• Authors:
    • De Bolt, Seth
    • Montross, Michael D.
    • Adams, William C.
  • Source: GCB Bioenergy Volume 5, Issue 6, pages
  • Volume: 5
  • Issue: 6
  • Year: 2013
  • Summary: The interplay between nitrogen fertilization (N), yield, nitrous oxide emissions (N2O), and diesel fuel utilization associated with harvest and transport logistics of biomass crops remains poorly understood. In this research, we show that intensification (in terms of N) of bioenergy cropping to maximize yield supports not only minimized land use but also maximized logistics efficiency in terms of diesel use. This paradigm was examined within the scope of the billion-ton biofuels vision and the Energy Independence and Security Act of 2007 using potential yields on marginal and prime agricultural land. Sixteen scenarios were investigated that considered the primary factors with agriculture bioenergy; biomass yield (11.2 and 22.4 Mgha(-1)yr(-1)), two nitrogen fertilizer application rates (50 and 100kg N ha(-1)yr(-1)), two Greenhouse Gas Emissions (GHGE) factors for synthetic nitrogen to nitrous oxide (1.5 and 5%), and three harvest/transportation efficiencies (50, 65, and 80%). These scenarios resulted in energy consumption between 747 and 1351 MJ Mg-1 and GHGE between 72 and 311 kg CO2 eq Mg-1. GHGE emissions are strongly related to the emission of nitrous oxide from soils due to nitrogen fertilization and could represent over 80% of the GHGE relative to biomass harvest logistics. These data imply that synthetic N supplementation to maximize yield could reduce the burden due to diesel fuel for harvest, but would rapidly become the most significant contributor to GHGE. Minimizing the impact of N fertilization will be critical for reducing the GHGE associated with biomass production.
  • Authors:
    • Pellegrino Cerri,Carlos Eduardo
    • Galdos,Marcelo Valadares
    • Nunes Carvalho,Joao Luis
    • Feigl,Brigitte Josefine
    • Cerri,Carlos Clemente
  • Source: Scientia Agricola
  • Volume: 70
  • Issue: 5
  • Year: 2013
  • Summary: Strategies to mitigate climate change through the use of biofuels (such as ethanol) are associated not only to the increase in the amount of C stored in soils but also to the reduction of GHG emissions to the atmosphere. This report mainly aimed to propose appropriate methodologies for the determinations of soil organic carbon stocks and greenhouse gas fluxes in agricultural phase of the sugarcane production. Therefore, the text is a piece of contribution that may help to obtain data not only on soil carbon stocks but also on greenhouse gas emissions in order to provide an accurate life cycle assessment for the ethanol. Given that the greenhouse gas value is the primary measure of biofuel product quality, biorefiners that can show a higher offset of their product will have an advantage in the market place.
  • Authors:
    • Robertson, F.
    • Nash, D.
  • Source: Agriculture, Ecosystems & Environment
  • Volume: 165
  • Year: 2013
  • Summary: The extent to which soil C storage can be increased in Australian agricultural soils by adoption of improved management practices is poorly understood. There is a pressing need for such information in order to evaluate the potential for soil C sequestration to offset greenhouse gas emissions. In this study we used the RothC model to assess whether soil C accumulation under cropping using stubble retention and pasture rotations could be a significant offset for greenhouse gas emissions. We chose eight regions to represent the climatic range of the Victorian cropping industry: Walpeup, Birchip, Horsham, Bendigo, Rutherglen, Lismore, Bairnsdale and Hamilton (annual rainfall 330-700 mm). For each region, we chose two representative soil types, varying in clay and total organic C contents. For each region x soil combination, we compared the effects of five rotations: Canola-wheat-pulse-barley (C-W-P-B); Canola-wheat-triticale (C-W-T); Canola-wheat-barley-5 year perennial pasture (C-W-B-Pt5); Canola-wheat-fallow (C-W-F) and Continuous pasture (Pt). We compared the cropping rotations with cereal stubble burnt and with cereal stubble retained and, for two regions, with cereal stubble grazed by sheep. The results of the simulations showed that, across all scenarios, the equilibrium C density varied between 19 and 135 t C/ha to 300 mm depth, with potential soil C change being strongly influenced by crop yield, crop rotation, climate, initial soil C content, stubble management and continuity of management The simulations suggested that soil C stocks could be increased under a crop-pasture rotation (C-W-B-Pt5) with stubble retention, with rates of increase of 0.3-0.9 t C/ha yr over 25 years. If all of Victoria's cropland were converted to C-W-B-Pt5 rotation with stubble retention, and if 50% of the modelled potential C change were achieved, this would represent 3.0-4.5 MtCO(2)-e/year, equivalent to 2.5-3.7% of Victoria's greenhouse emissions. Less C accumulation would be possible under continuous cropping with stubble retention; even using the most conservative rotation (C-W-T) rates of C change varied from loss of 0.3 t C/ha yr to accumulation of 0.5 t C/ha yr over 25 years. If all of Victoria's cropland were converted to C-W-T rotation with stubble retention, and if 50% of the modelled potential C change were achieved, this would be equivalent to 0.8-2.3 MtCO(2)-e/year, or 0.7-1.9% of Victoria's greenhouse emissions. It would generally take 10-25 years for the soil C changes to become measurable using conventional soil sampling and analytical methods. Thus we conclude that, with current technology, the potential for significant and verifiable soil C accumulation in Victoria's croplands is limited.
  • Authors:
    • Fraser, T. J.
    • Amiro, B. D.
    • Taylor, A. M.
  • Source: Agricultural and Forest Meteorology
  • Volume: 182-183
  • Year: 2013
  • Summary: Eddy covariance flux towers were used to measure net ecosystem production over three adjacent agricultural fields in Manitoba, Canada, from 2009 to 2011. Two fields were converted from long-term perennial hay/pasture to annual cropping, while the third field served as a control field that was maintained as hay/pasture. One converted field had a rotation of oat-canola-oat crops, while the second was hay-oat-fallow. Weather was an important driver of inter-annual variability, with poor yields on all fields in 2011 because of dry conditions in summer, with the summer-fallow condition on one field caused by excess spring moisture not allowing planting. The cumulative net ecosystem production of the oat-canola-oat field showed a net CO2 emission of 100 g Cm-2, the hay-oat-fallow field emitted 500 g Cm-2, and the hay field gained 550 g C m(-2) by the end of the 30-month study period. The hay field had the highest cumulative gross primary production of 2500 g C m(-2), whereas the oat-canola-oat and hay-oat-fallow fields had only about 1400 g C m(-2). The perennial field had the advantage of both early- and late-season growth when crops were absent on the other fields. The hay and hay-oat-fallow fields had comparable cumulative ecosystem respiration (1400 g Cm-2). Manure additions contributed 300 g C m(-2) on the two converted fields. With harvest exports and manure additions included, the oat-canola-oat field was a carbon source of 240 g Cm-2, the hay-oat-fallow field was a source of 415 g C m(-2), and the hay/pasture field was a sink of 120 g C m(-2) over the 30-month period.
  • Authors:
    • Pereira, G. T.
    • Panosso, A. R.
    • Cerri, C. E. P.
    • Bicalho, E. S.
    • Teixeira, D. D. B.
    • La Scala, N.
  • Source: Agriculture, Ecosystems & Environment
  • Volume: 167
  • Year: 2013
  • Summary: The characterization of soil CO2 emissions (FCO2) is important for the study of the global carbon cycle. This phenomenon presents great variability in space and time, a characteristic that makes attempts at modeling and forecasting FCO2 challenging. Although spatial estimates have been performed in several studies, the association of these estimates with the uncertainties inherent in the estimation procedures is not considered. This study aimed to evaluate the local, spatial, local-temporal and spatial-temporal uncertainties of short-term FCO2 after harvest period in a sugar cane area. The FCO2 was featured in a sampling grid of 60 m x 60 m containing 127 points with minimum separation distances from 0.5 to 10 m between points. The FCO2 was evaluated 7 times within a total period of 10 days. The variability of FCO2 was described by descriptive statistics and variogram modeling. To calculate the uncertainties, 300 realizations made by sequential Gaussian simulation were considered. Local uncertainties were evaluated using the probability values exceeding certain critical thresholds, while the spatial uncertainties considering the probability of regions with high probability values together exceed the adopted limits. Using the daily uncertainties, the local-spatial and spatial-temporal uncertainty (Ftemp) was obtained. The daily and mean emissions showed a variability structure that was described by spherical and Gaussian models. The differences between the daily maps were related to variations in the magnitude of FCO2, covering mean values ranging from 1.28 +/- 0.11 mu mol m(-2) s(-1) (F197) to 1.82 +/- 0.07 mu mol m(-2) s(-1) (F195). The Ftemp showed low spatial uncertainty coupled with high local uncertainty estimates. The average emission showed great spatial uncertainty of the simulated values. The evaluation of uncertainties associated with the knowledge of temporal and spatial variability is an important tool for understanding many phenomena over time, such as the quantification of greenhouse gases or the identification of areas with high crop productivity.
  • Authors:
    • Novara,Agata
    • Gristina,Luciano
    • La Mantia,Tommaso
    • Ruehl,Juliane
  • Source: Geoderma
  • Volume: 193-194
  • Year: 2013
  • Summary: Clarifying which factors cause an increase or decrease in soil organic carbon (SOC) after agricultural abandonment requires integration of data on the temporal dynamics of the plant community and SOC. A chronosequence of abandoned vineyards was studied on a volcanic island (Pantelleria, Italy). Vegetation in the abandoned fields was initially dominated by annual and perennial herbs, then by Hyparrhenia hirta (L.) Stapf, and finally by woody communities. As a consequence, the dominant photosynthetic pathway changed from C-3 to C-4 and then back to C-3. Conversion of a plant community dominated by one photosynthetic pathway to another changes the C-13/C-12 ratio of inputs to SOC. Using the time since abandonment and the shift in belowground delta C-13 of SOC relative to the aboveground delta C-13 plant community, we estimated C-3-C and C-4-C changes during secondary succession. SOC content (g kg(-1)) increased linearly (R-2=0.89 and 0.73 for 0-15 and 15-30 cm soil depth) with the age of abandonment, increasing from 12 g kg(-1) in cultivated vineyards to as high as 26 g kg(-1) in the last stage of the succession. delta C-13 increased in the bulk soil and its three aggregate fractions (> 250,250-25, and < 25 mu m) during succession, but the effect of soil depth and its interaction with succession age were significant only for soil aggregate fractions. Polynomial curves described the change in delta C-13 over the chronosequence for both depths. delta C-13 in the bulk soil had increased from -28 parts per thousand. to -24 parts per thousand. by 35 years after abandonment for both depths but then decreased to -26 parts per thousand. at 60 years after abandonment (corresponding with maturity of the woody plant community). Overall, the results indicate that abandoned vineyards on volcanic soil in a semi-arid environment are C sinks and that C storage in these soils is closely related to plant succession. (C) 2012 Elsevier B.V. All rights reserved.
  • Authors:
    • Shi,Tiezhu
    • Cui,Lijuan
    • Wang,Junjie
    • Fei,Teng
    • Chen,Yiyun
    • Wu,Guofeng
  • Source: Plant and Soil
  • Volume: 366
  • Issue: 1-2
  • Year: 2013
  • Summary: This study aimed to compare stepwise multiple linear regression (SMLR), partial least squares regression (PLSR) and support vector machine regression (SVMR) for estimating soil total nitrogen (TN) contents with laboratory visible/near-infrared reflectance (Vis/NIR) of selected coarse and heterogeneous soils. Moreover, the effects of the first (1st) vs. second (2nd) derivative of spectral reflectance and the importance wavelengths were explored. The TN contents and the Vis/NIR were measured in the laboratory. Several methods were employed for Vis/NIR data pre-processing. The SMLR, PLSR and SVMR models were calibrated and validated using independent datasets. Results showed that the SVMR and the PLSR models had similar performances, and better performances than the SMLR. The spectral bands near 1450, 1850, 2250, 2330 and 2430 nm in the PLSR model were important wavelengths. In addition, the 1st derivative was more appropriate than the 2nd derivative for spectral data pre-processing. PLSR was the most suitable method for estimating TN contents in this study. SVMR may be a promising technique, and its potential needs to be further explored. Moreover, the future studies using outdoor and airborne/satellite hyperspectral data for estimating TN content are necessary for testing the findings.
  • Authors:
    • Huffman, T.
    • Green, M.
    • Coote, D.
  • Source: Canadian Journal of Soil Science
  • Volume: 92
  • Issue: 3
  • Year: 2012
  • Summary: Agricultural soils that are covered by vegetation or crop residue are less susceptible to degradation by wind and water erosion, organic matter depletion, structural degradation and declining fertility. In general, perennial crops, higher yields, reduced tillage and continuous cropping provide more soil cover than annual crops, lower yields, intensive tillage, residue harvesting and fallowing. This study presents a model for estimating the number of days in a year that the soil surface is protected and demonstrates its application on the Canadian prairies over the period from 1981 to 2006. Over the 25-yr study period, the average soil cover on Canadian prairie soils increased by 4.8% overall. The improvement came primarily as a result of widespread adoption of no-till and a decline in the use of summerfallow, but the gains were offset to a great deal by a shift from higher-cover crops such as wheat, oats and barley to more profitable but lower-cover crops such as canola, soybeans and potatoes. The implication of these trends is that, even though protection of prairie agricultural soils has improved over the past 25 yr, soil cover could decline dramatically over the next several decades if crop changes continue, the adoption of conservation tillage reaches a peak and residue harvesting for biofuels becomes more common.
  • Authors:
    • Robertson, G.
    • Tausig, J.
    • Hamilton, S.
    • Basso, B.
    • Syswerda, S.
  • Source: Agricultural Ecosystems and Environment
  • Volume: 149
  • Year: 2012
  • Summary: Nitrate (NO 3-) loss from intensively farmed cropland is a long-standing, recalcitrant environmental problem that contributes to surface and groundwater pollution and coastal zone hypoxia. Here nitrate leaching losses are reported from nine replicated cropped and unmanaged ecosystems in southwest Michigan, USA. Ecosystems include four annual corn-soybean-winter wheat rotations under conventional, no-till, reduced-input, and organic/biologically-based management, two perennial cropping systems that include alfalfa and hybrid poplar trees, and three unmanaged successional communities including an early successional community analogous to a cellulosic biofuel system as well as a mature deciduous forest. The organic, alfalfa, and unmanaged systems received no synthetic, manure, or compost nitrogen. Measured nitrate concentrations were combined with modeled soil water drainage to provide estimates of nitrate lost by leaching over 11 years. Among annual crops, average nitrate losses differed significantly ( pno-till (41.33.0)>reduced-input (24.30.7) > organic (19.00.8) management. Among perennial and unmanaged ecosystems, nitrate loss followed the pattern alfalfa (12.81.8 kg N ha -1 yr -1)=deciduous forest (11.04.2) >> early successional (1.10.4)=mid-successional (0.90.4) > poplar (<0.010.007 kg N ha -1 yr -1) systems. Findings suggest that nitrate loss in annual row crops could be significantly mitigated by the adoption of no-till, cover crops, and greater reliance on biologically based inputs, and in biofuel systems by the production of cellulosic rather than grain-based feedstocks.
  • Authors:
    • Cardenas, L.
    • Lopez, A. L.
    • Sawamoto, T.
    • Gigliotti, G.
    • Bol, R.
    • Pezzolla, D.
    • Chadwick, D.
  • Source: Rapid Communications in Mass Spectrometry
  • Volume: 26
  • Issue: 20
  • Year: 2012
  • Summary: RATIONALE The application of organic materials to agricultural lands is considered good practice to improve soil organic matter content and recycle nutrients for crop growth. The anaerobic treatment of food waste may have environmental benefits, particularly with regard to greenhouse gases (GHGs) mitigation and enhancement of carbon sequestration. METHODS This work presents the results from a field experiment to evaluate CO2, CH4 and N2O emissions from grassland amended with digestate produced by anaerobic fermentation of food waste. Experimental plots, located close to Rothamsted Research-North Wyke, were established using a randomized block design with three replicates and two treatments, added digestate (DG) and the unamended control (CNT). The digestate was applied on three occasions at an equivalent rate of 80?kg?N ha1. RESULTS The application of digestate led to an increase in CO2 emissions, especially after the 2nd application (74.1?kg CO2-C ha1?day1) compared with the CNT soil (36.4?kg CO2-C ha1?day1), whereas DG treatment did not affect the overall CH4 and N2O emissions. The total grass yield harvested on a dry matter basis was greater in the DG treated plots (0.565?kg?m2) than in the CNT plots (0.282?kg?m2), as was the 15?N content in the harvest collected from the DG plots. CONCLUSIONS The results suggest that the digestate can be applied to agricultural land as a fertilizer to grow crops. Our study was conducted in an exceptionally dry growing season, so conclusions about the effect of digestate on GHG emissions should take this into account, and further field trials conducted under more typical growing seasons are needed.