• Authors:
    • Spargo, J. T.
    • Teasdale, J. R.
    • Mirsky, S. B.
    • Cavigelli, M. A.
    • Doran, J.
  • Source: Renewable Agriculture and Food Systems
  • Volume: 28
  • Issue: 2
  • Year: 2013
  • Summary: Organic grain cropping systems can enhance a number of ecosystem services compared with conventional tilled (CT) systems. Recent results from a limited number of long-term agricultural research (LTAR) studies suggest that organic grain cropping systems can also increase several ecosystem services relative to conventional no-till (NT) cropping systems: soil C sequestration and soil N fertility (N mineralization potential) can be greater while global warming potential (GWP) can be lower in organic systems that use animal manures and cover crops compared with conventional NT systems. However, soil erosion from organic systems and nitrous oxide (N2O, a greenhouse gas) emissions from manure-based organic systems appear to be greater than from conventional NT systems, though data are limited. Also, crop yields, on average, continue to be lower and labor requirements greater in organic than in both tilled and NT conventional systems. Ecosystem services provided by organic systems may be improved by expanding crop rotations to include greater crop phenological diversity, improving nutrient management, and reducing tillage intensity and frequency. More diverse crop rotations, especially those that include perennial forages, can reduce weed pressure, economic risk, soil erosion, N2O emissions, animal manure inputs, and soil P loading, while increasing grain yield and soil fertility. Side-dressing animal manures in organic systems may increase corn nitrogen use efficiency and also minimize animal manure inputs. Management practices that reduce tillage frequency and intensity in organic systems are being developed to reduce soil erosion and labor and energy needs. On-going research promises to further augment ecosystem services provided by organic grain cropping systems.
  • Authors:
    • Lal, R.
    • Smith, P.
    • Datta, A.
  • Source: Agriculture, Ecosystems & Environment
  • Volume: 171
  • Year: 2013
  • Summary: Advance tillage research sugests that tillage decreases soil fertility and adversely affects the environment. The objective of this research was to estimate the greenhouse gas (GHG) flux vis-a-vis GHG production potential at different soil depths (0-100 cm) from tillage and drainage management treatments during the fallow period (October 2009 to April 2010) in a continuous (since 1994) corn (Zea mays) growing field at the Waterman farm in central Ohio. The Crosby silt loam (Aeric ochraqualf) soil of the experimental farm has been managed with the same practice since 1994 with two tillage sub-factors: no till (NT) and chisel tillage (T) and two drainage sub-factors: tile drainage (D) and no-drainage (ND). The fallow period was from the middle of October to the middle of April. The field was under snow cover during the middle of December to the first week of March. GHG fluxes (CO2, CH4 and N2O) were significantly lower during the snow cover period. This study suggests that the CO2 flux was significantly higher from T and D plots compared to NT and ND plots. Neither CH4 nor N2O fluxes were influenced by tillage or drainage. The CO2 flux from T + D treatments was significantly higher (25.98-398.65 mg m(-2) h(-1)) throughout the fallow period. Significantly higher N2O flux (87.07-125.76 mu g m(-2) h(-1)) was recorded from all treatments during the thawing period in the first week of March. Considering that the total C flux involves only the loss from the SOC stock, as much as 3.05% of the total SOC stock (1.23 Mg C ha(-1)) was lost during the fallow period from T-D plots as CO2 and CH4. Analysis of soil from different soil depths suggests that the CO2 and N2O emissions from soil were mostly dependent on production potential at 0-10 cm and 0-30 cm of soil depths, respectively. However, there was no such trend for CH4 emissions from soil. (C) 2013 Elsevier B.V. All rights reserved.
  • Authors:
    • Wang, M. Q.
    • Kwon, H.-Y.
    • Mueller, S.
    • Dunn, J. B.
  • Source: Biotechnology for Biofuels
  • Volume: 6
  • Year: 2013
  • Summary: Background: The greenhouse gas (GHG) emissions that may accompany land-use change (LUC) from increased biofuel feedstock production are a source of debate in the discussion of drawbacks and advantages of biofuels. Estimates of LUC GHG emissions focus mainly on corn ethanol and vary widely. Increasing the understanding of LUC GHG impacts associated with both corn and cellulosic ethanol will inform the on-going debate concerning their magnitudes and sources of variability. Results: In our study, we estimate LUC GHG emissions for ethanol from four feedstocks: corn, corn stover, switchgrass, and miscanthus. We use new computable general equilibrium (CGE) results for worldwide LUC. U.S. domestic carbon emission factors are from state-level modelling with a surrogate CENTURY model and U. S. Forest Service data. This paper investigates the effect of several key domestic lands carbon content modelling parameters on LUC GHG emissions. International carbon emission factors are from the Woods Hole Research Center. LUC GHG emissions are calculated from these LUCs and carbon content data with Argonne National Laboratory's Carbon Calculator for Land Use Change from Biofuels Production (CCLUB) model. Our results indicate that miscanthus and corn ethanol have the lowest (-10 g CO(2)e/MJ) and highest (7.6 g CO(2)e/MJ) LUC GHG emissions under base case modelling assumptions. The results for corn ethanol are lower than corresponding results from previous studies. Switchgrass ethanol base case results (2.8 g CO(2)e/MJ) were the most influenced by assumptions regarding converted forestlands and the fate of carbon in harvested wood products. They are greater than miscanthus LUC GHG emissions because switchgrass is a lower-yielding crop. Finally, LUC GHG emissions for corn stover are essentially negligible and insensitive to changes in model assumptions. Conclusions: This research provides new insight into the influence of key carbon content modelling variables on LUC GHG emissions associated with the four bioethanol pathways we examined. Our results indicate that LUC GHG emissions may have a smaller contribution to the overall biofuel life cycle than previously thought. Additionally, they highlight the need for future advances in LUC GHG emissions estimation including improvements to CGE models and aboveground and belowground carbon content data.
  • Authors:
    • Kucharik, C. J.
    • Duran, B. E. L.
  • Source: Soil Science Society of America Journal
  • Volume: 77
  • Issue: 5
  • Year: 2013
  • Summary: Greenhouse gas emissions from soils are often measured using trace-gas flux chamber techniques without a standardized protocol, raising concerns about measurement accuracy and consistency. To address this, we compared measurements from non-steady-state non-through-flow (NTF) chambers with a non-steady-state through-flow (TF) chamber system in three bioenergy cropping systems located in Wisconsin. Additionally, we investigated the effects of the NTF flux calculation method and deployment time on flux measurements. In all cropping systems, when NTF chambers were deployed for 60 min and a linear regression (LR) flux calculation was used, soil CO2 and N2O fluxes were, on average, 18 and 12% lower, respectively, than fluxes measured with a 15-min deployment. Fluxes calculated with the HMR method, a hybrid of nonlinear and linear approaches, showed no deployment time effects for CO2 and N2O and produced 27 to 32% higher CO2 fluxes and 28 to 33% higher N2O fluxes in all crops than the LR approach with 60-min deployment. Across all crops, CO2 fluxes measured with the TF chamber system were higher by 24.4 to 84.9 mg CO2-C m(-2) h(-1) than fluxes measured with NTF chambers using either flux calculation method. These results suggest that NTF chamber deployment time should be shortened if the LR approach is used, although detection limits should be considered, and the HMR approach may be more appropriate when long deployment times are necessary. Significant differences in absolute flux values with different chamber types highlight the need for significant effort in determining the accuracy of methods or alternative flux measurement technologies.
  • Authors:
    • Long, S. P.
    • Keogh, C.
    • Davis, S. C.
    • Anderson-Teixeira, K. J.
    • Duval, B. D.
    • Parton, W. J.
    • DeLucia, E. H.
  • Source: PLoS ONE
  • Volume: 8
  • Issue: 8
  • Year: 2013
  • Summary: Bioenergy related land use change would likely alter biogeochemical cycles and global greenhouse gas budgets. Energy cane (Saccharum officinarum L.) is a sugarcane variety and an emerging biofuel feedstock for cellulosic bio-ethanol production. It has potential for high yields and can be grown on marginal land, which minimizes competition with grain and vegetable production. The DayCent biogeochemical model was parameterized to infer potential yields of energy cane and how changing land from grazed pasture to energy cane would affect greenhouse gas (CO2, CH4 and N2O) fluxes and soil C pools. The model was used to simulate energy cane production on two soil types in central Florida, nutrient poor Spodosols and organic Histosols. Energy cane was productive on both soil types (yielding 46-76 Mg dry mass.ha(-1)). Yields were maintained through three annual cropping cycles on Histosols but declined with each harvest on Spodosols. Overall, converting pasture to energy cane created a sink for GHGs on Spodosols and reduced the size of the GHG source on Histosols. This change was driven on both soil types by eliminating CH4 emissions from cattle and by the large increase in C uptake by greater biomass production in energy cane relative to pasture. However, the change from pasture to energy cane caused Histosols to lose 4493 g CO2 eq.m(-2) over 15 years of energy cane production. Cultivation of energy cane on former pasture on Spodosol soils in the southeast US has the potential for high biomass yield and the mitigation of GHG emissions.
  • Authors:
    • Frisvold, G. B.
    • Konyar, K.
  • Source: Journal of Contemporary Water Research & Education
  • Volume: 151
  • Issue: 1
  • Year: 2013
  • Summary: This study examines how the proposed American Clean Energy and Security Act (H.R. 2454) would affect U.S. agriculture with special reference to water resources. The bill's cap and trade provisions for greenhouse gases would significantly raise fertilizer, irrigation pumping, and other energy-related costs. By 2030, it would reduce U.S. irrigation water use by >11 percent and fertilizer use by >18 percent with positive implications for water conservation and quality. Carbon offset provisions create financial incentives for farmers to sequester carbon by planting trees on cropland, reducing agricultural production and raising prices. Because sequestration potential differs by region, most of the estimated 51 million acres of converted cropland would be in the Corn Belt and Mississippi Delta. Afforestation would reduce Delta water use further, but increase water use in other regions compared to cap and trade alone. Compared to a no-policy baseline, irrigation water use declines 10 percent nationally, but increases in the Southern Plains. H.R. 2454 may have significant water conservation effects in some regions, but increase competition for water in others. By reducing fertilizer use and dramatically altering land use patterns in parts of the Mississippi Basin, it may also provide unexpected water quality benefits. Unintended water use and quality consequences of climate policies merit further research.
  • Authors:
    • Prokopy, L. S.
    • Barnard, J. M.
    • Gramig, B. M.
  • Source: Climate Research
  • Volume: 56
  • Issue: 2
  • Year: 2013
  • Summary: Agricultural land management practices are frequently discussed in the context of domestic and international policies to mitigate and adapt to future climate change. Agriculture has not been one of the economic sectors covered by proposed or enacted greenhouse gas emissions limits; thus, agriculture has been the subject of much research on its technical and economic potential to mitigate climate change impacts. We report the results of a survey of Indiana row crop farmers' (n = 724) beliefs about climate change, the effect of climate change on their farm operation, and the best way to create incentives for farmers to store more carbon in agricultural soils. Farmer beliefs and their strength of opinions about these issues are important for developing future policy proposals, decision support tools, and emissions markets that involve agricultural emissions offsets. We found that 79% of surveyed Indiana farmers believe that climate change is an ongoing natural process, compared to 45% who believe that human activities are contributing to climate change. A total of 31% of respondents expressed neither belief nor disbelief that humans are contributing to climate change, suggesting that nearly one-third of respondents either do not know or have not made up their minds about the causes of climate change. We found clear differences in farmers' beliefs about occurrence and causes of climate change compared to the general population. Our results suggest that farmers require a better understanding of the expected effects of climate change on weather and cropping systems management, and that farmers' beliefs are capable of being informed through outreach and extension of climate change research.
  • Authors:
    • Ragsdale, D. W.
    • Hill, J. D.
    • Yang, Y.
    • Heimpel, G. E.
  • Source: PLOS ONE
  • Volume: 8
  • Issue: 8
  • Year: 2013
  • Summary: Greenhouse gas emissions associated with pesticide applications against invasive species constitute an environmental cost of species invasions that has remained largely unrecognized. Here we calculate greenhouse gas emissions associated with the invasion of an agricultural pest from Asia to North America. The soybean aphid, Aphis glycines, was first discovered in North America in 2000, and has led to a substantial increase in insecticide use in soybeans. We estimate that the manufacture, transport, and application of insecticides against soybean aphid results in approximately 10.6 kg of carbon dioxide (CO2) equivalent greenhouse gasses being emitted per hectare of soybeans treated. Given the acreage sprayed, this has led to annual emissions of between 6 and 40 million kg of CO2 equivalent greenhouse gasses in the United States since the invasion of soybean aphid, depending on pest population size. Emissions would be higher were it not for the development of a threshold aphid density below which farmers are advised not to spray. Without a threshold, farmers tend to spray preemptively and the threshold allows farmers to take advantage of naturally occurring biological control of the soybean aphid, which can be substantial. We find that adoption of the soybean aphid economic threshold can lead to emission reductions of approximately 300 million kg of CO2 equivalent greenhouse gases per year in the United States. Previous studies have documented that biological control agents such as lady beetles are capable of suppressing aphid densities below this threshold in over half of the soybean acreage in the U.S. Given the acreages involved this suggests that biological control results in annual emission reductions of over 200 million kg of CO2 equivalents. These analyses show how interactions between invasive species and organisms that suppress them can interact to affect greenhouse gas emissions.
  • Authors:
    • Hao, X. M.
    • Thelen, K. D.
    • Gao, J.
  • Source: Agronomy Journal
  • Volume: 105
  • Issue: 3
  • Year: 2013
  • Summary: Corn ( Zea mays L.) and corn stover are currently considered the most abundant and readily accessible feedstock resources for renewable bioethanol. Whole-plant corn harvest could increase bioethanol yield compared with a conventional separated grain and stover harvest. There is limited research, however, on the environmental effects of whole-plant harvest strategies, including nonrenewable energy efficiency, greenhouse gas (GHG) emission intensity, and soil organic C (SOC) changes. In this study, harvest methods together with bioprocessing steps were combined through life cycle analysis (LCA) models, and SOC changes for corn farming with different harvest methods were simulated by a Daycent ecosystem model. The harvest data were from four agronomy farms (Branch, Ingham, Huron, and Menominee) of Michigan State University across south to north in Michigan. The LCA results showed that a whole-plant harvest strategy could increase energy efficiency 3.4 to 4.3 times and reduce GHG emissions by 382% relative to a traditional separate grain and stover harvest strategy. The analyses also indicated, however, that whole-plant harvest could reduce SOC (66.922.9 g CO 2 equivalent m -2) annually during 50 yr of continuous corn farming at Branch, Ingham, and Huron, while the conventional harvest system could sequestrate CO 2 into SOC at Ingham, Huron, and Menominee. The Daycent simulation also showed that a winter cover crop planted after whole-plant immature corn harvest could compensate for part of the SOC loss associated with a whole-corn-plant harvest.
  • Authors:
    • Hatfield, J. L.
    • Hanan, N. P.
    • Glenn, A. J.
    • Fischer, M. L.
    • Burba, G. G.
    • Billesbach, D. P.
    • Bernacchi, C. J.
    • Baron, V. S.
    • Meyers, T. P.
    • Tieszen, L. L.
    • Wylie, B. K.
    • Gilmanov, T. G.
    • Heuer, M. W.
    • Hollinger, S. E.
    • Howard, D. M.
    • Matamala, R.
    • Prueger, J. H.
    • Tenuta, M.
    • Young, D. G.
  • Source: Agriculture Ecosystems and Environment
  • Volume: 164
  • Year: 2013
  • Summary: We analyzed net CO 2 exchange data from 13 flux tower sites with 27 site-years of measurements over maize and wheat fields across midcontinent North America. A numerically robust "light-soil temperature-VPD"-based method was used to partition the data into photosynthetic assimilation and ecosystem respiration components. Year-round ecosystem-scale ecophysiological parameters of apparent quantum yield, photosynthetic capacity, convexity of the light response, respiration rate parameters, ecological light-use efficiency, and the curvature of the VPD-response of photosynthesis for maize and wheat crops were numerically identified and interpolated/extrapolated. This allowed us to gap-fill CO 2 exchange components and calculate annual totals and budgets. VPD-limitation of photosynthesis was systematically observed in grain crops of the region (occurring from 20 to 120 days during the growing season, depending on site and year), determined by the VPD regime and the numerical value of the curvature parameter of the photosynthesis-VPD-response, sigma VPD. In 78% of the 27 site-years of observations, annual gross photosynthesis in these crops significantly exceeded ecosystem respiration, resulting in a net ecosystem production of up to 2100 g CO 2 m -2 year -1. The measurement-based photosynthesis, respiration, and net ecosystem production data, as well as the estimates of the ecophysiological parameters, provide an empirical basis for parameterization and validation of mechanistic models of grain crop production in this economically and ecologically important region of North America.