• Authors:
    • Walter, C.
    • Viaud, V.
    • Michot, D.
    • McBratney, A.
    • Minasny, B.
    • Lacoste, M.
  • Source: Research Article
  • Volume: 213
  • Year: 2014
  • Summary: Soil organic carbon (SOC) is a key element of agroecosystems functioning and has a crucial impact on global carbon storage. At the landscape scale, SOC spatial variability is strongly affected by natural and anthropogenic processes and linear anthropogenic elements (such hedges or ditches). This study aims at mapping SOC stocks distribution in the A-horizons for a depth up to 105 cm, at a high spatial resolution, for an area of 10 km(2) in a heterogeneous agricultural landscape (North-Western France). We used a data mining tool, Cubist, to build rule-based predictive models and predict SOC content and soil bulk density (BD) from a calibration dataset at 8 standard layers (0 to 7.5 cm, 7.5 to 15 cm, 15 to 30 cm, 30 to 45 cm, 45 to 60 cm, 60 to 75 cm, 75 to 90 cm and 90 to 105 cm). For the models calibration, 70 sampling locations were selected within the whole study area using the conditioned Latin hypercube sampling method. Two independent validation datasets were used to assess the performance of the predictive models: (i) at landscape scale, 49 sampling locations were selected using stratified random sampling based on a 300-m square grid; (ii) at hedge vicinity, 112 sampling locations were selected along transects perpendicular to 14 purposively chosen hedges. Undisturbed samples were collected at fixed depths and analysed for BD and SOC content at each sampling location and continuous soil profiles were reconstructed using equal-area splines. Predictive environmental data consisted in attributes derived from a light detection and ranging digital elevation model (LiDAR DEM), geological variables, land use data and a predictive map of A-horizon thickness. Considering the two validation datasets (at landscape scale and hedge vicinity), root mean square errors (RMSE) of the predictions, computed for all the standard soil layers (up to a depth of 105 cm), were respectively 7.74 and 5.02 g kg(-1) for SOC content, and 0.15 and 021 g cm(-3) for BD. Best predictions were obtained for layers between 15 and 60 cm of depth. The SOC stocks were calculated over a depth of 105 cm by combining the prediction of SOC content and BD. The final maps show that the carbon stocks in the soil below 30 cm accounted for 33% of the total SOC stocks on average. The whole method produced consistent results between the two predicted soil properties. The final SOC stocks maps provide continuous data along soil profile up to 105 cm, which may be critical information for supporting carbon policy and management decisions. (C) 2013 Elsevier B.V. All rights reserved.
  • Authors:
    • Capriel, P.
  • Source: European Journal of Soil Science
  • Volume: 64
  • Issue: 4
  • Year: 2013
  • Summary: In the last 60 years traditional agriculture in industrialized European countries, which had initially been dependent on available natural resources, has shifted towards a massive intensification of nutrient turnover because of cheap energy and low-cost synthetic fertilizers. At the same time farm structure has undergone profound changes, resulting in an increase in the number of specialized farms to the detriment of traditional non-specialized ones. All these trends have had a significant impact on agricultural management. The intensification of agricultural management together with climate change could affect the quantity and quality of soil organic matter (SOM). That could imply decreasing soil fertility, reduced harvest yields, increasing nutrient losses and additional greenhouse gas emission. In order to measure the long-term development of SOM in agricultural soils a monitoring programme was initiated in Bavaria in 1986. The measurements are based on 92 representative plots located on cropland and 21 plots located on managed permanent grassland. Between 1986 and 2007 the monitoring plots have been sampled four times. The monitoring results suggest a decrease of soil organic carbon content, total nitrogen content and C:N ratio in cropland as well as in grassland in Bavaria between 1986 and 2007. Crops and organic fertilizers are together with the initial SOM content the main causes of the observed changes in SOM quantity and quality. A climatic effect could be neither proved nor excluded. The results in Bavaria are consistent with the reported changes in organic carbon of agricultural soils in Austria, Belgium, France, the Netherlands and England. In Bavaria we should expect declining SOM stocks, particularly soil organic carbon, in agricultural soils if the supply of organic matter remains constant or even decreases.
  • Authors:
    • Zeng, A.
    • Zhou, J.
    • Mao, X.
    • Dong, G.
  • Source: Ecological Economics
  • Volume: 91
  • Year: 2013
  • Summary: In recent decades, Chinese agriculture has moved towards higher-energy and higher carbon-input systems to increase food production in the country's limited area of croplands. To investigate the environmental impacts of this trend, this study aimed to develop an "Integrated Life Cycle Assessment and Environmental Input-Output Model" (LCA-EIO Model). Using the tri-scope carbon footprint (CF) accounting method, the agricultural carbon footprint of Zhejiang Province, China was calculated for the years from 1997 to 2007, and the categories and structure of carbon emissions sources were analyzed, including patterns of change. In addition, the carbon intensity of crop farming in Zhejiang Province was examined. While an overall reduction in cropland areas has resulted in a substantial decline in direct greenhouse gas emissions from agricultural production, the proportion of carbon emissions caused by energy and chemical consumption has increased dramatically, and this consumption has become the primary source of carbon emissions. A decomposition analysis also identified the key driving forces of energy-related CF dynamics, such as the machinery-labor substitution effect. The results of the decomposition analysis can support decision makers in understanding and promoting low-carbon output agriculture.
  • Authors:
    • Carneiro, M. A. C.
    • Resck, D. V. S.
    • Figueiredo, C. C.
    • Ramos, M. L. G.
    • Sa, J. C. M.
  • Source: Soil research
  • Volume: 51
  • Issue: 2
  • Year: 2013
  • Summary: Enhancement of organic matter plays an essential role in improving soil quality for supporting sustainable food production. Changes in carbon stocks with impacts on emissions of greenhouse gases may result from the stratification of organic matter as a result of soil use. The objective of this study was to evaluate the impact of soil management systems on soil carbon stocks and stratification ratios (SR) of soil organic matter pools. Total organic carbon (TOC), particulate organic carbon (POC), mineral-associated organic carbon, microbial biomass carbon (MBC) and nitrogen, basal respiration, and particulate organic matter nitrogen (PON) were determined. The field experiment comprised several tillage treatments: conventional tillage, no-till with biannual rotation, no-till with biannual rotation combined with a second crop, no-till with annual rotation, and pasture. The labile fractions indicated a high level of variation among management systems. Pasture proved to be an excellent option for the improvement of soil carbon. While the conventional tillage system reduced total carbon stocks of the soil (0-40 cm), no-tillage presented TOC stocks similar to that of native vegetation. Sensitivity of the TOC SR varied from 0.93 to 1.28, a range of 0.35; the range for POC was 1.76 and for MBC 1.64. The results support the hypothesis that the labile fractions (POC, MBC, and PON) are highly sensitive to the dynamics of organic matter in highly weathered soils of tropical regions influenced by different management systems. Reductions to SRs of labile organic matter pools are related to the impacts of agricultural use of Cerrado soils.
  • Authors:
    • Jaroslav, B.
    • Moudry, J.
    • Jelinkova, Z.
    • Moudry, J., Jr.
    • Marek, K.
    • Petr, K.
  • Source: Journal of Food, Agriculture & Environment
  • Volume: 11
  • Issue: 3/4
  • Year: 2013
  • Summary: The study presents a comparison of an effect of greenhouse gas emission load on the environment caused within the production of crops (rye, wheat, potato, carrot, cabbage, onion and tomato) under conventional and organic farming system in the Czech Republic. For evaluation, the simplified LCA analysis focused on evaluation of greenhouse gas emission load, expressed in carbon dioxide equivalents, was used. Outputs were converted into 1 kg of agricultural production. Within the evaluation of agricultural phase, total emissions from the cultivation of crops and emissions from particular parts of agricultural phase (agricultural engineering, fertilizers, pesticides, seeds and seedlings, field emission) were surveyed. The results show that except for onion growing, there is a reduction of emissions for all studied crops.
  • Authors:
    • Moudry, J.
    • Plch, R.
    • Jaresova, M.
    • Jelinkova, Z.
    • Moudry, J., Jr.
    • Konvalina, P.
  • Source: Outlook on Agriculture
  • Volume: 42
  • Issue: 3
  • Year: 2013
  • Summary: This study evaluates the impact of selected potato farming and processing activities on the environment in terms of greenhouse gas emissions. The Life Cycle Assessment (LCA) methodology was used for this evaluation, and was applied to products cultivated under both conventional and organic production, and processed under technological conditions common in the Czech Republic. Farm questionnaires were supplemented with information from the scientific literature to acquire the necessary data for modelling. The SIMA Pro software and the ReCiPe Midpoint (H) method were used for simulation. The results show a lower level of emissions under organic production (0.126 kg CO(2)e per kg of potatoes, compared with 0.145 kg CO(2)e per kg of conventionally grown potatoes). However, this benefit is cancelled out by higher emissions due to the transportation of organic products over long distances.
  • Authors:
    • Halberg, N.
    • Hermansen, J E.
    • Knudsen, M T.
    • Petersen, B M.
  • Source: Journal of Cleaner Production
  • Volume: 52
  • Year: 2013
  • Summary: Globally, soil carbon sequestration is expected to hold a major potential to mitigate agricultural greenhouse gas emissions. However, the majority of life cycle assessments (LCA) of agricultural products have not included possible changes in soil carbon sequestration. In the present study, a method to estimate carbon sequestration to be included in LCA is suggested and applied to two examples where the inclusion of carbon sequestration is especially relevant: 1) Bioenergy: removal of straw from a Danish soil for energy purposes and 2) Organic versus conventional farming: comparative study of soybean production in China. The suggested approach considers the time of the soil CO2 emissions for the LCA by including the Bern Carbon Cycle Model. Time perspectives of 20,100 and 200 years are used and a soil depth of 0-100 cm is considered. The application of the suggested method showed that the results were comparable to the IPCC 2006 tier I approach in a time perspective of 20 year, where after the suggested methodology showed a continued soil carbon change toward a new steady state. The suggested method estimated a carbon sequestration for the first example when storing straw in the soil instead of using it for bioenergy of 54, 97 and 213 kg C t(-1) straw C in a 200, 100 and 20 years perspective, respectively. For the conversion from conventional to organic soybean production, a difference of 32, 60 or 143 kg soil C ha(-1) yr(-1) in a 200,100 or 20 years perspective, respectively was found. The study indicated that soil carbon changes included in an LCA can constitute a major contribution to the total greenhouse gas emissions per crop unit for plant products. The suggested approach takes into account the temporal aspects of soil carbon changes by combining the degradation and emissions of CO2 from the soil and the following decline in the atmosphere. Furthermore, the results from the present study highlights that the choice of the time perspective has a huge impact on the results used for the LCA. For comparability with the calculation of the global warming potential in LCA, it is suggested to use a time perspective of 100 years when using the suggested approach for soil carbon changes in LCA. (C) 2013 Elsevier Ltd. All rights reserved.
  • Authors:
    • Paustian, K.
    • Ngugi, M. K.
    • Suddick, E. C.
    • Six, J.
  • Source: California Agriculture
  • Volume: 67
  • Issue: 3
  • Year: 2013
  • Summary: California growers could reap financial benefits from the low-carbon economy and cap-and-trade system envisioned by the state's AB 32 law, which seeks to lower greenhouse gas emissions statewide. Growers could gain carbon credits by reducing greenhouse gas emissions and sequestering carbon through reduced tillage and increased biomass residue incorporation. First, however, baseline stocks of soil carbon need to be assessed for various cropping systems and management practices. We designed and set up a pilot soil carbon and land-use monitoring network at several perennial cropping systems in Northern California. We compared soil carbon content in two vineyards and two orchards (walnut and almond), looking at conventional and conservation management practices, as well as in native grassland and oak woodland. We then calculated baseline estimates of the total carbon in almond, wine grape and walnut acreages statewide. The organic walnut orchard had the highest total soil carbon, and no-till vineyards had 27% more carbon in the surface soil than tilled vineyards. We estimated wine grape vineyards are storing significantly more soil carbon per acre than almond and walnut orchards. The data can be used to provide accurate information about soil carbon stocks in perennial cropping systems for a future carbon trading system.
  • Authors:
    • McManus, M. C.
    • Whittaker, C.
    • Smith, P.
  • Source: Environmental Modelling & Software
  • Volume: 46
  • Issue: August
  • Year: 2013
  • Summary: In light of concerns over climate change and the need for national inventories for greenhouse gas reporting, there has been a recent increase in interest in the 'carbon foot printing' of products. A number of LCA-based carbon reporting tools have been developed in both the agricultural and renewable energy sectors, both of which follow calculation methodologies to account for GHG emissions from arable cropping. A review was performed to compare 11 existing greenhouse gas (GHG) accounting tools produced in order to calculate emissions from arable crops, either for food or bioenergy production in the UK, and a multi-criteria-analysis was performed to test their relative strengths and weaknesses. Tools designed for farm-based accounting achieved a higher 'user-friendliness' score, however bioenergy-based tools performed better in the overall level of information provided in the results, transparency and the comprehensiveness of emission sources included in the calculations. A model dataset for UK feed wheat was used to test the GHG emissions calculated by each tool. The results showed large differences, mainly due to how greenhouse gas emissions from fertiliser manufacture and application are accounted fat Overall, the Cool Farm Tool (Hillier et al., 2011) was identified as the highest ranking tool that is currently available in the public domain. The differences in the results between the tools appear to be due to the goal and scope, the system boundaries and underlying emission factor data. Crown Copyright (C) 2013 Published by Elsevier Ltd. All rights reserved.
  • Authors:
    • Cheng,Xiaoli
    • Yang,Yuanhe
    • Li,Ming
    • Dou,Xiaolin
    • Zhang,Quanfa
  • Source: Plant and Soil
  • Volume: 366
  • Issue: 1-2
  • Year: 2013
  • Summary: Over recent decades, a large uncultivated area has been converted to woodland and shrubland plantations to protect and restore riparian ecosystems in the Danjiangkou Reservoir area, a water source area of China's Middle Route of the South-to-North Water Transfer Project. Besides water quality, afforestation may alter soil organic carbon (SOC) dynamics and stock in terrestrial ecosystems, but its effects remain poorly quantified and understood. We investigated soil organic C and nitrogen (N) content, and delta C-13 and delta N-15 values of organic soil in plant root-spheres and open areas in an afforested, shrubland and adjacent cropped soil. Soil C and N recalcitrance indexes (RIC and RIN) were calculated as the ratio of unhydrolyzable C and N to total C and N. Afforestation significantly increased SOC levels in plant root-spheres with the largest accumulation of C in the afforested soil. Afforestation also increased belowground biomass. The C:N ratios in organic soil changed from low to high in the order the cropped, the shrubland and the afforested soil. The RIC in the afforested and shrubland were higher than that in cropped soil, but the RIN increased from the afforested to shrubland to cropped soil. The delta N-15 values of the organic soil was enriched from the afforested to shrubland to cropped soil, indicating an increased N loss from the cropped soil compared to afforested or shrubland soil. Changes in the delta C-13 ratio further revealed that the decay rate of C in the three land use types was the highest in the cropped soil. Afforestation increased the SOC stocks resulted from a combination of large C input from belowground and low C losses because of decreasing soil C decomposition. Shifts in vegetation due to land use change could alter both the quantity and quality of the soil C and thus, have potential effects on ecosystem function and recovery.