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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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1. Background & Objectives To protect the environment, the European Union (EU) has adopted the National Emission Ceilings (NEC) directive (EC, 2001). This directive sets national goals for nitrogen oxides and ammonia emissions. Nitrogen (N) may be lost as ammonia from crop residues left on the soil surface. When residues are incorporated into the soil, ammonia volatilization is eliminated (de Ruijter et al., 2010;

Janzen and McGinn, 1991; Mohr et al., 1998). The objective of this paper is to assess the ammonia volatilization from a range of crop residues at a national level based on the N content of the residues, cultivated area and management.

2. Materials & Methods Literature was used to derive a relation for the ammonia volatilization depending on the N-content of crop residue. National statistics on cultivated areas, literature and expert knowledge were used to assess the area cultivated by different crops, the N content of crop residues and the management of crop residue. Ammonia volatilization from crop residues in the Netherlands was calculated per crop by multiplication of: cropped area (ha), N in residues (kg ha-1), volatilization (% of total N in kg ha-1) calculated from N content (g kg-1 dry matter) by the regression equation derived from literature, and amount and fraction of the residues that contributes to ammonia volatilization (based on degree of mixing with soil at harvest and duration between harvest and incorporation).

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The largest contribution to ammonia volatilization at the national scale is from grassland residues that arise during mowing and grazing (Figure 1). Of the arable crops, potato haulms show the largest ammonia volatilization (Figure 1, right). In our calculations, this is mainly derived from seed potatoes where the haulms are killed by herbicides.

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Figure 1. Total ammonia volatilization in the Netherlands from various crops Ammonia volatilization was estimated by the relationship between NH3-N volatilization (as % of N in residues) and the N content (in g kg-1 dry matter).

Variation in N content of the residues affects the % of total N that volatilizes as NH3 and the total N in the residues. Therefore, a reduction in N content of the residues has a more than proportionate effect on ammonia volatilization. For example, reducing the N content from 40 to 36 g kg-1 (10%) reduces ammonia volatilization (in kg NH3-N ha-1) by 23%. At a lower N content this effect is even larger.

4. Conclusion Crop residues may substantially contribute to the national ammonia losses. Ammonia volatilization from crop residues is related to their N content. Incorporation into the soil or decreasing fertilizer inputs may therefore have a large impact on ammonia volatilization from crop residues.

References Bremer E. and Vankessel C. 1992. Plant-available nitrogen from lentil and wheat residues during a subsequent growingseason. Soil Science Society of America Journal 56, 1155-1160.

Cherry K.A., Shepard M., Withers P.J.A. and Mooney S.J. 2008. Assessing the effectiveness of actions to mitigate nutrient loss from agriculture: A review of methods. Science of the Total Environment 406, 1-23.

De Ruijter F.J., Huijsmans J.F.M. and Rutgers B. 2010. Ammonia volatilization from crop residues and frozen green manure crops. Atmospheric Environment 44, 3362-3368.

EC 2001. Directive 2001/81/EC of the European Parliament and of the Council of 23 October 2001 on national emission ceilings for certain atmospheric pollutants. Official Journal L 309, 22 (accessed 27.11.01). European Communities, Brussels.

Janzen H.H. and McGinn S.M. 1991. Volatile Loss of Nitrogen During Decomposition of Legume Green Manure. Soil Biology and Biochemistry 23, 291-297.

Manneim T., Braschkat J. and Marschner H. 1997. Ammonia emissions from senescing plants and during decomposition of crop residues. Zeitschrift für Pflanzenernährung und Bodenkunde 160, 125-132.

Mohr R.M., Janzen H.H. and Entz M.H. 1998. Nitrogen dynamics under greenhouse conditions as influenced by method of alfalfa termination. 1. Volatile N losses. Canadian Journal of Soil Science 78, 253-259.

Ribas R.G.T., Santos R.H.S, Siqueira R.G., Diniz E.R., Peternelli L.A. and de Freitas G.B. 2010. Decomposition, release and volatilization of nitrogen from velvet bean (Mucuna cinerea) residues. Ciencia e Agrotecnologia 34, 878Whitehead D.C. and Lockyer D.R. 1989. Decomposing Grass Herbage as a Source of Ammonia in the Atmosphere.

Atmospheric Environment 23, 1867-1869.

Nitrogen Workshop 2012 Antecedent effect of lime on denitrification in grassland soils Higgins, S., Laughlin, R.J., Watson, C.J.

Agri-Food and Biosciences Institute, 18a Newforge Lane, Malone Upper, Belfast BT9 5PX, Northern Ireland, UK

1. Background & Objectives Sales of agricultural lime in Northern Ireland and the Republic of Ireland have fallen considerably during the past 30 years (DARDNI, 2011; Culleton et al., 1999) resulting in increasingly acidic soils in many areas. Soil pH has been shown to significantly affect the ratio of the end products (N2/N2O) of denitrification (Čuhel et al., 2010; Šimek and Cooper, 2002). The implications of lime use on this ratio were examined in a laboratory incubation study using a 15N-gas-flux method, followed by isotope-ratio mass spectrometry for the analysis of 15N in the gases.





2. Materials & Methods Two grassland soils (of contrasting texture and management but similar starting pH) were selected from the basalt area of County Antrim, Northern Ireland in 2006. Soil 1 was a clay loam soil under silage management with a starting pH of 5.4. Soil 2 was a sandy loam soil under grazing management, with a starting pH of 5.3. The soils were partially air-dried and sieved to 2 mm and 15 kg sub-samples of each soil were treated with 0, 2.3, 5.7 or 18.9 g CaCO3 kg-1 (neutralising value 56%), mixing thoroughly using a cement mixer, to obtain four pH values for each soil. The soils were placed in large polythene bags and sealed to prevent moisture loss, but maintain aerobic conditions, and incubated at 4ºC for a three year period (2006 to 2009). Periodic checks on soil pH (soil and water ratio of 1:2.5 (v/v)) and volumetric moisture content were carried out. Samples of soil (100 g oven-dry (OD) weight) were placed in acid-washed 500 ml Kilner jars and received one of three 15N treatments; ammonium (15NH4NO3), nitrate (NH415NO3), or both moieties (15NH415NO3) labelled with 60 atom % excess 15N, along with 5 ml acetate (C source) and 5 ml deionised water. Each treatment was replicated three times. The 15N was applied at a rate of 7.14 μmol NH4NO3 g-1 OD soil, pipetted uniformly over the soil surface. Additional water was added to each soil one week in advance of the incubation to ensure that all soils were adjusted to a waterfilled pore space of 65%. The jars were covered with Parafilm to prevent moisture loss but allow gaseous exchange, and were incubated in a controlled temperature environment at 20ºC. Headspace samplings were carried out on five consecutive days following the addition of treatments using polyacetyl lids containing a gas-sampling port and a viton O-ring to form a gas-tight seal. These were fitted onto each jar for a period of two hours per day. Two 15 ml headspace samples were extracted daily using a gas-tight syringe and transferred to evacuated (100 Pa) septum capped 12ml vials, to be analysed by isotope-ratio mass spectrometry for the 15N contents of the N2O and N2 in each vial, as described by Stevens et al. (1998). Residual Maximum Likelihood (REML) variance components analysis (Genstat Release 12) was used to examine the significance of fixed (pH, 15N treatment) and random (day, soil type) affects on N2-N and N2O-N fluxes.

3. Results & Discussion

During the three-year pre-incubation period, the two soils equilibrated at four different pH values:

Soil 1 pH 4.7, 5.8, 7.3 and 7.7, and Soil 2 pH 4.7, 5.2, 6.6 and 7.6. The number of days following treatment addition had a significant effect (P 0.05) on the flux of both N2 and N2O in the

headspace of the jars, with the largest fluxes of being recorded two days after 15N application (N2O:

Soil 1 0.0014 μmol g OD soil (Figure 1) and Soil 2 0.

0018 μmol g OD soil), and N2: Soil 1 0.126 μmol g OD soil and Soil 2 0.179 μmol g OD soil.

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Figure 2: Cumulative loss of N2 and N2O from soil as a % of N applied in Soil 2 at each pH.

4. Conclusions Lime enhances the loss of N from soil by denitrification, as both N2 and N2O. This can represent a significant loss of N from soil, and although emissions are dominated by N2 as soil pH increases, it would indicate that lime is not a potential mitigation strategy for reducing N2O emissions.

References Čuhel, J., Šimek, M., Laughlin, R.J., Bru, D., Chèneby, D., Watson, C.J. and Philippot, L. 2010. Insights into the effect of soil pH on N2O and N2 emissions and denitrifier community size and activity. Applied and Environmental Microbiology 76, 1870-1878.

Culleton, N., Murphy, W.E. and Coulter, B. 1999. Lime in Irish Agriculture [Online]. Available by The Fertilizer Association of Ireland www.fertilizer-assoc.ie Department of Agriculture and Rural Development for Northern Ireland. http://www.dardni.gov.uk.

Šimek, M. and Cooper, J.E. 2002. The influence of soil pH on denitrification: progress towards the understanding of this interaction over the last 50 years. European Journal of Soil Science 53, 345-354.

Stevens, R.J., Laughlin, R.J. and Malone, J.P. 1998. Soil pH affects the processes reducing nitrate to nitrous oxide and di-nitrogen. Soil Biology and Biochemistry 30, 1119-1126.

Nitrogen Workshop 2012 Assessing N availability from municipal solid waste compost during two consecutive lettuce cycles in Italy Fiorentino, N., Fagnano, M.

Department of Agricultural Engineering and Agronomy, University of Naples Federico II, Italy

1. Background & Objectives Soils of the Mediterranean area are prone to severe fertility losses, if agronomic tools are not managed to counterbalance the high soil organic matter (SOM) mineralization rate of this region.

Compost fertilization could be an interesting tool to increase soil fertility since its positive effects on humification, nutrient availability, porosity, structural stability and biological activity have been proven in different agricultural systems (Diacono and Montemurro, 2010). Moreover composting of the solid waste organic fraction could be a possible solution to the long-standing rubbish problem, limiting the amount of waste going to final disposal (Fagnano et al., 2011). This work focuses on the potential use of Municipal Solid Waste (MSW) compost in open field horticulture, assessing its effect on lettuce yield and soil-plant N dynamics on two consecutive cropping cycles.

2. Materials & Methods An open-field experiment was carried out in Caivano municipality (40°56’N, 14°19’E), 12 km from Naples City (Italy), with the aim to compare the agronomic performance of 3 MSW compost doses, 10 (CF10), 30 (CF30) and 60 (CF60) Mg ha-1, corresponding respectively to 56, 160 and 319 kg N ha-1 (the complete experimental set up is described in Fagnano et al., 2011). The compost was stable and fully mature with a C:N ratio of 20. Treatments, including ammonium nitrate fertilization with 84 kg ha-1 of N (MF) and a not fertilized control plot (NF), were laid on in a randomized complete block design with 3 replicates. The soil was sandy loam (sand, 565 g kg−1; silt, 285 g kg−1; clay, 150 g kg−1) with high C and N content (1.89% and 0.16% respectively). Lettuce was cropped in summer (cv. Audrian) and winter (cv. Sagess), spreading mineral fertilizers at both transplant times while compost was buried only at the beginning of the experiment. Soil mineral N (SMN) and N content of plant tissues were measured by HACH® and by Kjeldahl method respectively. A simplified N balance for the 0-20 cm layer was calculated as N uptake + SMN harvest – SMN seeding to estimate available N from SOM mineralization (AvN) on NF and from fertilizers (FAvN) on the other plots. The difference between FAvN-AvN was considered as Net available N from fertilizers (NAvN). N apparent recovery (NAR) was calculated as the difference between N uptake in fertilized and not fertilized plots divided by N input (Montemurro et al., 2006). All the data were subjected to ANOVA, using the MSTAT-C software (Version 2.0), and mean separation was made by using LSD test.

3. Results & Discussion In both cycles, marketable yield (Table 1) in C30 and C60 plots was not different from MF (average value of 47.6 and 37.9 Mg FW ha-1 for the 1st and the 2nd cycle respectively) while values recorded with C10 were significantly lower than the other treatments excepting NF. At DAT 10 of the 1st cycle N uptake with the two highest compost doses was 55% lower than NF, while the value decreased of 19% with C10 (Table 1). In the 2nd cycle N uptake were highest with MF, C60 and C30 (50.6 mg N pt-1 on average), while values were not different between C10 and NF and significantly lower (-38%) then the other treatments. At the end of both cropping cycles, N uptake was found at the same level among the fertilized plots (625 and 596 mg N pt-1, in the two cycles respectively). N from fertilizers (NAvN) in the summer cycle is shown in Figure 1.

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Figure 1. NAvN at DAT 10 AND 30 of the summer Different letters indicate different means with p0.

05 cycle (“treatment by date” interaction).



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