Seasonal Dynamics of Productivity and Photosynthesis of Three Biofuel Feedstocks: Field Comparisons of Miscanthus X Giganteus, Panicum Virgatum and Zea Mays

124 p.Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 2009.Global climate change and dwindling supplies of fossil based resources have led to increasing interest in the use of plant biomass as an alternative fuel source. One of the major limitations is in the amount of land area available to meet the needs of the expanding global population. To provide enough food, feed, fiber and fuel for the projected 9 billion people who will inhabit the Earth by 2050, land use decisions must be made carefully, and should be validated by statistically rigorous data. Furthermore, improvements in plant productivity will be necessary to ensure abundant supplies to meet the above demands. This thesis aims to compare the productivity and underlying causes of variation in productivity of three candidate species which are currently or projected to be used widely in bioenergy production, Miscanthus (Miscanthus x giganteus), switchgrass (Panicum virgatum L.) and maize (Zea mays L.), using fully-replicated field trials in the Midwestern USA. A comparison of M. x giganteus and P. virgatum cv. Cave-in-Rock over a range of 7 soil types at locations across Illinois showed that M. x giganteus produces on average 2.5 times more harvestable biomass than P. virgatum; however this difference varied considerably with location. Importantly some of the highest yields of M. x giganteus were obtained on marginal soils in southern Illinois. The first comparison of seasonal dynamics of below-ground biomass of mature M. x giganteus and P. virgatum stands over three consecutive growing seasons showed that on average, M. x giganteus has nearly double the amount of below-ground biomass than P. virgatum; the difference being due to a larger rhizome but not root mass. M. x giganteus is also shown to be more effective at cycling nutrients and energy from carbohydrates stored in the rhizomes to promote above-ground growth early in the growing season and in recycling the nutrients and carbohydrates back to the rhizomes during senescence late in the growing season. Diurnal gas exchange measurements over two growing seasons showed that M. x giganteus upper canopy sunlit leaves assimilate 33% more CO 2 than P. virgatum over two complete growing seasons, and it also uses water, light energy and nitrogen more efficiently than M. x giganteus Finally, the first replicated side-by-side trials of the two species showed that M. x giganteus produces 60% more peak biomass than Z. mays over two growing seasons, and that this difference is due to the ability of M. x giganteus to produce photosynthetically competent leaves earlier and maintain them later in the growing season than Z. mays. Even though midsummer levels of leaf-photosynthesis were higher in Z. mays, these leaf level differences were more than offset by the larger leaf area and its longer duration in M. x giganteus. Collectively, these results show that M. x giganteus produces exceptional biomass yields even by comparison to Z. mays in the Midwest by being far more efficient in capturing the available light energy and outpaces P. virgatum by being far more efficient in converting that captured energy into biomass The findings show that M. x giganteus can produce and sustain exceptional biomass yields at a range of locations. It also shows that understanding the molecular basic of its ability to maintain and develop leaves at lower temperatures than Z. mays, and to achieve higher leaf-level photosynthetic rates than P. virgatum, could aid in improving the productivity and in turn decreasing the land requirements of each of these important crops.U of I OnlyRestricted to the U of I community idenfinitely during batch ingest of legacy ETD

More Productive Than Maize in the Midwest: How Does Miscanthus Do It?1[W][OA]

In the first side-by-side large-scale trials of these two C4 crops in the U.S. Corn Belt, Miscanthus (Miscanthus × giganteus) was 59% more productive than grain maize (Zea mays). Total productivity is the product of the total solar radiation incident per unit land area and the efficiencies of light interception (εi) and its conversion into aboveground biomass (εca). Averaged over two growing seasons, εca did not differ, but εi was 61% higher for Miscanthus, which developed a leaf canopy earlier and maintained it later. The diurnal course of photosynthesis was measured on sunlit and shaded leaves of each species on 26 dates. The daily integral of leaf-level photosynthetic CO2 uptake differed slightly when integrated across two growing seasons but was up to 60% higher in maize in mid-summer. The average leaf area of Miscanthus was double that of maize, with the result that calculated canopy photosynthesis was 44% higher in Miscanthus, corresponding closely to the biomass differences. To determine the basis of differences in mid-season leaf photosynthesis, light and CO2 responses were analyzed to determine in vivo biochemical limitations. Maize had a higher maximum velocity of phosphoenolpyruvate carboxylation, velocity of phosphoenolpyruvate regeneration, light saturated rate of photosynthesis, and higher maximum quantum efficiency of CO2 assimilation. These biochemical differences, however, were more than offset by the larger leaf area and its longer duration in Miscanthus. The results indicate that the full potential of C4 photosynthetic productivity is not achieved by modern temperate maize cultivars

Benefitting productivity and the environment: Current and future maize cropping systems improve yield while reducing nitrate load

Increases in cereal crop yield per area have increased global food security. “Era” studies compare historical and modern crop varieties in controlled experimental settings and are routinely used to understand how advances in crop genetics and management affect crop yield. However, to date, no era study has explored how advances in maize (Zea mays L.) genetics and management (i.e., cropping systems) have affected environmental outcomes. Here, we developed a cropping systems era study in Iowa, USA, to examine how yield and nitrate losses have changed from “Old” systems common in the 1990s to “Current” systems common in the 2010s, and to “Future” systems projected to be common in the 2030s. We tested the following hypothesis: If maize yield and nitrogen use efficiency have improved over previous decades, Current and Future maize systems will have benefits to water quality compared to Old systems. We show that not only have maize yield and nitrogen use efficiency (kg grain kg−1 N), on average, improved over time but also yield-scaled nitrate load + soil nitrate was reduced by 74% and 91% from Old to Current and Future systems, respectively. Continuing these trajectories of improvement will be critical to meet the needs of a growing and more affluent population while reducing deleterious effects of agricultural systems on ecosystem services.This article is published as Dohleman, Frank G., Ty J. Barten, Nicholas Helland, Subash Dahal, Juan Lopez Arrizia, Sarah Gehlhar, Charles Foresman et al. Benefitting productivity and the environment: Current and future maize cropping systems improve yield while reducing nitrate load. Journal of Environmental Quality (2024). doi:10.1002/jeq2.20537. © 2024 The Authors.This is an open access article under the terms of the Creative Commons Attribution-NonCommercial-NoDerivs License, which permits use and distribution in any medium, provided the original work is properly cited, the use is non-commercial and no modifications or adaptations are made