• Authors:
    • Lugnot, M.
    • Decuq, C.
    • Garnier, J.
    • Vilain, G.
  • Source: Nutrient Cycling In Agroecosystems
  • Volume: 98
  • Issue: 2
  • Year: 2014
  • Summary: Nitrous oxide is produced in soils and sediments essentially through the processes of nitrification and denitrification, although several rival processes could be competing. This study was undertaken in order to better understand the controlling factors of nitrification, denitrification and associated N2O production as well as the contribution of these two processes to the average N2O production by soils and sediments. With this aim, soil and sediment samples were taken in contrasting periods and different land use types, each time at different depths (upper and lower soil horizons). They were incubated in separate batches in specific conditions to promote denitrification and nitrification: (1) a complete anaerobic environment adding KNO3 for the denitrification assay and (2) an aerobic environment (21 % O-2) with addition of NH4Cl for the nitrification assay. Potentials of nitrification and denitrification were determined by the rates of nitrate either reduced (for denitrification) or produced (for nitrification). Overall, denitrification potential varied from 70 to 2,540 ng NO (3) (-) -N g(-1) dry soil h(-1) and nitrification potential from 30 to 1,150 ng NO3 (-)-N g(-1) dry soil h(-1). Nitrous oxide production by denitrification was significantly (P < 0.05) greater in topsoils (10-30 cm) than in subsoils (90-110 cm), ranging, respectively, from 26 to 250 ng N2O-N g(-1) dry soil h(-1) versus 1.5 to 31 ng N2O-N g(-1) dry soil h(-1), i.e., a mean 19.5 versus. 6.0 % of the NO3 (-) denitrified for the upper and lower horizons, respectively. Considering the N2O production in relation with the nitrate production (e.g., nitrification), no significant difference (P < 0.05) was found in the soil profile, which ranged from 0.03 to 6 ng N2O-N g(-1) dry soil h(-1). This production accounts for 0.21 and 0.16 % of the mean of the NO3 (-) produced for the top and subsoils, respectively. On the basis of the average production by both top- and subsoils, N2O production by denitrification is clearly greater than by nitrification under the measurement conditions used in this study, from 30- to 100-fold higher. Such a high potential of N2O emission must be taken into account when reducing nitrate contamination by increasing denitrification is planned as a curative measure, e.g. in rehabilitation/construction of wetlands.
  • Authors:
    • Hoeppner, F.
    • Fuss, R.
    • Wolf, U.
    • Flessa, H.
  • Source: Nutrient Cycling in Agroecosystems
  • Volume: 100
  • Issue: 1
  • Year: 2014
  • Summary: Fertilization with biogas residues from the digestion of energy crops is of growing importance. Digestate from silage maize (Zea mays L.) is a new fertilizer with a high potential for ammonia (NH3) and nitrous oxide (N2O) emission. The aim of this study was to determine the effect of different maize fertilization systems [180 kg N ha(-1) in form of calcium nitrate (MIN), biogas digestate from maize (DIG) and biogas digestate from maize mixed with the nitrification inhibitor Piadin (DIG + NI)] on the emission of NH3 and N2O from a sandy soil and to assess the total greenhouse gas emission of these fertilization systems. The study is based on a randomized field plot experiment in central Germany and an experimental period of a full year. Annual N2O-N emission was generally low [0.21 (MIN) to 0.37 (DIG) kg N ha(-1)] without differences between treatments. The application of Piadin reduced N2O emissions by 37 and 62 % during the weeks following digestate application but the annual N2O emission was not affected by the fertilization treatment. NH3 emission was only significant for treatments fertilized with digestate. It was not affected by Piadin and accounted for 27 % (+NI) and 29 % of the applied ammonium. Total greenhouse gas emission was dominated by NH3 losses (reducing the fertilizer value and inducing indirect N2O emissions) for the treatments fertilized with maize digestate. The most important greenhouse gas emission source of the MIN treatment were emissions from fertilizer production. Our results show the high potential of digestate from maize as a new source of NH3 emission. Mitigation measures are essential to save the value of this new fertilizer type and to reduce atmospheric and environmental pollution by direct emission of NH3 and indirect emission of greenhouse gases.
  • Authors:
    • Aoun,W. B.
    • El-Akkari,M.
    • Gabrielle,B.
    • Flenet,F.
  • Source: Proceedings of the 9th International Conference on Life Cycle Assessment in the Agri-Food Sector
  • Year: 2014
  • Summary: Nitrogen fertilization practices have a significant effect on the LCA results of biodiesel chains, which warrants reliable inventory data. In this study focused on the Lorraine region (eastern France), we established a typology of oilseed rape fields based on fertilization practices, and used the agro-ecosystem model CERES-EGC in lieu of generic emission factors to simulate the productivity and externalities associated with oilseed farming. The results were subsequently used to generate an LCA of biodiesel from oilseed rape. We also tested the effect of improved practices on the LCA results. In Lorraine, oilseed rape crops appeared to be frequently over fertilized compared to best management practices. Switching to improved practices with optimal fertilization has a potential to reduce the GWP of 1 megajoule of biodiesel by around 6 gr CO 2eq, against a total life-cycle of 43.9 gr CO 2eq.
  • Authors:
    • Escobar,N.
    • Ribal,F. J.
    • Clemente,G.
    • Sanjuan,N.
  • Source: Proceedings of the 9th International Conference on Life Cycle Assessment in the Agri-Food Sector
  • Year: 2014
  • Summary: Imported biodiesel has accounted for a large share of the total amount consumed in Spain, the main supplier of which was Argentina at least until anti-dumping duties on biodiesel imports from this origin were approved by the European Commission in November 2013. A consequential LCA is carried out in the present study to compare this pathway, which was the prevailing one until almost 2014, with the alternative of using domestic biodiesel from Used Cooking Oil (UCO). System expansion is performed in order to take the indirect functions of both systems into account, functions arising from interactions between co-products (protein meals) in the animal feed market. The marginal suppliers of these co-products in the international market are identified and emissions from direct and indirect Land Use Change (LUC) are calculated. When they are not considered, imported soybean biodiesel leads to lower GHG emissions, due to the carbon uptake by biomass. However, when global LUC is taken into account, UCO biodiesel generates a much lower impact, because it causes a contraction in the area diverted to biofuel feedstock production in other parts of the world. The results underline the importance of considering emissions from LUC when comparing biodiesel alternatives and, thus, interactions in the global market must be addressed.
  • Authors:
    • Vazquez-Rowe,I.
    • Villanueva-Rey,P.
    • Otero,M.
    • Moreira,M. T.
    • Feijoo,G.
  • Source: Proceedings of the 9th International Conference on Life Cycle Assessment in the Agri-Food Sector (LCA Food 2014)
  • Year: 2014
  • Summary: Land use changes (LUCs) are an important source of environmental changes in production systems, especially in the agricultural sector, where LUCs have been found to be a relevant factor to take into consideration when analyzing greenhouse gas (GHG) emissions. The viticulture subsector, as part of a broader agricultural sector, is not alien to the problematic of GHG emissions and climate change. Spain, as one of the main producers of wine worldwide, but also due to the important legislative and productive changes that have occurred ever since it joined the European Union, plays an important role in the analysis of how LUCs linked to the viticulture sector have effects on the environment. Therefore, in the current study we examined the LUCs that have occurred in the Ribeiro appellation in NW Spain between 1989 and 2009. For this, GIS was used to map the gradual dynamic changes on an annual basis of the areas used for wine production. Thereafter, the different land uses that substituted or were substituted by vineyards were identified in order to calculate the carbon storage and carbon emission dynamics based on the IPCC guidelines. Finally, operational activities linked to viticulture, including changes in technology over time, were added to the model in order to obtain a broad picture of entire impact of viticulture in terms of GHG emissions. The results present an interesting pattern, with GHG emissions linked to LUCs steadily decreasing in the timeframe analyzed. Similarly, the improvement of machinery, the reduction on fossil dependency in the Spanish electricity mix and the stricter use of specific standards for the use of plant protection agents also contributed to a gradual decrease in GHG emissions per functional unit (i.e. 1 ha of cultivated vineyards). These results are aimed at providing the appellation and other appellations throughout with environmentally relevant information regarding how different factors influencing their change through time can be analyzed to give support in policy making and decision making at a business level.
  • Authors:
    • Stamatiadis,S.
    • Evangelou,L.
    • Yvin,J. -C
    • Tsadilas,C.
    • Mina,J. M. G.
    • Cruz,F.
  • Source: Journal of Applied Psychology
  • Volume: 27
  • Issue: 1
  • Year: 2014
  • Summary: A greenhouse experiment was conducted to evaluate the effects of foliar application of an Ascophyllum nodosum seaweed extract (AZAL5) on the growth, nutrient uptake, and yield of winter wheat in a surface soil of the Thessaly Plain classified as TypicXerorthent. Twelve treatment combinations in a randomized complete block design with a factorial arrangement were composed of two rates of inorganic fertilizer (0 and 50 ppm N), three rates of AZAL5 (0, 1.5, and 3 % diluted extract), and two levels of water supply (75 and 45 % of field capacity). Under soil P and K sufficiency, the addition of fertilizer N greatly increased grain yield and nutrient uptake in the shoots (N and K) and grain (N, P, and K). Reduced water supply decreased grain yield and caused water stress as evidenced by decreased Δ13C in the N-deficient treatments and decreased nutrient uptake. AZAL5 application caused increased grain K uptake and a 25 % increase in yield only when mineral N was added. Differences in the efficacy of the two AZAL5 concentrations indicated that optimal dilution ratios were directly or indirectly dependent on soil water content. Complex interaction effects between AZAL5 and water supply on grain Δ13C could not be explained by conventional physiological response to water stress. The lack of biomass, nutrient content, and Δ13C differences between AZAL5 and control treatments in the shoot indicated that the reproductive organs of wheat were the main site of biostimulant action. Overall, the results underline the potential of this product to enhance the effectiveness of inorganic N fertilizers in intensively managed cropping systems under optimal irrigation, deficit irrigation, or rainfed conditions. © 2014, Springer Science+Business Media Dordrecht.
  • Authors:
    • Goge,Fabien
    • Gomez,Cecile
    • Jolivet,Claudy
    • Joffre,Richard
  • Source: Geoderma
  • Volume: 213
  • Year: 2014
  • Summary: Numerous studies on the prediction of soil properties from visible and near-infrared spectroscopy, based on large libraries at county scale or small size soil libraries at local scales have been reported in literature. However, difficulties appear when large libraries are used to estimate the soil properties of a small area. The aim of this paper was to compare various strategies to predict soil properties of local samples using a French national database. Models were built: i) from the national database alone and ii) from the national database spiked with subsets of the local database. Two regression methods were tested: partial least square [PLS] and a local regression method (fast Fourier transform local weighted [FFT-LW]). No general rule was obtained in this study as the best strategy differed according to the property under study. It seems that when strong spectral features are related to the characteristic under study (as for CaCO3 content), the addition of local samples did not bring a decisive advantage over calibration based on a wide national database. There are three important and encouraging points of this work to emphasize: i) the evidence of the added value brought by the national library for the prediction of some soil properties over a local area, ii) the pertinence of spiking with local samples to the global database to reach accurate predictions, and iii) the interest of the FFT-LW non-linear method. As we examined only one local site with peculiar land-use and geologic characteristics, further researches are needed to elucidate the way in which these results depend on intrinsic properties of the local site samples and on the relationship between spectral features and considered soil properties. (C) 2013 Elsevier B.V. All rights reserved.
  • Authors:
    • Hardie,Marcus
    • Clothier,Brent
    • Bound,Sally
    • Oliver,Garth
    • Close,Dugald
  • Source: Plant and Soil
  • Volume: 376
  • Issue: 1-2
  • Year: 2014
  • Summary: This study aims to (i) determine the effects of incorporating 47 Mg ha(-1) acacia green waste biochar on soil physical properties and water relations, and (ii) to explore the different mechanisms by which biochar influences soil porosity. The pore size distribution of the biochar was determined by scanning electron microscope and mercury porosimetry. Soil physical properties and water relations were determined by in situ tension infiltrometers, desorption and evaporative flux on intact cores, pressure chamber analysis at -1,500 kPa, and wet aggregate sieving. Thirty months after incorporation, biochar application had no significant effect on soil moisture content, drainable porosity between -1.0 and -10 kPa, field capacity, plant available water capacity, the van Genuchten soil water retention parameters, aggregate stability, nor the permanent wilting point. However, the biochar-amended soil had significantly higher near-saturated hydraulic conductivity, soil water content at -0.1 kPa, and significantly lower bulk density than the unamended control. Differences were attributed to the formation of large macropores (> 1,200 mu m) resulting from greater earthworm burrowing in the biochar-amended soil. We found no evidence to suggest application of biochar influenced soil porosity by either direct pore contribution, creation of accommodation pores, or improved aggregate stability.
  • 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:
    • Wiaux,F.
    • Cornelis,J. -T
    • Cao,W.
    • Vanclooster,M.
    • Van Oost,K.
  • Source: Geoderma
  • Volume: 216
  • Year: 2014
  • Summary: At the scale of hillslopes, a detailed mechanistic understanding of the processes controlling OC stabilization is still lacking. Here, we aimed to study the impact of geomorphic and pedogenic processes on the distribution of OC quality (ability of OC to release carbon dioxide through metabolic pathways) along an agricultural hillslope in the Belgian loess belt We collected soil cores at four topographic positions along the hillslope (summit convex shoulder, backslope and footslope). We assessed (i) cumulative soil erosion using diagnostic soil horizons and the Cs-137 techniques, (ii) OC stocks and its quality (NaOCl-resistant OC), and (iii) reactive soil mineral phases (concentration of Fe, Al and Si in specific oxalate and dithionite-citrate-bicarbonate extractants). Our results show that ongoing erosion has resulted in a small amount of reactive soil phases (e.g. Fe and Al-oxyhydroxides) in the upper first meter of the most eroded soil profile (backslope position). The erosion observations show that this is related to the truncation and rejuvenation of the backslope soil profile by bringing unweathered and calcareous loess to the soil surface. As a consequence, the potential of soil to stabilize OC by molecular interactions with soil minerals is substantially reduced by erosion when calcareous loess is reached. This was supported by the observed amount of mineral-protected OC (using NaOCl-resistant OC as an indicator) which was significantly lower at the eroded midslope than at the other slope positions. The combined effect of geomorphic and pedogenic processes thus strongly impacts the distribution of soil OC quality along the hillslope. We observed a spatial differentiation of the labile OC pool (i.e. the OC not resistant to NaOCl) along the hillslope with a significant enrichment at the depositional site. The labile OC pool contributed 64 +/- 5%, 69 +/- 5%, 40 +/- 22% and 49 +/- 6% of total OC at the footslope, backslope, convex shoulder and summit, respectively. Despite the fact that a part of this high labile OC stock at the footslope (5.8 +/- 0.2 kg OC m(-2)) can be protected from microbial degradation due to specific environmental conditions, our results suggest that a large part of this depositional OC stock has a high potential for mineralization given its quality. (C) 2013 Elsevier B.V. All rights reserved.