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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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www.agrarforschung.de/download/07_wiesler.pdf This study was funded by the German ‘Federal Office for Agriculture and Food’ (BLE) Nitrogen Workshop 2012 Effect of nitrogen fertilizer amount and a nitrification inhibitor on the N2O emissions from a loamy soil cropped with winter wheat Guzman Bustamante, I.a, Schulz, R.a, Müller, T.a, Hähndel, R.b, Ruser, R.a a Institute of Crop Science, Fertilization and Soil Matter Dynamics (340i), University of Hohenheim, Stuttgart, Germany b K+S Nitrogen GmbH, Mannheim, Germany

1. Background & Objectives Nitrous oxide (N2O) is a climate relevant trace gas which contributes 8% to the anthropogenic greenhouse effect (IPCC, 2007). Furthermore it is also involved in stratospheric ozone depletion. In agricultural used soils nitrogen (N) fertilization supplies the substrate for the processes of nitrification and denitrification causing potential N2O losses.A promising N2O reducing strategy in agricultural used soils is the use of nitrification inhibitors (NI). Compared with a conventional Nfertilizer application, Akiyama et al. (2010) calculated a reduction potential of 30% when NIs were added to the fertilizer.The objective of this study is to quantify the effect of a NI application and the N-fertilizer amount on the annual N2O emissions from a loamy soil cropped with winter wheat.

2. Materials & Methods N2O emissions were measured in a fully randomized block experiment on the experimental station “Heidfeldhof” of the University of Hohenheim, 13 km south of Stuttgart, Germany, between midMarch and mid-December 2011. A nitrogen fertilization rate of 0 (unfertilized control), 120 (N1), 175 (N2) or 230 (N3) kg N ha-1 was applied as ammonium sulfate nitrate (ASN) or ENTEC26® (ASN+NI) to winter wheat sown in 2010. N2 fertilization amount was calculated according to the German Fertilizer Ordinance (“good practice”), N1 and N3 as a reduction or an increase of a 30% of N2, respectively.

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Figure 1. Mean N2O flux rates as affected by N-fertilization and by the addition of a NI.

Unfertilized control, N2 -NI or +NI. Solid arrow indicates N fertilization, long dashed arrow harvest and soil tillage, and dashed arrow stubble tillage.

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High N2O fluxes immediately after N fertilization were not observed (Figure 1). Nevertheless, cumulative emissions during the vegetation period (15.03.-27.07.2011) varied between 764 and 2237 g N2O-N ha-1 (Figure 2), mainly as a result of high emissions after rewetting events. The highest N2O fluxes were observed the 26th of May (158 µg N2O-N m-2 h-1, not shown). In the period after the harvest a high variability between all treatments could be observed. The addition of an NI to the N2 and N3 treatments tended to reduce the N2O emission over a period of approximately 8 weeks (mid-May until mid-July). This effect was also observed for approximately three weeks after harvest. The N1 treatment did not show the same trend. The prolonged N2O reducing effect of ENTEC26® was already observed by Pfab et al. (2012). Despite the application of N fertilizer dated back 10 to 15 weeks before, they found a significant decrease of N2O winter fluxes by ENTEC26®.

In comparison with the N2 treatments +NI and –NI, the reduction and the increase by a 30% of the N amount had neither a significant effect on grain yield, nor a significant reduction of the mean cumulative N2O emissions.

after harvest vegetation period

-1 kg N2O-N ha

4. Conclusion Our investigations were carried out under unusually dry conditions. As compared to other studies in our experimental region, the N2O emissions were very low. However, a trend of reduced fluxes was observed when NI was added to the N fertilizer. Interestingly, N2O fluxes after stubble management were again lower in the N2 and N3 +NI than in the respective –NI treatments. On-going investigations will focus on that long-term effect of a NI on N2O fluxes and the microbial community structure.

References Akiyama H., Yan X. and Yagi K. 2010. Evaluation of effectiveness of enhanced-efficiency fertilizers as mitigation options for N2O and NO emissions from agricultural soils: meta-analysis. Global Change Biology 16, 1837-1846.

IPCC. 2007. Changes in Atmospheric Constituents and in Radiative Forcing. In: Solomon S. et al., Climate Change 2007: The Physical Science Basis. Contribution of Working Group I to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change, Cambridge University Press, Cambridge, United Kingdom and New York, USA.

Pfab H., Palmer I., Buegger F., Fiedler S., Müller T. and Ruser R. 2012. Influence of a nitrification inhibitor and placed N-fertilization on N2O fluxes from a vegetable cropped loamy soil. Agriculture, Ecosystems and Environment, (under review).

Nitrogen Workshop 2012

Effect of soil compaction and nitrogen fertilization on nitrous oxide emission from highly productive grassland Loges R., Schmeer M., Taube F.

Christian-Albrechts-University of Kiel, Institute for Crop Science and Plant Breeding, Grass and Forage Science/Organic Agriculture, Germany

1. Background & Objectives Nitrous oxide (N2O) emissions induced by agricultural systems represent 50% of the world’s N2O emissions. This can significantly be attributed to an intensification of modern agriculture which includes increased nitrogen fertilization and also the employment of larger and heavier machines.

Heavier machines can cause an increase in soil compaction and a reduction in soil porosity which can result in more anaerobic conditions in the upper soil layers. In combination with intensive nitrogen fertilization these can contribute to an undesirable increase in N2O emissions (Yamulki and Jarvis, 2002; Velthof et al., 1997). Since most studies dealing with soil compaction focus on tilled arable land, our main aim was to study the interaction between soil compaction and nitrogen fertilization and its impact on N2O emissions in highly productive grassland.

2. Materials & Methods The field experiment was set-up on the experimental station Hohenschulen in Northern Germany (54:18:49N; 9:57:56E; mean annual temperature 8.3°C, and mean annual precipitation 777 mm, soil: sandy loam) on a uniform grassland (seed mixture of Lolium perenne, Dactylis glomerata, Medicago sativa and Trifolium repens) in a split-plot factorial design with three replicates. The

experiment comprised the following factors:

• Controlled soil compaction (control versus contact area pressure of 228 kPa) in early April N fertilization with calcium ammonium nitrate (0 and 360 kg N ha-1) • • Year of first controlled soil compaction on separate plots (2006, 2007 and 2008) Soil compaction was carried out each year on originally non compacted plots. It was achieved by a single passage of a tractor with a slurry tanker (total weight 22 t). Each plot was harvested three times per year. N2O emissions were determined according to the “closed-chamber”-method during a time period from early April to mid-November in each experimental year (Hutchinson and Mosier, 1981). PROC MIXED of SAS 9.1 was used for statistical analysis. Means were compared by t-test and Bonferroni-Holm adjustment. Significance was declared at P0.05.

3. Results & Discussion N2O emission rates were strongly affected by the tested treatments as indicated by a significant threefold interaction (experimental year x compaction x fertilization) (Table 1).

Table 1. P-value of the analysis of variance of the parameter N2O-emission (cumulative N2O-N kg*ha-1) (y = year, comp = compaction, N = N-fertilization).

y comp N y*comp y*N comp*N y*comp*N N 2O 0.0953 0.0587 0.0001 0.3861 0.2618 0.0270 0.0084 No compaction-induced effects are perceptible on the unfertilized treatments (Figure 1). In 2006 and 2008, the compaction led to a sharp increase of N2O emissions on fertilized plots. In both years soil compaction was carried out on moist soil. In 2007, however, no effects of compaction could be

Nitrogen Workshop 2012

detected due to dry weather conditions in spring. The high N2O emissions of 2007 in both, the compacted and the non-compacted fertilized treatments originate in rewetting of soil after heavy rains in summer (detailed data not shown). In the legume-dominated unfertilized treatment, soil compaction had no influence on N2O emissions in spring. Due to a high proportion of alfalfa (67% of DM) the DM-yields of the unfertilised plots (16.2 t ha-1 year-1) did not differ significantly from the fertilised treatments (data not shown).

Figure 1. Cumulative nitrous oxide emissions [kg N2O-N ha-1] for soil compaction and N-fertilization treatments in 2006-2008; Capital letters indicate significant differences due to fertilization, lower case indicate significant differences due to soil compaction.

4. Conclusion To minimise N2O emissions from grassland, soil compaction should be avoided, especially under wet soil conditions and simultaneous high N-application. Forage legumes can compensate for the absence of nitrogen fertilisation, in terms of DM yield, and showed potential to reduce N2O emissions by approx. 75%.

References Hutchinson G. L. and Mosier A. R. 1981. Improved soil cover method for field measurement of nitrous oxide fluxes.

Soil Science Society of America 45, 311-316.

Velthof G.L., Oenema O., Postma R. and Van Beusichem M.L. 1997. Effects of type and amount of applied nitrogen fertilizer on nitrous oxide fluxes from intensively managed grassland. Nutrient Cycling in Agroecosystems 46, 257-267.

Yamulki S. and Jarvis S. C. 2002. Short-term effects of tillage and compaction on nitrous oxide, nitric oxide, nitrogen dioxide, methane and carbon dioxide fluxes from grassland. Biology and Fertility of Soils 36, 224-231.

Nitrogen Workshop 2012

Effects of anaerobic digestion of organic manures on N turnover and N utilization Sørensen, P.a, Khan, A.R.a, Møller, H.B.b, Thomsen.I.K.a a Aarhus University, Department of Agroecology, 8830 Tjele, Denmark b Aarhus University, Department of Biosystems Engineering, 8830 Tjele, Denmark

1. Background & Objectives Animal manures and plant-based manures are used for biogas production by anaerobic digestion (AD). After AD the concentration of ammonium-N in manure is increased and the concentration of decomposable C is decreased. Thus, the potential first year fertilizer value of the manure can be increased by the treatment. However, pH is also increased by AD thereby increasing the risk of ammonia losses. The objective of this paper was to compare N turnover in soil after application of digested and corresponding undigested manures, and to compare N fertilizer values of digested manures after direct injection or surface-banding in cereals.

2. Materials & Methods Cattle and pig slurries, a dairy cattle feed mixture (mainly maize silage), cattle faeces (cow fed on the same diet) and plant-based green manures were digested in continuously fed pilot digesters at thermophilic conditions (47-53°C) as described by Møller et al. (2007). The average hydraulic retention time was about 20 days. Two experiments were carried out each involving selected digested and non-digested products. In the first experiment the net release of mineral N from digested and non-digested manures applied to soil was measured in a laboratory incubation study with a sandy loam soil incubated at 20°C. Soil mineral N was extracted with 1M KCl 4, 7, 14, 28, 84 and 119 days after manure application. In the second experiment, the mineral fertilizer replacement values of total N (MFRV) were measured in framed field plots on a loamy sandy soil where grain yields and N uptake were compared to plots receiving increasing amounts of mineral N fertilizer (Sørensen and Eriksen, 2009). The manures were surface-banded in spring in winter wheat simulating a trailing hose application (150 kg total N ha-1) or applied in a band at 10 cm depth simulating a direct injection before sowing spring barley (80 kg total N ha-1).

3. Results & Discussion In the incubation experiment the proportion of total N on ammonium form increased after AD and more mineral N was released during decomposition in soil (Figure1). For slurry the increase in mineral N release was equivalent to about 10-25% of total slurry N. After AD of the cattle feed mixture the mineral N release in soil increased from about 20% of total N to about 80%, and AD of cattle faeces (from cattle fed the same diet) increased the mineral N release in soil from about 20% of total N to about 60% (Figure 1). In the field experiment the MFRV of the two injected cattle slurries applied to barley increased from 58% and 75% of total N to 69% and 82% with AD (Table 1). The MFRV of cattle slurry after surface-banding in winter wheat was significantly lower. The low availability after surface-banding was ascribed to high ammonia volatilization losses. The MFRV of injected pig slurry was high (89-91%) and similar with and without AD. After surface banding of pig slurry MFRV was 75% for untreated and 87% for digested pig slurry. Thus, the reduced fertilizer value after surface banding was most significant for the manures with the highest dry matter content as was expected due to lower infiltration in soil. The MFRV of digested plantbased manures was in the same range as digested cattle slurries, 73-77% after injection and only 43after surface-banding of the manure.

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4. Conclusion After AD of pig and cattle slurry the increase in potential plant availability was equivalent to 10of total manure N. AD of cattle faeces and a mixed cattle diet increased the net mineral N release in soil even more to about 60 and 80% of total N, respectively. The present results indicate that the plant availability of N of digested plant materials is similar to that of digested cattle slurry.

After surface-banding of digested manures rich in fibers, such as cattle and plant-based manures, significant ammonia loss can be expected resulting in relatively poor utilization of manure N.

References Møller, H.B., Nielsen, A.M., Nakakubo, R. and Olsen, H.J. 2007. Process performance of biogas digesters incorporating pre-separated manure. Livestock Science 112, 217-223.

Sørensen, P. and Eriksen, J. 2009. Effects of slurry acidification with sulfuric acid combined with aeration on the turnover and plant availability of nitrogen. Agric. Ecosyst. Environ. 131, 240-246.

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