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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 The majority of ammonia (NH3) emissions in the atmosphere are due to agricultural activities, with the major source being field-applied manure, followed by the use of inorganic fertilizer (Erisman et al., 2003). This loss of nitrogen (N) due to NH3 emission may significantly reduce N-fertilizer efficiency and cause environmental problems (Asman et al., 1998). NH3 volatilization from urea fertilizers has a slower dynamic than manure since urea does not contain ammoniacal N (NH4+). In this case, it is necessary that hydrolysis process takes place under favourable conditions of soil water content and temperature. Appreciable NH3 loss could occur within few days after the fertilizer application. Afterward the loss rate decreases due to the reduction of the total ammoniacal nitrogen (TAN = NH3+NH4+) which could be dissolved in increasing volumes of soil water (Sommer et al., 2004). The TAN depletion is shared by the NH3 emission to the atmosphere and by the processes of immobilization and nitrification, through microbial activity. In this work, to define the end of the volatilization phenomenon, the NH3 release has been discussed in relation to the pH and NH4+ and nitrate (NO3-) concentrations measured into the soil.

2. Materials & Methods The trial was carried out in a corn field of approximately 10 ha located in Landriano (Po Valley, Northern Italy, Lat. 45°19′ N, Long. 9°16′ E, Alt. 88 m a.s.l.). From 14 June 2010, NH3 concentration was measured daily for 24 days using the passive samplers ALPHA developed by Tang et al. (2001). Samplers were exposed in triplicate both in the center of the field and distant from the fertilized area, away from known NH3 sources (about 1500 m). The ALPHAs in the field were maintained 1 m above the canopy, for up to 12 hours. Urea in granular form was surface spread the 18 June 2010 at a rate of 106 kg N ha-1, and during the period of the experimentation the crop (maize, at stage V8) was not irrigated. A sonic anemometer (USA-1, METEK GmbH, Elmshorn, Germany) was placed in the centre of the field in order to collect data relative to the turbulent state of atmosphere (i.e. friction velocity, roughness and Monin-Obukhov lengths) and used as input for the WindTrax model (Flesch et al., 1995). A standard meteorological station was employed for measuring temperature and humidity of the air, global solar radiation, rain and wind speed. Random soil samples were collected (three replicates at 0-10 cm depth) in order to evaluate pH and the concentration of NH4+ and NO3-, the latter by using a spectrophotometer (FOSS, FIAstar 5000 system, Denmark); the timing of the soil sampling is reported in Table 1.

3. Results & Discussion The hydrolysis of urea took place 1 day post application with a rain event occurred in the morning, which dissolved the fertilizer into the soil. The NH3 volatilization reached a main peak of emission (about 5 μg m-2 s-1) around midday (no rain), followed by a decreasing due to an increasing in rainfall (about 20 and 13 mm during the day 19th and 20th, respectively). During the following four days, the NH3 fluxes showed peaks around 1 μg m-2 s-1 during the morning, while starting from the 25th of June, the NH3 fluxes decreased to rise slightly up on the 6th of July in occasion of a particular windy day. In order to evaluate if the volatilization of NH3 was exhausted when the trial

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The availability of NH4+ increased immediately after the start of urea hydrolysis, promoting NH3 volatilization. However, at the same time of NH3 fluxes decreasing (25th June), the NH4+ concentration decreased, while the NO3- concentration started to increase since the process of nitrification of the TAN mixed with soil had taken place. This later process is largely affected by soil pH, being negligible at values lower than ca. 4 and increasing linearly with pH increasing.

During the trial, the pH increased when the hydrolysis took place (OH- formation) and decreased with the course of the volatilization (H+ release). Nitrification, therefore, reduces NH3 emission due to reduction in both concentration of TAN in soil solution and a reduction in the NH3 component of TAN.

4. Conclusion Considering the dynamic of concentration of the two N compounds analysed into the soil, it seems reasonable suppose that the NH3 volatilization was exhausted at the end of the experimental campaign, in combination with reduced pH values. The total NH3 loss was around 5 kg N ha-1, i.e.

about 4.7% of the N supplied.

References Asman, W.A.H., Sutton, M.A. and Schjoerring, J.K. 1998. Ammonia: emission, atmospheric transport and deposition, New Phytologist 139, 27-48.

Erisman, J.W., Grennfelt, P. and Sutton, M. 2003. The European perspective on nitrogen emission and deposition.

Environment International 29, 311-325.

Flesch, T., Wilson, J.D. and Yee, E. 1995. Backward-time Lagrangian stochastic dispersion models, and their application to estimate gaseous emissions, Journal of Applied Meteorology 34, 1320-1332.

Sommer, S.G., Schjoerring, J.K. and Denmead, O.T. 2004. Ammonia emission from mineral fertilizers and fertilized crops. Advances in Agronomy, Volume 82, 557-622.

Tang, Y.S., Cape, J.N. and Sutton, M.A. 2001. Development and Types of Passive Samplers for Monitoring Atmospheric NO2 and NH3 Concentrations. In Proceedings of the International Symposium on Passive Sampling of Gaseous Pollutants in Ecological Research. The Scientific World 1, 513-529.

Nitrogen Workshop 2012

Dynamics of in situ nitrogen mineralization from five organic fertilizers Costa, L.A.d.M.a, Costa, M.S.S.d.M.a, Pereira, D.C., Cordovil, C.M.d.S.b, de Varennes, A.b a UNIOESTE, Campus de Cascavel, Rua Universitária 2069, Cascavel, Paraná, CEP. 85819110, Brazil b TU Lisbon, Instituto Superior de Agronomia, CEER, Tapada da Ajuda, 1349-017 Lisboa, Portugal

1. Background & Objectives The use of organic residues as fertilizers has become a common practice both in organic as well as in traditional farming. The total available nitrogen (N) contained in organic fertilizers, and its rate of release, are important factors determining crop yield as well as potential losses into the environment through the processes of nitrification, leaching, and denitrification or other gaseous losses. Decomposition of organic materials and the subsequent release of inorganic N from the organic N pool occur through the activity of soil microorganisms, mainly bacteria and fungi (Hanselman et al., 2004; Flavel et al., 2006; Cordovil et al., 2011). Environmental and soil mineralogy factors affect the microbial players and their actions, which in turn determine the rate of N mineralization in the soil and thus the amount mineralized over time. Soil temperature and moisture content have a strong effect on N mineralization rates. A field experiment was set up to determine the rates of mineralization of five different organic fertilizers, in order to evaluate the potential for the release of available forms of N to the soil.

2. Materials & Methods Different organic fertilizers (pelletized vermicompost (V); pelletized vermicompost + phosphate Arad (VP); compost (C); biodynamic compost (BC); poultry litter (PL)), were buried inside incubation capsules made of a porous ceramic material that allows water and nutrient exchange with the external environment. Each capsule had a diameter of 5.1 cm and a length of 9.8 cm and was filled with 20 g of residue. The experimental design was in randomized blocks, and capsules were buried at a depth of 7 cm and covered with soil. Destructive samples were collected at 7, 14, 35, 65 and 100 days after the beginning of the incubation. The material inside the capsules was removed, oven-dried at 650C and weighed to determine decomposition by difference of mass. The samples were analyzed to determine the total nitrogen content (Kjeldhal digestion).

3. Results & Discussion As expected, the residue which mineralized more intensely was the poultry litter (PL) losing about 33% of its original mass by the end of the incubation period. Three residues lost about 10% of their original weight by the end of 100 days of incubation (V, VP and CB), while the most recalcitrant was the compost (C) which lost only 5% of its biomass within the same period (Figure 1). The N concentration in the residues was greatest in PL and smallest in vermicompost (V and VP) at the beginning of the incubation (Table 1). During the incubation period, the concentration of N in the residue remaining in the capsule tended to be constant in compost (CB and C) while it decreased in the other residues, suggesting that the more labile compounds had a greater N concentration than the more recalcitrant. The addition of phosphorus to the vermicompost had no effect of the concentration of N in the residues over all the incubation period. The biodynamic compost had a greater concentration of N at the beginning of the incubation, but the differences were not significantly different later on, suggesting that the additional N present was very labile.

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4. Conclusion This in situ incubation experiment showed the mineralization potential of five different residues, with poultry manure being the only residue capable of supplying a large amount of N within a 100days period. The other residues are more appropriate to built up the organic matter in soils as they decompose very slowly.

References Cordovil C.M.d.S., de Varennes A., Pinto R. and Fernandes R.C. 2011 Changes in mineral nitrogen, soil organic matter fractions and microbial community level physiological profiles after application of digested pig slurry and compost from municipal organic wastes to burned soils. Soil Biology and Biochemistry 43, 845-852.

Flavel T.C. and Murphy D.V. 2006 Carbon and nitrogen mineralization after application of organic amendments to soil.

Journal of Environmental Quality 35, 183-193.

Hanselman T.A., Graetz D.A. and Obreza T.A. 2004 A comparison of in situ methods for measuring net nitrogen,mineralization rates of organic soil amendments. Journal of Environmental Quality 33, 1098-1105.

Nitrogen Workshop 2012

Effect of fertiliser type, rate and method of application on nitrogen leaching in organic olive oil farming Gómez-Muñoz, B.a, Bol, R.b, Hatch, D.J.b, García-Ruiz, R.a a Área de ecología. Universidad de Jaén, Jaén, Spain b Rothamsted Research, North Wyke, Okehampton, United Kingdom

1. Background & Objectives Nitrogen (N) fertilisers are the most common amendments used in agroecosystems. However, N use efficiency is usually lower than 50 %, although this is highly dependent on crop type, environmental conditions and agroecosystem management practices, such as rates of fertiliser application, tillage and irrigation (Maeda et al., 2003). An optimum N fertilisation protocol should, as far as possible, synchronize fertiliser-N supply with plant demand, thereby minimizing the risk of N loss by leaching. Considering the wide diversity in the many types, of organic fertilisers used in organic agriculture (including N content), the potential risk for N leaching during decomposition of a variety of organic fertilisers needs to be evaluated under natural conditions. The objectives of this study were to assess the effect of fertiliser type, rate and method of application and tillage method on inorganic N leaching.

2. Materials & Methods To evaluate N losses by leaching, a pot experiment was set up. Each pot contained 4 kg of sieved ( 4 mm) soil from an organic olive grove and received one of the following organic fertilisers commonly used in organic olive oil farming: i) Composted olive mill pomace (COMP), ii) Sheep manure (Sheep M) and iii) a commercial organic fertiliser with a total N content of 14 % (CPR).

For comparison, a fourth treatment received NaNO3 (Inor). N fertilisation rates were: 1) 250 g N gsingle’, hereafter) and 2) 500 g N g-1 (‘double’, hereafter). All fertilisers were added using 2 different application methods 1) at the soil surface (S), or 2) were mixed (M) within the soil. Two sets of control soils were also prepared; one set was undisturbed (simulating treatment S), whereas soil from the second set was mixed with the soil (simulating treatment M). Treatments were replicated four times, and the pots were randomly distributed in the open air at the garden facilities of the University of Jaén, Spain from November 2007 to May 2009. All pots were maintained with no vegetation. Each pot was fitted with a funnel connected to a 1 L plastic bottle to collect leachate after each rainfall event. Inorganic N (ammonium and nitrate) was analysed in the leachate after filtration. Differences in the treatments were tested using one-way analysis of variance (ANOVA) and Fisher’s post hoc test.

3. Results & Discussion Overall, ammonium leaching was negligible, accounting for a maximum of 6 % of the combined inorganic N forms (nitrate+ammonium). As expected, the overall temporal pattern of leached nitrate followed that of precipitation and the largest losses of nitrate coincided with the most intense rainfall periods in autumn and spring (Figure 1a). The highest losses occurred between late winter to early spring. The magnitude of nitrate losses differed between fertilisers. Up until the following spring, nitrate losses from the inorganic N fertilised pots were always the highest, especially after the first rainfall event following fertiliser addition, in which up to 15 % of the added N was lost.

Figure 1b shows the fertiliser–derived IN lost after one year of incubation under a natural temperature and precipitation regime. There were significant effects of fertiliser type and application method on IN leaching, whereas the effects of application rate depended on the treatments (P0.05) (Figure 1b). The lowest losses were for COMP amended soils (up to 7 % of

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