Use Of Nitrification Inhibitors Research Articles

Meeting the Demand for Different Nitrogen Forms in Potato Plants Without the Use of Nitrification Inhibitors.

The preference of potato plants for specific nitrogen (N) form changes with growth stage. Potato plants prefer nitrate N before tuber formation, while they favor ammonium N after tuber formation. However, few studies have focused on N species management in potato production. In this study, 2-year field experiments were conducted from 2020 to 2021 in Inner Mongolia, China, under drip irrigation with four N treatments: (1) CK (no N was used), (2) conventional farming practices (F) (urea was the only N source applied for potato growth), (3) nitrate N supplied before tuber formation and ammonium N with nitrification inhibitor supplied after tuber formation (N-NI), and (4) nitrate N supplied before tuber formation and frequent, low-dose ammonium N applied after tuber formation (Opt). The results demonstrated that, compared with the F, the Opt treatment facilitated potato N uptake, with a 33-40% increase in plant N accumulation, and significantly increased potato growth, which ultimately resulted in a yield increase of 12-20% and an increase of 11-22 percentage units in NUE. In addition, the Opt treatment reduced the soil N residual by ~14% after harvest. Compared with the N-NI, the Opt treatment did not result in a decrease in tuber yield or NUE. Therefore, supplying nitrate N before tuber formation and frequent, low-dose ammonium N after tuber formation can result in a better match between the supply and demand of potato plants for N forms without the use of nitrification inhibitors, improving both potato yield and NUE, which is of substantial agronomic and environmental value.

Addressing Climate Change: The Role of Agriculture in Greenhouse Gas Mitigation

Agriculture is a cornerstone of global food security, which is significantly affected by climate change, primarily driven by human activities that increase greenhouse gas (GHG) emissions. Accounting for approximately 13% of global anthropogenic GHG emissions, agricultural practices-such as livestock rearing, rice cultivation and synthetic fertilizer use which contribute substantially to global warming. Emissions from nitrous oxide (N₂O), methane (CH₄) and carbon dioxide (CO₂) exacerbate this issue, with N₂O being particularly concerning due to its high global warming potential. Mitigation strategies within the agricultural sector are essential, including improved nutrient management, the use of nitrification inhibitors and innovative fertilizer application technologies. Organic farming demonstrates lower N₂O emissions compared to conventional practices, emphasizing the importance of sustainable agricultural methods. Additionally, conservation tillage and practices like zero-tillage help reduce CO₂ emissions by minimizing soil disturbance and enhancing carbon sequestration. Biochar application further supports soil health and GHG reduction by enhancing carbon storage. To mitigate methane emissions from rice fields, reduced tillage and the introduction of electron acceptors can effectively inhibit methanogenesis. As CO₂ constitutes about 72% of total GHG emissions, agricultural practices that increase soil organic carbon (SOC) are critical for effective carbon sequestration. Overall, the agricultural sector holds significant potential for GHG mitigation, with studies suggesting that 89% of the mitigation potential can be achieved through carbon sequestration. Therefore, adopting these strategies is crucial not only for reducing emissions but also for ensuring sustainable agricultural productivity in the face of climate change challenges.

Copper pyrazole addition regulates soil mineral nitrogen turnover by mediating microbial traits.

The huge amount of urea applied has necessitated best-developed practices to slow down the release of nitrogen (N) fertilizer while minimizing nitrate loss. However, the impact of nitrification inhibitors on mineral-N turnover and the associated microbial mechanisms at different stages remains unknown. A 60-day incubation experiment was conducted with four treatments: no fertilizer (CK), urea (U), urea with copper pyrazole (UC), and urea coated with copper pyrazole (SUC), to evaluate the changes about soil ammonia N ( -N) and nitrate N ( -N) levels as well as in soil microbial community throughout the whole incubation period. The results showed that copper pyrazole exhibited significantly higher inhibition rates on urease compared to other metal-pyrazole coordination compounds. The soil -N content peaked on the 10th day and was significantly greater in UC compared to U, while the -N content was significantly greater in U compared to UC on the 60th day. Copper pyrazole mainly decreased the expression of nitrifying (AOB-amoA) and denitrifying (nirK) genes, impacting the soil microbial community. Co-occurrence network suggested that Mycobacterium and Cronobacter sakazakii-driven Cluster 4 community potentially affected the nitrification process in the initial phase, converting -N to -N. Fusarium-driven Cluster 3 community likely facilitated the denitrification of -N and caused N loss to the atmosphere in the late stage. The application of copper pyrazole may influence the process of nitrification and denitrification by regulating soil microbial traits (module community and functional genes). Our research indicates that the addition of copper pyrazole alters the community function driven by keystone taxa, altering mineral-N turnover and supporting the use of nitrification inhibitors in sustainable agriculture.

Pasture productivity benefits from strategic urease and nitrification inhibitor use are limited in rainfed temperate dairy pastures of southern Australia

Abstract Introduction Urea is the most commonly used nitrogen (N) fertiliser on Australian dairy pastures, but has low N use efficiency due to high loss potential. Urease and nitrification inhibitors can be used to reduce these losses, however, their efficacy is highly variable and the reported impacts on productivity are inconsistent, with assessments often made using a single inhibitor across all seasons. Research question We examined the effectiveness of two commonly used inhibitors, the urease inhibitor N-(n-butyl) thiophosphoric triamide (NBTPT) and the nitrification inhibitor 3,4-Dimethylpyrazole phosphate (DMPP) applied in a strategic program, on pasture responses to urea (U) fertiliser, and fertiliser N use efficiency in a temperate dairy pasture in Southern Australia. Materials and Methods Pasture productivity, N uptake, agronomic N use efficiency (NUAE), 15N fertiliser recovery and soil mineral N were monitored. The nitrogen was applied in the urea form at rates of 160, 320, 480 and 640 kg N ha−1 yr−1 Results and Conclusions The majority of the plant N (64%-85%), assessed over autumn and spring growth periods using 15N, was derived from mineralised soil organic matter (SOM). Neither of the inhibitors significantly altered pasture production or NUAE, most likely because of the major role of SOM in supplying N to plants, and because much of the applied 15N (up to 55%) was retained in the soil (0-40 cm depth) due to microbial immobilisation. Uptake of fertiliser N was highest, up to 29% of applied N, immediately following fertiliser application and then was substantially reduced over subsequent months, reflecting low levels of mineralisation of the previously immobilised N. The total loss of applied 15N was greater following autumn applications of N than spring applications, being 14% - 42% and 2% - 7% respectively and was attributed to volatilisation occurring primarily in autumn, with minimal leaching and denitrification predicted under the experimental conditions.

Efficiency of neem (Azadirachta indica) as a nitrification inhibitor under laboratory conditions

The use of nitrification inhibitors is a technology that can increase the efficiency of nitrogen fertilization, and synthetic and natural products can be used for this purpose. However, the use of these products is still poorly studied in tropical regions. The objective of this work was to evaluate the nitrification of nitrogen, under laboratory conditions, with urea covered with doses of neem leaf or cake, using DMPP (3,4-dimethylpyrazole phosphate) for comparison. The treatments consisted of a 2 x 4 + 2 factorial scheme, with the first factor represented by neem sources (leaf and cake), used to cover the urea and the second factor by neem doses, these doses being 0, 10 , 20 and 40% of the total applied N (200 mg kg-1, using urea as a N source) and two additional treatments: control (soil without nitrogen fertilizer) and urea + DMPP. Ammonium and nitrate contents were evaluated right after incubation (time 0) and on the 7th, 15th, 30th, 60th and 90th day after the start of incubation. For the ammonium content in the soil, there was influence of source and dose on the fifteenth day of incubation, with linear increments for both sources; and for nitrate levels, there was a significant effect (p<0.01) of neem doses on the 7th and 15th days of incubation, with a reduction in levels depending on the doses for the two sources tested. Significant differences (p<0.01) were found between additional and factorial treatments and between additional treatments for ammonium levels from the 7th to the 90th day of incubation. There was no significant interaction, in any of the dates, between neem sources and doses for ammonium and nitrate contents in the soil. Covering the urea with neem leaf and cake was efficient in reducing the levels of nitrate in the soil up to 15 days after incubation, resulting in higher levels of ammonium in the soil until this date. However, DMPP was more efficient in reducing nitrification, promoting inhibition up to 60 days of incubation.

The shape of reactive nitrogen losses from intensive farmland in China

Reactive nitrogen (Nr) pollution has changed radically accompanied by severe intensive farming. This pollution further contributes to ecological degradation and climate warming. Despite this recognition, little is known about the spatial pattern of various Nr loss from croplands and corresponding environmental costs. Here, we identified the major pathway of Nr loss based on provincial estimates in 2008 and 2018, and validated by synchronous observation of ammonia volatilization, N runoff and N leaching using historical literature synthesis. We also evaluated environmental costs at provincial scale and detected the influence factors that dominating the pollution swapping among different Nr forms. Our results show that the total Nr loss was 6.28 ± 1.81 and 5.56 ± 2.30 Tg N yr−1 for Chinese croplands in 2008 and 2018. Ammonia volatilization, which accounted for more than half of the total Nr at the national scale, was proven to be the major Nr loss for two-thirds of the provinces and 80 % of the field observations. The contribution of runoff, which is dominant by precipitation, soil clay content and CEC, was gradually smaller than that of leaching from southeast to northwest. Ammonia and nitrous oxide contributed of 59.3 % ∼ 65.4 % of TNr but 80.9 % ∼ 81.5 % of total environmental damage caused by Nr in China. The use of nitrification inhibitors and straw return indicated pollution swapping among various Nr forms. This study emphasizes that the future practices to reduce total Nr loss need to account for local environmental conditions and have pollution swapping in sights.

Nitrous oxide emissions and N-cycling gene abundances in a drip-fertigated (surface versus subsurface) maize crop with different N sources

Surface drip fertigation has demonstrated promising results regarding the mitigation of nitrous oxide (N2O) emissions. The use of subsurface irrigation may offer the possibility of reducing these emissions further due to the modification of the soil moisture profile and N allocation, both of which affect the biochemical processes leading to N2O fluxes. However, the mitigation potential of subsurface irrigation combined with different mineral nitrogen (N) fertilizers (ammonium or nitrate-based, use of nitrification inhibitors) still needs to be evaluated. To respond to this need, a 2-year field experiment was set up in central Spain to test two different drip-fertigation systems (surface and subsurface at 30 cm depth) and four N fertilization treatments (control, calcium nitrate, and ammonium sulfate with or without the nitrification inhibitor 3,4-dimethylpyrazole phosphate, DMPP) in an irrigated maize (Zea mays L.) crop. Nitrous oxide emissions, mineral N concentrations (ammonium, NH4+, and nitrate, NO3−), and abundance of key N genes involved in nitrification and denitrification processes were measured in two soil layers (0–20 and 20–40 cm). Regardless of the irrigation system, ammonium sulfate gave the highest cumulative N2O losses in both campaigns, while calcium nitrate and the use of DMPP were the most effective strategies to abate N2O fluxes in the first and second years, respectively. Differences between irrigation systems were not statistically significant for cumulative N2O emissions, despite the clear effect on topsoil mineral N (higher NH4+ and NO3− concentrations in surface and subsurface drip, respectively). Nitrous oxide emissions were positively correlated with soil NH4+ concentrations. Gene abundances were not a trustworthy predictor of N2O losses in the 1st year, although a clear inhibitory effect of fertilization on microbial communities (i.e., ammonia oxidizers, nitrite reducers, and N2O reducers) was observed during this campaign. During the second year, nitrifying and denitrifying genes were affected by irrigation (with higher abundances in the 20–40 cm layer in subsurface than in surface drip) and by the addition of DMPP (which had a detrimental effect on gene abundances in both irrigation systems that disappeared after the fertigation period). In conclusion, the use of DMPP or calcium nitrate instead of ammonium sulfate may enhance the chances for an additional mitigation in both surface and subsurface irrigation systems.

Drug discovery-based approach identifies new nitrification inhibitors

Nitrogen (N) fertilization is crucial to sustain global food security, but fertilizer N production is energy-demanding and subsequent environmental N losses contribute to biodiversity loss and climate change. N losses can be mitigated be interfering with microbial nitrification, and therefore the use of nitrification inhibitors in enhanced efficiency fertilizers (EEFs) is an important N management strategy to increase N use efficiency and reduce N pollution. However, currently applied nitrification inhibitors have limitations and do not target all nitrifying microorganisms. Here, to identify broad-spectrum nitrification inhibitors, we adopted a drug discovery-based approach and screened 45,400 small molecules on different groups of nitrifying microorganisms. Although a high number of potential nitrification inhibitors were identified, none of them targeted all nitrifier groups. Moreover, a high number of new nitrification inhibitors were shown to be highly effective in culture but did not reduce ammonia consumption in soil. One archaea-targeting inhibitor was not only effective in soil, but even reduced - when co-applied with a bacteria-targeting inhibitor - ammonium consumption and greenhouse gas emissions beyond what is achieved with currently applied nitrification inhibitors. This advocates for combining different types of nitrification inhibitors in EEFs to optimize N management practices and make agriculture more sustainable.

Emissions Reduction Strategies for the Orange and Cherry Industries in New South Wales.

The orange and cherry industries in New South Wales, Australia, are major horticulture industries with a high export value. Climate change has resulted in the carbon footprint of products being used by consumers to guide purchases meaning that products with a relatively high carbon footprint risk losing market access. The carbon footprint of cherry and orange production is unknown and there is no assessment of the success of climate change mitigation strategies to reduce the carbon footprint of their production and move production towards being carbon neutral. This study assesses the climate change mitigation potential of five management changes to on-farm cherry and orange production (revegetation, the use of nitrification inhibitors, renewable energy, green N fertilisers, and pyrolysis of orchard residues) over a 25-year period. for example, orchards in relevant growing regions. The results show that the carbon footprint of production can be reduced by 73 and 83% for cherries and oranges, respectively, when strategies that avoid emissions are included in their production. When strategies that sequester C from the atmosphere are also included, cherry and orange production becomes C negative in the first few years of the scenario. The economics of implementing these strategies are unfavourable, at present; however, our results indicate that the NSW cherry and orange industries can be confident in achieving emissions reductions in on-farm production to assure market access for their products.

Activity of ammonia-oxidizing bacteria in enriched cultures exposed to 3,4-dimethyl-1H-pyrazole dihydrogen phosphate nitrification inhibitor

The use of nitrification inhibitors is an interesting tool to achieve a higher N efficiency in plants while decreasing the environmental impact of N fertilization. However, an integrated evaluation of the efficiency of nitrification inhibitors over time, understood as the period in which the nitrifying activity is inhibited or slows down, is necessary to assess whether their use is ecofriendly and sustainable.To test the direct efficiency of 3,4-dimethyl-1H-pyrazole dihydrogen phosphate (DMPP) on nitrification, a study has been carried out in two cultures enriched with ammonia-oxidizing bacteria (AOB) obtained from a soil with continuous N fertilization (80 kg N ha−1 year−1 as NH4NO3) and from soil without N fertilization. In addition, Cu has been evaluated as a cofactor of ammonia monoxygenase, a key enzyme in the nitrifying activity of AOBs. On the other hand, the stability of DMP has been studied both in the cultivation system enriched in AOBs and in soil to assess the efficiency of the inhibitor due to its persistence over time.Our work reveals that nitrification rates observed in cultures enriched in AOBs from genus Nitrosospira isolated from soils with continuous N fertilization were not higher than those of cultures without N fertilization. In AOB cultures, DMPP was a very efficient inhibitor of nitrification (> 50 % inhibition of integrated AMO activity), mainly due to the stability of DMP (3,4-dimethyl-1 H-pyrazole) in the cultures. However, DMP stability was significantly lower under soil conditions (> 90 % of DMP was degraded in the first 30 days of incubation). Other metals are suggested as cofactors of the enzyme ammonia monooxygenase alternatively to Cu.

Innovative nitrogen management strategy reduced N2O emission while maintaining high pepper yield in subtropical condition

High N fertilizer inputs in subtropical vegetable systems under the warm and humid climatic conditions increase the risk of nitrous oxide (N2O) emissions. However, there is limited information available on integrated N management strategies to reduce N2O emissions from intensive open-field vegetable systems in subtropical region. Two plot-based field experiments were conducted in subtropical southwest China to examine the effects of different N management strategies on N2O emissions from a typical open-field pepper (Capsicum annuum L.) production system. Experiment 1 included five N rates (0, 175, 250, 325, and 400 kg ha−1) with conventional urea. Experiment 2 included a 0 N control and four N sources (conventional urea, organic fertilizer, nitrification inhibitor-based enhanced efficiency fertilizer ENTEC26, and controlled release urea) applied under an optimized N rate (250 kg N ha−1). The results of Experiment 1 showed that cumulative N2O emission and emission factor were 4.05 kg N ha−1 season−1 and 0.96%, respectively, under the conventional management (N400). N2O emissions increased exponentially with increasing N rates. Compared to the N400 treatment, application of conventional urea at the optimal rate (250 kg N ha−1) significantly reduced cumulative N2O emissions by 54% while maintaining similar pepper yield. The results from Experiment 2 indicated that the use of enhanced efficiency fertilizers at the optimal rate further reduced N2O emission by 30%− 50% compared to conventional urea, while increasing pepper yield by 6.7%− 9.0%. This resulted in a 36%− 53% reduction of yield-scaled N2O emission intensity. In particular, the use of nitrification inhibitor was 28% more effective than controlled release urea for N2O mitigation. These results suggest that the application of enhanced efficiency fertilizers at an optimum N rate could produce more vegetables while reducing N2O emission, thereby promoting sustainable vegetable production in the subtropic regions.

Targeting yield and reducing nitrous oxide emission by use of single and double inhibitor treated urea during winter wheat season in Northern Germany

Nitrous oxide (N2O) is a powerful greenhouse gas and has an adverse effect on stratospheric ozone. Field application of synthetic N fertilizers is the largest source of global N2O emission and different N forms (nitrate vs. ammoniacal N) may play a significant role. In addition, the use of nitrification inhibitor (NI) is considered as a reliable way to mitigate agricultural N2O emission, whereas this effect is still debated for urease inhibitors (UI). However, the efficacy of NI or UI is still variable among different inhibitor products and environmental conditions. This study was conducted to test the efficacy of N form (calcium ammonium nitrate CAN vs. urea) and the almost unstudied UI, N-(2-nitrophenyl) phosphoric triamide (2-NPT), as well as an NI, mixture of dicyandiamide and 1H-1,2,4-triazol (DCD/TZ) and the combination of both inhibitors on N2O emission and crop yield. The measurements were carried out in winter wheat growth season in the subsequent years of 2012–2013 in the North of Germany. No difference in cumulated N2O emissions were observed between urea and CAN. The results confirmed the positive effect of NI (DCD/TZ) on reducing N2O emission. Compared with untreated urea, NI addition caused ∼75 % reduction of fertilizer derived N2O emissions within the vegetation period. The combination of UI and NI did not result in a further reduction of relative or yield-scaled N2O emission, although it resulted in higher grain yield and nitrogen recovery. Addition of UI showed no consistent effect on N2O emission compared to untreated urea, however in year 2013 a significant reduction of fertilizer derived emissions by ∼50 % was observed. Higher yields were observed for CAN fertilization compared to urea, though not significant. For both treatments including UI the yield effects, in particular N use efficiency, were stronger than for untreated urea and urea solely treated with NI. Therefore, the combined treatment with UI and NI was the most advantageous fertilizer solution for concomitantly achieving high yield, high nitrogen utilization efficiency and N2O emission reduction.

Efficient Nitrogen Management Technologies for Sustainable Rice Production

The use of nitrogen (N) fertilizers in rice fields as a source of nutrition is the major source of emission of nitrous oxide (N2O). Two key factors which control the flux of N2O at the field level are the amount of N supplied and the efficiency at which it is absorbed by plants. To reduce the N2O emissions, optimum N fertilizer application (in terms of input rate and time of application) and ideal fertilizer selection are crucial. Optimizing N use efficiency (NUE) is crucial to sustain productivity and profitability. Depending on edaphic and climatic conditions, improved N management can dramatically cut greenhouse gases (GHGs) emissions. Producers must ensure that the kind, rate, and time of N application do not result in substantial losses owing to volatilization, leaching, or denitrification. Adoption of best nitrogen management practices like deep placement of urea, use of nitrification inhibitors, urease inhibitors, and slow-release nitrogen fertilizers will reduce the N loss and increase NUE. The goal of this review is to discuss in detail the various technologies that have been developed and refined to improve NUE and protect the environment.

Could the Use of Nitrification Inhibitor Optimize the Nitrogen Use Efficiency of Corn Production?

Could the Use of Nitrification Inhibitor Optimize the Nitrogen Use Efficiency of Corn Production?

Using DMPP with cattle manure can mitigate yield-scaled global warming potential under low rainfall conditions

Organic fertilisers can reduce the carbon (C) footprint from croplands, but adequate management strategies such as the use of nitrification inhibitors are required to minimise side-effects on nitrogen (N) losses to the atmosphere or waterbodies. This could be particularly important in a context on changing rainfall patterns due to climate change. A lysimeter experiment with maize (Zea mays L.) was set up on a coarse sandy soil to evaluate the efficacy of 3,4-dimethylpyrazole phosphate (DMPP) to mitigate nitrous oxide (N2O) emissions, nitrate (NO3−) leaching losses and net global warming potential from manure, with (R+) and without (R-) simulated rainfall events. Soil water availability was a limiting factor for plant growth and microbial processes due to low rainfall during the growing season. Nitrification was effectively inhibited by DMPP, decreasing topsoil NO3− concentrations by 28% on average and cumulative N2O losses by 82%. Most of the N2O was emitted during the growing season, with annual emission factors of 0.07% and 0.95% for manure with and without DMPP, respectively. Cumulative N2O emissions were 40% higher in R-compared to R+, possibly because of the higher topsoil NO3− concentrations. There was no effect of DMPP or rainfall amount on annual NO3− leaching losses, which corresponded to 12% of manure-N and were mainly driven by the post-harvest period. DMPP did not affect yield or N use efficiency (NUE) while R-caused severe reductions on biomass and NUE. We conclude that dry growing seasons can jeopardize crop production while concurrently increasing greenhouse gas emissions from a sandy soil. The use of nitrification inhibitors is strongly recommended under these conditions to address the climate change impacts.

Improving Nitrogen Use Efficiency in Rice for Sustainable Agriculture: Strategies and Future Perspectives.

Nitrogen (N) is an important nutrient for the growth and development of rice. The application of N fertilizer has become one of the inevitable ways to increase rice yield due to insufficient soil N content. However, in order to achieve stable and high yield, farmers usually increase N fertilizer input without hesitation, resulting in a series of problems such as environmental pollution, energy waste and low production efficiency. For sustainable agriculture, improving the nitrogen use efficiency (NUE) to decrease N fertilizer input is imperative. In the present review, we firstly demonstrate the role of N in mediating root architecture, photosynthesis, metabolic balance, and yield components in rice. Furthermore, we further summarize the current agronomic practices for enhancing rice NUE, including balanced fertilization, the use of nitrification inhibitors and slow-release N fertilizers, the split application of N fertilizer, root zone fertilization, and so on. Finally, we discuss the recent advances of N efficiency-related genes with potential breeding value. These genes will contribute to improving the N uptake, maintain the N metabolism balance, and enhance the NUE, thereby breeding new varieties against low N tolerance to improve the rice yield and quality. Moreover, N-efficient varieties also need combine with precise N fertilizer management and advanced cultivation techniques to realize the maximum exploitation of their biological potential.

Impact of cattle slurry application methods on ammonia losses and grassland nitrogen use efficiency

Optimal manure management is required to ensure efficient nutrient supply to farmland and to avoid adverse environmental impacts. Accordingly, ammonia (NH3) emissions associated with different slurry application techniques were investigated in grassland trials under different soil and weather conditions across Germany. Cattle slurry was applied in two dressings, early in spring and after the first silage cut, with a target amount of 170 kg N ha−1. The application treatments comprised: trailing shoe (TS), acidified slurry applied with trailing shoe (TS + A), open slot injection (SI), and slurry treated with a nitrification inhibitor (NI) applied by slot injection (SI + NI). In addition, slurry application techniques were compared with a non-N-fertilized control and a mineral fertilizer treatment (calcium ammonium nitrate, CAN). NH3 measurements followed each N application event. NH3 losses were equivalent to 1–39% of total ammoniacal nitrogen (TAN) applied. The average NH3 mitigation potential of the different slurry application techniques compared to TS was 45.7 ± 7, 21.2 ± 6.2 and 13.7 ± 8.2% for TS + A, SI and SI + NI, respectively. The use of nitrification inhibitor with slot injected slurry did not increase NH3 losses relative to TS (p > 0.05). Mean apparent N use efficiency was two times higher for CAN (49%) than the slurry treatments (24%) but was comparable between SI + NI and CAN in five out of the eight cases. Our results indicate that mean TAN related NH3 emissions of tested treatments (3.3, 22.6, 12.2, 17.8 and 19.3% for CAN, TS, TS + A, SI and SI + NI, respectively) were generally lower than described in previous studies. Moreover, the results suggested possible increases in NH3 mitigation and N use efficiency when cattle slurry is applied with acidification or injection techniques. We found no evidence that NI addition to slot injected slurry, a treatment discussed as a measure to reduce N2O emission and nitrate leaching, changed NH3 emission.

Effects of animal manure and nitrification inhibitor on N2O emissions and soil carbon stocks of a maize cropping system in Northeast China

The incorporation of animal manure (AM) in soil plays an essential role in soil carbon sequestration but might induce higher soil nitrous oxide (N2O) emissions. The use of nitrification inhibitors (NI) is an effective strategy to abate N2O emission in agro-ecosystems. However, very few studies have evaluated the effectiveness of applying NI under the combined application of organic and inorganic fertilizers for increasing soil carbon sequestration and reducing N2O emissions simultaneously in Northeast China. Here, a four-year field experiment was conducted with three treatments [inorganic fertilizer (NPK), inorganic fertilizer + manure (NPKM), and inorganic fertilizer with NI + manure (NPKI + M)], in a rainfed maize cropping system in Northeast China. Plots of different treatments were kept in the same locations for 4 years. Gas samples were collected using the static closed chamber technique, and nitrous oxide (N2O) concentration in gas samples was quantified using a gas chromatograph. Soil organic carbon sequestration rate (SOCSR) was calculated based on the changes in SOC from April 2012 to October 2015. Averaged over the four years, AM incorporation significantly increased soil N2O emissions by 25.8% (p < 0.05), compared to NPK treatment. DMPP (3,4-dimethylpyrazole phosphate) significantly decreased N2O emissions by 32.5% (p < 0.05) relative to NPKM treatment. SOC content was significantly elevated by 24.1% in the NPKI + M treatment than the NPK treatment after four years of manure application (p < 0.05). The annual topsoil SOCSR for the NPKM and NPKI + M treatments was 0.57 Mg ha−1 yr−1 and 1.02 Mg ha−1 yr−1, respectively, which were significantly higher than that of NPK treatment (− 0.61 Mg ha−1 yr−1, p < 0.05). AM addition significantly increased the aboveground biomass and crop yields of maize in the fourth year. Overall, combined application of DMPP, inorganic fertilizer and AM is strongly recommended in this rainfed maize cropping system, which can increase maize yield and SOC sequestration rate, and mitigate N2O emission.

Distinct driving mechanisms of non-growing season N2O emissions call for spatial-specific mitigation strategies in the US Midwest

Agricultural N2O emission is a growing concern for climate change. Recent field evidence suggests that non-growing seasons (NGS) may contribute one-third to half of the annual N2O emissions, but implications on management adaptations remain unclear. Here we used an advanced process-based model, ecosys, to investigate the magnitude and drivers of NGS N2O emissions from the US Midwest. Results showed that simulated NGS N2O emissions accounted for 6–60% of the annual fluxes under continuous corn systems, peaking in counties with NGS precipitation (PNGS) around 300 mm. Divergent patterns of spatial-temporal correlations between NGS N2O emissions and environmental variables were shown in the southeast (PNGS > 300 mm) and the northwest (PNGS < 300 mm) of the study area by simulations. Causal analysis indicates that more intensive freezing caused by decreased air temperature (Ta) is the dominant driver that leads to NGS N2O emissions increasing within the southeast of the study area, while increased PNGS and increased Ta cooperatively result in soil moisture decreasing at soil thaws that enhances NGS N2O production within the northwest of the study area. Scenario simulations suggest that annual N2O emissions in the US Midwest are likely to reduce under climate change primarily due to the reduction of NGS N2O emissions. Our estimates on monetized social benefits inform the necessity to implement spatial-specific mitigation strategies, i.e. determining fertilizer timing and use of nitrification inhibitors (NI). Spring fertilizer application is more beneficial than fall fertilizer application for most counties, however, the latter can bring extra benefits to some counties in the west of the study area. Introducing NI with either spring or fall applications can greatly increase social benefits by reducing N2O emissions and N leaching. This study addresses possibly effective adaptations by providing seasonal- and spatial-explicit mitigation potentials.

Split N application and DMP based nitrification inhibitors mitigate N2O losses in a soil cropped with winter wheat

Nitrogen (N) fertilization to crops might lead to formation and release of reactive N—e.g. nitrate, ammonium, ammonia, nitrous oxide (N2O) —, contributing to eutrophication, atmospheric pollution, and climate change. Use of nitrification inhibitors and splitting of N fertilizer may reduce the N2O emission from arable soils cropped with winter wheat. We tested different N fertilizers treated with 3,4-dimethylpyrazol phosphate (DMPP) and 3,4-dimethylpyrazol succinic acid (DMPSA) by applying 180 kg N ha−1 in different N splitting strategies in a full annual field experiment on a loamy soil in Southwest Germany. A threefold split fertilization led to an emission of 2.3 kg N2O–N ha−1 a−1 (corresponding to a reduction of 19%) compared to a single application of ammonium sulphate nitrate (ASN) (p = 0.07). A single application rate of ASN with DMPP resulted in an emission of 1.9 kg N2O–N ha−1 a−1 and reduced N2O emissions from an ASN treatment without NI by 33%. Calcium ammonium nitrate (CAN) with DMPSA reduced N2O emissions during the vegetation period by 38% compared to CAN without a nitrification inhibitor, but this was offset by high emissions after harvest, which was driven by soil tillage with an annual reduction of 26% (CAN: 2.9 kg N2O–N ha−1 a−1; CAN + DMPSA: 2.1 kg N2O–N ha−1 a−1; p = 0.11). Among our tested treatments, a twofold split application of ASN with DMPP efficiently reduced N2O emissions and maintained grain yield when compared to the traditional system with threefold application without nitrification inhibitor. Despite resulting in lower protein contents in the twofold split application, this treatment should be further investigated as a potential compromise between wheat yield and quality optimization and climate protection.