19722015
  • Authors:
    • Sinistore,J. C.
    • Reinemann,D. J.
    • Izaurralde,R. C.
    • Cronin,K. R.
    • Meier,P. J.
    • Runge,T. M.
    • Zhang,X.
  • Source: BioEnergy Research
  • Volume: 8
  • Issue: 3
  • Year: 2015
  • Summary: 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. © 2015, The Author(s).
  • Authors:
    • Thomazini,A.
    • Spokas,K.
    • Hall,K.
    • Ippolito,J.
    • Lentz,R.
    • Novak,J.
  • Source: Agriculture, Ecosystems and Environment
  • Volume: 207
  • Year: 2015
  • Summary: One potential strategy to abate increasing atmospheric carbon dioxide (CO 2) levels is to sequester CO 2 as biochar, a structural form of carbon created through the pyrolysis of various biomass materials. Biochar may be applied to soils, but has resulted in variable impacts on net soil greenhouse gas (GHG) emissions, with results spanning from suppression to stimulation. This laboratory incubation study examined the impacts of the same hardwood biochar (fast pyrolysis at 550°C) to elucidate driving variables affecting previously observed carbon dioxide (CO 2) fluctuations as well as nitrous oxide (N 2O), and methane (CH 4) production impacts across ten different US soils with and without biochar (10% w/w). Biochar application significantly impacted CO 2 ( P=0.04) and N 2O ( P=0.03) production following amendment across all soils, but there were no differences observed in CH 4 production/oxidation rates ( P=0.90). Interestingly, the induced biochar GHG alterations were significantly correlated to the original GHG production activity in the control soil, suggesting a more universal response across various soils to the same biochar than has been previously hypothesized. After correcting for the amount of CO 2 released from the biochar itself [24 g C g BC-1 d -1], there was no statistically significant alteration in the actual soil CO 2 mineralization rate for any soil. This suggests that the observed increase in CO 2 production was solely attributed to the abiotic CO 2 releases from the biochar. On the other hand, there was an average suppression of 63% in the N 2O production across all soils following biochar addition, which was again correlated to initial N 2O production activity. For this particular biochar, there are predictable impacts on the GHG production potential across various soils despite differences in soil chemistry, texture, and microbial communities.
  • Authors:
    • He, X.
    • Guan, Q.
    • Lu, X.
    • Lu, M.
    • Wu, H.
  • Source: Biology Article
  • Volume: 88
  • Year: 2015
  • Summary: Soil fauna can significantly affect soil CO2 and N2O emissions, but little is known about interactions between faunal groups and their relative contribution to such emissions. Over a 64-day microcosm incubation, we studied the effects of an epigeic earthworm (Eisenia fetida), mesofauna (Collembola plus oribatid mites) and their combinations on soil CO2 and N2O emissions under two faunal densities. Earthworms significantly enhanced soil CO2 and N2O emissions, while mesofauna only increased N2O emissions. Soil CO2 and N2O emissions were significantly affected by earthworm density, but not by mesofauna density. No significant interactive effects between earthworms and mesofauna were found on soil CO2 and N2O emissions. Our results indicate that earthworms probably play the dominant roles in determining soil CO2 and N2O emissions where they coexist with soil mesofauna. (C) 2015 Elsevier Ltd. All rights reserved.
  • Authors:
    • Jones, L. E.
    • Maddison, A. L.
    • Castle, M.
    • Barraclough, T. J. P.
    • Purdy, S. J.
    • Cunniff, J.
    • Shield, I. F.
    • Gregory, A. S.
    • Karp, A.
  • Source: Science Article
  • Volume: 80
  • Year: 2015
  • Summary: Willows ( Salix spp.) grown as short rotation coppice (SRC) are viewed as a sustainable source of biomass with a positive greenhouse gas (GHG) balance due to their potential to fix and accumulate carbon (C) below ground. However, exploiting this potential has been limited by the paucity of data available on below ground biomass allocation and the extent to which it varies between genotypes. Furthermore, it is likely that allocation can be altered considerably by environment. To investigate the role of genotype and environment on allocation, four willow genotypes were grown at two replicated field sites in southeast England and west Wales, UK. Above and below ground biomass was intensively measured over two two-year rotations. Significant genotypic differences in biomass allocation were identified, with below ground allocation differing by up to 10% between genotypes. Importantly, the genotype with the highest below ground biomass also had the highest above ground yield. Furthermore, leaf area was found to be a good predictor of below ground biomass. Growth environment significantly impacted allocation; the willow genotypes grown in west Wales had up to 94% more biomass below ground by the end of the second rotation. A single investigation into fine roots showed the same pattern with double the volume of fine roots present. This greater below ground allocation may be attributed primarily to higher wind speeds, plus differences in humidity and soil characteristics. These results demonstrate that the capacity exists to breed plants with both high yields and high potential for C accumulation.
  • Authors:
    • Jarchow, M.
    • Horton, R.
    • Pederson, C. H.
    • Helmers, M. J.
    • Zhou, X. B.
    • Daigh, A. L. M.
    • Liebman, M.
  • Source: Journal of Environmental Quality
  • Volume: 44
  • Issue: 5
  • Year: 2015
  • Summary: We compare subsurface-drainage NO 3-N and total reactive phosphorus (TRP) concentrations and yields of select bioenergy cropping systems and their rotational phases. Cropping systems evaluated were grain-harvested corn-soybean rotations, grain- and stover-harvested continuous corn systems with and without a cover crop, and annually harvested reconstructed prairies with and without the addition of N fertilizer in an Iowa field. Drainage was monitored when soils were unfrozen during 2010 through 2013. The corn-soybean rotations without residue removal and continuous corn with residue removal produced similar mean annual flow-weighted NO 3-N concentrations, ranging from 6 to 18.5 mg N L -1 during the 4-yr study. In contrast, continuous corn with residue removal and with a cover crop had significantly lower NO 3-N concentrations of 5.6 mg N L -1 when mean annual flow-weighted values were averaged across the 4 yr. Prairies systems with or without N fertilization produced significantly lower concentrations below <1 mg NO 3-N L -1 than all the row crop systems throughout the study. Mean annual flow-weighted TRP concentrations and annual yields were generally low, with values <0.04 mg TRP L -1 and <0.14 kg TRP ha -1, and were not significantly affected by any cropping systems or their rotational phases. Bioenergy-based prairies with or without N fertilization and continuous corn with stover removal and a cover crop have the potential to supply bioenergy feedstocks while minimizing NO 3-N losses to drainage waters. However, subsurface drainage TRP concentrations and yields in bioenergy systems will need further evaluation in areas prone to higher levels of P losses.
  • Authors:
    • Karlen,D. L.
    • Beeler,L. W.
    • Ong,R. G.
    • Dale,B. E.
  • Source: Journal of Soil and Water Conservation
  • Volume: 70
  • Issue: 5
  • Year: 2015
  • Authors:
    • Morillas,L.
    • Duran,J.
    • Rodriguez,A.
    • Roales,J.
    • Gallardo,A.
    • Lovett,G. M.
    • Groffman,P. M.
  • Source: Global Change Biology
  • Volume: 21
  • Issue: 10
  • Year: 2015
  • Summary: Climate change and atmospheric nitrogen (N) deposition are two of the most important global change drivers. However, the interactions of these drivers have not been well studied. We aimed to assess how the combined effect of soil N additions and more frequent soil drying-rewetting events affects carbon (C) and N cycling, soil:atmosphere greenhouse gas (GHG) exchange, and functional microbial diversity. We manipulated the frequency of soil drying-rewetting events in soils from ambient and N-treated plots in a temperate forest and calculated the Orwin & Wardle Resistance index to compare the response of the different treatments. Increases in drying-rewetting cycles led to reductions in soil NO 3- levels, potential net nitrification rate, and soil : atmosphere GHG exchange, and increases in NH 4+ and total soil inorganic N levels. N-treated soils were more resistant to changes in the frequency of drying-rewetting cycles, and this resistance was stronger for C- than for N-related variables. Both the long-term N addition and the drying-rewetting treatment altered the functionality of the soil microbial population and its functional diversity. Our results suggest that increasing the frequency of drying-rewetting cycles can affect the ability of soil to cycle C and N and soil : atmosphere GHG exchange and that the response to this increase is modulated by soil N enrichment.
  • Authors:
    • Mu,J. E.
    • Wein,A. M.
    • McCarl,B. A.
  • Source: Mitigation and Adaptation Strategies for Global Change
  • Volume: 20
  • Issue: 7
  • Year: 2015
  • Summary: We examine the effects of crop management adaptation and climate mitigation strategies on land use and land management, plus on related environmental and economic outcomes. We find that crop management adaptation (e.g. crop mix, new species) increases Greenhouse gas (GHG) emissions by 1.7 % under a more severe climate projection while a carbon price reduces total forest and agriculture GHG annual flux by 15 % and 9 %, respectively. This shows that trade-offs are likely between mitigation and adaptation. Climate change coupled with crop management adaptation has small and mostly negative effects on welfare; mitigation, which is implemented as a carbon price starting at $15 per metric ton carbon dioxide (CO2) equivalent with a 5 % annual increase rate, bolsters welfare carbon payments. When both crop management adaptation and carbon price are implemented the effects of the latter dominates. © 2013, Springer Science+Business Media Dordrecht.
  • Authors:
    • Panday,D.
    • Nkongolo,N. V.
  • Source: Procedia Environmental Sciences
  • Volume: 29
  • Year: 2015
  • Summary: Knowledge of the impact of soil and crop management practices on soil processes is important in the study of greenhouse gases emissions from agricultural fields. We assessed the effect of soil air (pore space indices) and water (content, theta; and potential, Psi) on greenhouse gases emissions in corn/soybean field. The study was conducted in 2011 and 2012 on a silt loam soil at Freeman farm of Lincoln University. Soil samples were collected at four depths: 0-10, 10-20, 20-40 and 40-60 cm and they were oven dried at 105°C for 72 h for the calculation of air filled porosity (AFP), total pore space (TPS) and other soil physical properties. Pore space indices were computed using diffusivity models based on AFP and TPS. Soil samples were later saturated then brought into a pressure plate for measurements of moisture content (theta) at five different water potentials (Psi). Soil air samples for the measurements of greenhouse gases emissions were collected using static and vented chambers of 30 cm height and 20 cm diameter. The concentrations of CO2, CH4 and N2O in soil air samples were determined using a Gas Chromatograph GC-14. Results showed that pore space indices significantly correlated with greenhouse gases fluxes (p<0.05) with correlation coefficient (r) ranged from 0.27 to 0.53. More correlations were found in 2012 than 2011. Similarly, significant correlations were found between greenhouse gases and theta at Psi=0 and Psi=-0.05. Moisture content (theta) held at Psi=0 positively correlated with CO2 (r=0.49), N2O (r=0.64) and negatively correlated with CH4 (r=-0.43) at p<0.05. Soil pore space indices and soil water (content and potential) seem to control greenhouse gases emissions in this soil. Inclusion of these controlling factors in models will certainly improve our understanding of the dynamics of greenhouse gases fluxes from soil.
  • Authors:
    • Schmer,Marty R.
    • Jin,Virginia L.
    • Wienhold,Brian J.
  • Source: Biomass and Bioenergy
  • Volume: 81
  • Year: 2015
  • Summary: Changes in direct soil organic carbon (SOC) can have a major impact on overall greenhouse gas (GHG) emissions from biofuels when using life-cycle assessment (LCA). Estimated changes in SOC, when accounted for in an LCA, are typically derived from near-surface soil depths (30 cm) could have a large positive or negative impact on overall GHG emissions from biofuels that are not always accounted for. Here, we evaluate how sub-surface SOC changes impact biofuel GHG emissions for corn (Zea mays L.) grain, corn stover, and switchgrass (Panicum virgatum L.) using the (Greenhouse Gases, Regulated Emissions, and Energy Use in the Transportation) GREET model. Biofuel GHG emissions showed as much as a 154% difference between using near-surface SOC stocks changes only or when accounting for both near- and sub-surface SOC stock changes. Differences in GHG emissions highlight the importance of accounting for sub-surface SOC changes especially in bioenergy cropping systems with potential for soil C storage to deeper soil depths. Published by Elsevier Ltd.