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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 1(a) Temporal pattern of Nitrate-N loss by leaching for soil which did not receive N (control) or received composted olive mill pomace (COMP), sheep manure (Sheep M), commercial organic fertilisers (CPR) and NaNO3 (Inor) at (1) 1 g N pot–1 or 1000 mg N pot-1, or (2) 2 g N pot–1 or 2000 mg N pot-1. M and S, stand for soil in which the fertilisers were mixed (M) with the soil or applied to the soil surface (S) and (b) cumulative fertiliser–derived IN leaching in year 1 under natural rainfall and temperature in outdoor conditions. Values are means of 4 replicates and bars denote standard deviations. Different letters denote significant differences (P0.05).

4. Conclusion This work highlights the importance of management practices to increase the N use efficiency in agroecosystems. The lowest amount of nitrate lost by leaching was obtained after compost application (viz. less than the control), intermediate losses were found for manure, followed by commercial fertiliser applications and the highest N leaching was after inorganic fertiliser application. Overall, fertiliser–N application rate had no effect on the amount of IN leached.

There were no significant differences in the fertiliser-N availability measured through IN leaching between the two methods of fertiliser applications (viz. to the soil surface or mixed in with the soil) for inorganic and commercial fertilisers, probably because fertiliser-N was already available for both. This was not true for compost or manure, where N leaching was higher when fertilisers were mixed with the soil. Overall, organic fertilisers might be applied mixed with the soil in autumn whereas chemical and organic with high N content should be applied on early spring independently of the application method (surface or mixed).

References Maeda M., Zhao B., Ozaki Y. and Yoneyama T. 2003. Nitrate leaching in an Andisol treated with different types of fertilizers. Environmental Pollution 121, 477-487.

Nitrogen Workshop 2012 Effect of long-term conservation and conventional tillage system on N2O emissions under rainfed Mediterranean agro-ecosystem.

Téllez, A.a,García-Marco, S.a, Ábalos, D.a, Sánchez-Martín, L.a, Sanz-Cobeña, A.a, Tenorio, J.L. b and Vallejo, A.a.

a ETSI Agrónomos, Technical University of Madrid, Ciudad Universitaria, 28040 Madrid, Spain b INIA, Departamento de Medio Ambiente. Ctra de La Coruña Km. 7,5. 28040 Madrid, Spain.

1. Background & Objectives Agricultural soils are considered a source of N2O emissions. This is due to the influence of many cropping and land management practices on the soil microclimate and cycling of C and N. Tillage practices affect chemical, physical and biological soil properties, and these interactions together with climatic conditions influence the magnitude of N2O emissions (Passianoto et al., 2003; Oorts et al., 2007). Currently, there is no consensus in the literature on the differences in field N2O emissions or mitigation between conservation tillage and conventional tillage (Snyder et al., 2009).

Moreover, there is a lack of data on long-term tillage system studies, particularly in Mediterranean agro-ecosystems. The aim of this study was to evaluate the effects of long-term (17 yr) tillage systems (conservation tillage and conventional tillage) and crop rotation on N2O emissions.

2. Materials & Methods The experiment was located in “Canaleja” field station (Madrid, Spain) on a sandy clay loam soil, where a long-term tillage trial began in 1994. The site has a semiarid Mediterranean climate with dry summer and wet winter. The 10 year mean annual average temperature and rainfall for this area were 13.6ºC and 370.7mm. The current study was conducted between November 2010 and July

2011. The experimental design was a complete randomized block and each treatment was replicated three times. Tillage system was the main treatment. Three tillage systems were imposed in each main plot: no tillage (NT), minimum tillage (MT), both considered as conservation tillage system, and conventional tillage (CT). A fallow-wheat-vetch-barley annual rotation was established for each tillage system, but we only took samples in wheat-vetch plots. The experimental field consisted of eighteen subplots of approximately 250 m2 (10 m wide and 25 m long) corresponding with each phase of rotation.Tillage management was carried out in autumn 2010. No tillage (NT) involved directly drilling and spraying with herbicides for weed control. Minimum tillage (MT) consisted of chisel ploughing (15 cm) and a cultivator pass. Conventional tillage (CT) consisted of a mouldboard plough pass (30 cm depth), followed by a cultivator pass for preparing the seedbed. In NT, crop residues were left on the soil surface. For MT, approximately 30% of the soil was covered with the previous crop residues. For CT, almost 100% of the crop residue was incorporated into the soil.

After tillage, wheat and vetch were sown at the beginning of November 2010. Fertilizer was applied only to the soil where there was wheat seeding. These plots were fertilized with 16 kgN ha-1 and 22 kg N ha-1, applied at seeding and before tillering, respectively. N2O fluxes were measured from November 2010 to July 2011, using the close chamber technique (Roelle et al., 1999). One chamber per plot was used for gas sampling. During the crop season, gas samples were taken from the chambers three times in the first and second weeks after fertilizer application and then twice per week during the first month. Subsequently, every two weeks sampling was carried out until the end of the crop period. Also, samples were taken two times per week during rainfall periods.

Cumulative N2O emissions during the sampling period were calculated by averaging the rate of loss between two successive determinations, multiplying that average rate by the length of the period between the measurements, and adding that amount to the previous cumulative total. Samples were

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analyzed by gas chromatography (HP-6890). Also, soil dissolved organic C (DOC) and mineral N (NO3– and NH4+) concentrations were measured every time gas samples were taken.

3. Results & Discussion During the experimental period, N2O fluxes in wheat plots ranged from -0.081 to 0.224 mg N- N2O m-2 d-1 for CT and NT, respectively, and in vetch plots ranged from -0.133 to 0.331 mg N- N2O m-2 d-1 for NT and MT, respectively. Cumulative N2O emissions were higher in conservation tillage system (0.050 kg N- N2O ha-1 and 0.074 kg N- N2O ha-1 for NT and MT) than in CT (0.025 kg NN2O ha-1, under wheat-vetch rotation (Figure 1). On the other hand, vetch, as a legume, has the capacity for fixing N2 and this crop showed greater N2O emissions than wheat. Plots under vetch showed a larger pool of mineral N (NH4+ and NO3-) available in the soil. Also, higher N2O cumulative emissions from vetch were observed in MT than in NT and CT. However, higher N2O cumulative emissions from wheat were observed in NT than in MT and CT. Moreover, in NT and MT there is a higher dissolved organic C content available for microorganism activity than CT and this may favor the creation of anaerobic microsites in the soil during microbial respiration; these conditions could lead to N2O emissions coming from denitrification in the soil. Therefore, CT could help to mitigate N2O emissions in wheat-vetch rotations under Mediterranean climates.

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Figure 1. N2O cumulative emissions in each tillage system: NT (no tillage), MT (minimum tillage) and CT (conventional tillage).

4. Conclusion After soil has been 18 years under three tillage systems, conventional tillage induced lower cumulative N2O cumulative emissions than conservation tillage (NT and MT) in wheat-vetch rotations under Mediterranean agro-ecosystems.

References Oorts, K., Merckx, R., Grehan, E., Labreuche, J. and Nicolardot, B., 2007. Determinants of annual fluxes of CO2 and N2O in long-term no-tillage and conventional tillage systems in northern France. Soil Till. Res. 95, 133-148.

Passianoto, C.C., Ahrens, T., Feigl, B., Steudler, P.A., do Carmo, J.B. and Melillo, J.M. 2003. Emissions of CO2, N2O, and NO in conventional and no-till management practices in Rondonia, Brazil. Biol. Fertil. Soils 38, 200-205.

Roelle, P., Aneja, V. P., O`Connor, J., Robarge, W., Kim, D. and Levine., J. S. 1999. Measurement of nitrogen oxide emissions from an agricultural soil with a dynamic chamber system. J. Geophys. Res. 104, 1609-1619.

Snyder, C.S.; Bruulsema, T.W.; Jensen, T.L. and Fixen, P.E. 2009. Review of greenhouse gas emissions from crop production systems and fertilizer management effects. Agric. Ecosyst. Environ. 133, 247-266.

Nitrogen Workshop 2012

Effect of N-fertilizer amount and nitrification inhibitor on N2O emissions from a sandy and a loamy soil under vegetable production Seiz, P.a, Schulz, R.a, Heger, A.b, Armbruster, M.b, Wiesler, F.b, Müller, T.a, Ruser, R.a a Institute of Crop Science, Department of Fertilisation and Soil Matter Dynamics (340i), University of Hohenheim, Stuttgart, Germany b Landwirtschaftliche Untersuchungs- und Forschungsanstalt Speyer, Speyer, Germany

1. Background & Objectives High soil N surpluses, and resultant losses of reactive N to the environment, during the production of vegetable crops, such as cauliflower, are currently a matter of intense debate in Germany. Measures such as the lowering of N-fertilizer inputs or the use of nitrification inhibitors (NIs) have been shown to reduce nitrate leaching (Wiesler et al., 2007). The effect of such measures on the release of the greenhouse gas, nitrous oxide (N2O), however, has rarely been quantified. Pfab et al. (2011) reported lower N2O emissions from a vegetable cropping system when fertilizer N inputs were reduced. However, this reduction in N inputs also reduced crop yield. The aim of this study was to quantify annual N2O emissions from different sites within two big vegetable production regions of Germany, and to assess the effectiveness of mitigation measures in reducing N-surpluses, and hence N2O emissions, without restricting crop yield.

2. Materials & Methods Field trials were conducted on two different study sites representative of two big vegetable production regions of Southern Germany. The first site is within the so called ‘Filderebene’ region (13 km south of Stuttgart 410 m a. s. l.). The soil type is a haplic luvisol (loamy soil), mean annual precipitation is 686 mm, and the long-term (LT) mean annual air temperature is

8.8°C. The second site is within the ‘Vorderpfalz’ vegetable production region (20 km south of Mannheim near Speyer, 99 m a. s. l.). The soil type is a sandy cambisol, mean annual precipitation is 593 mm, and the LT mean annual air temperature is 10.0°C. At both sites, fully randomized block experiments with four replicates, were established. In this study the results of the following treatments are presented: (i) control (0 N), (ii) High N (325 kg N ha-1 to cauliflower), (iii) Optimized N (250 kg N ha-1), (iv) Low N (190 kg N ha-1 with the option of additional N doses if the chlorophyll content decreased as compared to treatment 250 kg N), and (v) Optimized N with 3,4-dimethylpyrazole phosphate (DMPP) as NI. Fertilizer application was split as shown in Figure 2. Ammonium sulfate nitrate (ASN) was used as the N-fertilizer at all sites and in all treatments. N2O flux measurements, made using the closed chamber method (Flessa et al., 1995), were conducted weekly and additional event-oriented measurements were carried out following N-fertilization and heavy rain fall. In this paper, we present the first results of our investigations which are still on-going.

3. Results & Discussion Cumulative N2O emissions ranged from 0.71 kg N2O-N ha-1 on the unfertilized control treatment at ‘Vorderpfalz’ to 1.95 kg N2O-N ha-1 on the treatment ‘optimized N with NI’ at ‘Filderebene’(Figure 1). Since N-fertilization provides the substrates for N2O production in soils, the emissions from the fertilized treatments exceeded those from the unfertilized control. Among the fertilized treatments, the emissions from the sandy soil were lower than those from the loamy soil. These differences were significant for the treatment ‘N optimized with NI’. The higher N2O emission from the loamy soil compared to that from the sandy soil, might have been owed to the higher water holding capacity and hence lower aeration of the loamy soil, since this would have favored denitrification (Granli and Bøckman, 1994). The highest N2O fluxes during the experimental period occurred after the first application of N fertilizer, directly after planting the cauliflower (Figure 2). The lowest fluxes were measured Nitrogen Workshop 2012

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4. Conclusions N2O emissions from the fertilized sandy soil were considerably lower than those from the loamy soil. One reason for the higher fluxes from the loamy soil may have been its higher soil moisture content relative to the sandy soil. Subsequent measurements and parameterization of the N2O fluxes will show whether a soil moisture controlling irrigation system would help to reduce N2O emissions. The reduction of N-fertilization with the provision that additional N may be applied if needed, (‘Low N’) appears to be a suitable approach for mitigating N2O emissions. In contrast to earlier investigations, the use of a NI did not reduce N2O emissions at either study site. However, these conclusions are based on results collected over a very short time period and need to be further verified using annual data.

References Flessa, H., Dörsch, P. and Beese, F. 1995. Seasonal variation of N2O and CH4 fluxes in differently managed arable soils in southern Germany. J. Geophysical Res. 100, 115-124.

Granli, T. and Bøckman, O.C. 1994. Nitrous oxide from agriculture. Norwegian Journal of Agriculture, Supplement 12.

Pfab, H., Palmer, I., Buegger, F., Fiedler, S., Müller, T. and Ruser, R. 2011. N2O fluxes from a Haplic Luvisol under intensive production of lettuce and cauliflower as affected by different N-fertilizer strategies, J. Plant Nutr.

Soil Sci. 174, 545-553.

Wiesler, F., Laun, N. and Armbruster, M. 2007. Integriertes Stickstoffmanagement – eine Strategie zur

wirksamen Verringerung der Gewässerbelastung im Gemüsebau. Download:

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