• Authors:
    • Vrieling, A.
    • Tubiello, F. N.
    • Velde, M. van der
    • Bouraoui, F.
  • Source: Climatic Change
  • Volume: 113
  • Issue: 3-4
  • Year: 2012
  • Summary: Extreme weather conditions can strongly affect agricultural production, with negative impacts that can at times be detected at regional scales. In France, crop yields were greatly influenced by drought and heat stress in 2003 and by extremely wet conditions in 2007. Reported regional maize and wheat yields where historically low in 2003; in 2007 wheat yields were lower and maize yields higher than long-term averages. An analysis with a spatial version (10 x 10 km) of the EPIC crop model was tested with regards to regional crop yield anomalies of wheat and maize resulting from extreme weather events in France in 2003 and 2007, by comparing simulated results against reported regional crops statistics, as well as using remotely sensed soil moisture data. Causal relations between soil moisture and crop yields were specifically analyzed. Remotely sensed (AMSR-E) JJA soil moisture correlated significantly with reported regional crop yield for 2002-2007. The spatial correlation between JJA soil moisture and wheat yield anomalies was positive in dry 2003 and negative in wet 2007. Biweekly soil moisture data correlated positively with wheat yield anomalies from the first half of June until the second half of July in 2003. In 2007, the relation was negative the first half of June until the second half of August. EPIC reproduced observed soil dynamics well, and it reproduced the negative wheat and maize yield anomalies of the 2003 heat wave and drought, as well as the positive maize yield anomalies in wet 2007. However, it did not reproduce the negative wheat yield anomalies due to excessive rains and wetness in 2007. Results indicated that EPIC, in line with other crop models widely used at regional level in climate change studies, is capable of capturing the negative impacts of droughts on crop yields, while it fails to reproduce negative impacts of heavy rain and excessively wet conditions on wheat yield, due to poor representations of critical factors affecting plant growth and management. Given that extreme weather events are expected to increase in frequency and perhaps severity in coming decades, improved model representation of crop damage due to extreme events is warranted in order to better quantify future climate change impacts and inform appropriate adaptation responses.
  • 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:
    • 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:
    • Oehler, F.
    • Ferchaud, F.
    • Durand, P.
    • Salmon-Monviola, J.
    • Sorel, L.
  • Source: Computers and Electronics in Agriculture
  • Volume: 81
  • Issue: February
  • Year: 2012
  • Summary: Assessing the environmental impacts of agricultural practices at the catchment scale increasingly involves the use of spatially distributed models that include cropping systems as input. Use of these models for diagnosis and evaluation requires large datasets at large spatial and temporal scales. The description of spatial dynamics of cropping systems at a fine resolution (i.e. field level) is particularly needed. As these data are scarce or not available, our objective was to propose a model that first reconstructs spatial dynamics of past cropping systems from available data, and second constructs alternative spatial cropping systems, corresponding to agricultural practice scenarios. Classification systems for farms and fertilisation practices were defined to classify farm-level organisation for crop-succession and crop management strategies, in particular nitrogen fertilisation. Winter cover crops and multiple strategies per crop at the farm level can be represented with this model. Cropping systems are modelled in three steps: we modelled crop cover succession in summer with Markov chains based on empirical data and in winter with rules based on expert agronomic knowledge: lastly a Knapsack-based algorithm was used to allocate a crop management system to fields with constraints on several crop management strategies per crop type. Results of a case study performed on the Fremeur catchment (western France) show that this model respects the main constraints for cropping system modelling to assess agricultural practices at the catchment scale. From a scenario discussed with stakeholders and regional authorities characterised by stable areas of summer crops, the decrease in bare soil area in winter and overall reduction in total nitrogen fertilisation for different types of crops and farms we demonstrate the model's ability to simulate coherent cropping systems. Thus, if faced with a lack of data or knowledge about the local factors that drive changes in cropping systems, the model can construct the spatial dynamics of cropping systems, which can be used as input to distributed nitrate transfer models to assess agricultural practices at the catchment scale. (C) 2011 Elsevier B.V. All rights reserved.
  • Authors:
    • Devienne, S.
    • Delaby, L.
    • Durand, P.
    • Raimbault, T.
    • Mabon, F.
    • Ruiz, L.
    • Moreau, P.
    • Vertes, F.
  • Source: Agriculture Ecosystems and Environment
  • Volume: 147
  • Year: 2012
  • Summary: Integrated assessment tools are used ever more frequently for solving new environmental, social, and economic challenges related to agriculture sustainability. This is particularly relevant in ecologically vulnerable areas, where mitigation options include a complete redefinition of farming systems. This paper presents an assessment of mitigation options of a coastal agricultural watershed affected by algal proliferations (Lieue de Greve, western France). We developed a methodology based on two existing assessment approaches, an agrarian system diagnosis and an environmental assessment, to identify connections between farming systems and risky nitrogen-agricultural practices and to explore potential ways to reduce the environmental impact of farms while respecting their economic viability and technical feasibility. To understand the functioning of farming systems and calculate key indicators of economic performance, the agrarian system diagnosis combines landscape, historical, and techno-economic aspects of a farm. The environmental assessment includes (i) calculation of farm-gate nitrogen (N) budgets and N-use efficiency and (ii) use of a spatially explicit biophysical model, which simulates the effect of agricultural practices on water and N dynamics at the watershed scale and on N fluxes at the outlet. At the farm scale, the main outputs of the approach were (i) the identification of 11 farming-system types and factors influencing them in the past and present, (ii) the assessment of their techno-economic performances and (iii) for the main dairy systems, the assessment of their potential environmental impacts. Insights about the capacity of some systems to adapt to new constraints linked with environmental objectives were also brought out. Grass-based systems appeared to be the best alternative for existing farming systems since they display good economic results while limiting N emission risks. Scenarios of changes in agricultural practices at the watershed scale were tested with the biophysical model, comparing them to a reference scenario based on the continuation of current agricultural practices. The main results indicated that: (i) current water quality was in equilibrium with current agricultural practices, (ii) the response time of the watershed to changes in agricultural practices was relatively short (6-7 years) and (iii) the expansion of an agro-environmental incentive based on low-input practices and grass-based fodder proposed by local stakeholders to the whole watershed would result in a significant decrease in N fluxes but would not fulfill water-quality objectives. This integrated assessment approach demonstrated its ability to promote the emergence of mitigation solutions and to improve decision support.
  • Authors:
    • Leblanc, H. A.
    • Harmand, J.-M.
    • Fernandez, M. P.
    • Nygren, P.
  • Source: Nutrient Cycling in Agroecosystems
  • Volume: 94
  • Issue: 2-3
  • Year: 2012
  • Summary: We compiled quantitative estimates on symbiotic N-2 fixation by trees in agroforestry systems (AFS) in order to evaluate the critical environmental and management factors that affect the benefit from N-2 fixation to system N economy. The so-called "N-2-fixing tree" is a tripartite symbiotic system composed of the plant, N-2-fixing bacteria, and mycorrhizae-forming fungi. Almost 100 recognised rhizobial species associated with legumes do not form an evolutionary homologous clade and are functionally diverse. The global bacterial diversity is still unknown. Actinorrhizal symbioses in AFS remain almost unstudied. Dinitrogen fixation in AFS should be quantified using N isotopic methods or long-term system N balances. The general average +/- A standard deviation of tree dependency on N-2 fixation (%Ndfa) in 38 cases using N isotopic analyses was 59 +/- A 16.6 %. Under humid and sub-humid conditions, the percentage was higher in young (69 +/- A 10.7 %) and periodically pruned trees (63 +/- A 11.8 %) than in free-growing trees (54 +/- A 11.7 %). High variability was observed in drylands (range 10-84 %) indicating need for careful species and provenance selection in these areas. Annual N-2 fixation was the highest in improved fallow and protein bank systems, 300-650 kg [N] ha(-1). General average for 16 very variable AFS was 246 kg [N] ha(-1), which is enough for fulfilling crop N needs for sustained or increasing yield in low-input agriculture and reducing N-fertiliser use in large-scale agribusiness. Leaf litter and green mulch applications release N slowly to the soil and mostly benefit the crop through long-term soil improvement. Root and nodule turnover and N rhizodeposition from N-2-fixing trees are sources of easily available N for the crop yet they have been largely ignored in agroforestry research. There is also increasing evidence on direct N transfer from N-2-fixing trees to crops, e.g. via common mycelial networks of mycorrhizal fungi or absorption of tree root exudates by the crop. Research on the below-ground tree-crop-microbia interactions is needed for fully understanding and managing N-2 fixation in AFS.
  • Authors:
    • Maigne, E.
    • Leger, F.
    • Cahuzac, E.
    • Allaire, G.
    • Teillard, F.
    • Tichit, M.
  • Source: Agriculture Ecosystems and Environment
  • Volume: 149
  • Year: 2012
  • Summary: The objective of this study was to map agricultural intensity on the scale of France with spatial resolution adequate for policy targeting. Using the French Farm Accountancy Data Network (FADN), we computed an intensity indicator based on input costs per ha ("IC/ha"). Common variables between the FADN and four other datasets were included in a two steps multinomial regression to estimate the IC/ha value of each Small Agricultural Region ("SAR", units with homogeneous agro-ecological characteristics with mean width=22.4 km). The local indicator of spatial association was used to reveal clusters where SARs with homogeneous intensities were aggregated. We showed that the IC/ha indicator displayed a broad intensity gradient where production types were fairly evenly distributed. Multinomial regression models provided a reliable estimate of the intensity indicator (mean cross-validation error=23%, mean r2=0.7) with SAR resolution. At the scale of France and within the two intensity extremes (500 Euro/ha), SARs were significantly aggregated in several clusters. Most low-input SARs were aggregated into a large cluster ranging across several mountainous regions. Less high-input SARs were significantly aggregated. Our results could be used for infra-regional targeting of conservation policies.
  • Authors:
    • Recous, S
    • Cadoux, S.
    • Bertrand, I.
    • Amougou, N.
  • Source: GCB Bioenergy
  • Volume: 4
  • Issue: 6
  • Year: 2012
  • Summary: Energy crops are currently promoted as potential sources of alternative energy that can help mitigate the climate change caused by greenhouse gases (GHGs). The perennial crop Miscanthus x giganteus is considered promising due to its high potential for biomass production under conditions of low input. However, to assess its potential for GHG mitigation, a better quantification of the crop's contribution to soil organic matter recycling under various management systems is needed. The aim of this work was to study the effect of abscised leaves on carbon (C) and nitrogen (N) recycling in a Miscanthus plantation. The dynamics of senescent leaf fall, the rate of leaf decomposition (using a litter bag approach) and the leaf accumulation at the soil surface were tracked over two 1-year periods under field conditions in Northern France. The fallen leaves represented an average yearly input of 1.40 Mg C ha-1 and 16 kg N ha-1. The abscised leaves lost approximately 54% of their initial mass in 1 year due to decomposition; the remaining mass, accumulated as a mulch layer at the soil surface, was equivalent to 7 Mg dry matter (DM) ha-1 5 years after planting. Based on the estimated annual leaf-C recycling rate and a stabilization rate of 35% of the added C, the annual contribution of the senescent leaves to the soil C was estimated to be approximately 0.50 Mg C ha-1yr-1 or 10 Mg C ha-1 total over the 20-year lifespan of a Miscanthus crop. This finding suggested that for Miscanthus, the abscised leaves contribute more to the soil C accumulation than do the rhizomes or roots. In contrast, the recycling of the leaf N to the soil was less than for the other N fluxes, particularly for those involving the transfer of N from the tops of the plant to the rhizome.
  • Authors:
    • Zegada-Lizarazu, W.
    • Walter, K.
    • Valentine, J.
    • Djomo, S. Njakou
    • Monti, A.
    • Mander, U.
    • Lanigan, G. J.
    • Jones, M. B.
    • Hyvonen, N.
    • Freibauer, A.
    • Flessa, H.
    • Drewer, J.
    • Carter, M. S.
    • Skiba, U.
    • Hastings, A.
    • Osborne, B.
    • Don, A.
    • Zenone, T.
  • Source: GCB Bioenergy
  • Volume: 4
  • Issue: 4
  • Year: 2012
  • Summary: Bioenergy from crops is expected to make a considerable contribution to climate change mitigation. However, bioenergy is not necessarily carbon neutral because emissions of CO2, N2O and CH4 during crop production may reduce or completely counterbalance CO2 savings of the substituted fossil fuels. These greenhouse gases (GHGs) need to be included into the carbon footprint calculation of different bioenergy crops under a range of soil conditions and management practices. This review compiles existing knowledge on agronomic and environmental constraints and GHG balances of the major European bioenergy crops, although it focuses on dedicated perennial crops such as Miscanthus and short rotation coppice species. Such second-generation crops account for only 3% of the current European bioenergy production, but field data suggest they emit 40% to >99% less N2O than conventional annual crops. This is a result of lower fertilizer requirements as well as a higher N-use efficiency, due to effective N-recycling. Perennial energy crops have the potential to sequester additional carbon in soil biomass if established on former cropland (0.44 Mg soil C ha(-1) yr(-1) for poplar and willow and 0.66 Mg soil C ha(-1) yr(-1) for Miscanthus). However, there was no positive or even negative effects on the C balance if energy crops are established on former grassland. Increased bioenergy production may also result in direct and indirect land-use changes with potential high C losses when native vegetation is converted to annual crops. Although dedicated perennial energy crops have a high potential to improve the GHG balance of bioenergy production, several agronomic and economic constraints still have to be overcome.
  • Authors:
    • Coquet, Y.
    • Justes, E.
    • Benoit, P.
    • Alletto, L.
  • Source: Agriculture, Ecosystems & Environment
  • Volume: 153
  • Year: 2012
  • Summary: Water drainage and herbicide degradation and leaching were studied during four years in a continuous maize field managed with two tillage systems and two types of fallow periods. The tillage systems consisted of either a conventional practice with mouldboard ploughing (28 cm-depth) or a conservation practice with superficial tillage (