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2. Materials & Methods Fresh dairy cattle excreta (dung and urine) were collected from a farm in early July 2011 and mixed with differing ratios of straw or sawdust to provide additional C. The high ratio of excreta to straw or sawdust was chosen to represent current practice on two South Otago dairy farms with housed wintering systems, while the low ratio was chosen to determine the effect of increasing inputs of these C materials. The straw was a mixture of barley and wheat in a ratio of 1:3 to represent the mix used on the representative farm. Characteristics of excreta and C materials are shown in Table 1 while treatments are shown in Table 2. On 6 July 2011 each treatment, replicated three times, was placed into a series of 0.5 m long upright plastic pipe, sealed at the base and buried, with the surface at ground level. NH3 volatilisation was regularly measured over 6 months. Lids were placed over the gas measurement columns on 21 occasions for ca. 24 hours with air drawn through the headspace and dreshel bottles containing dilute sulphuric acid to trap ammonia. Following sample analysis, cumulative emissions were calculated by integrating measured losses.
3. Results & Discussion Ammonia losses from stored excreta with no added C-rich material was equivalent to 48% of the initial total N content: this was reduced by 31-94% with the addition of C-rich materials (Table 3).
As the straw and sawdust had the same C content (39%; Table 1), it was possible to relate C input to NH3 loss, resulting in a significant negative relationship (R2 = 0.991, P = 0.004; Figure 1).
Addition of C-rich material such as straw and sawdust will increase the C:N ratio of the manure, thereby immobilising NH4+, leading to a reduction in NH3 loss. While sawdust was found to be more effective, due to a combination of higher rates, higher C:N ratio and lower pH, access to this material may limit its widespread use as bedding material. This work will be expanded to include N2O and methane emissions, to provide full greenhouse gas accounting.
4. Conclusion This study has shown that the addition of straw and sawdust as bedding material also provides an effective method for reducing NH3 losses through immobilisation of mineral N. However, inputs of C-rich material need to consider cost of material and increases in bulk manure to be land applied following storage.
References Webb, J., Menzi, H., Pain, B.F., Misselbrook, T.H., Dammgen, U., Hendriks, H., Dohler, H. 2005. Managing ammonia emission from livestock production in Europe. Environmental Pollution 135, 399-406.
Clemens, J. and Ahlgrimm, H-J. 2011. Greenhouse gases from animal husbandry: mitigation options. Nutrient Cycling in Agroecosystems 60, 287-300.
Nitrogen Workshop 2012
Modeling the effect of nitrogen management on nitrogen losses, net energy balance and plant quality in a wheat-rapeseed rotation Gallejones, P.a, Aizpurua, A.b, Del Prado, A.a a BC3. Basque Centre for Climate Change. Bilbao, Spain.
b NEIKER-Basque Institute for Agricultural Research and Development, Derio, Spain.
1. Background & Objectives Nitrogen (N) is the main nutrient limiting factor in most agricultural systems, requiring the application of N fertilizers to optimize crop production. A well balanced fertilizer strategy does not necessarily imply using a yield-based target only; it may also involve plant quality parameters. Management practices involving fertilizer N should be efficient in order to minimize adverse effects on the environment. Since only a fraction of the applied N is taken up by the crop, the remainder is subject to loss, representing economic cost and environmental risk contributing to eutrophication in waters via nitrate leaching losses, acidification of terrestrial ecosystems by ammonia and mono-nitrogen oxides emissions and global warming by nitrous oxide (N2O). Other gasses such as carbon dioxide (CO2) and methane (CH4) are generated at different levels of the agricultural systems. These gasses and the N2O, form the greenhouse gasses (GHG) which contribute to climate change. Some measures as bioenergy crops can reduce indirectly the GHG emissions substituting fossil fuels by biofuels. It is important to develop tools that can estimate the fertilizer N requirements of a crop and predict N losses to the environment. The aim of this study is to describe a framework that integrates simulation of energy and N flows and losses with emissions from the rest of the stages from bioenergy cropping systems.
2. Materials & Methods This study describes the principles and stages to develop a mass-balance N cycle model for arable cropping systems using some of the principles used for mass-balance N modeling in grasslands (Scholefield et al., 1991; Brown et al., 2005). The new model was constructed using data from several experiments carried out in different areas of Spain (Quemada, 2006) and is intended to be applicable to wheat-rapeseed rotations in northern Spain. The model simulates the cycling of N in arable cropping systems and predicts environmental losses on the basis of fertilizer application and soil and site characteristics. Field-scale simulated N losses can be integrated within a life cycle assessment (LCA) to study the effect of fertilization on N emissions of some products and byproducts such as biofuels from energy crops. Data from a field experiment conducted under the humid Mediterranean climate in northern Spain (Gallejones et al., subm.) were used to determine a parcial LCA of winter oilseed rape (Brassica napus L.) as affected by N fertilization. The environmental and energy flows associated with biodiesel production were quantified for different N fertilizer rates. The life cycle inventory of biofuels in this analysis included four subsystems: crop production, handling and storage of seeds, transport of the seeds and biofuel production.
3. Results & Discussion Nitrogen fertilization significantly increased yield of rapeseed by 60% (p 0,001) but it reduced the oil concentration in the seed. The highest oil yield (kg ha-1), however, was achieved with the highest N rate which increased the total amount of biodiesel obtained (energy output, MJ ha-1). Rathke et al., (2005) indicate that oil content is expected to decrease in a linear fashion with increasing fertilizer N; so we
Nitrogen Workshop 2012
could have expected a maximum oil yield at a lower fertilizer rate than that observed for maximum yield. The energy input (MJ ha-1) was also higher if N fertilizer was applied but taking into account the energy output, the zero N application resulted in the highest energy consumption in terms of MJ MJ -1.
The total GHG emissions increased with N application by increasing the percentage of GHG emissions from N fertilizer up to 56% with the highest rates of N fertilizer (180 and 220 kg ha-1). The emissions of N2O also increased with N fertilizer and corresponded to 50% of the GHG emissions from N fertilizer. Overall soil N2O emissions accounted for 21% to 28% of the GHG emissions associated with biodiesel production.
Figure 1. Estimated GHG emissions from biodiesel production (left) and display of different kind of GHG emissions from N fertilizer production and use (right) in CO2-equivalents per MJ of biodiesel at field-scale.
4. Conclusion The optimal N rate applied to winter oilseed rape depends on the aim of production. High N rates are required for high yield but normally a lower rate is needed for higher energy output. GHG emissions from N fertilisation were the most important item of the total emissions in the biodiesel production at field-scale, with the emissions of N2O from soil being a significant factor. However, future research should include allocation methods for a more precise calculation and results of N2O emissions from field studies as there is much variation depending on the type of soil and weather conditions.
References Brown, L., Scholefield, D., Jewkes, E.C., Lockyer, D.R. and del Prado, A. 2005. NGAUGE: a decision support system to optimise N fertilisation of British grassland for economic and/or environmental goals. Agriculture, Ecosystems and Environment 109, 20-39.
Callejones, P., Castellón, A., del Prado, A., Unamunzaga O. and Aizpurua A. (subm.). Nitrogen and sulphur fertilization effect on leaching losses, nutrient balance and plant quality in a wheat-rapeseed rotation under humid Mediterranean climate. Nutrient Cycling in Agroecosystems.
Quemada, M. 2006. Balance de nitrógeno en sistemas de cultivo de cereal de invierno y de maíz en varias regiones españolas. Monografías INIA, serie agrícola nº21.
Rathke, G.W., Christen, O. and Diepenbrock, W. 2005. Effects of nitrogen source and rate on productivity and quality of winter oilseed rape (Brassica napus L.) grown in different crop rotations. Field Crops Res. 94 (2-3), 103-113.
Scholefield, D., Lockyer, D.R., Whitehead, D.C. and Tyson, K.C. 1991. A model to predict transformations and losses of nitrogen in UK pastures grazed by beef-cattle. Plant Soil 1322, 165-177.
Nitrogen Workshop 2012
N fertilization and diazotrophic bacteria inoculation in sugarcane for bioenergy production Cantarella, H.a, Montezano, Z.F.a, Gava, G.J.C.b, Rossetto, R.c,Vitti, A.C.c;Vargas, V.P.a, Soares, J.a, Oliveira, C.A.a, Joris, H.A.W.a, Kölln, O.T.d, Dias, F.L.F.c, Urquiaga, S.e a Agronomic Institute of Campinas, Campinas, SP, Brazil; bAPTA, Jau, SP, Brazil; cAPTA, Piracicaba, SP, Brazil;
d CENA-USP, Piracicaba, SP, Brazil; eEMBRAPA, Seropédica, RJ, Brazil
1. Background & Objectives Ethanol from sugarcane represents almost half of the liquid fuels used for light vehicles in Brazil.
Nitrogen (N) fertilizers are responsible for 25% of the energy input in agriculture operations for sugarcane production (Boddey et al., 2008) or almost 40% of the green house gases emissions (Lisboa et al., 2011). Therefore, N fertilization can significantly affect the energy balance and environmental benefits of sugarcane ethanol. It is known that diazotrophic bacteria can supply part of the N of sugarcane (Urquiaga et al., 2011) and recently an inoculant was developed for this crop, containing five species of bacteria. The objective of this paper was to evaluate the response of sugarcane to N fertilization with and without inoculation of N-fixing endophytic bacteria.
4. Conclusion Despite evidences of BNF in sugarcane, inoculation of N-fixing bacteria cannot replace mineral N fertilization in the sites studied.
References Boddey, R.M., Soares, L.H.B., Alves, B.J.R. and Urquiaga, S. 2008. Bio-ethanol production in Brazil, In: Pimentel D.
(ed.), Renewable Energy Systems: Environmental and Energetic Issues, Springer, New York. pp. 321-356.
Hoefsloot, G., Termorshuizen, A.J., Watt, D.A. and Cramer, M.D. 2005. Biological nitrogen fixation is not a major contributor to the nitrogen demand of a commercially grown South African sugarcane cultivar. Plant and Soil 277, 85Lisboa, C.C., Butterbach-Bahl, K., Mauder, M. and Kiese, R. 2011. Bioethanol production from sugarcane and emissions of greenhouse gases - known and unknowns. Global Change Biology Bioenergy. DOI: 10.1111/j.1757x Pereira, W. 2011. Productivity and technological quality of sugarcane inoculated with diazotrophic bacteria. Instituto de Agronomia, UFRRJ, Seropédica, RJ. Master Dissertation, pp. 70. (In Portuguese) Rossetto, R., Dias, F.L.F., Landell, M.G.A., Cantarella, H., Tavares, S., Vitti, A.C. and Perecin, D. 2010. N and K fertilisation of sugarcane ratoons harvested without burning. Proceedings of the International Society of Sugar Cane Technologists, 27, 1-8 Urquiaga, S., Cruz, K.H.S. and Boddey, R.M. 1992. Contribution of nitrogen fixation to sugar cane: nitrogen-15 and nitrogen balance estimates. Soil Science Society of America Journal 56, 105-114.
Urquiaga S., Xavier R.P., Morais R.F., Batista R.B., Schultz N., Leite J.M., Sa J.M., Barbosa K.P., Resende A.S., Alves B.J.R., Boddey R.M. 2011. Evidence from field nitrogen balance and 15N natural abundance data for the contribution of biological N2 fixation to Brazilian sugarcane varieties. Plant and Soil online. DOI: 10.1007/s11104-011-1016-3.
Nitrogen Workshop 2012
N2O emissions from radiata pine, Douglas fir and beech forest stands in the Basque Country.
Barrena, I.a, Estavillo, J.M.a, Duñabeitia, M.a, Merino, P.b, González-Murua, C.a, Menéndez, S.c a Department of Plant Biology and Ecology, University of the Basque Country (UPV/EHU), Apdo. 644, E-48080 Bilbao, Spain.
b NEIKER-Tecnalia. Dept. Ecotecnologías. Barrio Berreaga, 1. 48160 Derio (Bizkaia), Spain c Agrobiotechnology Institute (IdAB). Campus de Arrosadía, E-31192, Mutilva Baja, Spain.
1. Background & Objectives Nitrous oxide (N2O) is considered a problematic greenhouse gas due to its longevity in the atmosphere (120 years) and its high relative absorption capacity. Forests are considered excellent systems for carbon sequestration to mitigate the greenhouse effect. However, there are no studies regarding N2O emissions from forest systems in our edaphoclimatic conditions. Forestry in the Basque Country is one of the most important primary sector activities, being 55% of the total area of the Basque Autonomous Community forest surface (Inventario Forestal CAE, 2005). The aim of this work was to determine and compare the magnitude of N2O emissions in the main forest plantation in our region (radiata pine) with another forestry interest plantation such as Douglas fir and with a beech forest as representative of natural forests.
2. Materials & Methods The experiment was carried out in three different mature stands of radiata pine (Pinus radiata D.
Don), Douglas fir (Pseudotsuga mensiezii Mirb.) and beech (Fagus sylvatica L.). Radiata pine and Douglas fir stands are located at Artzentales (43º13’ N, 3º 11’ W, 350m altitude), while the beech stand is at the Natural Park of Gorbea (43º 6´ N, 2º 48´ W, 400m altitude). Soil properties for the stands are described in Table 1.
Table 1. Soil properties in each stand.