Modeling Denitrification : Can We Report What We Don't Know?

Funding Information: This study is the products of a workshop funded by the Deutsche Forschungsgemeinschaft through the research unit DFG‐FOR 2337: Denitrification in Agricultural Soils: Integrated Control and Modelling at Various Scales (DASIM), and by the German Federal Ministry of Education and Research (BMBF) under the “Make our Planet Great Again—German Research Initiative”, Grant 306060, implemented by the German Academic Exchange Service (DAAD). This work was supported by the European Union's Horizon 2020 research and innovation programme project VERIFY (grant agreement no. 776810). We would like to thank the contribution of all workshop participants of the II. DASIM Modeler Workshop. Publisher Copyright: © 2023. The Authors.Peer reviewedPublisher PD

Effect of Stocking Rate on Soil-Atmosphere CH4 Flux during Spring Freeze-Thaw Cycles in a Northern Desert Steppe, China

BACKGROUND: Methane (CH(4)) uptake by steppe soils is affected by a range of specific factors and is a complex process. Increased stocking rate promotes steppe degradation, with unclear consequences for gas exchanges. To assess the effects of grazing management on CH(4) uptake in desert steppes, we investigated soil-atmosphere CH(4) exchange during the winter-spring transition period. METHODOLOGY/MAIN FINDING: The experiment was conducted at twelve grazing plots denoting four treatments defined along a grazing gradient with three replications: non-grazing (0 sheep/ha, NG), light grazing (0.75 sheep/ha, LG), moderate grazing (1.50 sheep/ha, MG) and heavy grazing (2.25 sheep/ha, HG). Using an automatic cavity ring-down spectrophotometer, we measured CH(4) fluxes from March 1 to April 29 in 2010 and March 2 to April 27 in 2011. According to the status of soil freeze-thaw cycles (positive and negative soil temperatures occurred in alternation), the experiment was divided into periods I and II. Results indicate that mean CH(4) uptake in period I (7.51 µg CH(4)-C m(-2) h(-1)) was significantly lower than uptake in period II (83.07 µg CH(4)-C m(-2) h(-1)). Averaged over 2 years, CH(4) fluxes during the freeze-thaw period were -84.76 µg CH(4)-C m(-2) h(-1) (NG), -88.76 µg CH(4)-C m(-2) h(-1) (LG), -64.77 µg CH(4)-C m(-2) h(-1) (MG) and -28.80 µg CH(4)-C m(-2) h(-1) (HG). CONCLUSIONS/SIGNIFICANCE: CH(4) uptake activity is affected by freeze-thaw cycles and stocking rates. CH(4) uptake is correlated with the moisture content and temperature of soil. MG and HG decreases CH(4) uptake while LG exerts a considerable positive impact on CH(4) uptake during spring freeze-thaw cycles in the northern desert steppe in China

Micrometeorological methods for greenhouse gas measurement

Micrometeorological techniques are useful if greenhouse gas (GHG) emissions from larger areas (i.e. entire fields) should be integrated. The theory and the various techniques such as flux-gradient, aerodynamic, and Bowen ratio as well as Eddy correlationmethods are described and discussed. Alternativemethods also used areEddy correlation, mass balance techniques, and tracer-based methods.The analytical techniques with current state-of-the-art approaches as well as the calculation procedures are presented

Greenhouse gases from agriculture

The rapidly changing global climate due to increased emission of anthropogenic greenhouse gases (GHGs) is leading to an increased occurrence of extreme weather events such as droughts, floods, and heatwaves. The three major GHGs are carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O). The major natural sources of CO2 include ocean-atmosphere exchange, respiration of animals, soils (microbial respiration) and plants, and volcanic eruption; while the anthropogenic sources include burning of fossil fuel (coal, natural gas, and oil), deforestation, and the cultivation of land that increases the decomposition of soil organic matter and crop and animal residues. Natural sources of CH4 emission include wetlands, termite activities, and oceans. Paddy fields used for rice production, livestock production systems (enteric emission from ruminants), landfills, and the production and use of fossil fuels are the main anthropogenic sources of CH4. Nitrous oxide, in addition to being a major GHG, is also an ozone-depleting gas. N2O is emitted by natural processes from oceans and terrestrial ecosystems. Anthropogenic N2O emissions occur mostly through agricultural and other land-use activities and are associated with the intensification of agricultural and other human activities such as increased use of synthetic fertiliser (119.4 million tonnes of N worldwide in 2019), inefficient use of irrigation water, deposition of animal excreta (urine and dung) from grazing animals, excessive and inefficient application of farm effluents and animal manure to croplands and pastures, and management practices that enhance soil organic N mineralisation and C decomposition. Agriculture could act as a source and a sink of GHGs. Besides direct sources, GHGs also come from various indirect sources, including upstream and downstream emissions in agricultural systems and ammonia (NH3) deposition from fertiliser and animal manure

Induction of transient nitrous oxide emissions by freeze-thaw treatment: relation to nutritional status, microbial population and microfaunal grazing in an arable soil

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Induction of transient nitrous oxide emissions by freeze-thaw cycles : relation to nutritional status, microbial population and faunal grazers in arable soils

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Overwinter greenhouse gas fluxes in two contrasting agricultural habitats

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N₂O emission from organic barley cultivation as affected by green manure management

Legumes are an important source of nitrogen in stockless organic cereal production. However, substantial amounts of N can be lost from legume-grass leys prior to or after incorporation as green manure (GM). Here we report N₂O emissions from a field experiment in SE Norway exploring different green manure management strategies: mulching versus removal of grass-clover herbage during a whole growing season and return as biogas residue to a subsequent barley crop. Grass-clover ley had small but significantly higher N₂O emissions as compared with a non-fertilised cereal reference during the year of green manure (GM) production in 2009. Mulching of herbage induced significantly more N₂O emission (+0.37 kg N₂O-N ha⁻¹) throughout the growing season than removing herbage. In spring 2010, all plots were ploughed (with and without GM) and sown with barley, resulting in generally higher N₂O emissions than during the previous year. Application of biogas residue (60 kg NH₄⁺-N + 50 kg organic N ha⁻¹) before sowing did not increase emissions neither when applied to previous ley plots nor when applied to previously unfertilised cereal plots. Ley management (mulching vs. removing biomass in 2009) had no effect on N₂O emissions during barley production in 2010. In general, GM ley (mulched or harvested) increased N₂O emissions relative to a cereal reference with low mineral N fertilisation (80 kg N ha⁻¹). Based on measurements covering the growing season 2010, organic cereal production emitted 95 g N₂O-N kg⁻¹ N yield in barley grain, which was substantially higher than in the cereal reference treatment with 80 kg mineral N fertilisation (47 g N₂O-N kg⁻¹ N yield in barley grain)

Prognostic Impact of Pedicle Clamping during Liver Resection for Colorectal Metastases

Pedicle clamping (PC) during liver resection for colorectal metastases (CRLM) is used to reduce blood loss and allogeneic blood transfusion (ABT). The effect on long-term oncologic outcomes is still under debate. A retrospective analysis of the impact of PC on ABT-demand regarding overall (OS) and recurrence-free survival (RFS) in 336 patients undergoing curative resection for CRLM was carried out. Survival analysis was performed by both univariate and multivariate methods and propensity-score (PS) matching. PC was employed in 75 patients (22). No increased postoperative morbidity was monitored. While the overall ABT-rate was comparable (35 vs. 37, p = 0.786), a reduced demand for more than two ABT-units was observed (p = 0.046). PC-patients had better median OS (78 vs. 47 months, p = 0.005) and RFS (36 vs. 23 months, p = 0.006). Multivariate analysis revealed PC as an independent prognostic factor for OS (HR = 0.60; p = 0.009) and RFS (HR = 0.67; p = 0.017). For PC-patients, 1:2 PS-matching (N = 174) showed no differences in the overall ABT-rate compared to no-PC-patients (35 vs. 40, p = 0.619), but a trend towards reduced transfusion requirement (>2 ABT-units: 9 vs. 21, p = 0.052; >4 ABT-units: 2 vs. 11, p = 0.037) and better survival (OS: 78 vs. 44 months, p = 0.088; RFS: 36 vs. 24 months; p = 0.029). Favorable long-term outcomes and lower rates of increased transfusion demand were observed in patients with PC undergoing resection for CRLM. Further prospective evaluation of potential oncologic benefits of PC in these patients may be meaningful