• Authors:
    • Zimmerman, A. R.
    • Lal, R.
    • Mukherjee, A.
  • Source: Science of The Total Environment
  • Volume: 487
  • Issue: July
  • Year: 2014
  • Summary: Short and long-term impacts of biochar on soil properties under field conditions are poorly understood. In addition, there is a lack of field reports of the impacts of biochar on soil physical properties, gaseous emissions and C stability, particularly in comparison with other amendments. Thus, three amendments - biochar produced from oak at 650°C, humic acid (HA) and water treatment residual - (WTR) were added to a scalped silty-loam soil @ 0.5% (w/w) in triplicated plots under soybean. Over the 4-month active growing season, all amendments significantly increased soil pH, but the effect of biochar was the greatest. Biochar significantly increased soil-C by 7%, increased sub-nanopore surface area by 15% and reduced soil bulk density by 13% compared to control. However, only WTR amendment significantly increased soil nanopore surface area by 23% relative to the control. While total cumulative CH4 and CO2 emissions were not significantly affected by any amendment, cumulative N2O emission was significantly decreased in the biochar-amended soil (by 92%) compared to control over the growing period. Considering both the total gas emissions and the C removed from the atmosphere as crop growth and C added to the soil, WTR and HA resulted in net soil C losses and biochar as a soil C gain. However, all amendments reduced the global warming potential (GWP) of the soil and biochar addition even produced a net negative GWP effect. The short observation period, low application rate and high intra-treatment variation resulted in fewer significant effects of the amendments on the physicochemical properties of the soils than one might expect indicating further possible experimentation altering these variables. However, there was clear evidence of amendment-soil interaction processes affecting both soil properties and gaseous emissions, particularly for biochar, that might lead to greater changes with additional field emplacement time.
  • Authors:
    • Mladenoff, D. J.
    • Rothstein, D. E.
    • Forrester, J. A.
    • Palmer, M. M.
  • Source: Biomass and Bioenergy
  • Volume: 62
  • Issue: March
  • Year: 2014
  • Summary: Uncertainty exists over the magnitude of greenhouse gas (GHG) emissions associated with open land conversion to short-rotation woody biomass crops (SRWC) for bioenergy in the Northern U.S. Lake States. GHG debts incurred at the plantation establishment phase may delay the climate mitigation benefits of SRWC production. To better understand GFIG debts associated with converting open lands to SRWC, we established research plantations with willow (Salix spp), hybrid-poplar (Populus spp.), and control plots in spring 2010 at two sites in northern Michigan (ES) and Wisconsin (RH). These sites had similar climates, but differed in time since last cultivation: 5 vs. 42 years. To address the short-term effects of plantation establishment, we compared two-year biomass production and GHG emissions. We hypothesized that the long-idle ES site, with higher initial soil C and N stocks, would have higher GHG emissions following conversion compared to the recently-idle RH site, but that this would be balanced in part by greater SRWC productivity at the ES site. As hypothesized, grassland conversion resulted in two-year net GHG emissions due to land conversion of 43.21 and 33.02 Mg-CO(2)eq ha(-1) for poplar and willow at ES that was far greater than the 4.81 and 1.54 Mg-CO(2)eq ha(-1) for poplar and willow at RH. Contrary to our hypothesis, we did not observe greater SRWC productivity at ES, which will take longer than RH to reach C neutrality and begin mitigating GHG emissions. Our results show that site-specific soil and management factors determine the magnitude of GHG emissions. Published by Elsevier Ltd.
  • Authors:
    • Percival, D.
    • Dias, G.
  • Source: Acta Horticulturae, International Society for Horticultural Science
  • Issue: 1017
  • Year: 2014
  • Summary: The amount of energy and greenhouse gas emissions involved in the production of wild blueberries was examined from 2005 to 2008. Typical production practices including mowing, agrochemical applications and use of a double headed harvester resulted in energy and greenhouse gas emissions of 1,398 MJ and 80.7 kg CO 2 per 1,000 kg of berries produced. Inclusion of energy intensive management practices including the use of oil-fired burners and diesel powered supplementary irrigation systems increased total energy consumption and fossil fuel production to values of 7,200 MJ and 239.7 kg CO 2 per 1,000 kg of berries produced. Agrochemical manufacturing, transportation and application accounted for 73.7% of the energy required for the "typical" production system. Therefore, results from this study illustrate the variability in energy use and carbon production that can occur in wild blueberry production and the ongoing need to diligent with the development of environmentally sustainable management technologies.
  • Authors:
    • Dalgaard, T.
    • Jorgensen, U.
    • Olesen, J. E.
    • Pugesgaard, S.
  • Source: Renewable Agriculture and Food Systems
  • Volume: 29
  • Issue: 1
  • Year: 2014
  • Summary: Anaerobic digestion of manure and crops provides the possibility of a combined production of renewable energy and organic fertilizer on organic farms and has been suggested as an option to improve sustainability of organic agriculture. In the present study, the consequences of implementation of anaerobic digestion and biogas production were analyzed on a 1000ha model farm with combined dairy and cash crop production, representing organic agriculture in Denmark. The effects on crop rotation, nitrogen flows and losses, yield, energy balance and greenhouse gas (GHG) emissions were evaluated for four scenarios of biogas production on the farm. Animal manure was digested for biogas production in all scenarios and was supplemented with: (1) 100ha grass-clover for biogas, (2) 100ha maize for biogas, (3) 200ha grass-clover for biogas and reduced number of livestock, and (4) 200ha grass-clover for biogas, reduced number of livestock and import of biomass from cuttings made in ungrazed meadows. These four scenarios were compared with the current situation in organic agriculture in Denmark and to a situation where slurry from conventional agriculture is no longer imported. Implementation of anaerobic digestion changed the nitrogen flows on the farm by increasing the slurry nitrogen plant availability and introducing new nitrogen sources from legume-based energy crops or meadows. The amount of nitrogen available for application as fertilizer on the farm increased when grass-clover was used for biogas production, but decreased when maize was used. Since part of the area was used for biogas production, the total output of foodstuffs from the farm was decreased. Effects on GHG emissions and net energy production were assessed by use of the whole-farm model FarmGHG. A positive farm energy balance was obtained for all biogas scenarios, showing that biomass production for biogas on 10% of the farm area results in an energy surplus, provided that the heat from the electricity production is utilized. The energy surplus implies a displacement of fossil fuels and thereby reduced CO2 emission from the farm. Emissions of N2O were not affected substantially by biogas production. Total emissions of methane (CH4) were slightly decreased due to a 17-48% decrease in emissions from the manure store. Net GHG emission was reduced by 35-85% compared with the current situation in organic agriculture. It was concluded that production of biogas on organic farms holds the possibility for the farms to achieve a positive energy balance, provide self-sufficiency with organic fertilizer nitrogen, and reduce GHG emissions.
  • Authors:
    • Horwath, W. R.
    • Zhu, X.
    • You, M.
    • Han, X.
    • Miao, S.
    • Qiao, Y.
  • Source: Field Crops Research
  • Volume: 161
  • Year: 2014
  • Summary: Long-term agronomic studies are useful to determine cropping system nitrogen (N) use efficiency and the fate of applied fertilizers. We used a subtractive fertilizer experiment incorporating N, phosphorous (P), potassium (K) and swine manure to determine long-term changes in grain yield, soil organic carbon (SOC), total soil nitrogen (N), as well as carbon dioxide (CO2) and nitrous oxide (N2O) emissions. The experiment was conducted on a 22-year maize-soybean-wheat rotation in Northeastern China. Crop residues were removed for cooking fuel and forage according to local practices. Five fertilizer treatments were applied annually: control (no fertilizer), NK, NP, NPK, and NPKOM (N, P. K and manure). The NPKOM treatment increased SOC and total soil N by 4.59 and 0.45 Mg ha(-1), respectively. In contrast, SOC decreased by 10.6 and 6.64 Mg ha(-1) in the control and NK treatments, respectively. The NPKOM treatment had an average of 2.9 times more N2O emissions than the other fertilizer treatments. The cropping system balances for N and SOC, together with fuel use for farming practices and manure handling, were used to calculate the global warming potential (GWP) of the different fertilizer treatments. Due to SOC sequestration, the GWP of the NPKOM treatment (6.77 Mg C equivalent ha(-1)) was significantly lower than that of both the control (14.4 Mg C equivalent ha(-1)) and the NK treatment (12.8 Mg C equivalent ha(-1)). The results suggest that in rainfed agricultural systems in Northeastern China, the application of manure supplemented with NPK can simultaneously achieve higher grain yield and lower GWP compared to mineral fertilizers alone.
  • Authors:
    • Caesar-Tonthat, T.
    • Stevens, W. B.
    • Sainju, U. M.
    • Liebig, M. A.
    • Wang, J.
  • Source: Journal of Environmental Quality
  • Volume: 43
  • Issue: 3
  • Year: 2014
  • Summary: Little information exists about how global warming potential (GWP) is affected by management practices in agroecosystems. We evaluated the effects of irrigation, tillage, crop rotation, and N fertilization on net GWP and greenhouse gas intensity (GHGI or GWP per unit crop yield) calculated by soil respiration (GWP R and GHGI R) and organic C (SOC) (GWP C and GHGI C) methods after accounting for CO 2 emissions from all sources (irrigation, farm operations, N fertilization, and greenhouse gas [GHG] fluxes) and sinks (crop residue and SOC) in a Lihen sandy loam from 2008 to 2011 in western North Dakota. Treatments were two irrigation practices (irrigated vs. nonirrigated) and five cropping systems (conventional-till malt barley [ Hordeum vulgaris L.] with N fertilizer [CTBN], conventional-till malt barley with no N fertilizer [CTBO], no-till malt barley-pea [ Pisum sativum L.] with N fertilizer [NTB-P], no-till malt barley with N fertilizer, and no-till malt barley with no N fertilizer [NTBO]). While CO 2 equivalents were greater with irrigation, tillage, and N fertilization than without, N 2O and CH 4 fluxes were 2 to 218 kg CO 2 eq. ha -1 greater in nonirrigated NTBN and irrigated CTBN than in other treatments. Previous year's crop residue and C sequestration rate were 202 to 9316 kg CO 2 eq. ha -1 greater in irrigated NTB-P than in other treatments. Compared with other treatments, GWP R and GWP C were 160 to 9052 kg CO 2 eq. ha -1 lower in irrigated and nonirrigated NTB-P. Similarly, GHGI R and GHGI C were lower in nonirrigated NTB-P than in other treatments. Regardless of irrigation practices, NTB-P may lower net GHG emissions more than other treatments in the northern Great Plains.
  • Authors:
    • Dyer, J. A.
    • Worth, D. E.
    • McConkey, B. G.
    • Desjardins, R. L.
    • Shrestha, B. M.
    • Cerkowniak, D. D.
  • Source: Renewable Energy
  • Volume: 63
  • Issue: March
  • Year: 2014
  • Summary: Accounting for greenhouse gas (GHG) emissions at the production stage of a bioenergy crop is essential for evaluating its eco-efficiency. The objective of this study was to calculate the change in GHG emissions for canola (Brassica napus L.) production on the Canadian Prairies from 1986 to 2006. Net GHG emissions in the sub-humid and semi-arid climatic zones were estimated for fallow-seeded and stubble-seeded canola in intensive-, reduced- and no-tillage systems, with consideration given to emissions associated with synthetic nitrogen (N) fertilizer input, mineralized N from crop residues, N leaching and volatilization, farm operations, the manufacturing and transportation of fertilizer, agrochemicals and farm machinery, and emission and removal of CO2 associated with changes in land use (LUC) and land management (LMC). The GHG emissions on an area basis were higher in stubble-seeded canola than in fallow-seeded canola but, the opposite was true on a grain dry matter (DM) basis. Nitrous oxide emissions associated with canola production, CO2 emissions associated with farm energy use and the manufacturing of synthetic N fertilizer and its transportation contributed 49% of the GHG emissions in 1986 which increased to 66% in 2006. Average CO2 emissions due to LUC decreased from 27% of total GHG emissions in 1986 to 8% in 2006 and soil C sequestration due to LMC increased from 8% to 37%, respectively. These changes caused a reduction in net GHG emission intensities of 40% on an area basis and of 65% on a grain DM basis. Despite the reduction in GHG emission intensities, GHG emissions associated with canola in the Prairies increased from 3.4 Tg CO2 equiv in 1986 to 3.8 Tg CO2 equiv in 2006 because of the more than doubling of canola production. Crown Copyright (C) 2013 Published by Elsevier Ltd. All rights reserved.
  • Authors:
    • Dalgaard, R.
    • Petersen, B. M.
    • Oudshoorn, F. W.
    • Halberg, N.
    • Sorensen, C. G.
  • Source: Biosystems Engineering
  • Volume: 120
  • Issue: April
  • Year: 2014
  • Summary: Different tillage systems result in different resource uses and environmental impacts. Reduced tillage generates savings in direct energy input and the amount of machinery items needed. As the basics for holistic Life Cycle Assessments, both the influencing direct and indirect energy as sources of greenhouse gas emissions are required. Life Cycle inventories (LCI) were aggregated for a number of optimised machinery systems and tillage scenarios integrating a four crop rotation consisting of spring barley, winter barley, winter wheat and winter rape seed. By applying Life Cycle Assessments to a number of tillage scenarios and whole field operations sequences, the energy efficiency and environmental impact in terms of greenhouse gas emissions (GHG) were evaluated. Results showed that the total energy input was reduced by 26% for the reduced tillage system and by 41% for the no-tillage system. Energy used for traction and machine construction contributed between 6 and 8% of the total GHG emission per kg product. The total emission of GHG was 915 g CO2 equivalents per kg product by using the conventional tillage system, 817 g CO2 equivalents for the reduced tillage system and 855 g CO2 equivalents for the no tillage system. The no tillage system was expected to yield 10% less. The mineralisation in the soil contributed the most (50-60%) to this emission, while the fertiliser production contributed with 28-33%. The results stress the importance of applying a systems approach to capture the implications of, for example, sustained yields as otherwise the environmental benefits can be compromised. (C) 2014 IAgrE. Published by Elsevier Ltd. All rights reserved.
  • Authors:
    • Lehmann, J.
    • Enders, A.
    • Whitman, T.
  • Source: Soil Biology and Biochemistry
  • Volume: 73
  • Issue: June
  • Year: 2014
  • Summary: Important due to both its role in fire-affected ecosystems, and also its proposed intentional production and application for carbon (C) management, pyrogenic organic matter (Py0M) is thought to contain very stable forms of C. However, the mechanisms behind its interactions with non-PyOM soil organic C (SOC) remain speculative, with studies often showing short-term positive and then long-term negative "priming effects" on SOC decomposition after PyOM applications. Furthermore, studies of these interactions to date have been limited to systems that do not include plants. This study describes results from a 12-week greenhouse experiment where PyOM-SOC priming effects with and without plants were investigated using stable isotope partitioning. In addition, we investigated the optimal delta C-13 proxies for sources of SOC, PyOM, and plant-derived CO2 emissions. The two-factorial experiment included the presence or absence of corn plants and of 13C-labelled PyOM. In order to control for pH and nutrient addition effects from PyOM, its pH was adjusted to that of the soil and optimal nutrient and water conditions were provided to the plants. The delta C-13 of PyOM sub-components were significantly different. Significant losses of 0.4% of the applied PyOM-C occurred in the first week. We find evidence for a "negative priming" effect of PyOM on SOC in the system (SOC losses are 48% lower with PyOM present), which occurred primarily during the first week, indicating it may be due to transient effects driven by easily mineralizable PyOM. Additionally, while the presence of corn plants resulted in significantly increased SOC losses ("positive priming"), PyOM additions counteract this effect, almost completely eliminating net C losses either by decreasing SOC decomposition or increasing corn C additions to soil. This highlights the importance of including plants in studies of PyOM-SOC interactions.
  • Authors:
    • Koegel-Knabner, I.
    • von Luetzow, M.
    • Schilling, B.
    • Reischl, A.
    • Hangen, E.
    • Geuss, U.
    • Spoerlein, .P.
    • Huebner, R.
    • Wiesmeier, M.
  • Source: Global Change Biology
  • Volume: 20
  • Issue: 2
  • Year: 2014
  • Summary: Sequestration of atmospheric carbon (C) in soils through improved management of forest and agricultural land is considered to have high potential for global CO2 mitigation. However, the potential of soils to sequester soil organic carbon (SOC) in a stable form, which is limited by the stabilization of SOC against microbial mineralization, is largely unknown. In this study, we estimated the C sequestration potential of soils in southeast Germany by calculating the potential SOC saturation of silt and clay particles according to Hassink [Plant and Soil 191 (1997) 77] on the basis of 516 soil profiles. The determination of the current SOC content of silt and clay fractions for major soil units and land uses allowed an estimation of the C saturation deficit corresponding to the long-term C sequestration potential. The results showed that cropland soils have a low level of C saturation of around 50% and could store considerable amounts of additional SOC. A relatively high C sequestration potential was also determined for grassland soils. In contrast, forest soils had a low C sequestration potential as they were almost C saturated. A high proportion of sites with a high degree of apparent oversaturation revealed that in acidic, coarse-textured soils the relation to silt and clay is not suitable to estimate the stable C saturation. A strong correlation of the C saturation deficit with temperature and precipitation allowed a spatial estimation of the C sequestration potential for Bavaria. In total, about 395Mt CO2-equivalents could theoretically be stored in A horizons of cultivated soils - four times the annual emission of greenhouse gases in Bavaria. Although achieving the entire estimated C storage capacity is unrealistic, improved management of cultivated land could contribute significantly to CO2 mitigation. Moreover, increasing SOC stocks have additional benefits with respect to enhanced soil fertility and agricultural productivity.