11. No-till in northern, western and south-western Europe: a review of problems and opportunities for crop production and the environment.

• Authors:
  • Roger-Estrade, J.
  • Basch, G.
  • Moreno, F.
  • Soane, B. D.
  • Ball, B. C.
  • Arvidsson, J.
• Source: Soil & Tillage Research
• Volume: 118
• Year: 2012
• Summary: Recent literature on no-till is reviewed with particular emphasis on research on commercial uptake and environmental concerns in northern, western and south-western Europe. Increased interest in no-till, and minimum or reduced tillage, results from changes in the economic circumstances of crop production, the opportunity to increase the area of more profitable autumn-sown crops and increased concern about environmental damage associated with soil inversion by ploughing. Highly contrasting soil and climate types within and between these regions exert a strong influence on the success of no-till. While no-till may often result in crop yields which equal or exceed those obtained after ploughing, modest reductions in yield may be tolerated if production costs are lower than with ploughing. The relative costs of fuel and herbicides have changed appreciably in recent years making no-till more attractive commercially. While effective weed control is an essential aspect of no-till, current herbicide technology may not yet fully achieve this. In northern regions no-till usually allows earlier drilling of winter-sown crops but will give lower soil temperature and higher moisture content in spring, causing delayed drilling of spring-sown crops. No-till soils have greater bulk density and bearing capacity than ploughed soils with a pronounced vertical orientation of macroporosity allowing penetration of roots and water, especially in view of the increased population of deep-burrowing earthworms. Particular care must be taken with no-till to minimise soil damage at harvest and to ensure the even distribution of crop residues prior to drilling. Reduced erosion and runoff after adoption of no-till are widely observed and are of particular importance in southwestern Europe. No-till reduces losses of phosphorus in runoff and, in some cases, reduces the loss of nitrate through leaching. Emissions of greenhouse gases CO 2 and N 2O from no-till soils are highly variable and depend on complex interactions of soil properties. Emission of CO 2 from fuel during machinery usage is always appreciably reduced with no-till. Increased soil organic carbon in surface layers of no-till soils is widely found but may not be associated with increased carbon sequestration throughout the profile. The evaluation of the relative carbon balance for no-till and ploughing depends upon complex inter-relationships between soil and climate factors which are as yet poorly understood. Adoption of no-till could be encouraged by government financial assistance in recognition of environmental benefits, although future restrictions on the use of herbicides may be a deterrent. Opportunities for further research on no-till are outlined.

12. Land-use change to bioenergy production in Europe: implications for the greenhouse gas balance and soil carbon

• 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.

13. Management effects on net ecosystem carbon and GHG budgets at European crop sites

• Authors:
  • Dejoux, J. F.
  • Aubinet, M.
  • Bernhofer, C.
  • Bodson, B.
  • Buchmann, N.
  • Carrara, A.
  • Cellier, P.
  • Di Tommasi, P.
  • Elbers, J. A.
  • Eugster, W.
  • Gruenwald, T.
  • Jacobs, C. M. J.
  • Jans, W. W. P.
  • Jones, M.
  • Kutsch, W.
  • Lanigan, G.
  • Magliulo, E.
  • Marloie, O.
  • Moors, E. J.
  • Moureaux, C.
  • Olioso, A.
  • Osborne, B.
  • Sanz, M. J.
  • Saunders, M.
  • Smith, P.
  • Soegaard, H.
  • Wattenbach, M.
  • Ceschia, E.
  • Beziat, P.
• Source: Agriculture, Ecosystems & Environment
• Volume: 139
• Issue: 3
• Year: 2010
• Summary: The greenhouse gas budgets of 15 European crop sites covering a large climatic gradient and corresponding to 41 site-years were estimated. The sites included a wide range of management practices (organic and/or mineral fertilisation, tillage or ploughing, with or without straw removal, with or without irrigation, etc.) and were cultivated with 15 representative crop species common to Europe. At all sites, carbon inputs (organic fertilisation and seeds), carbon exports (harvest or fire) and net ecosystem production (NEP), measured with the eddy covariance technique, were calculated. The variability of the different terms and their relative contributions to the net ecosystem carbon budget (NECB) were analysed for all site-years, and the effect of management on NECB was assessed. To account for greenhouse gas (GHG) fluxes that were not directly measured on site, we estimated the emissions caused by field operations (EFO) for each site using emission factors from the literature. The EFO were added to the NECB to calculate the total GHG budget (GHGB) for a range of cropping systems and management regimes. N2O emissions were calculated following the IPCC (2007) guidelines, and CH4 emissions were estimated from the literature for the rice crop site only. At the other sites, CH4 emissions/oxidation were assumed to be negligible compared to other contributions to the net GHGB. Finally, we evaluated crop efficiencies (CE) in relation to global warming potential as the ratio of C exported from the field (yield) to the total GHGB. On average, NEP was negative (-284 +/- 228 gC m(-2) year(-1)), and most cropping systems behaved as atmospheric sinks, with sink strength generally increasing with the number of days of active vegetation. The NECB was, on average, 138 +/- 239 gC m(-2) year(-1), corresponding to an annual loss of about 2.6 +/- 4.5% of the soil organic C content, but with high uncertainty. Management strongly influenced the NECB, with organic fertilisation tending to lower the ecosystem carbon budget. On average, emissions caused by fertilisers (manufacturing, packaging, transport, storage and associated N2O emissions) represented close to 76% of EFO. The operation of machinery (use and maintenance) and the use of pesticides represented 9.7 and 1.6% of EFO, respectively. On average, the NEP (through uptake of CO2) represented 88% of the negative radiative forcing, and exported C represented 88% of the positive radiative forcing of a mean total GHGB of 203 +/- 253 gC-eq m(-2) year(-1). Finally, CE differed considerably among crops and according to management practices within a single crop. Because the CE was highly variable, it is not suitable at this stage for use as an emission factor for management recommendations, and more studies are needed to assess the effects of management on crop efficiency.

14. Towards an agronomic assessment of N2O emissions: a case study for arable crops

• Authors:
  • van Groenigen, K. J.
  • van Kessel, C.
  • Oenema, O.
  • Velthof, G. L.
  • van Groenigen, J. W.
• Source: European Journal of Soil Science
• Volume: 61
• Issue: 6
• Year: 2010
• Summary: Agricultural soils are the main anthropogenic source of nitrous oxide (N2O), largely because of nitrogen (N) fertilizer use. Commonly, N2O emissions are expressed as a function of N application rate. This suggests that smaller fertilizer applications always lead to smaller N2O emissions. Here we argue that, because of global demand for agricultural products, agronomic conditions should be included when assessing N2O emissions. Expressing N2O emissions in relation to crop productivity (expressed as above-ground N uptake: "yield-scaled N2O emissions") can express the N2O efficiency of a cropping system. We show how conventional relationships between N application rate, N uptake and N2O emissions can result in minimal yield-scaled N2O emissions at intermediate fertilizer-N rates. Key findings of a meta-analysis on yield-scaled N2O emissions by non-leguminous annual crops (19 independent studies and 147 data points) revealed that yield-scaled N2O emissions were smallest (8.4 g N2O-N kg-1N uptake) at application rates of approximately 180-190 kg Nha-1 and increased sharply after that (26.8 g N2O-N kg-1 N uptake at 301 kg N ha-1). If the above-ground N surplus was equal to or smaller than zero, yield-scaled N2O emissions remained stable and relatively small. At an N surplus of 90 kg N ha-1 yield-scaled emissions increased threefold. Furthermore, a negative relation between N use efficiency and yield-scaled N2O emissions was found. Therefore, we argue that agricultural management practices to reduce N2O emissions should focus on optimizing fertilizer-N use efficiency under median rates of N input, rather than on minimizing N application rates.

15. Forest Carbon Partnership Facility - Introduction and Early Lessons -- Briefing to Guyana Civil Society

• Authors:
  • Andrasko, K.
  • Bosquet, B.
• Year: 2010

16. The European carbon balance. Part 1: fossil fuel emissions

• Authors:
  • Schulze, E. D.
  • Houwelling, S.
  • Rivier, L.
  • Friedrich, R.
  • Scholz, Y.
  • Pregger, T.
  • Levin, I.
  • Piao, S. L.
  • Peylin, P.
  • Marland, G.
  • Paris, J. D.
  • Ciais, P.
• Source: Global Change Biology
• Volume: 16
• Issue: 5
• Year: 2010
• Summary: We analyzed the magnitude, the trends and the uncertainties of fossil-fuel CO2 emissions in the European Union 25 member states (hereafter EU-25), based on emission inventories from energy-use statistics. The stability of emissions during the past decade at EU-25 scale masks decreasing trends in some regions, offset by increasing trends elsewhere. In the recent 4 years, the new Eastern EU-25 member states have experienced an increase in emissions, reversing after a decade-long decreasing trend. Mediterranean and Nordic countries have also experienced a strong acceleration in emissions. In Germany, France and United Kingdom, the stability of emissions is due to the decrease in the industry sector, offset by an increase in the transportation sector. When four different inventories models are compared, we show that the between-models uncertainty is as large as 19% of the mean for EU-25, and even bigger for individual countries. Accurate accounting for fossil CO2 emissions depends on a clear understanding of system boundaries, i.e. emitting activities included in the accounting. We found that the largest source of errors between inventories is the use of distinct systems boundaries (e.g. counting or not bunker fuels, cement manufacturing, non-energy products). Once these inconsistencies are corrected, the between-models uncertainty can be reduced down to 7% at EU-25 scale. The uncertainty of emissions at smaller spatial scales than the country scale was analyzed by comparing two emission maps based upon distinct economic and demographic activities. A number of spatial and temporal biases have been found among the two maps, indicating a significant increase in uncertainties when increasing the resolution at scales finer than ~200 km. At 100 km resolution, for example, the uncertainty of regional emissions is estimated to be 60 g C m-2 yr-1, up to 50% of the mean. The uncertainty on regional fossil-fuel CO2 fluxes to the atmosphere could be reduced by making accurate 14C measurements in atmospheric CO2, and by combining them with transport models.

17. Full accounting of the greenhouse gas (CO2, N2O, CH4) budget of nine European grassland sites

• Authors:
  • Valentini, R.
  • Tubaf, Z.
  • Sutton, M.
  • Manca, G.
  • Stefani, P.
  • Skiba, U.
  • Rees, R. M.
  • Baronti, S.
  • Raschi, A.
  • Neftel, A.
  • Nagy, Z.
  • Martin, C.
  • Kasper, G.
  • Jones, M.
  • Horvath, L.
  • Hensen, A.
  • Fuhrer, J.
  • Flechard, C.
  • Domingues, R.
  • Czobel, S.
  • Clifton-Brown, J.
  • Ceschia, E.
  • Campbell, C.
  • Amman, C.
  • Ambus, P.
  • Pilegaard, K.
  • Allard, V.
  • Soussana, J. F.
• Source: Agriculture, Ecosystems & Environment
• Volume: 121
• Issue: 1-2
• Year: 2007
• Summary: The full greenhouse gas balance of nine contrasted grassland sites covering a major climatic gradient over Europe was measured during two complete years. The sites include a wide range of management regimes (rotational grazing, continuous grazing and mowing), the three main types of managed grasslands across Europe (sown, intensive permanent and semi-natural grassland) and contrasted nitrogen fertilizer supplies. At all sites, the net ecosystem exchange (NEE) of CO2 was assessed using the eddy covariance technique. N2O emissions were monitored using various techniques (GC-cuvette systems, automated chambers and tunable diode laser) and CH4 emissions resulting from enteric fermentation of the grazing cattle were measured in situ at four sites using the SF6 tracer method. Averaged over the two measurement years, net ecosystem exchange (NEE) results show that the nine grassland plots displayed a net sink for atmospheric CO2 of -240 +/- 70 g C m(-2) year(-1) (mean confidence interval at p > 0.95). Because of organic C exports (from cut and removed herbage) being usually greater than C imports (from manure spreading), the average C storage (net biome productivity, NBP) in the grassland plots was estimated at -104 +/- 73 g cm(-2) year(-1) that is 43% of the atmospheric CO2 sink. On average of the 2 years, the grassland plots displayed annual N2O and CH4 (from enteric fermentation by grazing cattle) emissions, in CO2-C equivalents, of 14 +/- 4.7 and 32 +/- 6.8 g CO2-C equiv. m(-2) year(-1), respectively. Hence, when expressed in CO2-C equivalents, emissions of N2O and CH4 resulted in a 19% offset of the NEE sink activity. An attributed GHG balance has been calculated by subtracting from the NBP: (i) N2O and CH4 emissions occurring within the grassland plot and (ii) off-site emissions of CO2 and CH4 as a result of the digestion and enteric fermentation by cattle of the cut herbage. On average of the nine sites, the attributed GHG balance was not significantly different from zero (-85 +/- 77 g CO2-C equiv. m(-2) year(-1)).

18. Precise Soil Management as a Tool to Reduce CH4 and N2O Emissions from Agricultural Soils

• Authors:
  • Dolfing, J.
  • Rappoldt, C.
  • Hol, J. M. G.
  • Mosquera, J.
• Volume: 2010
• Year: 2007
• Summary: Soil compaction stimulates the emission of nitrous oxide (N2O) and methane (CH4) from agricultural soils. N2O and CH4 are potent greenhouse gases, with a global warming potential respectively 296 times and 23 times greater than CO2. Agricultural soils are an important source of N2O. Hence there is much interest in a systematic evaluation of management options that are available to minimize agricultural greenhouse gas emissions, in particular N2O soil emissions. One such option would be to minimize soil compaction due to the use of heavy machinery. Soil compaction in arable land is relatively general. Here we report that emissions of N2O and CH4 from an arable field where soil compaction was minimized through application of the so-called "rijpaden" (riding track) system was substantially lower than from plots where a traditional system was used. Laboratory experiments were used to underpin these observations. From these observations we developed a simple calculation model that relates N2O emission to gas filled pore space and soil respiration as input parameters. We suggest to implement the riding track system on clay rather than sand as farmers benefit from lower compaction in terms of lower risk of compaction and better accessibility of fields for work. The potential reduction of the N2O emission from arable farming in the Netherlands is estimated at ~169 ton N2O-N per year (~0.1 Mton CO2-equivalent). This calculation is based on several assumptions and would benefit from testing assumptions and monitoring effects in agricultural day to day practice.

19. Update of emissions factors for nitrous oxide from agricultural soils on the basis of measurements in the Netherlands

• Authors:
  • Zwart, K.
  • Smit, A.
  • van der Hoek, K. W.
  • Kuikman, P. J.
• Year: 2006
• Summary: Emissions of nitrous oxide (N2O) in the Netherlands are reported to the UNFCCC on the basis of a country specific methodology. In this study we have identified and anlysed the values for emission facotrs in measurement from in the Netherlands in the period 1993 - 2003. The overall averaged emission factor extracted from over 86 series of one year measurements on nitrous oxide emission from agricultural fields in the Netherlands is 1.1% and a weighed average for soil types is 1.01%. The average for mineral soils is 0.88%. The calculated emissions factors are lower than the value suggested by the IPCC for EF1 for fertilizer and animal manure of 1.25%. We recommend to use a value of 1.0% for EF1 and to use corrections of EF1 in reporting the use of fertilizers without nitrate (0.5%), for subsurface application of manure (1.5%) and for fertilizer, manure and urine on organic soils (2.0%).

20. Genetic diversity in perennial ryegrass and white clover among old Dutch grasslands as compared to cultivars and nature reserves

• Authors:
  • Van Soest, L. J. M.
  • Jansen, J.
  • Goossens, P. J.
  • Bas, N.
  • Van Treuren, R.
• Source: Molecular ecology
• Volume: 14
• Issue: 1
• Year: 2005
• Summary: To support conservation policies for old Dutch grasslands that are still in agricultural use, morphological variation and AFLP-based (amplified fragment length polymorphism-based) genetic diversity was studied in perennial ryegrass and white clover populations and compared with the diversity in reference varieties. In addition, AFLP variation was also studied in grasslands located in nature reserves. From principal component analysis (PCA), it appeared that date of ear emergence in perennial ryegrass and characters related to plant vigour in white clover were the main morphological characters separating the reference varieties from the old Dutch grassland populations, and some of the grassland populations from each other. In both species, intrapopulation variation was lower for the reference varieties. Lower heterogeneity within the reference varieties was also found in the AFLP analysis. All common AFLP's observed in old Dutch grasslands could also be found in the reference varieties and nature reserves. Only a small number of low-frequency alleles found in old Dutch grasslands were absent from the other two groups. However, band frequencies of markers could vary considerably between populations, which may have been caused by selection. Analysis of the AFLP data by PCA distinguished the majority of reference varieties from the old Dutch grasslands, and showed genetic differentiation only between some grasslands. Comparison of old Dutch grasslands with grasslands in nature reserves indicated that basically the same range of genetic variation is covered by the two groups. Our study indicates that the Netherlands harbour a more or less continuous population for major parts of the diversity of perennial ryegrass and white clover. It was concluded that no specific conservation measures are presently needed to maintain genetic diversity of perennial ryegrass and white clover occurring in old Dutch grasslands.