Response of soil N2O emission and nitrogen utilization to organic matter in the wheat and maize rotation system

The appropriate nitrogen (N) fertilizer regulator could increase N utilization of crops and reduce N losses in the North China Plain. We investigated the effects of reduced inorganic-N rate combined with an organic fertilizer on nitrous oxide (N2O) emissions in winter wheat and summer maize rotation system. Simultaneously studied the effect of different treatments on N use efficiency (NUE), N balance and net income. After reducing the amount of nitrogen fertilizer in the wheat-corn rotation system, the results showed that the cumulative emission of soil N2O from the RN40% + HOM [40% of RN (recommended inorganic-N rate) with homemade organic matter] treatment was 41.0% lower than that of the RN treatment. In addition, the N production efficiency, agronomic efficiency, and apparent utilization were significantly increased by 50.2%, 72.4% and 19.5% than RN, respectively. The use of RN40% + HOM resulted in 22.0 and 30.1% lower soil N residual and N losses as compared with RN. After adding organic substances, soil N2O cumulative emission of RN40% + HOM treatment decreased by 20.9% than that of the HAN (zinc and humic acid urea at the same inorganic-N rate of RN) treatment. The N production efficiency, N agronomic efficiency and NUE of RN40% + HOM treatment were 36.6%, 40.9% and 15.3% higher than HAN’s. Moreover, soil residual and apparent loss N were 23.3% and 18.0% less than HAN’s. The RN40% + HOM treatment appears to be the most effective as a fertilizer control method where it reduced N fertilizer input and its loss to the environment and provided the highest grain yield.

Release Kinetics Studies of Early-Stage Volatile Secondary Oxidation Products of Rapeseed Oil Emitted during the Deep-Frying Process

The research concerns the use of proton transfer reaction mass spectrometer to track real-time emissions of volatile secondary oxidation products released from rapeseed oil as a result of deep-frying of potato cubes. Therefore, it was possible to observe a sudden increase of volatile organic compound (VOC) emissions caused by immersion of the food, accompanied by a sudden release of steam from a potato cube and a decrease of the oil temperature by more than 20 °C. It was possible to identify and monitor the emission of major secondary oxidation products such as saturated and unsaturated aldehydes, namely acrolein, pentanal, 2-hexenal, hexanal, 2-nonenal and 2-decenal. Each of them has an individual release characteristic. Moreover, the impact of different initial frying temperatures on release kinetics was investigated. Subsequently, it was possible to approximate the cumulative emission by a second-degree polynomial (R2 ≥ 0.994). Using the proposed solution made it possible for the first time to observe the impact of the immersion of food in vegetable oil on the early emission of thermal degradation products oil.

Effect of biochar and compost application on nitrogen dynamics in organically managed nutrient-poor paddy soil system and in organic rice cultivation system

Nitrogen (N) is an essential plant nutrient, and its retention in the soil is beneficial to plant growth and productivity. High levels of N can leach from soil with organic amendments, particularly in water-rich paddy rice cultivation. Biochar has the potential to influence the soil N cycle. The study included four treatments applied to organically managed nutrient-poor paddy soil (S) and rice cultivation (R) systems, respectively over two growing seasons: biochar only (BA), compost only (CA), biochar and compost mixed at an equal rate (BC), and no amendment (control). Biochar produced from mangrove (Rhizophora apiculata) which obtained from slow pyrolysis in a traditional kiln, whereas compost generated from organic municipal solid waste. The results showed that, on average, BA and BC maintained NO3--N and NH4+-N in the soil and reduced absolute N leaching compared to the control and CA, respectively. System R maintained nitrogen better than system S. BA reduced N mass leaching by 27.25% in system S and by 59.21% in system R, compared to the control, while BC reduced N mass leaching by 24.85% in system S and by 58.48% in system R, compared to CA. However, the reduction in N2O emission fluxes was not significant in both BA and BC in both seasons, although cumulative emission fluxes after a year of cultivation decreased significantly. BC significantly boosted water use efficiency relative to yield in system R. These results show that co-application of biochar and compost to nutrient-poor soil in an organically managed system substantially reduced N leaching and suggests that it could be an effective management option for organic rice cultivation in Thailand. Keywords: Biochar, compost, nitrogen leaching, N2O emmision, nitrogen balance, organic rice cultivation.

Is there warming in the pipeline? A multi-model analysis of the Zero Emissions Commitment from CO₂

The Zero Emissions Commitment (ZEC) is the change in global mean temperature expected to occur following the cessation of net CO2 emissions and as such is a critical parameter for calculating the remaining carbon budget. The Zero Emissions Commitment Model Intercomparison Project (ZECMIP) was established to gain a better understanding of the potential magnitude and sign of ZEC, in addition to the processes that underlie this metric. A total of 18 Earth system models of both full and intermediate complexity participated in ZECMIP. All models conducted an experiment where atmospheric CO2 concentration increases exponentially until 1000 PgC has been emitted. Thereafter emissions are set to zero and models are configured to allow free evolution of atmospheric CO2 concentration. Many models conducted additional second-priority simulations with different cumulative emission totals and an alternative idealized emissions pathway with a gradual transition to zero emissions. The inter-model range of ZEC 50 years after emissions cease for the 1000 PgC experiment is −0.36 to 0.29 ∘C, with a model ensemble mean of −0.07 ∘C, median of −0.05 ∘C, and standard deviation of 0.19 ∘C. Models exhibit a wide variety of behaviours after emissions cease, with some models continuing to warm for decades to millennia and others cooling substantially. Analysis shows that both the carbon uptake by the ocean and the terrestrial biosphere are important for counteracting the warming effect from the reduction in ocean heat uptake in the decades after emissions cease. This warming effect is difficult to constrain due to high uncertainty in the efficacy of ocean heat uptake. Overall, the most likely value of ZEC on multi-decadal timescales is close to zero, consistent with previous model experiments and simple theory.

Uncertainty in remaining carbon budgets increases with less ambitious targets

<blockquote> <div dir="ltr"> <div> <p><span lang="en-US">In this work, we present estimates and uncertainties of the remaining carbon budget for a range of different global temperature targets. To model how atmospheric CO2 and methane concentrations depend on emissions, we use impulse response functions estimated from emission-pulse experiments in Earth System Models (ESMs). We use box-model ESM emulators to model the temperature response to radiative forcing and analyze a range of emission scenarios from Integrated Assessment Models. Taking into account uncertainties in the approximately linear relationship between cumulative emission and peak temperature, as well as internal climate variability and uncertainties in the carbon and climate models, we estimate the remaining carbon budgets for varying targets. The results show that the carbon-budget-uncertainties increase significantly with less ambitious targets.</span></p> </div> </div> </blockquote>

Quantifying Gas Emissions and Denitrifying Genes in a Salt-Affected Soil

Salinity effects on microbial community relative to greenhouse gas emissions are not well understood in salt-affected soils. A better understanding of this interaction would be useful for agricultural practices to reduce nitrogen gas losses and manage environmental pollution. We hypothesized that elevated salinity would increase the abundance of denitrifier genes resulting in a low rate of gas emissions. Objectives of this study were to measure induced-soil greenhouse gas emissions and to quantify denitrifying genes in a salt-affected soil over a 3-week incubation period. This incubation study was conducted by submerging field-moist samples of an acid sulphate soil in different saline solutions. A quantitative polymerase chain reaction (qPCR) was used to quantify the abundance of resident bacterial denitrification genes in the salt-affected soil. It was found that increased salinity caused a decrease in both flux and cumulative emission of N2O from the incubated soil, relative to fresh water. Soil respiration was significantly reduced in salinity treatments compared to the treatment of distilled water. The study results showed that elevated salinity increased the denitrifying genes in the incubated acid sulfate soil. The abundance of the nir genes was usually high between the first and second week of incubation, while number copies of the nosZ gene were significantly low at those times. The study concludes that salinity controls the biological aspects of denitrification leading to a reduction of greenhouse gas emissions. Findings from this investigation extend our knowledge about the underlying molecular ecological mechanisms of denitrification that manage nitrogen cycling in salt-affected soils.

Yield-scaled N2O and CH4 emissions as affected by combined application of stabilized nitrogen fertilizer and pig manure in rice fields

A field experiment was conducted to study the effects of stabilized nitrogen fertilizer combined with pig manure on rice yield and nitrous oxide (N₂O) and methane (CH₄) emissions. Four treatments were established: urea (U); pig manure (PM); PM and urea (PM + U); PM and stabilized nitrogen fertilizer (urea plus 1% NBPT (N-(n-butyl) thiophosphoric triamide), 1% PPD (phenylphosphorodiamidate) and 2% DMPP (3,4-dimethylpyrazole phosphate)) (PM + U + I). In this study, compared with PM, PM + U significantly increased cumulative N₂O emission, but PM + U + I showed no significant difference from PM on N₂O cumulative emission, indicating that stabilized nitrogen fertilizer combined with PM is effective at reducing N₂O emissions. The cumulative emission of CH₄ from PM + U + I treatment was significantly lower than that from PM and PM + U, indicating that stabilized nitrogen fertilizer combined with PM can effectively reduce CH₄ emissions as well. The yields of PM + U and PM + U + I were not significantly different from those of U and PM, indicating that local conventional nitrogen application and returns of PM can provide sufficient nitrogen for rice growth. For yield-scaled emissions (YSE), PM was the highest, while PM + U + I significantly decreased YSE. Concomitant application of stabilized nitrogen fertilizer can achieve the goal of reducing YSE when PM is returned to the field.

Incorporation and harvest management of hairy vetch-based green manure influence nitrous oxide emissions

In this study, we measured nitrous oxide (N2O) emissions from plots of fall-planted hairy vetch (HV, Vicia villosa) grown as a green nitrogen (N) source for following summer forage crabgrass (Digitaria sanguinalis). Two treatments were compared: (i) HV grown solely as green manure where all biomass was incorporated by tillage, and (ii) harvesting of aboveground HV biomass prior to planting of crabgrass. Fluxes of N2O were measured with closed chamber systems on 27 dates during a 2-month growth period of crabgrass after the termination of HV in early May. At termination, the average aboveground biomass yield of HV was 4.6 Mg ha−1 with 146 kg N ha−1 content. The N2O emissions were as high as 66 g N2O-N ha−1 day−1 on day 1 after HV incorporation, but reached close to zero within a week. Emissions of N2O increased with subsequent rainfall and irrigation events from both treatments but emission peaks were not observed during the rapid growth of crabgrass. Two-month cumulative emission of N2O (mean ± s.e., n = 4) from HV incorporated plots (921 ± 120 g N2O-N ha−1) was three times (P < 0.05) of HV harvested plots (326 ± 30 g N2O-N ha−1). However, crabgrass biomass yields, N concentrations and total biomass N uptake were decreased significantly by harvesting HV. In conclusion, the results suggested that whereas removal of HV biomass for use as forage may significantly reduce N2O emissions, quantity and quality of the following recipient crops may be constrained.

Life Cycle Assessment of Lead Production in China

This study analyzed the environmental impacts due to lead production in China, which is the largest producer and consumer of lead in the world, by the method of life cycle assessment (LCA). Based on the Chinese refined lead smelting process, a process-based life cycle assessment model was established to assess the environmental load of lead production system which includes the processes of mining, beneficiation, smelting, electrorefining and transportation. The result shows that the cumulative consumption of electricity and the cumulative emission of green house gases for the production of 1t of refined lead are 1111.93kWh and 2.06E+03kg CO2 eq, respectively. Smelting process is the largest contributor to the environmental impact load, accounting for 51.16% of the total environmental impact. The environmental category of human toxicity potential(HTP), accounting for 35.26% of the total environmental impact, is the largest contributor between different environmental categories to the total environmental impact, followed by metal depletion potential(MDP) and fossil depletion potential(FDP), accounting for 27.94% and 11.80% of the total environmental impact, respectively. Improving the resource efficiencies of the processes of smelting and beneficiation, and using cleaner energy to generate electricity are the key approaches to reduce the overall environmental impact of lead production in China.