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«International 17 Workshop th Nitrogen The was jointly organised by Teagasc and AFBI Printed by Print Depot Suggested citation Authors, 2012. Title ...»

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Figure 2. Values of NH3 fluxes estimated and measured in Landriano during and after slurry spreading; the values in the first 6 and half hours are estimated by the presented model as lower and upper limits.

Moreover, the operational relationship between ln(Γs) and hours after slurry application is shown.

4. Conclusion Considering that the model worked well in one site (Cornaredo), we applied it in another site (Landriano) where the first flux data were not available, showing that it is an useful tool for estimating the missing NH3 fluxes during the first hours after slurry spreading, which is the dominant period for NH3 volatilization.

References Dasgupta P.K. and Dong S. 1986. Solubility of ammonia in liguid water and generation of trace levels of standard gaseous ammonia. Atmos. Environ. 20, 565-570.

Flechard C.R., Spirig C., Neftel A. and Ammann C. 2010. The annual ammonia budget of fertilised cut grassland – Part 2: seasonal variation an dcompensation point modling. Biosciences 7, 537-556.

Flesch, T., Wilson, J.D. and Yee, E., 1995. Backward-time Lagrangian stochastic dispersion models, and their application to estimate gaseous emissions. J. Appl. Meteor. 34, 1320-1332.

Kaimal J.C. and Finnigan J.J. 1994. Atmospheric Boundary Layer Flows: Their Structure and Measurement. Oxford University Press, 289 pp.

Spirig C., Flechard C.R., Ammann C. and Neftel A. 2010. The annual ammonia budget of fertilised cut grassland – Part 1: micrometetorological flux measurements and emissions after slurry application. Biogeosciences 7, 521-536.

Sutton M.A., Miners B., Tang Y.S., Milford C., Wyers G.P., Duyzer J.H. and Fowler D. 2001. Comparison of low-cost measurement techniques for long-term monitoring of atmospheric ammonia. J. Env. Monit. 3, 446-453.

Sutton, M.A., Burkhardt J., Guerin D., Nemitz E. and Fowler D. 1998. Development of resistance models to describe measurements of bi-directional ammonia surface atmosphere exchange. Atmos. Environ. 32(3), 473-480.

Zahniser M.S., Nelson D.D., McManus J.B., Shorter J.H., Herndon S. and Jimenez R. 2005. Development of a Quantum Cascade Laser-Based Detector for Ammonia and Nitric Acid. Final Report, U.S. Department of Energy, SBIR Phase II, Grant No. DE-FG02-01ER83139.

Nitrogen Workshop 2012 Generation of N-balances to describe N-flows and N-transformations -The example of composting Körner, I.

Hamburg University of Technology, Institute of Waste Water Management and Water Protection, Bioconversion and Emission Control Group, Hamburg, Germany

1. Background & Objectives The global N-household involves of a multitude of reactions and N containing compounds transform permanently from one form into another. In composting many of the globally important reactions are taking place as well – ammonification, nitrification, denitrification and Nimmobilisation – and connections to other spheres exist via N-releases by leaching and off-gas evolution (Körner, 2008). In the literature few articles present N-balances and those that do mostly only consider in- and output and without a time dependent series. The objective of this paper is to show, that it is possible to generate N-balance-series accurate enough to describe processes of Ndynamics. Guidelines to generate such balances shall be given and the limitations shown.

2. Materials & Methods 53 composting experiments were carried out using 100 litres reactors and a broad range of substrates as well as process control variants. N-compounds were determined at different phases of composting – organic N, NH4+/ NH3, NO3-, NO2- in the substrate and in the leachate as well as N2, NH3, N2O and partly NO in the off-gas. The milieu and process conditions (temperature, pH, water content, aeration rate, turning rhythm) were registered as well. In total 708 N-balances were calculated using the various N-concentrations and the respective masses of substrates, leachates and off-gases. Additionally, the N-losses due to sampling were considered (Figure 1). A statistical evaluation of all N-balances was carried out to conclude about the N-flows and N-transformations.

To judge accuracy of the balances, all measurements were quantitatively evaluated regarding systemic uncertainties and mathematically summarized to an overall uncertainty. An extended uncertainty analyses was carried out to judge different substrates. All methods are documented in Körner (2008).

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Knowing the accuracy of the balances is essential for correct conclusions. Systemic uncertainties were determined with ±10%. Additionally the sample had an impact. In early phases of composting the total uncertainties summarized to ±15-25%, for very inhomogeneous substrates even up to ±85%. In later phases the homogeneity increased and uncertainty was between ±15-25% (Figure 2).

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Figure 2. N-balance-series of composting processes: Left) Balance with high accuracy; Right) Balance with lower accuracy and a lack due to compounds not measured quantitatively (dm -0: initial dry-matter content)

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References Körner, I. 2008. Stickstoffhaushalt bei der Kompostierung: Bilanzen, Gehalte, Umsetzungs- und Austragsprozesse.

Habilitation, Hamburg University of Technology; Verlag Abfall aktuell, ISBN 978-3-9812867-0-0 Nitrogen Workshop 2012 Impact of point injection of ammonium fertilizer on nitrous oxide fluxes and nitrogen dynamics in soil Deppe, Ma, Well, R.a, Kücke, M.b, Flessa, H.a a Institute of Agricultural Climate Research, Johann Heinrich von Thünen-Institut, Federal Research Institute for Rural Areas, Forestry and Fisheries, Braunschweig, Germany b Institute of Crop and Soil Science, Julius Kühn-Institut, Federal Research Centre for Cultivated Plants, Braunschweig, Germany

1. Background & Objectives Nitrogen fertilization can have an important impact on the amount of N2O produced and emitted.

Injection of nitrogen fertilizer has been widely used, but measured effects on N2O emission are contradictory (Millar et al., 2010). High concentrations of ammonium are known to inhibit nitrification (Wetselaar et al., 1972); however, it has not yet been clarified how N2O production is affected. Injection of nitrate-free ammonium-N fertilizer, in Germany also known as CULTAN (controlled uptake long-term ammonia nutrition), is supposed to inhibit nitrification of NH4fertilizer, leading to lower rates of nitrate leaching and lower rates of N2O emission. To test this assumption, emission rates of N2O are measured in two arable soils in Northern Germany with different textures (loamy sand and clay loam) cropped with winter wheat to compare two application methods (point injection and surface application) of nitrogen fertilizer.

2. Materials & Methods Ammonium sulphate (130 kg N ha-1) was applied either by point injection (24 x 17 cm grid) or by broadcast/surface application. Unfertilized plots serve as control. N2O emissions are measured weekly using static chambers (closure time was approx. 1h). Nitrate and ammonium concentrations at injection spots and in bulk soil are measured at least biweekly in soil extracts (1M KCl, segmented flow analyser) to monitor nitrogen dynamics. Measurements started in February 2011 and will end in winter 2012/2013. At the loamy sand site, 5% 15N-ammonium sulphate is used as a tracer to distinguish between fertilizer-N and soil-N derived N2O.

3. Results & Discussion NH4+ -N from point injection was largely depleted within 6 (loamy sand) and 10 (clay loam) weeks after fertilization in 2011. Surface application led to longer periods with high ammonium content in soil, and nitrate concentrations at both sites were always higher compared to plots with point injection. Emission rates of N2O were low at both sites in 2011. During spring, when the soil was relatively dry, N2O emissions only occurred at single times, leading to high standard deviations of calculated fluxes. These emission events mostly occurred after fertilization, precipitation and/or tillage (Figure 1) and accounted for most of the total N2O lost. Apart from these single events, flux measurements were generally near the limits of detection during the measuring period. There was no significant effect of point injection on total N2O emissions. Higher emissions from the clay loam site were the result of one plot (n=3) with extremely high rates at single dates; at the sandy loam site, emissions from injection plots were slightly lower than from plots with surface application (Figure 2). Fertilizer derived N2O fluxes were calculated from δ15N in gas samples taken between fertilization and harvest in 2011. Integrated over this period, fertilizer derived N2O contributed about one third to total N2O emissions. However, whereas N2O fluxes derived from chamber concentrations were often close to the detection limit, fluxes estimated from δ15N of N2O from the tracer experiment could always be calculated and therefore provided improved precision at low emission rates.

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4. Conclusion Point injection of ammonium sulphate led to lower nitrate content in soils compared to surface application. Due to the low N2O fluxes of all treatments, no significant impact of the fertilizer application technique on total N2O emission could be detected.

References Wetselaar, R., Singh, B. R. and Passioura, J. B. 1972. Consequences of Banding Nitrogen Fertilizer in Soil. 1. Effects on Nitrification. Plant and Soil 36(1), 159-175.

Millar, N., Robertson, G. P., Grace, P. R., Gehl, R. J. and Hoben, J. P. 2010. Nitrogen fertilizer management for nitrous oxide N2O mitigation in intensive corn (Maize) production: an emissions reduction protocol for US Midwest agriculture. Mitigation and Adaptation Strategies for Global Change 15(4), 411-411

Nitrogen Workshop 2012

Impact of quality of residue mulches and their decomposition on N dynamics in soil in conservation agriculture Iqbal, A.a, Recous, S.a, Aslam, S.b, Alavoine, G.a, Benoit, P.b, Garnier, P.b a INRA, UMR Fractionnement des AgroRessources et Environnement, F-51000 Reims, France b INRA, UMR Environnement et Grandes Cultures, F-78500 Thiverval-Grignon, France

1. Background & Objectives Improving crop rotations, reducing or suppressing soil tillage, and maintaining a mulch of crop residues at the soil surface are gaining popularity throughout the world. But the impacts of these practices and of their combination on soil processes are not well understood. The general objective of the work was to study, for different crop associations and pedo-climatic conditions in temperate (France) and tropical (Madagascar and Brazil) agrosystems under conservation agriculture, the effects of residue mulch characteristics on their decomposition, N mineralization-immobilization, N transport in soil and N2O emissions. And to assess, by modeling, how these factors affect agroecosystem services in a range of agricultural conditions met in conservation agriculture of France, Brazil and Madagascar. The hypotheses were that the chemical quality of mulches at the soil surface significantly affects the water exchange between soil, mulch and the atmosphere, the dynamics of mulch decomposition and the N fluxes in soil and to the atmosphere (Figure 1).

This work is part of a larger project on conservation agriculture (PEPITES, ANR SYSTERRA) which brings together researchers and stakeholders, working on social processes, technical innovation and ecological processes, particularly those linking organic matter and soil biological functioning.

Figure 2. Experimental design for the soil columns CO2, N20 emissions

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2. Materials & Methods A series of experiments were performed under controlled conditions with repacked soil columns,

15.4 cm wide x 30 cm deep (Figure 2). The treatments were two mulch types, a mixture of Zea mais & Doliquos lablab and Triticum aestivum & Medicago sativa, two soil types (sandy or loamy soils) and two water regimes (manipulated through the intensity and frequency of rain applied with a rain simulator to the columns). Amended columns were incubated for 84 days at 20°C. CO2 and N2O were continuously measured by infrared photoacoustic spectroscopy. Mulch C and N (by total combustion), Soil microbial biomass C (fumigation-extraction) and mineral N (KCL extraction)

Nitrogen Workshop 2012

were measured through destructive sampling at 0, 14, 41 and 84 days. The Pastis_Mulch model (Findeling et al., 2007) was tested and used to calculate fluxes that are not measureable (gross mineralization and immobilization, nitrate and soluble C leaching) and to extrapolate the longer term fate of C and N.

3. Results & Discussion The results show significant differences between the two mulches in term of C mineralization (Figure 3a), net N mineralization (data not shown) and N2O emissions, due to the difference in the chemical composition of the plant residues (data not shown). The CO2 evolved with M+D mulch was much higher for the loamy soil compared to the sandy soil (Figure 3b), due to the difference in C mineralization of the two soils. Conversely, the decomposition of the mulch was not influenced by the type of soil, under the controlled conditions of the experiment (data not shown). The emission of N2O was nil during the decomposition of the M+D mulch on the sandy soil, while N2O emission was observed during the first two days of mulch incubation with the loamy soil. The maximal rate was 110 mg N2O m-2 day-1 at 20°C. The simulation with Pastis model confirmed the importance of water dynamics in controlling the decomposition rates and the fate of C into the soils, while the chemical quality of mulches is less crucial when the system is controlled by moisture.

Figure 3a,b: C-CO2 emission during decomposition of wheat+alfafa mulch (W+A) and maize+dolichos mulch (M+D) on loamy soil (left) and comparison of sandy and loamy soil with decomposing M+D mulch (right). Peaks correspond to application of rain on columns.

Acknowledgements This work is supported by the French ANR Systerra program (2009-2012) de Tourdonnet S., Triomphe B., Scopel E. et al. Processus Ecologiques et Processus d’Innovation Technique et Sociale en agriculture de conservation (PEPITES) and by INRA.

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