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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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Rathke, G.W., Behrens, T. and Diepenbrock, W. 2006. Integrated nitrogen management strategies to improve seed yield, oil content and nitrogen efficiency of winter oilseed rape (Brassica napus L.): A review. Agr. Ecosys. Environ.

117, 80-108.

Schultz, J.E.R. 1972. Undersøgelser af vinterrapsens (Brassica napus L.) tørstofproduktion og næringsstofoptagelse gennem vækstperioden. Tidsskrift for Planteavl 76, 415-435. (in Danish).

Wallenhammar, A.C., Pettersson, B. and Redner, A. 2005. Ekologisk oljeväxtodling kartlagd i fält. Svensk Frötidning 1, 18-21. (in Swedish).

Nitrogen Workshop 2012

Soil N2O emission as affected by 3,5-Dimethilphirazolphosphate, a nitrification inhibitor, applied on different soil types in Southern Italy Vitale, L.a, Polimeno, F.b, Ottaiano, L.c, Maglione, G.b, Fierro, A.d, Di Tommasi, P.a, Mori, M.c, Magliulo, V.a a CNR-ISAFoM, Ercolano (Na), Italy.

b CNR-ISPAAM, Naples, Italy.

c DIAAT, University of Napled Federico II, Naples, Italy.

d DBSF, University of Napled Federico II, Naples, Italy.

1. Background & Objectives Nitrous oxide (N2O) is a greenhouse gas contributing 6% to global warming. It is emitted from soils by microbial processes of nitrification and denitrification which are controlled by different soilrelated factors such as moisture, temperature and nitrogen content (Han Jian-gang et al., 2007).

Recently, fertilizers have been produced which contain microbial inhibitors and are being widely used in intensive agricultural systems, where it is estimated that can reduce total N2O efflux by up to 90% (Weiske et al., 2006; Pfab et al., 2009). In this study we analyze the effect of 3,5Dimethilphirazolphosphate (DMPP), a nitrification inhibitor, on soil N2O emission from two cropping systems (potato on a sandy soil and maize on a sandy loam soil).

2. Materials & Methods The experiments were carried out in two farms located in Naples and Acerra (southern Italy), on a sandy and a sandy-loam soil which were cropped with potato and maize crops, respectively. Two treatments were applied at both sites: nitrogenous fertilizer (ammonium nitrate, 26%) (Control plots) and nitrogenous fertilizer (ammonium nitrate, 26%) added with nitrification inhibitor (DMPP, Entec®) (DMPP plots). Plots (3 m x 3 m) were randomly set up in the fields. The fertilizer was applied at sowing and at 30 days after sowing. Soil N2O fluxes were weekly measured using static chambers during spring and summer 2011. Air samples were collected every 10 minutes and N2O concentrations in the samples were determined using gas chromatography. N2O fluxes were calculated as: V C/A T where V is chamber volume, A is the area covered by the chamber, and C/T is the rate of gas concentration increase with sampling time interval. Differences between treatments were tested by the Student t-test.

3. Results & Discussion Application of the nitrification inhibitor at sowing significantly reduced soil N2O emission at both sites, although a lot of variability in emissions at control plots was observed (Figure 1). After the second application of fertilizer, N2O fluxes from DMPP plots were similar to those from the control plots in Naples, whereas a peak and higher values of N2O emission compared to control plots were observed at the Acerra site. The strong and significant reductions in N2O emission at both sites was distinctly due to the nitrification inhibitor use. However, the different behaviour observed at two sites might be ascribed both to time of the year, since potato growing cycle was anticipated with respect to maize and soil-related factors such as texture, moisture and temperature. In fact, N2O fluxes at Acerra site could be predicted by a multi-linear regression with soil moisture and soil temperature, whereas no relationship at Naples site could be found. In the first case, measurements were conducted during late winter and spring when substantial rainfall occurred; in the other case, the higher air evaporative demand and coarse texture lead to drier soil conditions. The higher N2O emission peaks at the Naples site may also be related to the higher soil gas diffusion permittivity of the sandy soil.

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3/ 4/ 5/ 6/ 7/ 1/ 1/ 1/ 1/

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/1 /1 /1 /1 /1 /5 /6 /6 /7 /7

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Figure 1. Soil N2O emission from Acerra (upper panel) and Naples (lower panel) sites.

Red circles: control plots;

green circles: plots with DMPP. The arrows indicate the fertilizer application times.

4. Conclusion Soil N2O emissions of potato and maize crops grown in coarse textured soils of Southern Italy was reduced by the addition of a nitrification inhibitor to inorganic N fertilizers. The degree of reduction was dependent on soil moisture and temperature. Soil N2O emission rates were different between the two sites, a likely effect of soil texture and time of the year, since potato growing cycle was anticipated with respect to maize.

References Pfab, H., Ruser, R., Palmer, I., Fiedler, S., Buegger, F. and Muller, T. 2009. N2O Emissions from a high N-Input system as influenced by fertilizer amount and type. In: Grignani C, Acutis M, Zavattaro L, Bechini L, Bertora C, Marino Gallina, P, Sacco, D (eds) Proceedings of the 16th Nitrogen Workshop- Connecting different scales of nitrous use in agricultural. 28th June–1st July 2009, Turin, Italy, pp 197-198 Jian-gang, H., Yong-li, Z., Hong-ying, B., Dong, Q., Jin-yu, C. and Chun-du, W. 2007. N2O emission under different moisture and temperature regimes. Bull Environ Contam Toxicol 78, 284-287.

Weiske, A., Vabitsch, A., Olesen, J.E., Schelde, K., Michel, J., Friedrich, R. and Kaltschmitt, M. 2006. Mitigation of greenhouse gas emissions in European conventional and organicdairy farming. Agr Ecosyst Environ 112, 221-2321

Nitrogen Workshop 2012

Soil Organic Matter Priming: effect of labile Carbon on N mineralisation in Irish grassland soils Murphy C.J.abc, Baggs E.M.a, Morley N.a, Paterson E.b, Schulte P.R.O.c, Wall D.P.c a School of biological Sciences, University of Aberdeen, AB24 3UU, Aberdeen, Scotland, UK b James Hutton Institute, Craigiebuckler, AB15 8QH, Aberdeenshire, Scotland, UK c Teagasc, Environment, Soils and Land Use Research Department, Johnstown Castle, Wexford, Rep. of Ireland

1. Background & Objective In Ireland, N management is based on a ‘one soil fits all’ philosophy for grassland which may not be the optimal approach. Ireland has a diverse range of soil types which in turn have a wide range of net N mineralisation values (56-220 Kg N ha-1 yr-1, O’Connell and Humphreys, 2005). The main aim of this study was to determine the underlying processes that control N-mineralisation by investigating and quantifying the limiting factors controlling N-mineralisation in different soil types. The objectives were (1) to assess if the addition of labile C to the soil results in an increase in mineralised N (C limitation) (2) to quantify the rate of mineralisation (12CO2 efflux) and use this to predict the amount of N mineralized during an incubation period, and (3) to investigate if the relationship between C inputs (priming effect) and N mineralisation is similar for different soil types. This study will provide new information to better understand the N mineralisation process.

This information may form the basis for the development of new soil-specific N-advice for grassland soils in Ireland which is critical for environmentally sustainable farming in the future.

2. Materials & Methods Techniques developed by Paterson et al. 2009 and Davidson et al. 1991 were adapted to investigate and quantify the interaction of C and N. Soils of different chemical and physical characteristics were incubated in microcosms over a 14 day period. On day 0, 13C labelled glucose (3 atm%) and NH414N03 (30 atm%) was added to the microcosm On days 1, 3, 8, and 14 samples were destructively harvested for 15N isotopic analysis (isotopic dilution) and mineral N analysis to quantify gross N mineralization from soil organic matter (SOM). On days 1, 3, 5, 8, 11, and 14 gas samples were taken for total CO2 efflux and 13C isotope partitioning of soil CO2 efflux into glucose and SOM-derived components.

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2.0 1.5 1.0 0.5

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Addition of labile carbon to soil resulted in an increase in N-mineralisation from soil organic matter. SOM-derived CO2 efflux was concurrent with release of N from SOM (measured by 15N pool dilution). Consequently, labile plant-derived inputs to soil may be an important driver of soil N-cycling processes.

4. Conclusion The results of these experiments provide valuable information about the factors controlling the N mineralisation processes that are not captured by ‘standard’ methods to assess potential Nmineralisation in contrasting soil types. This study provides a platform to conduct further research on the factors controlling the rate of N-mineralisation e.g. C-to-N ratio of SOM and the quality of plant C inputs.

5. References Davidson, E.A, H. S., Shanks, C.A. and Firestone, M.K. 1991. "Measuring gross nitrogen mineralisation, immobilization, and nitrification by 15N isotopic poll dilution in intact soil cores " J Soil Sci 42, 335-349.

O’Connell KE and Humphreys, J. 2005. Accounting for nitrogen mineralisation in fertilizer nitrogen advice. In: Schulte RPO, Richards K, Finn J and Culleton N (eds.) The Science of Ireland’s Rural Environment (1st Ed). Teagasc, ISBN: 1 Paterson, E., Midwood, A.J. and Millard, P. 2009. Through the eye of the needle: a review of isotope approaches to quantify microbial processes mediating soil carbon balance. New Phytologist 184, 19-33  

Nitrogen Workshop 2012

Soil pH, and NO3- concentrations regulates the N2O and N2 emission from soil under anoxia Senbayram, M.a, Baken, L. b, Budai, A.b, Marton, L.c, Lammel, J.a a Research Center Hanninghof, Yara International, 48249 Duelmen, Germany b Institute of Plant and Environmental Sciences, Norwegian University of Life Sciences, As, Norway c Research Institute for Soil Science and Agricultural Chemistry of the Hungarian Academy of Sciences, Hungary

1. Background & Objectives The effect of soil pH on denitrification and its product stoichiometry is difficult to study because of limitations in measuring all products of denitrification such as NO and N2. Nevertheless, numerous studies concluded that if the pH of a soil is low, denitrification rates decrease, but denitrification would emit more N2O as a result of a higher N2O/(N2O+N2) product ratio (Cuhel and Simek, 2011;

Liu et al., 2010). It is assumed that, under acidic pH, the activity of N2O reductase is lowered and the synthesis of new N2O reductases is inhibited (Cuhel and Simek, 2011; Simek and Cooper 2002).

In previous study, we showed that higher concentration of NO3- in soil may retard the reduction of N2O to N2 regardless of soil type (Senbayram et al., 2011). In this context, the positive effect of higher soil pH on the N2O/(N2O+N2) product ratio of denitrification in soils with high NO3- content is still poorly understood and more research is needed to unravel quantitative relationships under well-defined conditions. In this study, we set up two incubation experiments, in order to test the short-term (24 h, in Exp.1) and the long-term (450 h, in Exp.2) effect of soil pH and NO3concentration on denitrification rate and its product stoichiometry by measuring N2O, NO as well as elemental N2 in a soils with two pH levels (pH 4.1, and pH 6.9) collected from a long-term liming experiment.

2. Materials & Methods The soils were collected in spring 2011 from a long-term liming experiment in Hungary. The experiment was established in 1962. Initial soil pH was 4.3 and soil pH values measured in 2011 were 4.1 and 6.9 in non-limed and limed soils respectively. The first incubation experiment was done to determine the short-term effects of NO3− concentration on potential denitrification and its N2O/(N2O+N2) product ratios in high and low pH soils under complete anoxic conditions. Prewetted soils (low pH soil (LpH), and high pH soil (HpH)) were flooded and drained with 0.2, 2, 10, and 20 mM KNO3 solution prior to the experiment. Then, the soil was immediately transferred to 120-ml serum flasks which were sealed and made anoxic by repeated evacuation and filling with He. Production of N2O, NO and N2 during batch incubation of soils was monitored for 24 h.

Kinetics of NO, N2O and N2 accumulation during the incubation period were used to calculate the N2O product share of denitrification and total denitrification rate. In Exp. 2, we used a continuous flow incubation system (under He) with larger vessels. Briefly, 1 kg moist soil was placed in PVC vessels then flooded and drained with 15 mM KNO3 solution prior to the experiment to 20% gravimetric water content. All vessels were evacuated and filled with He, and then fresh He was directed through an inlet in the lid at a flow rate of 15 ml min-1. Gas samples were analyzed twice a day for N2O by ECD and for N2 by TCD detectors (gas chromatography, GC-450 Varian Inc., USA) during 450 h of incubation.

3. Results & Discussion In Exp. 1, denitrification rate in HpH increased in some proportion to the nitrate concentration within the entire concentration range (0.2-10 mM KNO3) as seen in Figure 1A. In LpH, the rate of denitrification was essentially unaffected by nitrate concentration within the range 2-10 mM, but 24% lower with 0.2 mM NO3-. With 10 mM KNO3, the denitrification potential in HpH was 2 fold

Nitrogen Workshop 2012

higher than in LpH. We attributed lower denitrification rates below 10 mM KNO3 in HpH and below 2 mM KNO3 in LpH to the shortage of NOx (lack of electron acceptor). The N2O/(N2O+N2) product ratios of denitrification were consistently lower in HpH than LpH below N level of 10 mM KNO3 (Figure1 B). In situations where the organisms experience a shortage of NOx, the relative rate of N2O reduction (in relation to N2O production) increases, thus low N2O/(N2O+N2) product ratios of denitrification dominate (Senbayram et al., 2011). Therefore, higher N2O/(N2O+N2) product ratios in LpH than HpH only with low level KNO3 treatments, may be explained by the reduced demand of electron acceptors (low denitrification potential).

mg N (N2O‐N; N2‐N) kg‐1 dry soil h‐1

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