• Authors:
    • Miller, R.
    • Rothstein, D.
    • Nikiema, P.
  • Source: Biomass & Bioenergy
  • Volume: 39
  • Year: 2012
  • Summary: We assessed the short-term effects of converting pastureland to hybrid poplar and willow bioenergy plantations on soil greenhouse gas (GHG) fluxes and nitrogen (N) leaching in northern Michigan, USA. We used static chambers to measure soil carbon dioxide (CO2), nitrous oxide (N2O) and methane (CH4) efflux, and tension lysimeters to measure nitrate (NO3-) leaching, in newly-established poplar and willow plantation plots, and in reference pasture plots. Emissions of N2O increased markedly following cultivation with cumulative direct N2O emissions of 0.3, 4.6 and 5.9 Mg ha(-1) of CO2 equivalents (CO(2)eq) in the reference, willow and poplar plots, respectively. Similarly, land conversion resulted in large increases of NO3 leaching with losses of 2.6, 38.8 and 53.9 kg ha(-1) of N from the reference, willow and poplar plots, respectively. Soil CO2 fluxes were significantly affected by land-use conversion; soils from willow and poplar plots emitted 29-42% less CO2 relative to the reference plots. Greater root respiration in the pastureland likely explained the greater soil CO2 efflux in these plots. Estimates of the net GHG emissions due to land-use conversion were strongly influenced by assumptions regarding the root contribution (RC) to total soil CO2 efflux. Assuming an RC = 50%, we estimate that pastureland conversion at this site incurred GHG debts of 7.4 and 11.6 Mg ha(-1) y(-1) as CO(2)eq for willow and poplar, respectively, during the establishment year. These results demonstrate the need to include soil disturbance impacts on the N cycle in future life cycle assessment of these bioenergy crops. (C) 2012 Elsevier Ltd. All rights reserved.
  • Authors:
    • Torbert, H.
    • Watts, D.
    • Way, T.
    • Mays, D.
    • Nyakatawa, E.
    • Smith, D.
  • Source: Journal of Sustainable Agriculture
  • Volume: 36
  • Issue: 8
  • Year: 2012
  • Summary: Soil management practices can alter the natural balance at the soil-plant-atmosphere ecosystem interface, which can significantly affect the environment. This study compared CO2 fluxes in conventional tillage (CT) and no-tillage (NT) corn (Zea mays L.) production systems receiving poultry litter (PL) and ammonium nitrate (AN) fertilizers on a Decatur silt loam soil in the Tennessee Valley region of North Alabama from Spring 2008 to Fall 2009. Soil CO2 flux in CT plots (9.5 kg CO2 ha(-1) day(-1)) was significantly greater than that in NT plots (4.9 kg CO2 ha(-1) day(-1) in summer. Soil CO2 fluxes were lowest in fall where CT plots had a mean soil CO2 emission of 0.8 kg CO2 ha(-1) day(-1), while plots under NT and grass fallow system were sinks of CO2 with fluxes -0.6 and -1.0 kg CO2 ha(-1) day(-1), respectively. Mean soil CO2 flux averaged over seasons in NT plots was 36% lower than that in CT plots. Grass fallow plots were net sinks of CO2 with a mean CO2 flux of -0.4 kg CO2 ha(-1) day(-1). Our study showed that application of PL or AN fertilizer in NT systems can significantly reduce soil CO2 emissions compared to CT systems in corn production.
  • Authors:
    • Paustian, K.
    • Swan, A.
    • Ogle, S.
  • Source: Agriculture Ecosystems & Environment
  • Volume: 149
  • Year: 2012
  • Summary: The efficacy of no-till agriculture for increasing C in soils has been questioned in recent studies. This is a serious issue after many publications and reports during the last two decades have recommended no-till as a practice to mitigate greenhouse gas emissions through soil C sequestration. Our objective was to investigate the possibility that the lack of C increase in some no-till systems may be due to changes in crop productivity and subsequent C input to soils. A meta-analysis of 74 published studies was conducted to determine if crop production varies between no-till and full tillage management. The results were used to estimate the change in C input due to no-till adoption and the influence on soil organic C stocks at steady-state using the Century model. We found that crop productivity can be reduced with adoption of no-till, particularly in cooler and/or wetter climatic conditions. The influence varies, however, and crop productivity can even increase in some regions following adoption of no-till. In cases where crop production and C inputs decreased due to no-till, the potential reduction in soil organic C stocks was offset by a decrease in soil C decomposition rates, except in cases where C inputs declined by 15% or more. Challenges still remain for understanding the full impact of no-till adoption on soil organic C stocks, such as changes on C inputs in deeper subsurface horizons, the influence of variation in NT seeding methods on soil disturbance, and changes in SOM stabilization due to saturation limits in mineral soil fractions, which may further modify net C storage in soils. (C) 2011 Elsevier B.V. All rights reserved.
  • Authors:
    • King, A.
    • Liebig, M.
    • West, T.
    • Izaurralde, R.
    • Post, W.
  • Source: Frontiers in Ecology and the Environment
  • Volume: 10
  • Issue: 10
  • Year: 2012
  • Summary: The potential for mitigating increasing atmospheric carbon dioxide concentrations through the use of terrestrial biological carbon (C) sequestration is substantial. Here, we estimate the amount of C being sequestered by natural processes at global, North American, and national US scales. We present and quantify, where possible, the potential for deliberate human actions - through forestry, agriculture, and use of biomass-based fuels - to augment these natural sinks. Carbon sequestration may potentially be achieved through some of these activities but at the expense of substantial changes in land-use management. Some practices (eg reduced tillage, improved silviculture, woody bioenergy crops) are already being implemented because of their economic benefits and associated ecosystem services. Given their cumulative greenhouse-gas impacts, other strategies (eg the use of biochar and cellulosic bioenergy crops) require further evaluation to determine whether widespread implementation is warranted. Front Ecol Environ 2012; 10(10): 554-561, doi:10.1890/120065
  • Authors:
    • Gramig, B.
    • Reeling, C.
  • Source: Agriculture, Ecosystems & Environment
  • Volume: 146
  • Issue: 1
  • Year: 2012
  • Summary: Agricultural ecosystems are a source of greenhouse gas (GHGs) emissions and losses of nutrients to waterways. Several studies have recognized this and have documented the potential to reduce GHG fluxes and nutrient loss to waterways by using carbon offsets to fund the implementation of land retirement and afforestation. However, the ability to use land for both agricultural production and environmental conservation is also important. This study develops a novel analytical framework that is used to examine the cross-media (water and air) environmental effects of implementing offset-funded conservation practices in a working-lands setting. The framework is applied to a case study which examines the extent to which carbon pricing can affect practice implementation costs and the optimal distribution of these practices throughout an agricultural watershed. Results indicate that carbon offsets can reduce conservation practice implementation costs and have the potential to reduce greater amounts of nonpoint source pollution for a given cost of implementation. This conclusion has significant implications for policymaking, particularly with regard to using markets for GHG emissions to achieve water quality improvements where water quality trading or government conservation programs have historically been unsuccessful. (C) 2011 Elsevier B.V. All rights reserved.
  • Authors:
    • Ort, D.
    • Gleadow, R.
    • Fauquet, C.
    • Cavagnaro, T.
    • Grennan, A.
    • Miller, R.
    • Slattery, R.
    • Rosenthal, D.
  • Source: Global Change Biology
  • Volume: 18
  • Issue: 8
  • Year: 2012
  • Summary: Globally, cassava is the second most important root crop after potatoes and the fifth most important crop overall in terms of human caloric intake. In addition to its growing global importance for feed, fuel, and starch, cassava has long been vital to food security in Sub-Saharan Africa. Climate change is expected to have its most severe impact on crops in food insecure regions, yet little is known about how cassava productivity will respond to climate change. The most important driver of climate change is globally increasing atmospheric CO2 concentration ([CO2]). However, the potential for cassava to enhance food security in an elevated [CO2] world is uncertain as greenhouse and open top chamber (OTC) study reports are ambiguous. Studies have yielded misleading results in the past regarding the effect of elevated [CO2] on crop productivity, particularly in cases where pots restricted sink growth. To resolve these conflicting results, we compare the response of cassava to growth at ambient (ca. 385 similar to ppm) and elevated [CO2] (585 similar to ppm) under field conditions and fully open air [CO2] elevation. After three and half months of growth at elevated [CO2], above ground biomass was 30% greater and cassava root tuber dry mass increased over 100% (fresh weight increased 89%). High photosynthetic rates and photosynthetic stimulation by elevated [CO2], larger canopies, and a large sink capacity all contributed to cassava's growth and yield stimulation. Cassava exhibited photosynthetic acclimation via decreased Rubisco capacity early in the season prior to root tuber initiation when sink capacity was smaller. Importantly, and in contrast to a greenhouse study, we found no evidence of increased leaf N or total cyanide concentration in elevated [CO2]. All of our results are consistent with theoretical expectations; however, the magnitude of the yield increase reported here surpasses all other C3 crops and thus exceeds expectations.
  • Authors:
    • Caesar, A.
    • Caesar-TonThat, T.
    • Sainju, U. M.
  • Source: Soil and Tillage Research
  • Volume: 118
  • Issue: January
  • Year: 2012
  • Summary: Portable chamber provides simple, rapid, and inexpensive measurement of soil CO2 flux but its effectiveness and precision compared with the static chamber in various soil and management practices is little known. Soil CO2 flux measured by a portable chamber using infrared analyzer was compared with a static chamber using gas chromatograph in various management practices from May to October 2008 in loam soil (Luvisols) in eastern Montana and in sandy loam soil (Kastanozems) in western North Dakota, USA. Management practices include combinations of tillage, cropping sequence, and N fertilization in loam and irrigation, tillage, crop rotation, and N fertilization in sandy loam. It was hypothesized that the portable chamber would measure CO2 flux similar to that measured by the static chamber, regardless of soil types and management practices. In both soils, CO2 flux peaked during the summer following substantial precipitation and/or irrigation (>15 mm), regardless of treatments and measurement methods. The flux varied with measurement dates more in the portable than in the static chamber. In loam, CO2 flux was 14-87% greater in the portable than in the static chamber from July to mid-August but 15-68% greater in the static than in the portable chamber from late August to October in all management practices. In sandy loam, CO2 flux was 10-229% greater in the portable than in the static chamber at all measurement dates in all treatments. Average CO2 flux across treatments and measurement dates was 9% lower in loam but 84% greater in sandy loam in the portable than in the static chamber. The CO2 fluxes in the portable and static chambers were linearly to exponentially related (R-2 = 0.68-0.70, P < 0.01, n = 40-56). Although the trends of CO2 fluxes with treatments and measurement dates were similar in both methods, the flux varied with the methods in various soil types. Measurement of soil CO2 flux by the portable chamber agreed more closely with the static chamber within 0-10 kg C ha(-1) d(-1) in loam soil under dryland than in sandy loam soil under irrigated and non-irrigated cropping systems. Published by Elsevier B.V.
  • Authors:
    • Barsotti, J. L.
    • Lenssen, A. W.
    • Caesar-TonThat, T.
    • Sainju, U. M.
  • Source: Soil Science Society of America Journal
  • Volume: 76
  • Issue: 5
  • Year: 2012
  • Summary: Information is needed to mitigate dryland soil greenhouse gas (GHG) emissions by using novel management practices. We evaluated the effects of cropping sequence and N fertilization on dryland soil temperature and water content at the 0- to 15-cm depth and surface CO2, N2O, and CH4 fluxes in a Williams loam (fine-loamy, mixed, superactive, frigid, Typic Argiustolls) in eastern Montana. Treatments were no-tilled continuous malt barley (Hordeum vulgaris L.) (NTCB), no-tilled malt barley-pea (Pisum sativum L.) (NTB-P), and conventional-tilled malt barley-fallow (CTB-F) (control), each with 0 and 80 kg N ha(-1). Gas fluxes were measured at 3 to 14 d intervals using static, vented chambers from March to November 2008 to 2011. Soil temperature varied but water content was greater in CTB-F than in other treatments. The GHG fluxes varied with date of sampling, peaking immediately after substantial precipitation (>15 mm) and N fertilization during increased soil temperature. Total CO2 flux from March to November was greater in NTCB and NTB-P with 80 kg N ha(-1) than in other treatments from 2008 to 2010. Total N2O flux was greater in NTCB with 0 kg N ha(-1) and in NTB-P with 80 kg N ha(-1) than in other treatments in 2008 and 2011. Total CH4 uptake was greater with 80 than with 0 kg N ha(-1) in NTCB in 2009 and 2011. Because of intermediate level of CO2 equivalent of GHG emissions and known favorable effect on malt barley yield, NTB-P with 0 kg N ha(-1) might mitigate GHG emissions and sustain crop yields compared to other treatments in eastern Montana. For accounting global warming potential of management practices, however, additional information on soil C dynamics and CO2 associated with production inputs and machinery use are needed.
  • Authors:
    • Liebig, M. A.
    • Caesar-TonThat, T.
    • Stevens, W. B.
    • Sainju, U. M.
  • Source: Journal of Environmental Quality
  • Volume: 41
  • Issue: 6
  • Year: 2012
  • Summary: Management practices, such as irrigation, tillage, cropping system, and N fertilization, may influence soil greenhouse gas (GHG) emissions. We quantified the effects of irrigation, tillage, crop rotation, and N fertilization on soil CO2, N2O, and CH4 emissions from March to November, 2008 to 2011 in a Lihen sandy loam in western North Dakota. Treatments were two irrigation practices (irrigated and nonirrigated) and five cropping systems (conventional-tilled malt barley [Hordeum vulgaris L.] with N fertilizer [CT-N], conventional-tilled malt barley with no N fertilizer [CT-C], no-tilled malt barley pea [Pisum sativum L.] with N fertilizer [NT-PN], no-tilled malt barley with N fertilizer [NT-N], and no-tilled malt barley with no N fertilizer [NT-C]). The GHG fluxes varied with date of sampling and peaked immediately after precipitation, irrigation, and/or N fertilization events during increased soil temperature. Both CO2 and N2O fluxes were greater in CT-N under the irrigated condition, but CH4 uptake was greater in NT-PN under the nonirrigated condition than in other treatments. Although tillage and N fertilization increased CO2 and N2O fluxes by 8 to 30%, N fertilization and monocropping reduced CH, uptake by 39 to 40%. The NT-PN, regardless of irrigation, might mitigate GHG emissions by reducing CO2 and N2O emissions and increasing CH4 uptake relative to other treatments. To account for global warming potential for such a practice, information on productions associated with CO2 emissions along with N2O and CH4 fluxes is needed.
  • Authors:
    • Phillips, R. L.
    • Tanaka, D. L.
    • Hendrickson, J. R.
    • Liebig, M. A.
    • Schmer, M. R.
  • Source: Biomass and Bioenergy
  • Volume: 45
  • Issue: October
  • Year: 2012
  • Summary: Switchgrass (Panicum virgatum L.) is being evaluated as a bioenergy crop for the northern Great Plains. Field measurements of CO2, CH4, and N2O flux are needed to estimate the net greenhouse gas (GHG) balance of this biofeedstock. The study objective was to determine effects of recommended Nitrogen (N) fertilization (67 kg ha(-1) of N applied) and unfertilized switchgrass on growing season soil-atmosphere CO2, CH4, and N2O flux using static chamber methodology. Mean hourly CO2 flux was greatest during periods of active switchgrass growth and was similar between N fertilizer treatments (P = 0.09). Mean hourly N2O flux was consistently greater under N fertilization than without N throughout the growing season. Overall, N fertilization of switchgrass affected cumulative growing-season N2O flux (27.6 kg ha(-1) +/- 4.0 kg ha(-1) vs. 86.3 kg ha(-1) +/- 14.3 kg ha(-1) as CO2 equivalents (CO(2)eq) for 0 kg ha(-1) and 67 kg ha(-1) of N applied, respectively; P < 0.01), but not cumulative CO2 or CH4 flux (P = 0.08 and 0.51, respectively). Aboveground biomass production was greater with N application (6.8 Mg ha(-1) +/- 0.5 Mg ha(-1) dry matter) than without N (3.2 Mg ha(-1) +/- 0.5 Mg ha(-1)) (P < 0.05). Net greenhouse gas intensity (GHGI; kg GHG flux kg(-1) harvest yield as CO(2)eq) for switchgrass production was similar between N treatments (0.71 vs. 0.44 for 0 kg ha(-1) and 67 kg ha(-1) of N applied, respectively; P = 0.18). Published by Elsevier Ltd.