The efficacy of C4 grasses as feedstocks for liquid fuel production and their climate mitigation ... more The efficacy of C4 grasses as feedstocks for liquid fuel production and their climate mitigation potential remain unresolved in the tropics. To identify highly convertible C4 grasses, we measured final fuels and postprocess biomass produced in two laboratory-scale conversion pathways across 12 species and varieties within the Poaceae (grass) family. Total mass, carbon, and energy in final fuels and postprocess biomass were assessed based on field mass and area-based production. Two lignocellulosic processes were investigated: (1) anaerobic digestion (AD) to methane and (2) hot water pretreatment and enzymatic hydrolysis (HWP-EH) to ethanol. We found AD converted lignocellulose to methane more efficiently in terms of carbon and energy compared to ethanol production using HWP-EH, although improvements to and the optimization of each process could change these contrasts. The resulting data provide design limitations for agricultural production and biorefinery systems that regulate thes...
ABSTRACT Decisions are being made that will determine the path to be taken for biofuel production... more ABSTRACT Decisions are being made that will determine the path to be taken for biofuel production and use. The objectives of this chapter were to describe some simulation modeling tools as they have been applied to issues related to biofuel production and to describe how to use the Agricultural Land Management Alternative with Numerical Assessment Criteria (ALMANAC) model for these applications. To verify that the biomass yields are realistic, we compared mean simulated yields for four sites in the Central Great Plains to reported yields of maize (Zea mays L.) and switchgrass (Panicum virgatum). We were successful in getting mean simulated values close to the mean measured values in each case. The model was then used to simulate water use efficiency (WUE) of different production systems and biomass yield stability of these systems. This study demonstrated the usefulness of this process-based model for these portions of life cycle analyses. Further work developing parameters to simulate other candidate plant species will prove useful to extend this type of approach. Likewise, further validation of the plant yields on various soils in various rainfall zones will be invaluable as a proof of concept for this approach.
ABSTRACT Considerations for using corn (Zea mays L.) residues for biofuel should include impacts ... more ABSTRACT Considerations for using corn (Zea mays L.) residues for biofuel should include impacts on the subsequent soybean [Glycine max (L.) Merr.] crop. We used the Agricultural Policy Environmental Extender (APEX) model to study the effects of: four rates of corn residue removals, 0%, 40%, 60%, and 80%, across site-specific conditions of two land types, highly erodible land (HEL) and non-HEL; three soil textural classes, clayey, loamy, and sandy; and the four soil hydrologic groups, A, B, C, and D, on soybean yield and nitrogen (N) dynamics, for 3703 farm fields within the Upper Mississippi River Basin. Overall, residue removal reduced soybean yield, N fixation, uptake, losses, and soil storage by 8%, 6%, 7%, and 5%, respectively. There is a positive tradeoff of residue removal, that is, it reduces the pool of nutrients available for loss, which resulted in a 9% decline in N losses when compared to no residue removal. Corn residue removal-induced reduction in soil organic N storage could affect the magnitude of the soybean N credit, implying that increased fertilization rates could be needed to sustain corn productivity in corn/soybean rotation systems. Responses were however subject to site-specific conditions, key considerations when determining residue removal thresholds.
ABSTRACTAllometric models are important for quantifying biomass and carbon storage in terrestrial... more ABSTRACTAllometric models are important for quantifying biomass and carbon storage in terrestrial ecosystems. Generalized allometry exists for tropical trees, but species‐ and site‐specific models are more accurate. We developed species‐specific models to predict aboveground biomass in two of the most ubiquitous natives in Hawaiian forests and shrublands, Metrosideros polymorpha and Dodonaea viscosa. The utility of the M. polymorpha allometry for predicting biomass across a range of sites was explored by comparing size structure (diameter at breast height vs. tree height) of the trees used to develop the models against trees from four M. polymorpha‐dominated forests along a precipitation gradient (1630–2380 mm). We also compared individual tree biomass estimated with the M. polymorpha model against existing generalized equations, and the D. viscosa model with an existing species‐specific model. Our models were highly significant and displayed minimal bias. Metrosideros polymorpha si...
HighlightsThe APEX model was adapted to simulate detasseling in inbred corn for hybrid seed produ... more HighlightsThe APEX model was adapted to simulate detasseling in inbred corn for hybrid seed production.The adapted model satisfactorily predicted detasseling effects on LAI, grain yield, and N content.An inbred corn model could be applied to evaluate best management practices for inbred corns.. Hybrid seed corn production comprises approximately 10% of the entire corn acreage in the U.S. Because of seed corn’s high economic value, and to maximize yields, seed corn growers often over-irrigate or apply nitrogen (N) fertilizers equal to or in excess of those recommended for commercial hybrid corn. Detasseling female corn inbred lines during hybrid corn seed production is critical to ensure the purity of seeds. In addition to the removal of tassels, detasseling also results in the removal of several leaves, which may lead to reduced seed yields. The objective of this study was to adapt the Agricultural Policy/Environmental eXtender (APEX) model to simulate the detasseling of female inbr...
Sorghum is the world’s fifth major cereal in terms of production and acreage. It is expected that... more Sorghum is the world’s fifth major cereal in terms of production and acreage. It is expected that its growth will be affected by the increase in air temperature, an important component of global climate change. Our objective was to use the Agricultural Land Management Alternatives with Numerical Assessment Criteria (ALMANAC) model to (a) evaluate the impact of climate warming on forage and grain sorghum production in Argentina and (b) to analyze to what extent yield changes were associated with changes in water or nitrogen stress days. For model calibration, we used previous information related to the morpho-physiological characteristics of both sorghum types and several soil parameters. We then used multiyear field data of sorghum yields for model validation. Yield simulations were conducted under three possible climate change scenarios: 1, 2, and 4 °C increase in mean annual temperature. ALMANAC successfully simulated mean yields of forage and grain sorghum: root mean square error...
Screening of a number of amphiploids between wheat and species of Agropyron, Thinopyrum [Elymus],... more Screening of a number of amphiploids between wheat and species of Agropyron, Thinopyrum [Elymus], Secale, Hordeum and Aegilops indicated a high level of Al tolerance in S. cereale and S. montanum which could be expressed in a Chinese Spring (CS) genetic background. The CS/S. cereale cv. King II and CS/S. montanum amphiploids consistently expressed high Al tolerance for height, tiller number, spikelets per ear and other characters. Combined analysis of CS/King II, CS/S. cereale cv. Imperial and CS/S. montanum addition lines indicated that Al tolerance in rye is controlled by factors on more than one chromosome though predominantly on chromosome 5R. Al toxicity generally caused increases in Al uptake and large decreases in Ca and Mg uptake.
Field and green house experiments were conducted at Mt. Makulu and Magoye Research Stations in th... more Field and green house experiments were conducted at Mt. Makulu and Magoye Research Stations in the 1995/96 and 1996/97 seasons. The objective of the study was to quantify the nitrogen use efficiency of some Zimbabwean dwarf hybrids and Zambian normal maize (Zea mays L.) hybrids by the 15N methodology. In the first season, six Zimbabwean dwarf (ACFD951 - 956) and three Zambian (GV 408, 507 and 607) pre-released maize hybrids were evaluated. Four rates of urea-N were applied at 0, 40, 80, 120 kg N ha-1 with 1.83% atom excess 15N applied only at Magoye at 80 kg N ha-1. Subsequently a pot experiment with seven Zimbabwean dwarf hybrids (ACFD961 - 967) and two Zambian normal hybrids (GV 607 and 408) was planted. Two grammes 15N was applied at 5% atom excess to 3 kg soil per pot. In 1996/97 season, five dwarf hybrids (ACFD 3351-261, 3351-225, 797725, 797754 and 21-244) and the same three Zambian hybrids were planted. Nitrogen was applied at 0, 50, 100 and 150 kg N ha-1 with 1.83% atom exce...
ABSTRACT Hydrotreated Renewable Jet (HRJ) fuel has increasingly become important for the aviation... more ABSTRACT Hydrotreated Renewable Jet (HRJ) fuel has increasingly become important for the aviation sector to address energy security and climate change mitigation. Rapeseed (Brassica Napus) is a favored candidate feedstock for HRJ because of its high quality oil content and agroeconomic benefit to replace the fallow period in wheat/fallow rotations. We conducted research to evaluate regional differences in nitrous oxide (N2O) emissions for rapeseed cultivation in several counties in 10 states in the United States (U.S.). The Roundtable on Sustainable Biofuels (RSB) methodology was applied, and results were compared to the Intergovernmental Panel on Climate Change (IPCC) guidelines. In this study, yield, nitrogen fertilizer rate, and types were held constant for all locations in order to understand the similarities and differences in the RSB and IPCC methods for estimating N2O emissions. From the results, the RSB-calculated N2O emissions varied for different U.S. states, though regional differences were very small, 0.72–0.73 kg N2O Mg−1seed, while N2O emissions from IPCC method were the same for all sites, 0.87 kg N2O Mg−1seed. The difference between the RSB and IPCC methods is caused by the indirect N2O emissions from ammonia emissions and nitrate leaching. However, the influence of indirect effect is relatively small compared to overall N2O emissions. The utilization of the RSB method may not be justified for estimating regional variations in N2O emissions. As a consequence, the preliminary greenhouse gas (GHG) of rapeseed HRJ fuel using the RSB method in several locations had small differences in result, 42.7–43.0 g CO2 eq/MJ compared to 45.9 g CO2 eq/MJ using the IPCC method.
The efficacy of C4 grasses as feedstocks for liquid fuel production and their climate mitigation ... more The efficacy of C4 grasses as feedstocks for liquid fuel production and their climate mitigation potential remain unresolved in the tropics. To identify highly convertible C4 grasses, we measured final fuels and postprocess biomass produced in two laboratory-scale conversion pathways across 12 species and varieties within the Poaceae (grass) family. Total mass, carbon, and energy in final fuels and postprocess biomass were assessed based on field mass and area-based production. Two lignocellulosic processes were investigated: (1) anaerobic digestion (AD) to methane and (2) hot water pretreatment and enzymatic hydrolysis (HWP-EH) to ethanol. We found AD converted lignocellulose to methane more efficiently in terms of carbon and energy compared to ethanol production using HWP-EH, although improvements to and the optimization of each process could change these contrasts. The resulting data provide design limitations for agricultural production and biorefinery systems that regulate thes...
ABSTRACT Decisions are being made that will determine the path to be taken for biofuel production... more ABSTRACT Decisions are being made that will determine the path to be taken for biofuel production and use. The objectives of this chapter were to describe some simulation modeling tools as they have been applied to issues related to biofuel production and to describe how to use the Agricultural Land Management Alternative with Numerical Assessment Criteria (ALMANAC) model for these applications. To verify that the biomass yields are realistic, we compared mean simulated yields for four sites in the Central Great Plains to reported yields of maize (Zea mays L.) and switchgrass (Panicum virgatum). We were successful in getting mean simulated values close to the mean measured values in each case. The model was then used to simulate water use efficiency (WUE) of different production systems and biomass yield stability of these systems. This study demonstrated the usefulness of this process-based model for these portions of life cycle analyses. Further work developing parameters to simulate other candidate plant species will prove useful to extend this type of approach. Likewise, further validation of the plant yields on various soils in various rainfall zones will be invaluable as a proof of concept for this approach.
ABSTRACT Considerations for using corn (Zea mays L.) residues for biofuel should include impacts ... more ABSTRACT Considerations for using corn (Zea mays L.) residues for biofuel should include impacts on the subsequent soybean [Glycine max (L.) Merr.] crop. We used the Agricultural Policy Environmental Extender (APEX) model to study the effects of: four rates of corn residue removals, 0%, 40%, 60%, and 80%, across site-specific conditions of two land types, highly erodible land (HEL) and non-HEL; three soil textural classes, clayey, loamy, and sandy; and the four soil hydrologic groups, A, B, C, and D, on soybean yield and nitrogen (N) dynamics, for 3703 farm fields within the Upper Mississippi River Basin. Overall, residue removal reduced soybean yield, N fixation, uptake, losses, and soil storage by 8%, 6%, 7%, and 5%, respectively. There is a positive tradeoff of residue removal, that is, it reduces the pool of nutrients available for loss, which resulted in a 9% decline in N losses when compared to no residue removal. Corn residue removal-induced reduction in soil organic N storage could affect the magnitude of the soybean N credit, implying that increased fertilization rates could be needed to sustain corn productivity in corn/soybean rotation systems. Responses were however subject to site-specific conditions, key considerations when determining residue removal thresholds.
ABSTRACTAllometric models are important for quantifying biomass and carbon storage in terrestrial... more ABSTRACTAllometric models are important for quantifying biomass and carbon storage in terrestrial ecosystems. Generalized allometry exists for tropical trees, but species‐ and site‐specific models are more accurate. We developed species‐specific models to predict aboveground biomass in two of the most ubiquitous natives in Hawaiian forests and shrublands, Metrosideros polymorpha and Dodonaea viscosa. The utility of the M. polymorpha allometry for predicting biomass across a range of sites was explored by comparing size structure (diameter at breast height vs. tree height) of the trees used to develop the models against trees from four M. polymorpha‐dominated forests along a precipitation gradient (1630–2380 mm). We also compared individual tree biomass estimated with the M. polymorpha model against existing generalized equations, and the D. viscosa model with an existing species‐specific model. Our models were highly significant and displayed minimal bias. Metrosideros polymorpha si...
HighlightsThe APEX model was adapted to simulate detasseling in inbred corn for hybrid seed produ... more HighlightsThe APEX model was adapted to simulate detasseling in inbred corn for hybrid seed production.The adapted model satisfactorily predicted detasseling effects on LAI, grain yield, and N content.An inbred corn model could be applied to evaluate best management practices for inbred corns.. Hybrid seed corn production comprises approximately 10% of the entire corn acreage in the U.S. Because of seed corn’s high economic value, and to maximize yields, seed corn growers often over-irrigate or apply nitrogen (N) fertilizers equal to or in excess of those recommended for commercial hybrid corn. Detasseling female corn inbred lines during hybrid corn seed production is critical to ensure the purity of seeds. In addition to the removal of tassels, detasseling also results in the removal of several leaves, which may lead to reduced seed yields. The objective of this study was to adapt the Agricultural Policy/Environmental eXtender (APEX) model to simulate the detasseling of female inbr...
Sorghum is the world’s fifth major cereal in terms of production and acreage. It is expected that... more Sorghum is the world’s fifth major cereal in terms of production and acreage. It is expected that its growth will be affected by the increase in air temperature, an important component of global climate change. Our objective was to use the Agricultural Land Management Alternatives with Numerical Assessment Criteria (ALMANAC) model to (a) evaluate the impact of climate warming on forage and grain sorghum production in Argentina and (b) to analyze to what extent yield changes were associated with changes in water or nitrogen stress days. For model calibration, we used previous information related to the morpho-physiological characteristics of both sorghum types and several soil parameters. We then used multiyear field data of sorghum yields for model validation. Yield simulations were conducted under three possible climate change scenarios: 1, 2, and 4 °C increase in mean annual temperature. ALMANAC successfully simulated mean yields of forage and grain sorghum: root mean square error...
Screening of a number of amphiploids between wheat and species of Agropyron, Thinopyrum [Elymus],... more Screening of a number of amphiploids between wheat and species of Agropyron, Thinopyrum [Elymus], Secale, Hordeum and Aegilops indicated a high level of Al tolerance in S. cereale and S. montanum which could be expressed in a Chinese Spring (CS) genetic background. The CS/S. cereale cv. King II and CS/S. montanum amphiploids consistently expressed high Al tolerance for height, tiller number, spikelets per ear and other characters. Combined analysis of CS/King II, CS/S. cereale cv. Imperial and CS/S. montanum addition lines indicated that Al tolerance in rye is controlled by factors on more than one chromosome though predominantly on chromosome 5R. Al toxicity generally caused increases in Al uptake and large decreases in Ca and Mg uptake.
Field and green house experiments were conducted at Mt. Makulu and Magoye Research Stations in th... more Field and green house experiments were conducted at Mt. Makulu and Magoye Research Stations in the 1995/96 and 1996/97 seasons. The objective of the study was to quantify the nitrogen use efficiency of some Zimbabwean dwarf hybrids and Zambian normal maize (Zea mays L.) hybrids by the 15N methodology. In the first season, six Zimbabwean dwarf (ACFD951 - 956) and three Zambian (GV 408, 507 and 607) pre-released maize hybrids were evaluated. Four rates of urea-N were applied at 0, 40, 80, 120 kg N ha-1 with 1.83% atom excess 15N applied only at Magoye at 80 kg N ha-1. Subsequently a pot experiment with seven Zimbabwean dwarf hybrids (ACFD961 - 967) and two Zambian normal hybrids (GV 607 and 408) was planted. Two grammes 15N was applied at 5% atom excess to 3 kg soil per pot. In 1996/97 season, five dwarf hybrids (ACFD 3351-261, 3351-225, 797725, 797754 and 21-244) and the same three Zambian hybrids were planted. Nitrogen was applied at 0, 50, 100 and 150 kg N ha-1 with 1.83% atom exce...
ABSTRACT Hydrotreated Renewable Jet (HRJ) fuel has increasingly become important for the aviation... more ABSTRACT Hydrotreated Renewable Jet (HRJ) fuel has increasingly become important for the aviation sector to address energy security and climate change mitigation. Rapeseed (Brassica Napus) is a favored candidate feedstock for HRJ because of its high quality oil content and agroeconomic benefit to replace the fallow period in wheat/fallow rotations. We conducted research to evaluate regional differences in nitrous oxide (N2O) emissions for rapeseed cultivation in several counties in 10 states in the United States (U.S.). The Roundtable on Sustainable Biofuels (RSB) methodology was applied, and results were compared to the Intergovernmental Panel on Climate Change (IPCC) guidelines. In this study, yield, nitrogen fertilizer rate, and types were held constant for all locations in order to understand the similarities and differences in the RSB and IPCC methods for estimating N2O emissions. From the results, the RSB-calculated N2O emissions varied for different U.S. states, though regional differences were very small, 0.72–0.73 kg N2O Mg−1seed, while N2O emissions from IPCC method were the same for all sites, 0.87 kg N2O Mg−1seed. The difference between the RSB and IPCC methods is caused by the indirect N2O emissions from ammonia emissions and nitrate leaching. However, the influence of indirect effect is relatively small compared to overall N2O emissions. The utilization of the RSB method may not be justified for estimating regional variations in N2O emissions. As a consequence, the preliminary greenhouse gas (GHG) of rapeseed HRJ fuel using the RSB method in several locations had small differences in result, 42.7–43.0 g CO2 eq/MJ compared to 45.9 g CO2 eq/MJ using the IPCC method.
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