported mixed findings regarding species selection and responses of perennial energy crops to nitrogen fertilization. This dissertation examines several of these aspects in three studies: 1) An in-depth look at the effects of N fertility rates on biomass yield and individual yield components of Miscanthus across several seasons. Results demonstrated that applying 60 or 120 kg N ha-1 provides a 2x yield increase compared to unfertilized Miscanthus in a long-term study at Urbana, IL, USA. Total tillers per m2 were strongly correlated with increasing biomass yield, with tiller height, diameter, and phytomer number also correlating well with yield. 2) The productivity of side-by-side plots of Miscanthus and switchgrass was evaluated over two years in 11 locations in eastern North America. Results showed Miscanthus to be a greater producer of biomass than switchgrass across all sites, and showed variability among sites on the effect of applied nitrogen fertilizer. Most yield components were correlated with yield changes, but in some cases were affected differently by added fertility. Overall, proper selection of species or switchgrass cultivar played a role in biomass production at a given site. 3) A long-term field-scale comparison of three perennial grass systems: Miscanthus, switchgrass, and a high-diversity recreated tallgrass prairie. Monoculture stands of Miscanthus and switchgrass produced more biomass than the prairie system while the stands were young, but yields of monoculture crops declined with stand age. The monoculture stands produced more biomass than the prairie stand during the drought year of 2012, indicating that diverse systems are not necessarily more resistant to drought. Application of nitrogen fertilizer to declining Miscanthus stands starting in year six generated a nearly 2x yield increase over unfertilized plots, which still produced more biomass than the prairie. In addition, average annual energy production was greater in switchgrass and Miscanthus stands than in a corn-corn-soybean rotation system, due to the inconsistency of corn yields and the low energy potential of soybean. Finally, as a sidebar, harvest results using a plot-scale combine and a commercial harvest system were strongly correlated, which indicates that the plot-scale combine is a good estimator of overall yields. These results show that applied nitrogen fertilizer increases yields of bioenergy crops in certain situations, and measuring certain yield components may provide a good estimate of total biomass yield. Perennial grass systems are at least comparable to annual row-crop systems, and in many cases may exceed them in overall energy production

Biomass production of herbaceous energy crops in the United States: field trial results and yield potential maps from the multiyear regional feedstock partnership

Current knowledge of yield potential and best agronomic management practices for perennial bioenergy grasses is primarily derived from small-scale and short-term studies, yet these studies inform policy at the national scale. In an effort to learn more about how bioenergy grasses perform across multiple locations and years, the U.S. Department of Energy (US DOE)/Sun Grant Initiative Regional Feedstock Partnership was initiated in 2008. The objectives of the Feedstock Partnership were to (1) provide a wide range of information for feedstock selection (species choice) and management practice options for a variety of regions and (2) develop national maps of potential feedstock yield for each of the herbaceous species evaluated. The Feedstock Partnership expands our previous understanding of the bioenergy potential of switchgrass, Miscanthus, sorghum, energycane, and prairie mixtures on Conservation Reserve Program land by conducting long-term, replicated trials of each species at diverse environments in the U.S. Trials were initiated between 2008 and 2010 and completed between 2012 and 2015 depending on species. Field-scale plots were utilized for switchgrass and Conservation Reserve Program trials to use traditional agricultural machinery. This is important as we know that the smaller scale studies often overestimated yield potential of some of these species. Insufficient vegetative propagules of energycane and Miscanthus prohibited farm-scale trials of these species. The Feedstock Partnership studies also confirmed that environmental differences across years and across sites had a large impact on biomass production. Nitrogen application had variable effects across feedstocks, but some nitrogen fertilizer generally had a positive effect. National yield potential maps were developed using PRISM-ELM for each species in the Feedstock Partnership. This manuscript, with the accompanying supplemental data, will be useful in making decisions about feedstock selection as well as agronomic practices across a wide region of the country

Biomass production of herbaceous energy crops in the United States: field trial results and yield potential maps from the multiyear regional feedstock partnership

Current knowledge of yield potential and best agronomic management practices for perennial bioenergy grasses is primarily derived from small-scale and short-term studies, yet these studies inform policy at the national scale. In an effort to learn more about how bioenergy grasses perform across multiple locations and years, the U.S. Department of Energy (US DOE)/Sun Grant Initiative Regional Feedstock Partnership was initiated in 2008. The objectives of the Feedstock Partnership were to (1) provide a wide range of information for feedstock selection (species choice) and management practice options for a variety of regions and (2) develop national maps of potential feedstock yield for each of the herbaceous species evaluated. The Feedstock Partnership expands our previous understanding of the bioenergy potential of switchgrass, Miscanthus, sorghum, energycane, and prairie mixtures on Conservation Reserve Program land by conducting long-term, replicated trials of each species at diverse environments in the U.S. Trials were initiated between 2008 and 2010 and completed between 2012 and 2015 depending on species. Field-scale plots were utilized for switchgrass and Conservation Reserve Program trials to use traditional agricultural machinery. This is important as we know that the smaller scale studies often overestimated yield potential of some of these species. Insufficient vegetative propagules of energycane and Miscanthus prohibited farm-scale trials of these species. The Feedstock Partnership studies also confirmed that environmental differences across years and across sites had a large impact on biomass production. Nitrogen application had variable effects across feedstocks, but some nitrogen fertilizer generally had a positive effect. National yield potential maps were developed using PRISM-ELM for each species in the Feedstock Partnership. This manuscript, with the accompanying supplemental data, will be useful in making decisions about feedstock selection as well as agronomic practices across a wide region of the country