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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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IPCC (Intergovernmental Panel on Climate Change). 2006. In. Eggleston H. S., Buendia L., Miwa K., Ngara T., Tanabe K. (Eds.), Guidelines for National Greenhouse gas Inventories, vol. 4, Agriculture, Forestry and Other Land Use.

National Greenhouse gas Inventories Programme.

Nitrogen Workshop 2012

Nitrous oxide emissions from a clay soil after mouldboard ploughing or tine cultivation Stenberg, M.a, Kasimir Klemedtsson, Å.b, Nylinder, J.b, Weslien, P.c, Myrbeck, Å.d, Wetterlind, J.a, Rütting, T.c, Klemedtsson, L.c a SLU, Dept. of soil and environment, Precision agriculture and pedometrics, PO Box 234, SE-532 23 Skara, Sweden b University of Gothenburg, Dept. of earth sciences, PO Box 460, SE-405 30 Göteborg, Sweden c University of Gothenburg, Dept. of plant and environmental sciences, PO Box 461, SE-405 30 Göteborg, Sweden d SLU, Dept. of soil and environment, Soil and water management, PO Box 7014, SE-750 07 Uppsala, Sweden

1. Background & Objectives When calculating nitrogen (N) balances for clay soils, substantial amounts of N are found missing;

found neither in crops nor leaching losses. In these cases, losses by gaseous emissions can be suspected. Therefore, knowledge of a magnitude of nitrous oxide (N2O) emissions from Swedish clay soils is needed and also possible ways of mitigating these emissions by altering farming practice. Tillage is a management practice that may significantly influence emission rates both in the long and the short term. Depending on conditions ploughing may enhance mineralisation or deteriorate soil structure, influencing emissions. Reduced tillage may result in accumulation of N in the soil surface, which is also an emission source. Soil tillage under wet conditions can have negative effects on the soil structure, especially on clay soils (Myrbeck et al., 2012). While Wetterlind et al. (2005) found different degrees of mineral N accumulation in the soil profile between 0-90 depth; dry autumns had higher accumulation than wet. These could explain gaseous N losses from the soil in wet years as well as leaching losses. In this study we compare effects of early autumn ploughing with late ploughing as well as tine cultivation on emissions of N2O at the site described by Myrbeck et al. (2012).

2. Materials & Methods Lanna experimental farm is situated in south-west Sweden (lat. 58 21´N, long. 13 08´E) on a large agricultural plain. The soil was classified as an Uderic Haploboroll (USDA) (Bergström et al., 1994). The clay content increases with depth, 45% in 0-30 cm, 57% in 60-90 cm and 58% in the 60cm layer. Top soil pH (H2O) is 6.8. Organic carbon content is 3.4% in the top-soil and 0.6% and 0.0% in the sub-soil layers. The 1961-1990 average annual precipitation was 560 mm and annual temperature 6.1°C (Alexandersson and Eggertsson Karlström, 2001). Normally the soil is frozen during parts of the winter. The drains usually flow from November to April and for longer in some years (Larsson and Jarvis, 1999). The soil is normally unsaturated to a depth of 2.2 m and this zone is characterized by numerous cracks and biotic macro-pores.

Emissions of N2O from 3 tillage treatments; mouldboard ploughing to 20 cm depth early in September, mouldboard ploughing in November and tine cultivation to 10 cm depth twice in September, replicated in 3 blocks (9 plots in total) were determined in 3 chambers per plot by the static chamber method at the long-term soil tillage field experiment in autumn 2009 and spring

2010. A cereal crop rotation of spring sown wheat-barley-oat was grown during the experimental period and crop residues were left in the field and incorporated by tillage in all treatments. Grain yields from the crop were recorded from the start of the field experiment in 1997, described by Myrbeck et al. (2012). Soil physical characteristics in the treatments were reported by Myrbeck as well. The project continued until 2011 with measurements in chambers, in addition to a micrometeorological technique (Klemedtsson et al., 1997). Measurements in chambers were carried out at and between tillage operations during autumn, by measurements during 1 hour in 3 consecutive days at each occasion. The micrometeorological measurements were carried out

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continuously. The project was financed by The Swedish Farmers' Foundation for Agricultural Research.

3. Results & Discussion The N2O emissions were low overall and not significantly different between the tillage practices, however tine cultivation tended to give the highest emissions (Figure 1). Cumulative and average emissions were calculated for September to October, the period between early and late ploughing.

Cumulative emissions were 0.05 kg N20-N ha-1 for early ploughing, 0.03 for late and 0.48 for tine cultivation, but were not significantly different due to large variation (SD 0.05, 0.04 and 0.66 resp.).

Figure 1. N2O emissions at measurements during autumn 2009 to spring 2010.

Tillage operations represented by arrows were carried out on 23rd September, 7th and 27th October.

4. Conclusion The N2O emissions measured during the first year of the study were small and not influenced by timing of ploughing. Reduced tillage tended to give higher emissions during the first year, but not significantly different. The missing N losses were not due to N2O emissions.

References Alexandersson, H. and Eggertsson Karlström, C. 2001. Temperaturen och nederbörden i Sverige 1961-1990.

Referensnormaler - utgåva 2. Meteorologi no. 99. SMHI, Norrköping. 71 pp. (in Swedish).

Bergström, L., Jarvis, N.J. and Stenström, J. 1994. Pesticide leaching data to validate simulation models for registration purposes. J Environ Sc. Health A 29, 1073-1104.

Klemedtsson, L., Klemedtsson, Å.K., Moldan, F. and Weslien, P. 1997. Nitrous oxide emission from Swedish forest soils in relation to liming and simulated increased N-deposition. Biology and Fertility of Soils 25, 290-295.

Larsson, M.H. and Jarvis, N.J. 1999. Evaluation of a dual-porosity model to predict field scale solute transport in a macroporous soil. Journal Hydrology 215, 153-171.

Myrbeck, Å., Stenberg, M., Arvidsson, J. and Rydberg, T. 2012. Effects of autumn tillage of clay soil on mineral N content, spring cereal yield and soil structure over time. European Journal of Agronomy 37, 96-104.

Wetterlind, J., Stenberg, B., Lindén, B. and Stenberg, M. 2006. Tidig höstplöjning på lerjordar - riskbedömning av kväveutlakning. SLU, Skara. Avd. för precisionsodling. Rapport 6. (in Swedish).

Nitrogen Workshop 2012

Nitrous oxide emissions from grassland treated with different types of manure: comparison between slurry plus fertilizer plots and farmyard manure plus fertilizer plots Mori, A.a, Hojito, M.b a NARO Institute of Livestock and Grassland Science, Nasushiobara, Tochigi 329-2793, Japan b Field Science Center, School of Veterinary Medicine, Kitasato University, Towada, Aomori 034-8628, Japan.

1. Background & Objectives In Japan, approximately 660 Gg of nitrogen (N) is excreted from livestock annually, of which approximately 430 Gg is composted before application to agricultural soil. On the main island of Japan, bark or sawdust is often applied to dairy cattle excreta during the composting process to promote aerobic fermentation. As a result, the rate of N mineralization from compost after application to grassland is slower than that from fresh manure because of the persistence of organic materials in the manure. The objective of the present study is to compare the annual nitrous oxide emissions from slurry plus fertilizer plots and those from composted farmyard manure (FYM) plus fertilizer plots.

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The ratio of [cumulative N2O emission induced by N application]/[N application] in each grassgrowing period was greater with greater precipitation just after N application (Figure 2a), higher air temperature (Figure 2b) and greater soil moisture (Figure 2c) at the time of N application.

4. Conclusion The annual N2O emissions from slurry plus fertilizer plots were of similar magnitude to those from FYM plus fertilizer plots. The seasonal and interannual differences in the ratio of [N2O emission induced by N application]/[N application] in each grass-growing period were due to differences in precipitation after N application, air temperature and soil moisture status at times of N application.

However, no significant difference was observed between slurry plus fertilizer plots and FYM plus fertilizer plots.

Nitrogen Workshop 2012 Nitrous oxide emissions from two maize crop seasons in northwestern Spain Louro, A., Báez, D., García, M.I., Castro, J.

INGACAL-Centro de Investigaciones Agrarias de Mabegondo (CIAM). Apartado 10, 15080. A Coruña, Spain.

1. Background & Objectives Nitrogen (N) additions to cropland soils are the largest source of anthropogenic nitrous oxide (N2O) emissions and are an important contributor to global greenhouse gas radiative forcing. Regional estimates of fertilizer contributions to N2O emissions often utilice the IPCC methodology, which assumes that 1% of all N imputs are lost as N2O. However, due to the limited data avaliable to provide an emission factor, it does not account for differences between crop type, soil, climate.

Futher research is needed to determine the impact of best management practices on N2O emissions.

The aim of this study was to determine the effect of type of fertilizer applied to obtain N2O emissions from forage maize under the influence of humid-temperate climate typical of northwestern Spain and provide the resulting emission factors for the duration of the crop season.

2. Materials & Methods The experiment was carried out on two different sites located within at the experimental farm of CIAM (43ºN latitude, 8ºW longitude, 94 m altitude), during two growing seasons of Zea mays L.

(site 1: May-October 2008 and site 2: May-September 2009) on a silt loam soil. The mean annual temperature in the study area is 16.8 ºC and the mean annual rainfall 1088 mm (10 years average).

Experimental plots using a randomized block design with three replicates and four treatments were established in both years. The treatments were as follow: (1) no N application or control (C), (2) mineral fertilizer (M), (3) cattle slurry (CS) and (4) pig slurry (PS). A rate of 200 kg N ha-1 was applied in each fertilizer treatment: entirely distributed just before sowing in (CS) and (PS), and 125 kg N ha-1 in sowing and 75 kg N ha-1 for the top dressing in (M). Within each plot two closed chambers were placed (diameter: 25 cm; height: 36 cm; depth into the soil: 3 cm) to monitor N2O fluxes. Samples were collected in vacutainers 45-90 minutes after chamber enclosure and analyzed by a gas chromatography with an electron capture detector. In addition, soil samples, for the measurements of moisture as Water Filled Pore Space (WFPS) and mineral N, and meteorological station data were taken to see the influence of weather and soil properties on N2O fluxes.

3. Results & Discussion Both sites show (Figure 1) the first emissions peaks 20-30 days after fertilization events and rainfall. Emissions were higher under N fertilizer application than without N fertilizer but no significant effect of type of N fertilizer was observed from seeding to top dressing in M and from top dressing to harvesting in both sites (Table 1). Cumulative N2O fluxes in the first site were 40higher than the second one. This difference could be due to soil moisture content. In site 2 we found low correlations between N2O emissions and WFPS (p0.01), soil N-NH4+ (p0.01) and NN-NO3- concentrations (p0.01). Soil N-NO3- was correlated with- N-NH4+ (P0.01) and soil temperature at 10 cm depth (p0.01) This means that even though nitrate levels and soil temperature were adequate to observe higher N2O emissions, the high soil moisture content (average 97% WFPS) caused by rainfall would possibly have decrease the aerobic status of the soil, resulting in lower N2O:N2 ratios as products of the denitrification process (de Klein and van Logtestijn, 1996). The site 1 was the beginning of this study so that limited soil sampling carried out in N fertilized plots do not allow for correlations between moisture and mineral N. However it seems that values of WFPS between 60-90% (average 61%) and mineral N in soil were favorable for the N2O emission by denitrification. The resulting emission factors in both cropping seasons and

Nitrogen Workshop 2012

in all treatment studied were equal to 1.80, 2.15, 1.82% of the amount of N applied in site 1, and 1.81, 1.39, 1.44% in site 2 for M, CS and PS, respectively. Our values were in relationship with the EF reported in Rochette et al. (2004) in soils planted to maize and fertilized at a rate of 200 kg N haMineral fertilizer plots had the same EF in both sites while slurry treatments showed higher EFS in site 1 under favourable conditions for denitrification, increasing the risk of N2O emissions due to the easily available C for the denitrifying bacteria (Barton and Shipper, 2001).

Table 1. Average cumulative N2O-N emission ± standard deviation of the treatments studied in both experimental sites.

Period 1: From seading to the day before of the top dressing in M. Period 2: From the top dressing to the harvesting. C:

Control; M: Mineral fertilizer; CS: Cattle slurry; PS: Pig slurry.

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Figure 1. Nitrous oxide emission rates during the growing season of maize forage in sites 1 (a) and 2 (b). C: Control, M:

Mineral fertilizer, CS: Cattle slurry, PS: Pig slurry. Data represent means and standard deviation for emission rates (n:


4. Conclusion Our results suggest that in our climate conditions the use of pig and cattle slurries had the same impact on N2O emissions in comparison with a mineral fertilization. Soil moisture content was the main factor in the difference of the N2O emissions between sites. Emissions factors of the N fertilized treatments studied in both crop seasons were significantly higher than the reference IPCC value of 1%, especially when climatic and soil conditions were appropriate for the denitrification.

References Barton L. and Shipper L.A. 2001. Regulation of nitrous oxide emissions from soils irrigated with dairy farm effluent, Journal of Environmental Quality 30, 1881-1887.

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