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4. Conclusion The leaching increased by 0-15 kg N ha-1 after application of slurry in autumn compared to no slurry application or application in spring with no significant difference in leaching depending on how late in autumn slurry was applied. Since the effect on leaching was significant only when application rates were higher than intended (60 kg ha-1), autumn application may be appropriate as long as rates are limited. However, more results are needed before such limits can be defined.
References Djurhuus, J. 1990. Sammenligning af nitrat i jordvand udtaget med sugkopper og ekstrahert fra jordprøver.
Landbrugsministeriet, Statens Planteavlsforsøg, Særtryk af Tidsskrift for Planteavl 94, 487-495.
EEC, 1991. Council Directive 91/676/EEC of 12 December 1991 concerning the protection of waters against pollution caused by nitrates from agricultural sources
Nitrogen Workshop 2012
Nitrogen dynamics in agricultural Mediterranean catchments vs. temperate ones: Ebro, Oglio, Seine and Scheldt comparisons Lassaletta, L.a,b, Bartoli, M.c, Billen, G.a, Garnier, J.a, Grizzetti, B.a, Romero E.a, Soana E.c, Viaroli, P.c a CNRS/UPMC, UMR 7619 Sisyphe, 4 place Jussieu, 75005 Paris, France b Department of Ecology, Universidad Complutense de Madrid, c/ José Antonio Novais 28040 Madrid, Spain c Department of Environmental Sciences, University of Parma, Viale G.P. Usberti 33/A, 43124 Parma, Italy
1. Background & Objectives Ecological processes in regions with Mediterranean climates are affected in different ways than those subject to other climatic conditions. N inputs in Mediterranean catchments have been estimated to be lower than those in temperate European catchments (Grizzetti et al., 2011) but this does not fully justify the very low N loads finally exported to the Mediterranean Sea. Romero et al.
(submitted) have recently shown how N fluxes from Mediterranean catchments to the sea are on average over two times lower than those observed in European temperate catchments. A recent study conducted in the Ebro, a characteristic Mediterranean catchment, has shown that a high proportion of all N inputs never reach the sea, and this is due to the particular management that tipyfies agricultural areas in this type of climate (Lassaletta et al., 2012). On the other hand, in the Oglio, an affluent of the Po river, Bartoli et al. (2012) have estimated one of the highest fluvial N exports observed in a river outlet. The main objective of the present work is to synthesize and compare the information on N dynamics and retention from two Mediterranean and two temperate catchments, and to identify the main discrepancies and similarities.
2. Materials & Methods Four highly monitored catchments have been chosen: two under Mediterranean climate (the Ebro and the Oglio River Basins, in Spain and Italy respectively) and two in temperate areas (the Seine and the Scheldt River Basins, in France and Belgium) (Table 1). These catchments are relatively homogeneous in terms of agricultural surface but rather heterogeneous in terms of runoff, population density and livestock uses. We performed a soil system balance (Lassaletta et al., 2012) in the agricultural areas to estimate diffuse sources. Point sources and N retention in the catchment where also estimated based on national statistics. The term “retention” is used to designate all the processes preventing nitrogen load from being transferred to the outlet of the drainage network.
This unusual high retention has been related to the intense water regulation (by means of numerous dams and channels) that characterizes Mediterranean semi-arid agricultural catchments (Lassaletta et al., 2012). The Oglio catchment represents an opposite case. Despite being located in a Mediterranean area, the runoff is the highest of the four catchments studied and this, together with the very high agricultural inputs, results in a high amount of N being exported outside the catchment. Bartoli et al. (2012) have shown, however, how the dense channel network typical of Mediterranean catchments can induce high N retentions and also high N2O emissions.
4. Conclusion Mediterranean catchments can have very high N retention percentages when the catchment is semiarid, highly regulated and has low runoff levels. Despite being located in Mediterranean areas, highly impacted catchments with high runoff values can present a behavior that is similar to that of catchments placed on temperate ecosystems. Nitrogen dynamics and some pollution-associated problems can be very different according to catchment characteristics such as climate and water regulation. Further research should address the fate of the nitrogen which is retained, in particular verify whether it is permanently lost via denitrification or temporarily accumulated in soils or in the groundwater.
References Bartoli, M., Racchetti, E., Delconte, C.A., Sacchi, E., Soana, E., Laini, A., Longhi, D. and Viaroli, P. 2012. Nitrogen balance and fate in a heavily impacted watershed (Oglio River, Northern Italy): In quest of the missing sources and sinks, Biogeosciences 9, 361-373.
Billen, G., Silvestre, M., Grizzetti, B., Leip, A., et al. C.: 2011. Nitrogen flows from European regional watersheds to coastal marine waters, in: The European Nitrogen Assessment, edited by: Sutton, M. A., et al. Cambridge University Press, New York, 271-297.
Grizzetti, B., Bouraoui, F. and Aloe, A. 2012. Changes of nitrogen and phosphorus loads to European seas. Global Change Biology 18, 769–782.
Lassaletta, L., Romero, E., Billen, G., Garnier, J., García-Gómez, H. and Rovira, J. V. 2012. Spatialized N budgets in a large agricultural Mediterranean watershed: High loading and low transfer. Biogeosciences 9, 57-70.
Romero E., Garnier J., Lassaletta L., Billen G., Le Gendre R., Riou P. and Cugier P. 2012. Large-scale patterns of river inputs in SW Europe: seasonal and interannual variations and potential eutrophication effects, Biogeochemistry, submitted.
Nitrogen Workshop 2012
Nitrogen dynamics in maize based cropping systems for biogas production Sieling, K.a, Herrmann, A.b, Wienforth, B.a, Ohl, S.c, Taube, F. b, Kage, H.a a Institute of Crop Science and Plant Breeding; Agronomy and Crop Science; Christian-Albrechts-University, Kiel, Germany b Institute of Crop Science and Plant Breeding; Grass and Forage Science/Organic Agriculture; Christian-AlbrechtsUniversity, Kiel, Germany c Institute of Agricultural Engineering; Christian-Albrechts-University, Kiel, Germany
1. Background & Objectives Biogas production has gained importance as a contribution to climate change mitigation, notably in Germany. Biogas residues (BR), which are produced in large amounts, thus should be used in a sustainable way. Anaerobic digestion was shown increase the short-term N availability (Gutser et al., 2005), but also to promote ammonia emission (Gericke, 2009). Data on the fertiliser value of BR from co-fermentation is still limited. This paper aims to investigate the N supplying potential of co-digestion residues to maize monoculture and a maize rotation in terms of N balance, methane yield, and apparent N recovery (ANR), based on a 2-year field trial conducted in northern Germany.
2. Materials & Methods A 2-year field trial (2007-2009) was established as 4-factorial randomized block design with 4 replicates at Hohenschulen experimental station (750 mm, 8.3°C; luvisol) of Kiel University.
Treatments comprised crop rotation (R1: maize monoculture, R2: maize-whole crop winter wheatItalian ryegrass as catch crop), N fertilizer type (calcium ammonium nitrate (CAN), biogas residue (Mix), pig slurry (Pig)), and N amount (maize, wheat: 0, 120, 240, 360 kg N ha-1; Ital. ryegrass: 0, 80 kg N ha-1 for each of two cuts). Each crop of R2 was grown in each year. The N balance was calculated as difference between N fertilization and crop N offtake. Specific methane yield (SMY;
lN CH4 kg-1 OM) of the CAN and Mix treatments was obtained by the Hohenheim Biogas Yield Test (Helffrich and Oechsner, 2006). The relation between N amount and methane yield, N balance and ANR was quantified by SAS 9.2 Proc NLIN assuming a ‘Linear-Plateau’ model. Function parameters were compared by a modified t-test based on Zar (2009). Total N of organic fertilizers had been corrected for NH3-N losses during application as estimated by Gericke (2009).
3. Results & Discussion Methane yield production, N offtake and N balance were not affected by N fertilizer type, while rotation showed a significant impact on N dynamics and on maize yield performance. Maize monoculture achieved a maximum methane hectare yield of 6,774 m³N CH4 ha-1 at the N rate of 122 kg N ha-1 as Mix (Figure 1a). Rotation R2 had a significantly lower yield of 5,302 m³N CH4 ha-1, which, however, required an N input of 257 kg N ha-1. The superiority in yield of R1 was due to higher dry matter yield of maize, while differences in SMY among crops were small. Higher N contents of wheat and Italian ryegrass resulted in higher N offtake of R2 compared to R1 (Figure 1b). However, R2 required a significantly higher N input to achieve its N offtake maximum, whereas for the unfertilized control, N offtake of R2 was considerably lower than for R1.
Consequently, the N balance at N input required for maximum methane yield (Nopt) was significantly lower for R1 (Figure 1c). The apparent N recovery (ANR) of R2 remained constant at values of 72% (CAN), 63% (Mix), and 70% (Pig) for N input below 250 kg N ha-1 (CAN, Pig) or 280 kg N ha-1 (Mix) (Fig. 1d), whereas it decreased nonlinearly above, resulting in similar curves for all fertilizer types. Mix applied to R2 revealed a short-term N fertilizer value below that of pig slurry, which is in accordance to the lower NH4-N content of Mix (53.0%) compared to pig slurry
Nitrogen Workshop 2012
(72.0%) and a higher NH3 volatilization (Gericke, 2009). For R1, however, Mix showed a higher fertilizer value than Pig. This might be due to different temporal characteristics of N leaching, although the total leaching loss observed over the 2-year period was similar for Mix and Pig (Svoboda, 2011). Higher mineralization of organically bound N in Mix, due to a lower C/N ratio, and non-N effects seem unlikely. Because of their high plant N availability, BR, as liquid animal manure, present a considerable risk of nitrate leaching when the amount and timing of N fertilization is not adjusted to meet crop N demand. Mitigation of nitrate leaching by growing maize in a crop rotation proved effective in case of N oversupply (Svoboda, 2011).
A B Methane yield [m3 ha-1]
Figure 1. Average annual methane yield (m³N CH4 ha-1) (a), N offtake (b), N balance (c) and apparent N recovery (ANR) (d) of crop rotations R1 (thin lines, open symbols) and R2 (bold lines, closed symbols) fertilized with varying amounts of mineral N (solid lines, circles), biogas residue (broken lines, triangles) and pig slurry (dotted lines, squares).
4. Conclusion BR provide a valuable nutrient source which can reduce GHG emissions when replacing fossil fuel based fertilizer. If properly managed, they do not increase the risk of environmental impact compared to liquid animal manure. Long-term effects need to be evaluated by model simulations.
References Gericke D. 2009. Measurement and modelling of ammonia emissions after field application of biogas slurries. Doctoral thesis, Christian-Albrechts-Universität, Kiel, German.
Gutser, R., Ebertseder, T., Weber, A., Schraml, M. and Schmidhalter U. 2005. Short-term and residual availability of nitrogen after long-term application of organic fertilizers on arable land. J. of Plant Nutrition and Soil Science 168, 439Helffrich D. and Oechsner H. 2003. The Hohenheim Biogas Yield Test. Landtechnik 58, 148-149.
Svoboda N. 2011. Auswirkung der Gärrestapplikation auf das Stickstoff-Auswaschungspotential von Anbausystemen zur Substratproduktion. Doctoral thesis, Christian-Albrechts-Universität, Kiel, Germany Zar, J.H. 2009. Biostatistical Analysis. 5th Edition, Prentice Hall, 960 p.
Nitrogen Workshop 2012
Nitrogen losses from buffer zones: interactions with soil structure and hydrological pathways Carswell, A.M.a,b, Blackwell, M.S.Aa, Bol, R.a, Chadwick, D.a, Hawkins, J.M.B.a, Johnes, P.b, Whalley, R.c a Rothamsted Research, North Wyke, Okehampton, Devon, U.K.
b University of Reading, Whiteknights, Reading, Berkshire, U.K.
c Rothamsted Research, West Common, Harpenden, Hertfordshire, U.K.
1. Background & Objectives Pollution of surface waters by agriculturally derived nutrients, especially nitrogen (N) and phosphorus (P), is well known to cause eutrophication and has implications for drinking water quality. Implementation of buffer zones, at the downslope edge of agricultural fields, to mitigate diffuse nutrient pollution of surface waters is endorsed by Defra (Department for Environment, Food and Rural Affairs), as an option to gain Entry Level Stewardship status (Defra, 2010), whereby grants are awarded for environmentally beneficial land management techniques. However, hydrological bypassing, via artificial drainage, is known to reduce the efficacy of buffer zones (Leed-Harrison et al., 1999). Installation of a permeable reactive barrier (PRB) to intercept artificial drainage flow has the potential to increase flow residence time and provide optimal conditions for nutrient capture or transformation (Schipper et al., 2010; Grimsey, 2011) within the buffer zone.
The objectives of this study are to examine two key questions (1) whether the drained buffer zone works to capture and transform different N forms; and (2) whether installation of PRBs within buffer zones can be used to intercept drainage flow and encourage full denitrification of potential surface water pollutants. The application and examination of the efficiency of PRBs in conjunction with a buffer zone in a drained intensive grassland makes this work innovative, especially with regard to the replication and large scale at which investigations are being carried out (see below).
2. Materials & Methods The study site is the North Wyke Buffer Zone Experiment, Rothamsted Research, Devon, England.