Food, feed, and fuel production are vital for human well-being. Yet current agricultural practices have resulted in extensive multi-media damages, primarily due to reactive nitrogen (Nr) emissions (NH₃, N₂O, NO_x). Managing Nr sustainably to alleviate food and feed insecurity has been identified as a Grand Engineering Challenge. Systematically analysing source contributions, flows, and impacts of Nr is crucial for an agro-dominant country like India that faces the dual challenge of food and environmental security for 1.6 billion people by 2050. Here, we construct an Environmentally Extended Input-Output model for Nr in the Indian agriculture sector (cropland + livestock) for 2000–2020. Our findings indicate an increase in total N input to cropland from 23 Tg-N to 33 Tg-N (2000–2020), largely attributed to synthetic fertilizers (62%), biological N fixation (17%), atmospheric nitrogen deposition (11%), and livestock manure use (7%). Despite these increases, nitrogen use efficiency has only improved marginally (45% in 2000 to 57% in 2020). Nr losses to hyrosphere constitute 55%-60% of total N, with atmospheric emissions accounting for 40%-45% of total N. Key pollutants include nitrites/nitrates lost through runoff (40%), NH₃ emissions (34%), and NO₃ leakage to groundwater (20%). Noteworthy are NH₃ emissions from fertilizer (55%) and manure (28%) application, and nitrogen deposition (12%).

Flows from the cropland sector serves as an input to the livestock sector, e.g., the production of grain and straw as feed to turn plant protein into animal protein, with efficiency varying from 4% to 10%. The type of animal and manure management systems and practices influences the N flow outputs from the livestock sector. Nitrogen within the remaining fraction (90–96%) is found in urine and dung, leading to potential nitrogen losses, i.e., 13.7TgN in the year 2020 due to the volatilization, leaching, and runoff as a result of application on cropland and manure management system of manure. Bovine animals have the largest share in manure N production, i.e., non-dairy cattle (37%), dairy (20%), and buffalo (26%), which constitute 83% of the total manure N production. Of the total produced manure (17Tg-N), 80% is produced in agriculture, and 20% is in pastoral areas. Of the agriculturally produced region, 30% undergo manure management system for treatment, i.e., 4TgN, while 70% are used for fuel combustion. Manure subjected to treatment is reintegrated into cropland at a rate of 52%, with approximately half being environmentally lost. Of this loss, 27% is attributed to atmospheric dissemination, comprising 22% as NH₃ resulting from volatilization and 5% through direct emissions of N₂O. Furthermore, 22% of the nitrogen is lost to the hydrosphere, distributed as 19% through runoff (0.8TgN) and 3% (0.1TgN) via NO₃- leaching.   Opportunities to alleviate N losses and boost feed conversion efficiency involve refining animal feed composition and the herd's genetic potential. However, a challenge remains in upgrading manure management practices. Our study constraints national-scale inputs, accumulation, and flows of Nr in Indian agriculture to enable a holistic approach to co-develop agriculture and environmental policies while identifying levers to enable greener agricultural production practices.

How to cite: Babbar, D., Kumari, S., and Balasubramanian, S.: Environmental Footprint of Reactive Nitrogen in Indian Agricultural Sector: An Extended Input-Output Analysis  , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-7225, https://doi.org/10.5194/egusphere-egu24-7225, 2024.

Primary sources of ammonia (NH₃) emissions originate from agriculture, impacting the environment, climate, and human health, thereby concomitantly reducing fertilizer nitrogen use efficiency. Accurate measurements under field conditions are required to provide a basis process understanding and for recommendations to policymakers and farmers. However, uncertainties remain regarding the accuracy and reliability of different low-cost NH₃ measurement methods and new application of the eddy covariance method for emissions from low-intensity sources, such as synthetic fertilizers.

In this study we focused on the quantification of NH₃ concentrations and fluxes determined by a quantum cascade laser spectrometer (QCL) with passivated inlet line within an eddy covariance setup and the comparison to low-cost passive diffusion samplers (ALPHA sampler) used for emission estimations with the integrated horizontal flux (IHF) method. Measurements were carried out in Central Germany during the vegetation periods in 2021 - 2023 in a winter wheat crop field, which received three urea fertilizer applications (to a total of 170 kg N ha^-1) per year. The atmospheric NH₃ concentrations measured by the QCL and the ALPHA samplers were compared. Then, the cumulative losses of NH₃ over the measurement periods (March - July) in the different years (2021 - 2023) were calculated and compared between the two approaches (QCL-eddy covariance and ALPHA-IHF).

The NH₃ concentration measurements showed that the ALPHA samplers generally yielded lower concentration values compared to the time-integrated QCL values. While the relative mismatch decreased with higher concentrations (>20 ppb), significant deviations were observed in the lower concentration regime. When ALPHA concentrations were corrected for measurement height to precisely align with QCL sampling height, a systematic underestimation was found. Reasons for the differences are currently under investigation and may be explained by the vertical and horizontal sampler separation from the main eddy flux tower and possibly due to varying environmental conditions.  

First results of NH₃ eddy covariance fluxes (kg N ha^-1 period^-1) showed clear diurnal courses and emission peaks around noon on the days after each urea application throughout all years. High-frequency losses using a co-spectral method in the process of eddy flux calculation were estimated to be in the range of 25 to 30 %.

The performance of both methods (ALPHA-IHF and QCL-eddy covariance) in estimating NH₃ losses from field-scale fertilizer applications is discussed, along with the sensitivity of input concentrations on NH₃ emission estimates.

Our study is a step towards better comparability and integration of different NH₃ measurement techniques and is expected to provide useful tools for robust estimation of NH₃ emission factors for synthetic fertilizer applications.

How to cite: Kukowski, S., Kemmann, B., Wintjen, P., Rüffer, J., Jüdt, J.-K., Götze, H., Saul, M., Pacholski, A., Flessa, H., and Brümmer, C.: Measuring ammonia losses from winter wheat with eddy covariance: a comparative analysis with the integrated horizontal flux method, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-18307, https://doi.org/10.5194/egusphere-egu24-18307, 2024.

Agriculture and other land use practices are major contributors to greenhouse gas emissions. To meet the needs of an increasing global food demand while mitigating climate change, sustainable agricultural practices are necessary. Biochar seems to be a promising tool to support this transition to sustainability in agriculture. The application of nitrogen fertilizers increases N₂O emissions and NH₃ volatilisation. Nitrous oxide (N₂O) is a highly potent greenhouse gas and ammonia (NH₃) can re-react with soil and forms N₂O or can lead to other environmental issues in the surrounding. Besides its carbon sequestration potential, it is known that biochar can positively influence soil properties like water holding capacity, nutrient leaching and mitigation of nitrous oxide emissions and ammonia volatilisation. However, these effects depend on pedoclimatic conditions, the properties of the applied biochar, and other agricultural practises. Therefore, it is necessary to expand the knowledge of these effects, especially under field conditions, to generate valid estimates on biochar’s mitigation potential for N₂O and NH₃ emissions. A good and extensive data basis is essential for recommendations and a large-scale application in agriculture. In a two-year field experiment in Grabenegg (Lower Austria) we cultivated silage maize (Zea mays) in 2022 and spring wheat (Triticum aestivum) in 2023 with different organic (external organic matter, EOM) and inorganic (NPK) fertilisers. For the biochar treatments we applied 7 t/ha hardwood biochar additionally. The original soil was loamy, low in organic carbon and slightly acidic. We found substantial reductions with 36% (NPK) and 53% (compost) for N₂O and 56% (NPK) and 40% (compost) for NH₃ emissions. There are several factors discussed in literature how biochar mitigates N₂O and NH₃ emissions. We suggest that the immobilisation effect of biochar on NH₄⁺ and NO₃^- (which was observed in the soil), and possibly an increased dinitrogen monoxide reductase activity are responsible for this reduction. Our data support that biochar can be a suitable amendment for highly productive agroecosystems where high amounts of fertiliser are needed and often applied at one timepoint. Still, further investigations on the long-term effect on emission mitigation of biochar and the mechanisms behind are necessary.

How to cite: Hartmann, F., Spiegel, H., Diaz-Pines, E., and Hood-Nowotny, R.: Impacts of biochar on nitrous oxide emissions and ammonia volatilisation in wheat and maize cropping systems, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16270, https://doi.org/10.5194/egusphere-egu24-16270, 2024.

The positive and negative effects of animal manure application to agricultural soils on soil inorganic nitrogen content, crop yield, ammonia (NH₃), and nitrous oxide (N₂O) emissions are well known and integrated into biogeochemical models. However, it is unclear if the effects of using digestate from biogas plants as fertilizer can be described by biogeochemical process models too. Since in Germany, the number of biogas plants increased drastically in the last two decades, there is a need for an evaluation and calibration of biogeochemical models for the application of digestate on arable land. For this purpose, we used data from a field experiment consisting of a control without fertilization, 3 treatments with mineral fertilizer, and 3 treatments with biogas digestate application (each with 60%, 80%, and 100% of maximum required N) on two cereal/maize crop rotations. Digestate was applied using trailing hoses. Results from experiments are used to calibrate and improve the biogeochemical model DNDCv.Can. Starting from a simplified description of O₂ transport, a new sub-module quantifies O₂ concentration by coupling decomposition with a 1-dimensional diffusion approach. Since the size of the anaerobic balloon calculated by the model influences many processes occurring in the soil, such as nitrification and denitrification, we hypothesize that a more realistic description of O₂ concentration, together with a model calibration addressing the decomposition kinetics of digestate, will lead to a more precise process description and, thus, to a better estimation of N₂O and, indirectly, NH₃ gas fluxes, and to more reliable estimation of NO₃^- and NH₄⁺ contents in the topsoil.

How to cite: Grosz, B., Greef, J. M., Tendler, L., Jarrah, M., and Dechow, R.: Modeling N2O, NH3 fluxes, and Nmin concentrations in agricultural soils treated with biogas digestate using a modified DNDC model, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16666, https://doi.org/10.5194/egusphere-egu24-16666, 2024.

The application of ground silicate minerals to agricultural ecosystems has recently gained popularity as a mechanism for CO₂ removal via enhanced mineral weathering that also has the potential to provide valuable co-benefits, including improved crop yields and reduced emissions of other greenhouse gasses. In Greenland, finely grained glacial rock flour (GRF) is naturally generated in vast amounts by glacier movement causing bedrock erosion and deposition. The natural production of GRF means that less energy is needed for grinding the rock material prior to field application. To quantify the influence of GRF on ecosystem carbon balance and greenhouse gas emissions, we applied 10 to 50 t GRF ha^-1 yr^-1 to an agricultural field in Denmark in a gradient setup with 5 levels plus combinations with fertilizers. Preliminary results of the CO₂ fluxes measured by a combination of automated and manual chamber measurements, show that gross primary productivity (GPP, carbon uptake) and ecosystem respiration (Reco, carbon release) both increased gradually with the increased addition of GRF leading to a slightly increased net ecosystem uptake of CO₂. In contrast, CH₄ and N₂O emissions showed a negative response trend with the increasing addition of GRF. The annual quantifications of ecosystem carbon balance and greenhouse gas emissions need further observations including effects during the non-growing season to be finalized. However, our initial results support the hypothesis that silicate mineral amendment overall may enhance CO₂ removal in agricultural settings and reduce greenhouse gas emissions, and therefore may be a useful tool for improving the capacity of farmlands to serve as a greenhouse gas sink.

How to cite: Li, Q., Larsen, K. S., and Dietzen, C. A.: Positive mitigation effects of glacial rock flour (GRF) addition on ecosystem CO2, CH4 and N2O fluxes – first results from a gradient experiment, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-3488, https://doi.org/10.5194/egusphere-egu24-3488, 2024.

Decades of intensive agricultural production, consisting of monoculture crops like corn (Zea mays), has led to a drastic decline in soil health, indicated by a reduction in soil carbon, nutrient holding and water holding capacity. Shifting management from monoculture crops to perennial crops could improve these soil characteristics and boost the resilience of agricultural systems to climate change. Furthermore, dairy livestock production systems are major greenhouse gas (GHG) emitters. GHGs from crop-livestock systems originate from enteric fermentation, manure storage, soils, and farm energy use. Nevertheless, US dairy herd sizes have not changed significantly in recent decades, suggesting that annual enteric fermentation emissions remained constant, while manure and soil emissions (i.e., CO₂, N₂O, CH₄) increased from the intensive management, including tillage and the application of agricultural chemicals. However, soil emissions such as CO₂ efflux (efflux) also consists of natural biogenic emissions from plant and microbial activity. Hence, an efflux may indicate greater soil health, suggesting root activity and high soil microbial abundance. Similarly, less variability in soil moisture and temperature could indicate high compaction and inferior soil structure. Understanding the multiple responses of soils to agricultural management is critical for developing strategies to improve soil health.

Here we established a nested treatment experiment with four block replications and three replicated plots per block (30 by 30 feet) using six different cropping systems (corn, corn with cover crop, corn intercropped alfalfa (Medicago sativa), alfalfa, intermediate wheatgrass (IWG, Thinopyrum intermedium), and a five species mixture of pasture grasses and forbs), to understand the system tradeoffs among soil health, forage quality and milk production in a dairy agricultural system. To quantify changes in soil health, structure, and soil GHG emissions, we planted corn on all plots in year 1 (2020) before planting other treatments in year 2 (2021). We collected data on soil nutrients and carbon content, soil microbial abundance and diversity, soil CO₂ efflux, soil moisture and temperature, as well as forage samples and multispectral drone flights to assess forage quality.

Corn plots (monocultures and intercropped) had lower variability in environmental characteristics like soil moisture and temperature, while their magnitudes were elevated, indicating a more compacted and less aerated soil compared to plots with greater root density and lower bulk density (i.e., pasture plots). Similarly, corn plots respired significantly less CO₂, both in years 1 and 2, compared to perennial crop plots, conforming with soil microbial data, which indicated lower microbial diversity in corn plots compared to pasture plots. While corn biomass was greater at the time of harvest compared to other crops, pasture and alfalfa plots accumulated half of the corn biomass throughout three harvest cycles and showed to have lower variability in yield, while also having higher nutritious value compared to corn silage, with implications for milk quality. Our findings suggest that efforts to make dairy operations more resilient to climate change and weather extremes should focus on more variables than just GHG emissions and soil carbon storage, to sustain agricultural production, human nutrition, and biogenic nutrient recycling into the future.

How to cite: Wiesner, S., Gajbhiye, S., Mehta, S., Stoy, P., and Duff, A.: Understanding soil health across greenhouse gas emissions and soil characteristics, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11524, https://doi.org/10.5194/egusphere-egu24-11524, 2024.

Grasslands are a key component of boreal agriculture and can play a significant role in soil carbon sequestration and mitigation. Grasslands have the potential to store substantial amounts of carbon in their roots and soil, making them important for soil carbon sequestration. Finland, located in the boreal climate zone, is known for its milk production with one of the highest per cow milk yields in Europe. Milk production in Finland relies heavily on grassland management. The growing season is short and varies from 105 days in the north to 185 days in the south. Finnish grasslands are managed on two types of soils: mineral soils and organic soils. Mineral soils are typically well-drained and have a low organic matter content, whereas organic soils are characterized by high organic matter content and high-water retention capacity. Therefore, we have initiated a long-term GHG monitoring framework for a sustainable grassland management and agriculture at the Natural Resources Institute Finland (Luke) across several agricultural research sites in Finland. The results presented in this study will shed light on the variability of GHG-fluxes from grasslands on different soil types and on the key drivers of the temporal and site variability of GHG-fluxes in a comparative way.

How to cite: Shurpali, N., Peltola, O., Thentu, T., and Virkajärvi, P.: Impact of management and boreal climate on GHG exchange from Finnish grasslands on mineral and peat soils, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-5275, https://doi.org/10.5194/egusphere-egu24-5275, 2024.

Soil structure plays a crucial role in determining greenhouse gas (GHG) emissions from agricultural activities. Changes in soil structure, such as compaction, can alter the factors that govern GHG fluxes, leading to an increased potential for emissions. The extent to which soil compaction explains GHG emissions is still under investigation. To address this knowledge gap, a two-year experiment was conducted in Northeast Italy to examine the influence of soil compaction on GHG emissions. The experimental site comprised of 20 lysimeters representing five different cultivation systems, each with four replicates: bare soil (BS), conventional (CV), conventional + with cover crop (CC), conservation with shallow compaction (0-25 cm, CA1), and conservation with deep soil compaction (25-45 cm, CA2). Maize was cultivated as the main crop in 2022, followed by grain sorghum in 2023, with solid digestate (300 kg N ha^-1) originated from mixed agricultural waste used for fertilization. Winter wheat served as a cover crop where necessary. Continuous automatic measurements of CO₂, N₂O, and CH₄ emissions were collected using a non-steady state through-flow chamber system and an FTIR gas analyzer, enabling the capture of up to seven fluxes per day for each replicate. Additionally, water-filled pore space (WFPS) and soil temperature were continuously monitored in the 0-30 cm soil profile using Time Domain Reflectometry (TDR) sensors and thermocouples. Cumulative CO₂ reached its peak under CV, followed by CC. Notably, observable N₂O emissions were predominantly detected in the two weeks following fertilization with peaks reaching 0.8 kg N-N₂O ha^-1d^-1 under CC, while CA1 and CA2 exhibited lower emissions. Conversely, CH₄ emissions were negligible, and the soil primarily acted as a sink. The study provides crucial insights for sustainable agriculture by highlighting the impact of soil compaction on GHG.

How to cite: Lewis, E., Longo, M., Rocco, S., Dal Ferro, N., Cabrera, M., Lazzaro, B., and Morari, F.: Understanding the influence of soil compaction on greenhouse gas emissions, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-10130, https://doi.org/10.5194/egusphere-egu24-10130, 2024.

Global urbanization has significantly affected land use, with former agricultural or forested land being used for human settlements and urban green spaces. How this urbanization may have affected the spatial and temporal patterns of soil greenhouse gas (GHG) fluxes, especially those of nitrous oxide (N₂O), remains largely unexplored, although a recent study indicated that urbanization accelerates GHG fluxes from soils.

In this study, we investigated soil GHG fluxes at Aarhus University Park (AU Park), a public park located in a hilly landscape with different use intensities. Soil GHG fluxes were measured 2-3 times per week over a period of 7 months using a fast chamber approach at about 55 sampling points with different management, vegetation, and landscape position (uphill, slope, foothill, ponds). Specifically, we focused on the identification of GHG flux hot and cold spots, and thereby investigated the temporal persistence of such spatial emission patterns.

Our results show that GHG fluxes were highly variable over the observation period, but that major GHG flux hotspots, such as those near a pond, were hotspots at all observation times. In addition, we were able to relate the spatio-temporal variations in soil GHG fluxes to landscape parameters such as slope and exposition, and to soil parameters such as soil organic carbon concentration, pH, and texture.

Our measurements show that there are significant spatio-temporal variations in GHG fluxes in urban parks and that these variations are strongly influenced by environmental and landscape parameters. This observation may allow a better scaling of GHG fluxes of urban green spaces and thus a better assessment of how urbanization changes landscape fluxes.

How to cite: Bai, X., Andreassen, L., Dogan, G., and Butterbach-Bahl, K.: Spatial and temporal variability of soil GHG fluxes of urban greens, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-17542, https://doi.org/10.5194/egusphere-egu24-17542, 2024.

Global warming, mainly caused by greenhouse gas (GHG) emissions, is one of the major concerns of the current society. Accurate estimation of GHG emissions in various fields can help governments and international organizations to formulate emission reduction strategies.The main objectives of this study were to estimate CH₄ and N₂O emissions from rice-wheat crop fields using IPCC2006 Tier2 approach and DNDC model, and to compare the performance of the two methods; and to evaluate the accuracy of GHG emissions of the DNDC model with rotational and non-rotational simulation scenarios. In this study, we conducted a rice-wheat rotational field experiment from 2015 to 2018 to determine CH₄ and N₂O fluxes periodically using static chamber-gas chromatography measurement and analysis system. On this basis, combined with field management and meteorological data, we simulated GHG emissions from rotational and non-rotational crop scenarios using the IPCC2006 Tier2 approach and the DNDC model. The results show that (1) the DNDC model can simulate the time series of paddy CH₄ and N₂O emission fluxes and winter wheat N₂O emission fluxes with estimation errors of -4.8%, -11.6%, and -10.8%, respectively, and the modeling accuracy is better than that of the IPCC2006 Tier2 approach; (2) the accuracy of the DNDC model for simulating the GWP under the rotational cropping scenarios was higher than that of the IPCC2006 Tier2 approach, the relative errors of GWP simulation in the DNDC model were -5.9% and -21.7% for rice and wheat fields, respectively; (3) the relative errors of winter wheat cumulative CH₄ emissions in the rotational cropping scenario in the DNDC model were higher than those in the non-rotational cropping scenario, and the relative errors of cumulative emissions of other GHGs in the rotational cropping scenario were lower than those in the non-rotational cropping scenario.This study provides some references for estimating regional agricultural GHG emissions and formulating emission reduction targets and policies.

Keywords: Rice-wheat rotation; DNDC; IPCC2006 Tier2; Greenhouse gases

How to cite: Yuming, Y.: Study on the difference of rice-wheat rotation system greenhouse gas estimation by different simulation methods, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-7554, https://doi.org/10.5194/egusphere-egu24-7554, 2024.

Global climate change is forcing different sectors including agriculture to come up with mitigation strategies. Nitrous oxide is the most potent greenhouse gas that contributes to global warming and is mainly produced from agricultural soil management. Two mitigation strategies to potentially reduce nitrous oxide emissions while maintaining cash crop yields are (i) shifting from conventional tillage to no-till and (ii) incorporating winter rye (Secale cereale L.) into corn (Zea mays L.)-soybean (Glycine max L.) rotation as a typical production system in the Midwest, USA. We harnessed a long-term trial to evaluate soil N dynamics, moisture and temperature, soybean production, and nitrous oxide emissions during 2020 and 2022 growing seasons. Treatments were two tillage factors (no-till and conventional chisel-disk) and two cover crops (winter rye and a no-cover crop control) arranged in factorial design with three replications. Results indicated that in 2020, no-till-no-cover crop had less nitrous oxide fluxes than the winter rye treatments, however it had higher N₂O-N losses than 2022.  A combination of winter rye-no-till provided similar soybean morphology, shoot biomass and grain yield compared to a tillage-based system with no cover crop but promoted soybean root biomass leading to greater carbon inputs. These results indicate the tradeoffs in benefits of winter rye in soybean cropping systems.

How to cite: Adeyemi, F.: Soybean growth and nitrous oxide emissions in response to tillage and crop rotation, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6572, https://doi.org/10.5194/egusphere-egu24-6572, 2024.