• Authors:
    • Fiener, P.
    • Reichenau, T. G.
    • Schmidt, M.
    • Schneider, K.
  • Source: Agricultural and Forest Meteorology
  • Volume: 165
  • Issue: November
  • Year: 2012
  • Summary: Arable land occupies large areas of global land surface and hence plays an important role in the terrestrial carbon cycle. Therefore agro-ecosystems show a high potential of mitigating greenhouse gas emissions while optimizing agricultural management. Hence, there is a growing interest in analyzing and understanding carbon fluxes from arable land as affected by regional environmental as well as management conditions. The major goal of this study is to use a two year data set of eddy covariance measurements (October 2007 to October 2009) on a winter wheat field located in Western Germany to assess the seasonal and inter-annual variability of carbon fluxes as affected by meteorological variables and land management. During the study period, which was comprised of two full growing seasons, eddy covariance measurements together with measurements of various soil, plant, and meteorological data were performed. Flux partitioning and gap filling methods including uncertainty estimates were applied to derive complete time series of net ecosystem exchange (NEE), gross primary production (GPP), and ecosystem respiration (R-eco). Despite different management dates and slightly different meteorological conditions, annual NEE resulted in 270 g C m(-2) in both years. Although the period from sowing to harvesting was more than 20 days shorter in the first year, due to the later start of senescence, GPP was higher by 220 g C m(-2). In the annual carbon budget this was compensated by a stronger heterotrophic respiration after the harvest of sugar beet grown on the field before the study period. Taking into account the carbon losses due to removal of biomass during harvest, the winter wheat field acts as a carbon source with respective net biome productivities (NBP) of 246 and 201 g C m(-2) a(-1). To complete the carbon balance, releases due to energy consumption associated with crop production are taken into account. However, the relatively large carbon loss was probably, to a large extent, compensated by carbon input from plant residues left on the field after preceding sugar beet harvest. This underlines the importance of multi-annual measurements taking full crop rotations into account. (C) 2012 Elsevier B.V. All rights reserved.
  • Authors:
    • Smith, P.
  • Source: Global Change Biology
  • Volume: 18
  • Issue: 1
  • Year: 2012
  • Summary: Agricultural lands occupy about 4050% of the Earth's land surface. Agricultural practices can make a significant contribution at low cost to increasing soil carbon sinks, reducing greenhouse gas (GHG) emissions and contributing biomass feedstocks for energy use. Considering all gases, the global technical mitigation potential from agriculture (excluding fossil fuel offsets from biomass) by 2030 is estimated to be ca. 55006000 Mt CO2-eq. yr(-1). Economic potentials are estimated to be 15001600, 25002700 and 40004300 Mt CO2-eq. yr(-1) at carbon prices of up to $US20, 50 and 100tCO(2)-eq. yr(-1), respectively. The value of the global agricultural GHG mitigation at the same three carbon prices is $US32000, 130000 and 420000 millionyr-1, respectively. At the European level, early estimates of soil carbon sequestration potential in croplands were ca. 200 Mt CO2 yr(-1), but this is a technical potential and is for geographical Europe as far east as the Urals. The economic potential is much smaller, with more recent estimates for the EU27 suggesting a maximum potential of ca. 20Mt CO2-eq. yr(-1). The UK is small in global terms, but a large part of its land area (11Mha) is used for agriculture. Agriculture accounts for about 7% of total UK GHG emissions. The mitigation potential of UK agriculture is estimated to be ca. 12MtCO(2)-eq. yr(-1), accounting for less than 1% of UK total GHG emissions.
  • Authors:
    • Cook, F.
    • Francis, G.
    • Close, M.
    • Dann, R.
    • Waterland, H.
    • Thomas, S.
  • Source: Soil Science Society of America Journal
  • Volume: 76
  • Issue: 4
  • Year: 2012
  • Summary: Subsoil denitrification is a potential sink for leached nitrate (NO3-) that may otherwise contaminate ground water. A field trial was undertaken to assess the importance of subsoil denitrification and to examine the role of leached NO3- on subsurface nitrous oxide (N2O) (a potent greenhouse gas) dynamics. We monitored NO3-, Br-, N2O, CO2, and O-2 concentrations in alluvial vadose materials to a depth of 7 m over a 32-mo period following the application of N (400 kg ha(-1) as NH4NO3) and Br- to potatoes (Solanum tuberosum L.) followed by a second application (400 kg ha(-1) as NH4NO3) to ryegrass (Lolium multiflorum Lam.) 24 mo later. Our sampling system consisted of an array of ceramic cups and permeable silicone tubing chambers to sample soil solution and gases. Following rainfall and irrigation, subsoil N2O concentrations increased rapidly. Within days of NO3- leaching below 1 m, high concentrations of NO3-, Br-, and N2O were observed at 7-m depth. Based on N to Br- ratios, and NO3- leaching estimates from drainage amounts and leachate NO3- concentrations, 5 to 10% of the fertilizer and soil N was denitrified. Based on N2O flux estimates and NO3--N/Br- ratios, almost all of the net N2O production occurred in the subsoil above the gravel material (1-m depth). In the gravel matrix the NO3--N/Br- ratio did not change indicating a low capacity to attenuate NO3-.
  • Authors:
    • Astrup, T.
    • Wenzel, H.
    • Hamelin, L.
    • Tonini, D.
  • Source: Environmental Science & Technology
  • Volume: 46
  • Issue: 24
  • Year: 2012
  • Summary: In the endeavor of optimizing the sustainability of bioenergy production in Denmark, this consequential life cycle assessment (LCA) evaluated the environmental impacts associated with the production of heat and electricity from one hectare of Danish arable land cultivated with three perennial crops: ryegrass (Lolium perenne), willow (Salix viminalis) and Miscanthus giganteus. For each, four conversion pathways were assessed against a fossil fuel reference: (I) anaerobic co-digestion with manure, (II) gasification, (III) combustion in small-to-medium scale biomass combined heat and power (CHP) plants and IV) co-firing in large scale coal-fired CHP plants. Soil carbon changes, direct and indirect land use changes as well as uncertainty analysis (sensitivity, MonteCarlo) were included in the LCA. Results showed that global warming was the bottleneck impact, where only two scenarios, namely willow and Miscanthus co-firing, allowed for an improvement as compared with the reference (-82 and -45 t CO2-eq. ha(-1), respectively). The indirect land use changes impact was quantified as 310 + 170 t CO2-eq. ha(-1), representing a paramount average of 41% of the induced greenhouse gas emissions. The uncertainty analysis confirmed the results robustness and highlighted the indirect land use changes uncertainty as the only uncertainty that can significantly change the outcome of the LCA results.
  • Authors:
    • Roose-Amsaleg, C.
    • Garnier, J.
    • Vilain, G.
    • Laville, P.
  • Source: Web Of Knowledge
  • Volume: 92
  • Issue: 1
  • Year: 2012
  • Summary: The denitrification process and the associated nitrous oxide (N(2)O) production in soils have been poorly documented, especially in terms of soil profiles; most work on denitrification has concentrated on the upper layer (first 20 cm). The objectives of this study were to examine the origin of N(2)O emission and the effects of in situ controlling factors on soil denitrification and N(2)O production, also allowing the (N(2)O production)/(NO(3) (-)-N reduction) ratio to be determined through (1) the position on a slope reaching a river and (2) the depth (soil horizons: 10-30 and 90-110 cm). In 2009 and 2010, slurry batch experiments combined with molecular investigations of bacterial communities were conducted in a corn field and an adjacent riparian buffer strip. Denitrification rates, ranging from 0.30 mu g NO(3) (-)-N g(-1) dry soil h(-1) to 1.44 mu g NO(3) (-)-N g(-1) dry soil h(-1), showed no significant variation along the slope and depth. N(2)O production assessed simultaneously differed considerably over the depth and ranged from 0.4 ng N(2)O-N g(-1) dry soil h(-1) in subsoils (the 90-110-cm layer) to 155.1 ng N(2)O-N g(-1) dry soil h(-1) in the topsoils (the 10-30-cm layer). In the topsoils, N(2)O-N production accounted for 8.5-48.0% of the total denitrified NO(3) (-)-N, but for less than 1% in the subsoils. Similarly, N(2)O-consuming bacterial communities from the subsoils greatly differed from those of the topsoils, as revealed by their nosZ DGGE fingerprints. High N(2)O-SPPR (nitrous oxide semi potential production rates) in comparison to NO(3)-SPDR (nitrate semi potential reduction rates) for the topsoils indicated significant potential greenhouse N(2)O gas production, whereas lower horizons could play a role in fully removing nitrate into inert atmospheric N(2). In terms of landscape management, these results call for caution in rehabilitating or constructing buffer zones for agricultural nitrate removal.
  • Authors:
    • Frear, C.
    • Chen, S.
    • Wang, G.
  • Source: Geoderma
  • Volume: 170
  • Year: 2012
  • Summary: Quantitative information is critical in policy making related to the roles of agriculture in greenhouse gas (GHG) emissions. A Unit Response (UR) curve method was developed in this study for modeling GHG emissions from soil after liquid manure applications. The emission sources (soils and liquid manures) are conceptualized as a set of linear cascaded chambers with equal storage-release coefficients, or two sets of cascaded chambers in parallel, each set having equal storage-release coefficients. The model is based on a two-parameter gamma distribution. Three parameters in this model denote the number of cascaded chambers, the storage-release coefficient, and the multiplier (referring to the total net emissions) added to the gamma distribution function. These parameters can be expressed as functions of site-specific background fluxes without applications of manure/fertilizer. The method was assessed with emissions data from five fields in Washington State. The results showed that at the WSU and Lynden sites, the average excess CH4 emissions due to manure applications were 0.39 and 0.17 kg CH4-C ha(-1), respectively: the average excess CO2 emissions were 216.50 and 25.20 kg CO2-C ha(-1), respectively; and the average excess N2O were 0.37 and 0.03 kg N2O-N ha(-1), respectively. The UR method may fill the gaps between field measurements, simple emission factor (EF) method, and complex process-oriented models. This method has the potential to be used for estimating additional GHG emissions due to manure/fertilizer applications.
  • Authors:
    • Juszczak, R.
    • Augustin, J.
    • Yeluripati, J.
    • Smith, P.
    • Smith, J.
    • Jones, E.
    • Bell, M. J.
    • Olejnik, J.
    • Sommer, M.
  • Source: Web Of Knowledge
  • Volume: 92
  • Issue: 2
  • Year: 2012
  • Summary: The global warming potential of nitrous oxide (N2O) and its long atmospheric lifetime mean its presence in the atmosphere is of major concern, and that methods are required to measure and reduce emissions. Large spatial and temporal variations means, however, that simple extrapolation of measured data is inappropriate, and that other methods of quantification are required. Although process-based models have been developed to simulate these emissions, they often require a large amount of input data that is not available at a regional scale, making regional and global emission estimates difficult to achieve. The spatial extent of organic soils means that quantification of emissions from these soil types is also required, but will not be achievable using a process-based model that has not been developed to simulate soil water contents above field capacity or organic soils. The ECOSSE model was developed to overcome these limitations, and with a requirement for only input data that is readily available at a regional scale, it can be used to quantify regional emissions and directly inform land-use change decisions. ECOSSE includes the major processes of nitrogen (N) turnover, with material being exchanged between pools of SOM at rates modified by temperature, soil moisture, soil pH and crop cover. Evaluation of its performance at site-scale is presented to demonstrate its ability to adequately simulate soil N contents and N2O emissions from cropland soils in Europe. Mitigation scenarios and sensitivity analyses are also presented to demonstrate how ECOSSE can be used to estimate the impact of future climate and land-use change on N2O emissions.
  • Authors:
    • Thomas, M.
    • Sanderman, J.
    • Chappell, A.
    • Read, A.
    • Leslie, C.
  • Source: Global Change Biology
  • Volume: 18
  • Issue: 6
  • Year: 2012
  • Summary: Anthropogenically induced change in soil redistribution plays an important role in the soil organic carbon (SOC) budget. Uncertainty of its impact is large because of the dearth of recent soil redistribution estimates concomitant with changing land use and management practices. An Australian national survey used the artificial radionuclide caesium-137 ( 137Cs) to estimate net (1950s-1990) soil redistribution. South-eastern Australia showed a median net soil loss of 9.7 t ha -1 yr -1. We resurveyed the region using the same 137Cs technique and found a median net (1990-2010) soil gain of 3.9 t ha -1 yr -1 with an interquartile range from -1.6 t ha -1 yr -1 to +10.7 t ha -1 yr -1. Despite this variation, soil erosion across the region has declined as a likely consequence of the widespread adoption of soil conservation measures over the last ca 30 years. The implication of omitted soil redistribution dynamics in SOC accounting is to increase uncertainty and diminish its accuracy.
  • Authors:
    • Wesemael, B. van
    • Six, J.
    • Doetterl, S.
    • Oost, K. van
  • Source: Global Change Biology
  • Volume: 18
  • Issue: 7
  • Year: 2012
  • Summary: Recent studies have highlighted the tight coupling between geomorphic processes and soil carbon (C) turnover and suggested that eroding landscapes can stabilize more C than their non-eroding counterparts. However, large uncertainties remain and a mechanistic understanding of geomorphic effects on C storage in soils is still lacking. Here, we quantified the soil organic carbon (SOC) stock and pool distribution along geomorphic gradients and combined data derived from soil organic matter fractionation and incubation experiments. The size and composition of the SOC pools were strongly related to geomorphic position: 1.6 to 6.2 times more C was stabilized in the subsoils (25-100 cm) of depositional profiles than in those of eroding profiles. Subsoil C of depositional profiles is predominantly associated with microaggregates and silt-sized particles which are associated with pools of intermediate stability. We observed a significantly higher mean residence time for the fast and intermediate turnover pools of buried C at depositional positions, relative to non-eroding and eroding positions, resulting from the physical protection of C associated with microaggregates and silt particles. Conversely, significant amounts of C were replaced at eroding positions but the lower degree of decomposition and the lack of physically protected C, resulted in higher respiration rates. By considering C cycling at non-eroding, eroding and depositional positions, we found that the eroding landscapes studied store up to 10% more C due to soil redistribution processes than non-eroding landscapes. This is the result of the stabilization of C in former subsoil at eroding positions and partial preservation of buried C in pools of intermediate turnover at depositional positions. However, the sink strength was limited by significant losses of buried C as only a small fraction of the C was associated with stable pools.
  • Authors:
    • Baetens, J. M.
    • Vandepitte, J.
    • Audenaert, K.
    • Waegeman, W.
    • Landschoot, S.
    • De Baets, B.
    • Haesaert, G.
  • Source: Journal of Plant Pathology
  • Volume: 94
  • Issue: 1
  • Year: 2012
  • Summary: Models for predicting Fusarium head blight (FHB) and deoxynivalenol (DON) content in wheat provide farmers with a tool for preventing yield loss and mycotoxin contamination. Due to the complex nature of FHB, these models typically take only a subset of explanatory variables as inputs, such as weather conditions during anthesis and, to a lesser extent, field-specific variables and crop characteristics. We present a thorough statistical analysis of a broad spectrum of variables that affect FHB and DON content, using an unique database of field observations covering nine years. This study unveils new variables that play an important role in FHB incidence and DON content. Evidence is brought forward demonstrating the effect of species interactions on DON content and the effect of weather conditions during the vegetative growth stage. Indeed, temperature from November till May was positively correlated with FHB and DON content, whereas relative humidity was negatively correlated with DON content in November and December. In a broader view of the divergent results obtained regarding FHB and DON content in wheat crops, this study underscores that the prediction of FHB and DON content should be seen as two distinct goals.