BG3.19

The recycling of organic waste in biogas plants is proposed as a measure to close nutrient cycles and possibly reduce nitrogen losses such as nitrous oxide emissions and nitrate leaching. Ammonia volatilization after fertilizer spreading is yet another nitrogen loss pathway which is often understudied and not yet fully understood but the knowledge is needed in order to optimize fertilizer management. We therefore aimed to quantify the volatilization of ammonia after the trail-hose application of digestates compared to cattle slurry. We hypothesize that digestates have larger and longer lasting nitrogen losses via ammonia volatilization due to higher NH₄⁺ contents and pH values compared to fresh manure. In this project, digested and un-digested organic fertilizers were applied twice per year in a 2.5-years field experiment with three consecutive arable crops (maize, winter wheat and winter barley) under organic farming. We used Automated Low Cost Impinger Systems to measure ammonia emissions after fertilizer application. The emissions were then modeled using the backwards Langrangian stochastic dispersal model with respect to wind conditions. A preliminary presentation of the data indicates that ammonia emissions from the cattle slurry, slurry-based digestate, and industrial digestate are alternately higher or lower. In 2018, emissions from cattle slurry tended to be lower than those from slurry-based digestate and industrial digestate, while in 2019 and 2020 all three liquid organic fertilizers had similar emissions. In the measurement period after the second fertilizer application in 2018, which took place at the end of May, conspicuously high emissions were measured. This can be explained by the high temperatures during this period. Adaptive strategies in fertilizer management should thus consider reduced inputs of organic fertilizers  during warm periods.

How to cite: Efosa, N., Krause, H.-M., Häni, C., Six, J., and Bünemann, E.: Ammonia emissions from cattle slurry and digestates, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-15587, https://doi.org/10.5194/egusphere-egu21-15587, 2021.

The presence of cows on a pasture considerably modifies exchanges of biogenic volatile organic compounds (BVOCs). By regulating the biomass present, they can have an impact on the constitutive flux (exchanges from soil and grass that are not induced by leaf wounding or trampling by cows) but they can also cause direct emissions from exhalation and indirect emissions by leaf injury (grazing), trampling and wastes. In this study conducted on the ICOS pasture site of Dorinne (Belgium), we disentangled these different sources/sinks for three oxygenated BVOCs commonly exchanged on grasslands (methanol, acetaldehyde and acetone), using a combination of turbulent flux measurements, enclosure flux measurements, tools to detect the presence and activity of cows in the footprint of the turbulent flux measurements and a flux footprint model. Direct exhalation emissions were low, representing only 2.3% and 10% of the spring total flux of methanol and acetone respectively. Comparison of grazed and non-grazed enclosures pointed out that emissions following leaf wounding were significant for all studied BVOCs, decreased exponentially with time to become negligible after maximum five days. Cow indirect emissions at the pasture scale (turbulent flux measurements) where likely dominated by grazing and were shown to be a major component of the total diurnal flux for each of the three studied BVOCs. Comparison with a hay meadow also showed that the temporal dynamics of those BVOC emissions were very different according to the grass management type, calling for specific parametrization in up-scaling emission models.

How to cite: Heinesch, B., Michel, C., Amelynck, C., Schoon, N., Mozaffar, A., Aubinet, M., Bachy, A., and Dumortier, P.: The role of cows on OVOC exchanges of a pasture, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-13117, https://doi.org/10.5194/egusphere-egu21-13117, 2021.

The annual global leaf litter production has been estimated between 75 and 135 Pg DM yr^-1 contributing to the 10% of the global annual emission of acetone and methanol. Besides their impact on atmospheric chemistry, little attention has been drawn to leaves litter and their contribution to the bVOC emissions and their SOA formation potential.

The purpose of this study is to analyze the bVOC (biogenic volatile organic compounds) emissions from rapeseed leaves litter and their contribution to SOA (secondary organic aerosol) formation under three different conditions: (I) the presence of a UV light irradiation (II) the presence of ozone, and (III) a combination of the previous two. To reach this goal, bVOC and aerosol numbers have been measured for 6 days in a controlled atmospheric chamber containing leaf litter samples.

Results showed that VOC emission profiles were affected by the UV light irradiation, which increased the summed VOC emissions compared to the experiment with O₃. Furthermore, the diversity of the VOC emitted from the rapeseed litter increased with the UV light irradiation. The highlight of this study is that the SOA formation rate observed when leaf litter was exposed to both UV light and O₃ indicates a potentially large source of atmospheric pollution at the local scale. To our knowledge, this study investigates for the first time the effect of UV irradiation and O₃ exposure on both VOC emissions and SOA formation for leaf litter samples. A detailed discussion about the processes behind the biological production of the most important VOC is proposed.

How to cite: Abis, L., Kalalian, C., Wang, T., Lunardelli, B., Perrier, S., Loubet, B., Ciuraru, R., and George, C.: Biogenic VOC profiles emissions of Rapeseed leaf litter and their SOA formation potential, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-14981, https://doi.org/10.5194/egusphere-egu21-14981, 2021.

The ecosystem-atmosphere flux of biogenic volatile organic compounds (BVOCs) has important impacts on tropospheric oxidative capacity and the formation of secondary organic aerosols, influencing air quality and climate. In particular, this is true in managed boreal forests in the Northern Hemisphere, where BVOC emissions often dominate over anthropogenic sources of VOC.

Here we present measurements of BVOCs in a managed boreal forest located at the ICOS station Norunda in Sweden, collected using proton transfer reaction mass spectrometry (PTR-MS). This managed forest consists of a mix of Scots pine (Pinus sylvestris) and Norway spruce (Picea abies). These long-term PTR-MS measurements were collected at six heights (4m, 8.5m, 13.5m, 19m, 24.5m, and 33.5m) in the forest canopy over several periods during 2014 to 2016. Ozone concentrations were simultaneously measured in conjunction with these PTR-MS measurements. The main BVOCs investigated with the PTR-MS were isoprene, monoterpenes, methanol, acetaldehyde, and acetone. The distribution of BVOC sources and sinks in the forest canopy was explored using several Lagrangian dispersion matrix methods, including localized and continuous near-field theory. The canopy resistance and deposition velocities for ozone and the BVOCs were investigated, and the results for isoprene and monoterpene emissions were found to agree well with several standard BVOC emission algorithms. These results will have importance for constraining BVOC emission estimates from managed boreal forests in the future.

How to cite: Petersen, R. C., Rinne, J., Holst, T., and Mölder, M.: Sources and Sinks of BVOCs in a Managed Boreal Forest, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-15430, https://doi.org/10.5194/egusphere-egu21-15430, 2021.

Semiarid oak savannas (grasslands with scattered trees), partially covered, subject to regular droughts, grazing, and high levels of solar radiation, are nonetheless, typically carbon sinks regarding CO2. However, dehesas are a productive system, a trait shared with other savannas, and they are shaped by their uses for economic production. One of its multiple uses, livestock extensive farming, key to its economic profitability and to the preservation of the agrosilvopastoral system structure, modifies the Greenhouse gas (GHG) balance by adding a significant amount of CH4 and N2O into the cycle. Recent reports and publications have evaluated and compared different types of livestock management within the context of climate change. GHG emissions, extensive use of the soil resource, or the introduction of nitrogen into the system, are some of the generated effects that cause a negative evaluation of extensive farming. Nevertheless, the importance of this sector, given its extension and impact on production and rural development, demands a more rigorous evaluation. It is necessary to precisely account for the fluxes in their totality (including the CO2 sink effect) and the relationships between them. Currently, there are few studies that determine the GHG balance of dehesas, and they are mainly centred on CO2 fluxes without integrating the influence of livestock, or in meadows without a tree layer (which changes the CO2 balance). The net global warming potential of dehesas is unknown, given that very few direct and long-term flux measurements have been taken on them. In this work, CO2 and H2O fluxes from an eddy covariance tower located in an Andalusian dehesa were processed (standard corrections), filtered and homogenized, including filling gaps using artificial neural networks. We calculated the annual CO2 budget since 2015, to assess the sink/source nature of the area. In a modeling exercise to be able to close the carbon cycle, we estimated CH4 and N2O depending on the number of livestock present in the area by season/year, evaluating the tipping point.

How to cite: Andreu, A., Carpintero, E., Gómez-Giraldez, P., and González-Dugo, M. P.: Accounting for carbon exchanges in a semiarid oak savanna (dehesa)., EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-14189, https://doi.org/10.5194/egusphere-egu21-14189, 2021.

The Philippines' agriculture sector continues contributing to country-wide soil trace gas emissions; however, field-based estimation of emissions from this sector remains inadequate.  While there’s a need to increase crop production to provide for a fast-increasing population, it is equally essential to reduce greenhouse gases (GHG) from agricultural production to protect the environment. A reliable assessment of soil GHG is a requisite to attain these, thus the present study. We conducted spatially replicated quantification of soil greenhouse gas fluxes, i. e. N₂O, CH₄, and CO₂, with monthly measurements from May 2018 to May 2019, as well astheirsoil controlling factors in nine plots of secondary forest and ten farms, all on comparable Andosol soil in Leyte Island, the Philippines. The management practices of these vegetable farms were those implemented by the farmers, and our measurements were carried out on these actual farm practices, reflecting their commonly varied fertilization rates (200 – 610 kg N ha^-1 cropping period^-1 with 2 – 3 cropping periods each year). Soil N₂O emissions from vegetable farms were larger than the forest (P ≤0.01) and were stimulated during the dry than the wet season (P ≤0.01). Its temporal variation was mainly driven by soil NO₃^– (r = 0.52, P ≤0.01).  Large stocks of soil extractable NO₃^– in the top 50 cm (9250 ± 2830 mg N m^–2, mean ± SE) and 50 – 100 cm soil depth (11255 ± 5980 mg N m^–2) supported the substantial soil N₂O emissions from these vegetable farms, which were larger than those from other agricultural areas in South East Asia on similar soil and climate. These small-scale vegetable farms had annual fluxes of 12.7 ± 2.6 kg N₂O–N, –1.1 ± 0.1 kg CH₄–C and 11.6 ± 0.7 Mg CO₂–C ha^-1 yr^-1, whereas the secondary forest as reference land use had 0.10 ± 0.02 kg N₂O–N, –2.0 ± 0.2 kg CH₄–C, and 8.2 ± 0.7 Mg CO₂–C ha^-1 yr^-1. The forest had larger soil CH₄ uptake than the vegetable farms (P ≤0.01). For the forest, CH₄ uptake was positively correlated with soil moisture (r = 0.60, P ≤0.01), suggesting diffusion limitation of atmospheric CH₄ into the soil and/or soil CH₄ production during high rainfall months. For the vegetable farms, CH₄ uptake was negatively correlated with both soil NO₃^– and NH₄⁺ (r = –0.46, P ≤0.01), suggesting CH₄ consumption enhanced by mineral N. Soil CO₂ emissions were higher in vegetable farms relative to the forest (P ≤0.01), reflecting the former’s reduced soil organic carbon stocks in the top 1 m (P ≤0.01) but compensated with regular application of chicken manure (460 – 1940 kg C ha^-1 cropping period^-1) as organic fertilizer. Our study expounded understanding on the extent of changes in soil GHG from an Andosol soil that underwent land-use conversion. Such data will be beneficial in developing sound management and policy strategies for reducing soil GHG fluxes from this economically vulnerable agricultural sector.

How to cite: Quiñones, C. M. O., Veldkamp, E., Lina, S. B., Bande, M. J. M., Arribado, A. O., and Corre, M. D.: Soil trace gas fluxes from secondary forest converted to small-scale vegetable farms on an Andosol soil, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-2433, https://doi.org/10.5194/egusphere-egu21-2433, 2021.

Tillage practices influence soil CO₂ emissions, hence many research investigate the long-term effects of conservation and conventional tillage methods e.g. ploughing and no-tillage on soil greenhouse gas emission.

The experiment site is an 18-years-old long-term tillage trial established on chernozem soil. During 2020, we took weekly CO₂ emission measurements in the mouldboard ploughing (MP), no-tillage (NT), and shallow cultivation (SC) treatments Tillage depth was 26-30 cm, 12-16 cm and 0 cm in the cases of MP, SC and NT respectively. The experiment was under wither oat cultivation.

We investigated the similarity in the CO₂ emission trends of SC to MP or NT treatments. Besides CO₂ emission measurements, we also monitored environmental parameters such as soil temperature (Ts) and soil water content (SWC) in each treatment.

During the investigated year (2020 January - December) SC had higher annual mean CO₂ emission (0.115±0.083 mg m^-2 s^-1) compared to MP (0.099±0.089 mg m^-2 s^-1) and lower compared to NT (0.119±0.100 mg m^-2 s^-1). The difference of the CO₂ emissions was significant between SC and MP (p<0.05); however, it was not significant between SC and NT (p>0.05) treatments. The Ts dependency of CO₂ emission was moderate in all treatments. CO₂ emissions were moderately depended on SWC in MP and SC, and there was no correlation between these parameters in NT.

The annual mean CO₂ emission of the SC treatment was more similar to the NT, than to the MP treatment.

How to cite: Dencső, M., Horel, Á., Bakacsi, Z., and Tóth, E.: Comparison of soil CO2 emissions from three different tillage methods on chernozem soil, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-14675, https://doi.org/10.5194/egusphere-egu21-14675, 2021.

The need to sustain global food demand while mitigating greenhouse gases (GHG) emissions is a challenge for agricultural production systems. Since the reduction of GHGs has never been a breeding target, it is still unclear to which extend different crop varieties will affect GHG emissions. The objective of this study was to evaluate the impact of N-fertilization and of the use of growth regulators applied to three historical and three modern varieties of winter wheat on the emissions of the three most important anthropogenic GHGs, i.e. carbon dioxide (CO₂), methane (CH₄) and nitrous oxide (N₂O). Furthermore, we aimed at identifying which combination of cultivars and management practises could mitigate GHG emissions in agricultural systems without compromising the yield. GHG measurements were performed using the closed chamber method in a field experiment located in Göttingen (Germany) evaluating three historical and three modern winter wheat varieties, with or without growth regulators under two fertilization levels (120 and 240 kg nitrogen ha^-1). GHG measurements were carried out for 2 weeks following the third nitrogen fertilizer application (where one third of the total nitrogen was applied), together with studies on the evolution of mineral nitrogen and dissolved organic carbon in the soil. Modern varieties showed significantly higher CO₂ emissions (i.e. soil and plant respiration; +23 %) than historical varieties. The soils were found to be a sink for CH_4, but CH₄ fluxes were not affected by the different treatments. N₂O emissions were not significantly influenced by the variety age or by the growth regulators, and emissions increased with increasing fertilization level. The global warming potential (GWP) for the modern varieties was 7284.0 ± 266.9 kg CO_2-eq ha^-1. Even though the GWP was lower for the historic varieties (5939.5 ± 238.2 kg CO₂-_eq ha^-1), their greenhouse gas intensity (GHGI), which relates GHG and crop yield, was larger (1.5 ± 0.3 g CO₂-_eq g^-1 grain), compared to the GHGI of modern varieties (0.9 ± 0.0 g CO₂-_eq g^-1 grain), due to the much lower grain yield in the historic varieties. Our results suggest that in order to mitigate GHG emissions without compromising the grain yield, the best management practise is to use modern high yielding varieties with growth regulators and a fertilization scheme according to the demand of the crop.

How to cite: von der Lancken, E., Nasser, V., Hey, K., Siebert, S., and Meijide, A.: Effect of wheat varieties and growth regulators on soil greenhouse gas emissions, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-8605, https://doi.org/10.5194/egusphere-egu21-8605, 2021.

The agricultural emissions are the dominant sources of N₂O and CH₄ in the Netherlands. In this study, we have estimated nocturnal surface fluxes of both N₂O and CH₄ using atmospheric measurements at the Cabauw tall tower (4.927◦ E, 51.971◦ N, - 0.7 m a.s.l.). The nocturnal N₂O and CH₄ surface fluxes were derived using two different methods, the vertical gradient method (VGM), i.e. the sum of the storage flux and the turbulent flux, and the radon-tracer method (RTM), for the period of March 2017-December 2018 and 2016-2018, respectively. For N₂O, we show that a few events occurring between May 30 and June 4 in 2018 dominated the monthly means. Using the VGM, we have estimated the annual mean nocturnal surface flux to be 0.59 ± 0.38 g/m²/yr (1 σ, the same as below) and 0.53 ± 0.19 g/m²/yr with and without events, respectively. The fluxes are high in the summer and low in the winter, with a seasonal amplitude of around 1.0 g/m2/yr and 0.5 g/m²/yr, with and without events, respectively, which is likely caused by the seasonality of agricultural activities. For CH_4, the annual mean nocturnal surface flux is 12.1 ± 3.3 g/m²/yr and the amplitude is around 9.9 g/m²/yr. Using the RTM, the mean fluxes of the whole period for N₂O and CH₄ are estimated to be 1.18 ± 2.25 (1.08 ± 1.29, without the events) g/m²/yr and 26.9 ± 24.8 g/m²/yr, respectively; in contrast to the VGM, no apparent seasonal pattern has been found. However, there is a good linear correlation between the estimated N₂O fluxes from the two methods and the monthly means show a similar pattern when the same nights are considered; the R-squared value is around 0.9 with events and 0.6 without events, and the slope varies from 1.9 to 0.8 when different estimates of radon fluxes are used. Furthermore, we found that large N₂O fluxes are related to the amount of rainfall occurring days before, with the correlation coefficient of around 0.6 (p value<0.01). For CH₄, there is no correlation between the estimated CH₄ fluxes from the two methods. Our findings demonstrate that nocturnal N₂O and CH₄ fluxes in the Cabauw area are highly variable and vary over different seasons, and that both VGM and RTM are useful to quantify regional N₂O and CH₄ fluxes.

How to cite: Tong, X., Bosveld, F., Hensen, A., Scheeren, B., Frumau, A., and Chen, H.: Nocturnal surface fluxes of N2O and CH4 determined from atmospheric measurements at the Cabauw tall tower, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-14400, https://doi.org/10.5194/egusphere-egu21-14400, 2021.

Greenhouse gas (GHG) emissions contribute to climate change. Agricultural production contributes 10 – 14 % of the global anthropogenic GHG emission, including 37 % from soils (Paustian et al., 2016). Monitoring and analysis of emissions from agriculture is the basis for reducing GHG emissions and applying mitigation options. Measuring and estimating emissions from the agricultural sector are challenging and modelling is a useful tool to capture the heterogeneity of the dynamics. Agricultural management is the main driver for the carbon and nitrogen dynamics in croplands, which makes model approaches difficult, as potentially there is great heterogeneity in the influencing factors, but also a lack of robust data for management data for larger scales. Additionally, measurements of GHG emissions are scarce, on small (spatial and temporal) scales, or do not reflect the entire range of system variable combinations. This hinders the evaluation of large scale simulation results. The objective of the study was to simulate the GHG emissions (CO₂ and N₂O) for European croplands and use national inventory data for the evaluation of the results. We used the model ECOSSE which is based on the carbon model RothC and the nitrogen model SUNDIAL. For yield production, the primary production model MIAMI is coupled with ECOSSE. The model structure allows small scale differences (resolution for simulation is 0.1°) to be captured, while simulating monthly time steps. This balances the uncertainty of the available input data with the accuracy of the simulated results. The model shows reasonable results for the CO₂ emissions, but underestimates heterotrophic respiration, which leads to an overestimation of carbon fluxes to the soil. Nitrogen emissions are underestimated due to underestimation of fertilizer applications in some hot spots. The comparison with national inventories that depend mainly on statistics using simpler approaches shows differences to the simulation approach, which indicates the strong dependency of the emissions on the management data. The model approach provides the spatial distribution of the emissions as well as inter-annual dynamics. The changes on the model showed already the improved performances by the model and the extension to include more target variables. More sub-national and sub-annual data sets for evaluation will allow a further improvement of the model performance. 

How to cite: Kuhnert, M., Martin, M., Mcgrath, M., and Smith, P.: Modelling of greenhouse gas emissions from European croplands with the biogeochemical model ECOSSE, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-12249, https://doi.org/10.5194/egusphere-egu21-12249, 2021.

Agricultural soils are a significant source of greenhouse gas (GHG) emissions. To study these emissions, we are currently building three research platforms that consist of full eddy covariance instrumentation for determination of net ecosystem carbon dioxide exchange and fluxes of methane and nitrous oxide. These platforms will be completed with supporting weather, plant and soil data collection. Two of our platforms are sites on organic soils with a thick peat layer (>60 cm) and the third one is on a mineral soil (silt loam). To study the role of the grassland management practises at these sites, we have initiated ORMINURMI-project. Here, we will characterise the effects of ground water table (high vs. low), crop renewal methods (autumn vs. summer) and plant species (tall fescue vs. red glover grass) on greenhouse gas budgets of grass production. Also effect on yield amount and nutrient quality will be determined. In this presentation, we will present the preliminary data collected at these research platforms and our plans for the use of these data in the coming years.

How to cite: Lind, S., Maljanen, M., Myllys, M., Räty, M., Kykkänen, S., Korhonen, P., Termonen, M., Shurpali, N., and Virkajärvi, P.: GHG mitigation potential of agricultural management practises on mineral and organic soils, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-5567, https://doi.org/10.5194/egusphere-egu21-5567, 2021.

Monoculture croplands are considered as major sources of the greenhouse gas, nitrous oxide (N₂O). The conversion of monoculture croplands to agroforestry systems, e.g., integrating trees within croplands, is an essential climate-smart management system through extra C sequestration and can potentially mitigate N₂O emissions. So far, no study has systematically compared gross rates of N₂O emission and uptake between cropland agroforestry and monoculture. In this study, we used an in-situ ¹⁵N₂O pool dilution technique to simultaneously measure gross N₂O emission and uptake over two consecutive growing seasons (2018 - 2019) at three sites in Germany: two sites were on Phaeozem and Cambisol soils with each site having a pair of cropland agroforestry and monoculture systems, and an additional site with only monoculture on an Arenosol soil prone to high nitrate leaching. Our results showed that cropland agroforestry had lower gross N₂O emissions and higher gross N₂O uptake than in monoculture at the site with Phaeozem soil (P ≤ 0.018 – 0.025) and did not differ in gross N₂O emissions and uptake with cropland monoculture at the site with Cambisol soil (P ≥ 0.36). Gross N₂O emissions were positively correlated with soil mineral N and heterotrophic respiration which, in turn, were correlated with soil temperature, and with water-filled pore space (WFPS) (r = 0.24 ‒ 0.54, P < 0.01). Gross N₂O emissions were also negatively correlated with nosZ clade I gene abundance (involved in N₂O-to-N₂ reduction, r = -0.20, P < 0.05). These findings showed that across sites and management systems changes in gross N₂O emissions were driven by changes in substrate availability and aeration condition (i.e., soil mineral N, C availability, and WFPS), which also influenced denitrification gene abundance. The strong regression values between gross N₂O emissions and net N₂O emissions (R² ≥ 0.96, P < 0.001) indicated that gross N₂O emissions largely drove net soil N₂O emissions. Across sites and management systems, annual soil gross N₂O emissions and uptake were controlled by clay contents which, in turn, correlated with indices of soil fertility (i.e., effective cation exchange capacity, total N, and C/N ratio) (Spearman rank’s rho = -0.76 – 0.86, P ≤ 0.05). The lower gross N₂O emissions from the agroforestry tree rows at two sites indicated the potential of agroforestry in reducing soil N₂O emissions, supporting the need for temperate cropland agroforestry to be considered in greenhouse gas mitigation policies.

How to cite: Luo, J., Beule, L., Shao, G., Veldkamp, E., and Corre, M. D.: Gross rates of soil N2O emission and uptake and denitrification gene abundance in temperate cropland agroforestry and monoculture systems, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-886, https://doi.org/10.5194/egusphere-egu21-886, 2021.

Agricultural soils are an important source of nitrous oxide (N₂O) emission and are mainly affected by the application of N fertilization. In addition to the effect of fertilizer form (mineral/organic), N₂O production and consumption processes in agricultural systems are influenced by the soil characteristics. However, knowledge of this is still very limited for erosion-affected arable soils. Therefore, the aim of our investigations was to find the impact of soil erosion state associated with the landscape position and N fertilization form have on N₂O emission. This information is needed to evaluate the effects/benefits of new agricultural practices in future mitigation strategies aiming towards lower N₂O emissions.

We present 3 years of N₂O flux measurements in a two-factorial experiment by using a non-flow-through non-steady-state (NFT-NSS) manual chambers. Three sites were established on the summit position having similar soil type (Albic Luvisols; non-eroded soil) and were treated with organic fertilizer (100% organic biogas fermented residues (BFR)), mineral fertilizer (100% mineral calcium ammonium nitrate (CAN)), and a mixture of both fertilizers (50% CAN + 50% BFR). Two additional sites were established on the extremely eroded soil (Calcaric Regosols; on a steep slope with very dense parent material) and at a colluvial site in a depression (Endogleyic Colluvic Regosols) and treated with 100% CAN. The crop rotation was identical for all sites during the study period which includes: Maize (Zea mays L.) – Maize (Zea mays L.) – ­Winter rye (Secale cereale L.) – Sorghum (Sorghum bicolor) – Triticale (Triticosecale).

Our results show that the N₂O emission exhibited temporal and spatial variability and is mainly influenced by fertilization form and soil type. Among the three fertilization treatments within the same soil type (non-eroded soil), the site with the application of organic fertilization shows the highest cumulated N₂O emission which is accumulated to 13.5 kg N₂O-N ha^-1 compared to the site with mixed fertilization (11.4 kg N₂O-N ha^-1) and mineral fertilization (4.5 kg N₂O-N ha^-1). Among the three distinct soil types with an identical application of mineral fertilizer, the cumulated N₂O emission is higher at the depression (7.3 kg N₂O-N ha^-1) compared to the non-eroded (4.5 kg N₂O-N ha^-1) and extremely eroded soil (1.6 kg N₂O-N ha^-1). In general, our results suggest a stronger influence of N fertilization form than erosion affected soil on N₂O emission.

Keywords: NFT-NSS manual chamber; soil erosion; N fertilization form, nitrous oxide, soil type

How to cite: Vaidya, S., Macagga, R., Thalmann, M., Jurisch, N., Pehle, N., Verch, G., Sommer, M., Augustin, J., and Hoffmann, M.: Agricultural N2O emission is influenced by N-fertilization form rather than landscape position, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-1063, https://doi.org/10.5194/egusphere-egu21-1063, 2021.

Monoculture cropland is a major contributor to agriculture-related sources of N₂O emission, a potent greenhouse gas and an agent of ozone depletion. Cropland agroforestry has the potential to minimize deleterious environmental impacts. Presently, there is no systematic comparison of soil N₂O emission between cropland agroforestry (CAF) and monoculture systems (MC) in Western Europe. Our study aimed to (1) quantify the spatial-temporal dynamics of soil N₂O fluxes, and (2) determine their soil controlling factors in CAF and MC. We selected three sites with different soil types (Phaeozem, Cambisol, and Arenosol) in Germany. Each site has paired CAF and MC (agroforestry sites consisted of 12-m wide tree row and 48-m wide crop row and were established in 2007, 2008 and 2019 in these soil types, respectively). In each management system at each site, we had four replicate plots. In the CAF, we conducted measurements in the tree row and within the crop row at 1 m, 7 m, and 24 m from the tree row. We measured soil N₂O fluxes monthly over 2 years (March 2018‒February 2020) using static vented chambers method. Following gas sampling, we also measured soil temperature, water-filled pore space (WFPS), and mineral N (NH₄⁺ and NO₃^-) within the same day. Across all sites, soil moisture and N availability were major drivers of soil N₂O fluxes. Both CAF and MC were net sources of soil N₂O at all sites. At the site with Phaeozem soil, annual soil N₂O emissions from CAF in both years (1.84 ± 0.35 and 1.17 ± 0.30 kg N ha⁻¹ yr⁻¹) were greater than MC (0.89 ± 0.09 and 0.34 ± 0.05 kg N ha⁻¹ yr⁻¹) (P = 0.03). At the site with Cambisol soil, annual soil N₂O emission did not differ between MC (0.49 ± 0.07 kg N ha⁻¹ yr⁻¹) and CAF (0.73 ± 0.13 kg N ha⁻¹ yr⁻¹) in 2018/2019 (P = 0.20) whereas in 2019/2020 MC was 134% greater than CAF (2.92 ± 0.45 and 1.25 ± 0.08 kg N ha⁻¹ yr⁻¹, respectively; P = 0.03). The inter-annual differences were largely related to crop types and to climate conditions. At the site with Arenosol soil, there was no difference between CAF and MC. Our results indicated that CAF may decrease, maintain and/or increase soil N₂O emissions compared to MC depending on tree age, soil characteristics, management and precipitation.

How to cite: Shao, G., Martinson, G., Luo, J., Bischel, X., Niu, D., D. Corre, M., and Veldkamp, E.: Soil N2O emissions from temperate cropland agroforestry and monoculture systems, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-2553, https://doi.org/10.5194/egusphere-egu21-2553, 2021.

In grassland ecosystems nitrogen (N) inputs are mainly attributed to fertilizer applications for increasing  herbage productivity and to excreta of grazing animals. Cattle, for instance, excrete 75-95 % of the N intake. Accordingly, dung and urine patches of grazing animals form hotspots of nitrate leaching and gaseous N emissions as ammonia (NH₃) or the important greenhouse gas nitrous oxide (N₂O). Global default emission factor (EF) values for N₂O, 2.0 % for grazing based nitrogen inputs (EF3) and 1.0 % for nitrogen inputs via fertilizer applications (EF1) have been suggested by IPCC. However, some countries like New Zealand, Canada or the Netherlands have established country-specific EFs showing considerable regional differences.

In the present research study, we examine N₂O emissions of a pasture field in Switzerland in relation to possible drivers. Field scale emissions by eddy covariance are measured in parallel to patch-scale N₂O fluxes from controlled applications of urine, dung and fertilizer. The patch-scale fluxes are measured by a manually operated chamber ('fast-box') connected to an online gas analyzer. Besides estimating EF values on annual and seasonal basis, relevant factors that might control N₂O fluxes like environmental conditions (weather parameters, soil moisture, soil temperature), vegetation characteristics (height, composition, nitrogen and carbon content) and pasture management (patch age, grazing, fertilization, cut events, interactive effects) are analyzed. 

We present and discuss results of the first measurement year 2020. Three artificial urine applications during summer and autumn were performed. They show peak N₂O fluxes of 279-1718 μg m^-2 h^-1 directly after application that decrease to near-background fluxes within 19-43 days. Using a simple linear interpolation of measured N₂O fluxes, EF values of artificial urine patches vary between 0.57 and 2.44 % indicating a seasonal variability of N₂O fluxes.

How to cite: Barczyk, L., Kuntu-Blankson, K., Calanca, P., Six, J., and Ammann, C.: Quantification of N2O fluxes and EF values in a pasture using chamber and eddy-covariance technique, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-14398, https://doi.org/10.5194/egusphere-egu21-14398, 2021.