NH3 Volatilization Research Articles

Data-driven estimates of fertilizer-induced soil NH3 , NO and N2 O emissions from croplands in China and their climate change impacts.

Gaseous reactive nitrogen (Nr) emissions from agricultural soils to the atmosphere constitute an integral part of global N cycle, directly or indirectly causing climate change impacts. The extensive use of N fertilizer in crop production will compromise our efforts to reduce agricultural Nr emissions in China. A national inventory of fertilizer N-induced gaseous Nr emissions from croplands in China remains to be developed to reveal its role in shaping climate change. Here we present a data-driven estimate of fertilizer N-induced soil Nr emissions based on regional and crop-specific emission factors (EFs) compiled from 379 manipulative studies. In China, agricultural soil Nr emissions from the use of synthetic N fertilizer and manure in 2018 are estimated to be 3.81 and 0.73TgNyr-1 , with a combined contribution of 23%, 20% and 15% to the global agricultural emission total of ammonia (NH3 ), nitrous oxide (N2 O) and nitric oxide (NO), respectively. Over the past three decades, NH3 volatilization from croplands has experienced a shift from a rapid increase to a decline trend, whereas N2 O and NO emissions always maintain a strong growth momentum due to a robust and continuous rise of EFs. Regionally, croplands in Central south (1.51TgNyr-1 ) and East (0.99TgNyr-1 ) of China exhibit as hotspots of soil Nr emissions. In terms of crop-specific emissions, rice, maize and vegetable show as three leading Nr emitters, together accounting for 61% of synthetic N fertilizer-induced Nr emissions from croplands. The global warming effect derived from cropland N2 O emissions in China was found to dominate over the local cooling effects of NH3 and NO emissions. Our established regional and crop-specific EFs for gaseous Nr forms provide a new benchmark for constraining the IPCC Tier 1 default EF values. The spatio-temporal insight into soil Nr emission data from N fertilizer application in our estimate is expected to advance our efforts towards more accurate global or regional cropland Nr emission inventories and effective mitigation strategies.

Biological nitrification inhibitor co-application with urease inhibitor or biochar yield different synergistic interaction effects on NH3 volatilization, N leaching, and N use efficiency in a calcareous soil under rice cropping

Nitrogen management measures (NMMs) such as the application of urease inhibitors (UIs), synthetic nitrification inhibitors (SNIs), and biochar (BC) are commonly used in mitigating nitrogen (N) loss and increasing fertilizer recovery efficiency (FRE) in agriculture. Calcareous soil under rice cropping is characterized by high nitrification potential, N loss risk, and low FRE. Application of SNIs may stimulate NH3 volatilization in high pH soils and the effects of SNIs on FRE are not always positive. BNIs have many advantages over SNIs. Whether combined application of BNI, UI, and BC that can result in a synergistic effect of improving FRE and decreasing N loss in a calcareous soil under rice cropping worth investigating. In this study, we conducted pot experiments to investigate the effects of single and co-application of BNI (methyl 3-(4-hydroxyphenyl) propionate or MHPP, 500 mg kg−1 soil), UI (N-(n-butyl), thiophosphoric triamide or NBPT, 2% of urea-N), or BC (wheat straw, 0.5% (w/w)) with chemical fertilizer on NH3 volatilization, N2O emission, N leaching, crop N uptake, and FRE in a calcareous soil under rice cropping. Our results demonstrated that those NMMs could mitigate NH3 volatilization by 12.5%–26.5%, N2O emission by 62.7%–73.5%, and N leaching loss by 17.5%–49.0%. However, BNI might have a risk of increasing NH3 (5.98%) volatilization loss. Among those NMMs, double inhibitors (BNI plus UI) yielded a synergistic effect that could mitigate N loss to the maximum extent and effectively improve FRE by 25.4%. The mechanisms of the above effects could be partly ascribed to the niche differentiation between the abundance of AOA and AOB and the changed community structure of AOB, which could further influence nitrification and N fate. Our results demonstrated that co-application of BNI and UI with urea is an effective strategy in reducing N loss and improving FRE in a calcareous soil under rice cropping.

The potential importance of soil denitrification as a major N loss pathway in intensive greenhouse vegetable production systems

BackgroundAbout 30 % of vegetables in China are produced in intensively managed greenhouses comprising flood irrigation and extreme rates of nitrogen fertilizers. Little is known about denitrification N losses.MethodsSoil denitrification rates were measured by the acetylene inhibition technique applied to anaerobically incubated soil samples. Four different greenhouse management systems were differentiated: Conventional flood irrigation and over-fertilization (CIF, 800 kg N ha−1, 460 mm); CIF plus straw incorporation (CIF+S, 889 kg N ha−1, 460 mm); Drip fertigation with reduced fertilizer application rates (DIF, 314 kg N ha−1, 190 mm); DIF plus straw incorporation (DIF+S, 403 kg N ha−1, 190 mm). Soil denitrification was measured on nine sampling dates during the growing season (Feb 2019-May 2019) for the top-/ subsoil (0 – 20/ 20- 40 cm) and on three sampling dates for deep soils (40-60/ 80-100 cm). Data was used to constrain N-input-output balances of the different vegetable production systems.ResultsRates of denitrification were at least one magnitude higher in topsoil than in sub- and deep soils. Total seasonal denitrification N losses for the 0 – 40 cm soil layer ranged from 76 (DIF) to 422 kg N ha−1 (CIF+S). Straw addition stimulated soil denitrification in top- and subsoil, but not in deep soil layers. Integrating our denitrification data (0-100 cm) with additional data on N leaching, N2O emissions, plant N uptake, and NH3 volatilization showed, that on average 50 % of added N fertilizers are lost due to denitrification.ConclusionsDenitrification is likely the dominant environmental N loss pathway in greenhouse vegetable production systems. Reducing irrigation and fertilizer application rates while incorporating straw in soils allows the reduction of accumulated nitrate.

Bacterial Community Structure and Metabolic Function Succession During the Composting of Distilled Grain Waste.

Distilled grain waste (DGW) can be converted to organic fertilizer via aerobic composting process without inoculating exogenous microorganisms. To illustrate the material conversion mechanism, this study investigated the dynamic changes of bacterial community structure and metabolic function involved in DGW composting. Results showed that a significant increase in microbial community alpha diversity was observed during DGW composting. Moreover, unique community structures occurred at each composting stage. The dominant phyla were Firmicutes, Proteobacteria, Actinobacteriota, Bacteroidota, Myxococcota, and Chloroflexi, whose abundance varied according to different composting stages. Keystone microbes can be selected as biomarkers for each stage, and Microbispora, Chryseolinea, Steroidobacter, Truepera, and Luteimonas indicating compost maturity. Co-occurrence network analysis revealed a significant relationship between keystone microbes and environmental factors. The carbohydrate and amino acid metabolism were confirmed as the primary metabolic pathways by metabolic function profiles. Furthermore, nitrogen metabolism pathway analysis indicated that denitrification and NH3 volatilization induced higher nitrogen loss during DGW composting. This study can provide new understanding of the microbiota for organic matter and nitrogen conversion in the composting process of DGW.

Life cycle assessment and fertilization scheme optimization of paddy field crops in South China

Although the application of synthetic fertilizers remarkably improves crop yields, their excessive application can bring about serious environmental pollution. However, previous studies largely focused on life cycle assessment about environmental risk and impact through measuring environmental emissions, or fertilization scheme recommendation with single optimization goal based on field experiments. In this study, we used soil testing and formulated fertilization field data from the experimental region (Ezhou, South China) to acquire the optimal application scheme of synthetic fertilizers for paddy field crops. Based on four crops (i.e. rapeseed, early rice, middle rice and late rice) and two rotation systems (i.e. rapeseed-rice rotation and rice-rice rotation), we applied the life cycle assessment method to analyze life cycle inventories and assess environmental impacts. The fertilizer production and resource consumption were defined as the initial boundary, and the crop production and environmental emissions were defined as the terminal boundary. Four crops were assessed and compared under 1t crop grain functional unit and 1hm2 cropland area functional unit, and two rotation systems were assessed and compared under 1hm2 cropland area functional unit. The environmental impact categories assessed were energy consumption, climate change, eutrophication, environmental acidification, land use and water consumption. Based on three fertilization schemes (i.e. fertilization on benchmark value (Schemeb), yield balance value (Schemeyb) and threshold value (Schemet)), we subsequently simulated crop yields and environmental emissions of fertilization schemes. The results show that the estimated environmental impact category indicators assessed by life cycle per t of rapeseed were higher than rice, and that per hm2 of rapeseed-rice rotation were lower than rice-rice rotation. Eutrophication contributed the most (over 80%) to the environmental impact of producing 1t crop, followed by environmental acidification. Ammonia (NH3) emission accounted for a high contribution to eutrophication (about 30%) or environmental acidification (about 90%), and nitrate ion (NO3-) loss contributed the most to eutrophication (about 40%). The results also show that paddy field crops reached maximum yields but caused greatest environmental impact under the Schemeyb. Whereas, the Schemet could guarantee paddy field crops to keep average yields but cause minimum environmental impact, which was the optimal fertilization scheme. Our study indicates that producing 1t rice and 1hm2 rapeseed-rice rotation had higher environmental benefit than producing 1t rapeseed and 1hm2 rice-rice rotation respectively. Eutrophication could lead to the biggest threat to ecological environment, and the key to alleviating this environmental impact was reducing NH3 volatilization and NO3- loss. Our work implies that the optimal fertilization scheme can both guarantee food sufficiency and reduce environmental pollution, which is applicable combining with soil testing and formulated fertilization technology in Ezhou.

Modified lignite and black coal reduce ammonia volatilization from cattle manure

Modified lignite and black coal (BC) are potential amendments for animal bedding to abate ammonia (NH3) emissions due to their large adsorption capacities for ammoniacal nitrogen (N). However, the ability of modified lignite and BC in reducing NH3 volatilization from livestock manure and the underlying mechanisms remain unknown. The present study has investigated the effect of lignite, modified lignite, BC and modified BC on NH3 volatilization from cattle manure, biological immobilization of manure ammoniacal N and manure properties. Modified lignite and BC reduced the NH3 volatilization from manure by 44 and 36%, respectively, which were comparable with original lignite (43%). The biological immobilization of applied stable isotope labelled 15N in lignite, modified lignite, BC and modified BC amended manures was 15, 18, 11 and 16%, respectively, which were significantly higher than that in unamended manure (4%, P < 0.001). In addition, NH4+-N concentrations of lignite, modified lignite and modified BC amended manures (7.0–7.3 mg g−1) were significantly higher than that of the unamended and original BC amended manures (3.3 and 4.8 mg g−1, respectively, P < 0.001). However, the manure pH in all treatments remained alkaline (pH > 8.2). Our results highlight that the adsorption and immobilization of manure ammoniacal N induced by amendments are the key drivers in reducing NH3 loss from manure, outweighing the pH effect. The findings of this study provide new insights into the mechanisms of coal amendments reducing NH3 loss from animal manure and their potential applications in intensive livestock systems.

Effects of biochar and fertilizer sources on nitrogen uptake by chilli pepper plants under Mediterranean climate

AbstractThis study determined N uptake by serrano chilli pepper for two years and evaluated the effects of biochar amendment or organic N (org‐N) fertilizer on N use under a Mediterranean climate. A field experiment was conducted using microplots from 2016 to 2017 in California, USA. Treatments included biochar amendment rates [0 (control), 10, 30 and 50 tons (t) ha−1] biochar, all with 100% inorganic N fertilizer (165 kg N ha−1), and org‐N fertilizer applications at 50%, 75% and 100% of the total available N supply. Pepper yield, vegetative biomass, N uptake, ammonia (NH3) volatilization and changes in soil organic carbon (SOC), and nitrate were determined. Pepper yield was highest in the 50% org‐N and lowest in the 50 t ha−1 biochar treatment during the first year. There were no differences in fruit yield among the organic treatments during the second year, and all were higher than that from the control. The 100% org‐N treatment had less NH3 volatilization than all other treatments during the first year. The two‐year results showed that chilli pepper plants sequestered 4.6‒6.1 kg N to produce one ton fresh pepper fruits. During the first year, the 50% org‐N treatment resulted in the highest N productivity or yield with lowest projected N fertilizer application requirements as compared to other treatments although there were no differences among all treatments in the second year. Thus, a combination of inorganic and org‐N fertilizers can be an effective strategy to improve soil N productivity in long‐term management.

Potential of Chamomile recutita Plant Material to Inhibit Urease Activity and Reduce NH3 Volatilization in Two Agricultural Soils

The large amount of ammonia released during agricultural application of urea fertilizer can result in a partial loss of applied nitrogen, having a detrimental effect on air quality. Although Chamomile recutita has nitrogen transformation inhibitory properties, providing potential agricultural and environmental benefits, the full extent of the effects of the major constituents of this plant on urease activity and NH3 volatilization in soils is currently unknown. Soil incubation experiments were established using 2-Cyclopenten-1-one and Eugenol, two major constituents of C. recutita, to evaluate their effects on inorganic soil nitrogen pools, urease activity, and NH3 volatilization in grey desert soil and red soil. An application rate of 0.25 g N kg−1 soil fertilizer was applied as urea with and without additives. An unfertilized treatment was also included as a control. In order to compare results, N(butyl) thiophosphoric triamide (NBPT), a common synthetic urease inhibitor, was also used. NBPT, 2-Cyclopenten-1-one and Eugenol were applied at a rate of 0.00125 g kg−1 soil (equivalent to 0.5% N). The results indicated that the rate of urea hydrolysis was higher in grey desert soil compared to red soil. Soil in the urea-only treatments recorded urea hydrolysis to be almost complete within seven days of application. The rate of hydrolysis was inhibited by the two natural compounds, and higher concentrations of urea were maintained for more than two weeks. Soil amended with the two materials exhibited strong soil urease inhibition in both soil treatments (75.1% in the alkaline grey desert soil and 72.8% in the acidic red soil). The strongest inhibitory effect occurred one to three days after incubation in the Eugenol treatment. Moreover, the inhibitory effects of Cyclopenten-1-one and Eugenol were superior to that of NBPT in the two soils. Cyclopenten-1-one and Eugenol also significantly reduced soil NH3 emissions by 14.2 to 45.3%, especially in the acidic red soil. Molecular docking studies confirmed inhibition mechanisms, highlighting that natural compounds interacted with the amino acid residues of the urease active center. This action resulted in the urease active pocket being blocked, thereby inhibiting enzyme activity. Overall, our findings suggest that 2-Cyclopenten-1-one and Eugenol are both capable of hindering urease activity and reducing the risk of N loss in the two tested soils. Results highlight their applicability as urease inhibitors and their effect in delaying the release of ammonia nitrogen, thereby increasing fertilizer N use efficiency. However, in order to fully assess N use efficiency and the N balance due to the presence of Chamomile extract in soil-crop systems, further field scale investigations are required.

Ammonia Volatilization, Forage Accumulation, and Nutritive Value of Marandu Palisade Grass Pastures in Different N Sources and Doses

The reduction in ammonia (NH3) losses from volatilization has significant implications in forage production. The objective of this study was to evaluate the impact of N fertilizers (urea, ammonium nitrate, and ammonium sulfate) and four doses (0, 90, 180 and 270 kg N ha−1) on N losses by NH3 volatilization, accumulation, and forage chemical composition of Urochloa brizantha cv Marandu. Two field experiments were conducted to measure NH3 losses using semi-open chambers. The forage accumulation and chemical composition were evaluated in the third experiment; the response variables included forage accumulation, crude protein (CP), and neutral detergent fiber (NDF). Compared to urea, ammonium nitrate and ammonium sulfate reduced NH3 losses by 84% and 87% and increased total forage accumulation by 14% and 23%, respectively. Forage accumulation rate and CP increased linearly with the N levels, while NDF contents decreased linearly with the N levels. In both experiments, NH3 losses and forage characteristics were different according to the rainfall pattern and temperature variations. Our results indicate that the use of nitric and ammoniacal fertilizers and the application of fertilizer in the rainy season constitute an efficient fertilizer management strategy to increase forage yield and decrease losses from volatilization of NH3.

Climate change may interact with nitrogen fertilizer management leading to different ammonia loss in China's croplands.

Despite research into the response of ammonia (NH3 ) volatilization in farmland to various meteorological factors, the potential impact of future climate change on NH3 volatilization is not fully understood. Based on a database consisting of 1063 observations across China, nonlinear NH3 models considering crop type, meteorological, soil and management variables were established via four machine learning methods, including support vector machine, multi-layer perceptron, gradient boosting machine and random forest (RF). The RF model had the highest R2 of 0.76 and the lowest RMSE of 0.82 kg NH3 -N ha-1 , showing the best simulation capability. Results of model importance indicated that NH3 volatilization was mainly controlled by total input of N fertilizer, followed by meteorological factors, human managements and soil characteristics. The NH3 emissions of China's cereal production (paddy rice, wheat and maize) in 2018 was estimated to be 3.3Mt NH3 -N. By 2050, NH3 volatilization will increase by 23.1-32.0% under different climate change scenarios (Representative Concentration Pathways, RCPs), and climate change will have the greatest impact on NH3 volatilization in the Yangtze river agro-region of China due to high warming effects. However, the potential increase in NH3 volatilization under future climate change can be mitigated by 26.1-47.5% through various N fertilizer management optimization options.

Effects of pH, Total Solids, Temperature and Storage Duration on Gas Emissions from Slurry Storage: A Systematic Review

Gaseous emissions are the main loss pathways of nutrients during dairy slurry storage. In this study, we compiled published data on cumulative ammonia (NH3), nitrous oxide (N2O) and methane (CH4) emissions from dairy slurry storage and evaluated the integrated effects of slurry pH, total solids (TS), ambient temperature (T) and length of storage (LOS) on emissions using linear mixed effects models. Results showed that the average nitrogen (N) loss by NH3 volatilization from slurry storage was 12.5% of total nitrogen (TN), while the loss by N2O emissions only accounted for 0.05–0.39% of slurry TN. The NH3–N losses were highly related to slurry pH, lowering slurry pH leading to significant decrease of emissions. Temperature also affected NH3–N losses, with higher losses from slurry storage under warm conditions than cold conditions. No significant relationship was observed between NH3–N losses and slurry TS contents within a range from 21–169 g kg−1. The losses of N2O–N from dairy slurry storage were less affected by slurry pH, TS contents and temperature. The carbon (C) loss as CH4 emissions varied from 0.01–17.2% of total carbon (TC). Emissions of CH4–C presented a significant positive relationship with temperature, a negative relationship with slurry TS contents and no significant relationship with slurry pH ranging from 6.6–8.6. Length of storage (more than 30 days) had no significant influence on cumulative gas emissions from slurry storage. This study provides new emission factors of NH3, N2O and CH4 in the percentage of TN or TC from dairy slurry storage. Our results indicate the potential interactive effects of slurry characteristics and storage conditions on gaseous emissions from slurry storage. Farm-scale measurements are needed to accurately estimate nutrient losses from liquid manure storage.

Nitrogen balance acts an indicator for estimating thresholds of nitrogen input in rice paddies of China

Decision-making related to nitrogen (N) fertilization is a crucial step in agronomic practices because of its direct interactions with agronomic productivity and environmental risk. Here, we hypothesized that soil apparent N balance could be used as an indicator to determine the thresholds of N input through analyzing the responses of the yield and N loss to N balance. Based on the observations from 951 field experiments conducted in rice (Oryza sativa L.) cropping systems of China, we established the relationships between N balance and ammonia (NH3) volatilization, yield increase ratio, and N application rate, respectively. Dramatical increase of NH3 volatilizations and stagnant increase of the rice yields were observed when the N surplus exceeded certain levels. Using a piecewise regression method, the seasonal upper limits of N surplus were determined as 44.3 and 90.9 kg N ha−1 under straw-return and straw-removal scenarios, respectively, derived from the responses of NH3 volatilization, and were determined as 53.0–74.9 and 97.9–112.0 kg N ha−1 under straw-return and straw-removal scenarios, respectively, derived from the maximum-yield consideration. Based on the upper limits of N surplus, the thresholds of N application rate suggested to be applied in single, middle-MLYR, middle-SW, early, and late rice types ranged 179.0–214.9 kg N ha−1 in order to restrict the NH3 volatilization, and ranged 193.3–249.8 kg N ha−1 in order to achieve the maximum yields. If rice straw was returned to fields, on average, the thresholds of N application rate could be theoretically decreased by 17.5 kg N ha−1. This study provides a robust reference for restricting the N surplus and the synthetic fertilizer N input in rice fields, which will guide yield goals and environmental protection.

Biostimulants decreased nitrogen leaching and NH3 volatilization but increased N2O emission from plastic-shed greenhouse vegetable soil

Biostimulant application is an effective strategy to enhance soil fertility and plant growth. However, its comprehensive impacts on nitrogen (N) uptake and reactive N (Nr) losses via leaching, ammonia (NH3) volatilization, and nitrous oxide (N2O) emission from plastic-shed greenhouse vegetable system are still little known. Therefore, a field experiment was conducted with cauliflower-tomato growth rotation (from September 6, 2018, to July 17, 2019) receiving three biostimulants, i.e., humic acid (HA), algae extract (AE), and chitosan (CT), as well as a control without stimulant. The cumulative Nr losses over the cauliflower-tomato growth cycle via leaching, NH3 volatilization, and N2O emission were 104-175 kg N ha-1, 2.32-3.85 kg N ha-1, and 0.70-0.85 kg N ha-1, respectively. Biostimulant application significantly (P < 0.05) retarded the total N leaching by 17-44% in tomato season, while suppressed the NH3 volatilization by 18-38% in cauliflower season. Overall, AE showed the best inhibition efficiency on Nr losses by significantly (P < 0.05) decreasing total N leaching and NH3 volatilization by 36-44% and 38-52% in both vegetable seasons, compare to the control. However, all three biostimulants stimulated the N2O emission under both vegetable cycles. Interestingly, all biostimulant-added treatments promote the cauliflower and tomato yield, particularly following the HA and AE amendments, which bring local farmers approximately 4,384-10,035 yuan RMB ha-1 more income. Enhanced yield under biostimulant treatments was due to higher N uptake capacity and enhanced root morphology. In summary, biostimulants have a contrasting influence on three major Nr lost pathways in greenhouse vegetable production. We recommend that AE is the most optimal biostimulant as it increases vegetable yield and decreases total N leaching and NH3 volatilization while not dramatically increase the N2O emission.

DMPP reduces nitrogen fertilizer application rate, improves fruit quality, and reduces environmental cost of intensive apple production in China

In China, excessive application of nitrogen (N) fertilizer is common in intensive apple production. To resolve issues of benefit reduction and environmental pollution caused by excessive N, a two-year trial was conducted in an apple orchard with a split-plot design, in which the main factor was the N level (500, 400, 300, and 200 kg N ha−1 year−1, expressed as TN, TN80%, TN60%, and TN40%, respectively) and the deputy factor was whether or not to add 3,4-dimethylpyrazole phosphate (DMPP, expressed as +D). The effects of N reduction combined with DMPP on soil N transformation, fruit quality, economic benefits, and environmental effects were investigated. The results showed that DMPP reduced the production of nitrate and its vertical migration by inhibiting the abundance of AOB amoA and decreased N2O emission by reducing nirKC1 levels. Moreover, N reduction combined with DMPP improved N use efficiency (26.67–49.35%) and reduced N loss rate (15.25–38.76%). Compared with TN, TN60% + D increased the content of anthocyanin and soluble sugar by 21.15% and 13.09%, respectively, and decreased environmental costs caused by NH3 volatilization and N2O emission by 33.84%, while maintaining yield and N utilization rate at relatively high levels. Considering the agronomic, economic and environmental benefits, on the basis of traditional N application rate, 40% N reduction combined with DMPP (TN60% + D) could ensure target yield, corresponding quality and economic benefits, maintain soil N fertility, and reduce the risk of N losses to the environment. The present research could provide references for green, efficient, and sustainable development of apple production.

Effects of Nitrification Inhibitors on Soil Nitrification and Ammonia Volatilization in Three Soils with Different pH

The application of nitrification inhibitors (NIs) is considered to be an efficient way to delay nitrification, but the effect of NIs combinations on soil nitrification and ammonia (NH3) volatilization are not clear in soils with different pH values. In this study, we explored the effect of nitrapyrin (CP) and its combinations with 3, 4-dimethylepyrazole phosphate (DMPP), dicyandiamide (DCD) on the transformation of nitrogen, potential nitrification rate (PNR), and ammonia (NH3) volatilization in a 120-day incubation experiment with three different pH values of black soil. Treatments included no fertilizer (Control), ammonium sulfate (AS), AS+CP (CP), AS+CP+DMPP (CP+DMPP), and AS+CP+DCD (CP+DCD). The application of NIs significantly decreased NO3−-N contents and potential nitrification rate (p &lt; 0.05), while significantly increased NH4+-N contents (p &lt; 0.05), especially CP+DCD and CP+DMPP were the most effective in the neutral and alkaline soils, respectively. In the acid soil, CP significantly increased total NH3 volatilization by 31%, while CP+DCD significantly reduced by 28% compared with AS. However, no significant difference was found in NH3 volatilization with and without NIs treatments (p &gt; 0.05) in the neutral and alkaline soils. In conclusion, the combined nitrification inhibitors had the better efficiency in all three tested soils. CP+DCD and CP+DMPP are the most effective in inhibiting soil nitrification in the clay soils with higher pH value and lower organic matter, while CP+DCD had the potential in mitigating environment pollution by reducing N loss of NH3 volatilization in the loam soil with lower pH value and higher organic matter. It provided a theoretical basis for the application of high efficiency fertilizer in different soils. Further studies under field conditions are required to assess the effects of these nitrification inhibitors.

Food waste digestate composting: Feedstock optimization with sawdust and mature compost

Direct land application of food waste digestate (FWD) leads to 60–70% of nitrogen loss through NH3 volatilization due to its innate characteristics like high ammonium nitrogen (NH4+-N) (~6000 mg/kg dry matter) and high moisture content (~75%). Hence, bio stabilization of FWD through composting is a promising solution to curb the environmental and occupational hazards. Hence the aim of this study was to assess the feasibility of using sawdust and/or mature compost as a bulking agent to achieve effective composting. The results showed that mixing of FWD with sawdust alone or together with mature compost could produce quality compost with reduced NH4+-N (<700 mg/kg dry matter) and increased seed germination index (>80%) within 2 weeks of co-composting. Composting FWD with both sawdust and mature compost effectively reduced ~ 83% of NH3 volatilization demonstrating that this approach can effectively produce mature nitrogen enriched FWD compost.

Effect of vole bioturbation on N2O, NO, NH3, CH4 and CO2 fluxes of slurry fertilized and non-fertilized montane grassland soils in Southern Germany

Populations of rodents such as common vole (Microtus arvalis) can develop impressive soil bioturbation activities in grasslands. These burrowing and nesting activities highly impact soil physicochemical properties as well as vegetation coverage and diversity. Managed grasslands in livestock production regions receive significant amounts of slurry, commonly at high loads at the beginning of the vegetation period. However, nothing is known how the combination of vole bioturbation and slurry application may affect the fluxes of C and N trace gases from grasslands. Here we report on an in-situ experiment and supporting laboratory incubations carried out during the period March to May 2020 comparing C (CH4, CO2) and N (N2O, NO, NH3) trace gas fluxes from Lolium perenne and Trifolium repens dominated montane grasslands with and without vole bioturbation and with and without slurry application, whereby, with regard to the latter, we further differentiated between acidified and non-acidified slurry. Vole bioturbation significantly (p < 0.05) increased soil NO and NH3 emissions, while N2O fluxes were only significantly (p < 0.05) enhanced in vole affected grassland patches following slurry application (+17%). Effects of vole bioturbation on CH4 fluxes were non-significant, while slurry application significantly reduced CH4 uptake. Compared to applications of non-acidified slurry, application of acidified slurry significantly (p < 0.05) reduced NH3 volatilization by approx. 38% and 50%, for vole and non-vole affected grassland patches, respectively. A significant effect of acidified slurry application on soil NO emissions was only observed for vole affected grassland patches. Significant (p < 0.05) reductions in aboveground net primary productivity and reduced plant N uptake are likely the main mechanisms explaining the stimulation of gaseous N losses following slurry application. Long-term measurements are needed to better understand effects of vole bioturbation on grassland soil C and N cycling and ecosystem GHG balance.

Presence of microplastics alone and co-existence with hydrochar unexpectedly mitigate ammonia volatilization from rice paddy soil and affect structure of soil microbiome

Microplastics (MPs), as an emerging pollutant, may cause deleterious changes to the nitrogen cycle in terrestrial ecosystems. However, single impact of MPs and synergistic effects of MPs with hydrochar on ammonia (NH3) volatilization and soil microbiome in paddy fields has been largely unexplored. In this study, polyethylene (PE), polyacrylonitrile (PAN) and straw-derived hydrochar (HBC) were selected for observations in an entire rice cycle growth period. Results showed that under the condition of 0.5% (w/w) MPs concentration, presence of MPs alone and co-existence of MPs and HBC (MPs + HBC) unexpectedly mitigated cumulative NH3 volatilization from paddy soil compared with the control with no MPs or HBC addition. MPs + HBC increased NH3 volatilization by 37.8–46.2% compared with MPs alone, indicating that co-existence of MPs and HBC weaken the mitigation effect of MPs on NH3 volatilization. Additionally, results of nitrogen cycle related microorganisms closely related to NH3 volatilization demonstrated that MPs + HBC altered the bacterial community structure and species diversity. These findings provide an important opportunity to advance our understanding of the impacts of MPs in agricultural environment and soils, and provide a sound theoretical basis for rationalizing the application of HBC in soil with MPs.

Long-term trajectories of the C footprint of N fertilization in Mediterranean agriculture (Spain, 1860–2018)

Synthetic nitrogen (N) fertilization has helped boost agricultural yields, but it is also responsible for direct and indirect greenhouse gas (GHG) emissions. Fertilizer-related emissions are also promoted by irrigation and manure application, which has increased with livestock industrialization. Spanish agriculture provides a paradigmatic example of high industrialization under two different climates (temperate and Mediterranean) and two contrasting water management regimes (rainfed and irrigated). In this study, we estimated the historical evolution of the C footprint of N fertilization (including all the life cycle GHG emissions related to N fertilization) in Spanish agriculture from 1860 to 2018 at the province level (50 provinces) for 122 crops, using climate-specific N2O emission factors (EFs) adjusted to the type of water management and the N source (synthetic fertilizer, animal manure, crop residues and soil N mineralization) and considering changes in the industrial efficiency of N fertilizer production. Overall, N-related GHG emissions increased ∼12-fold, up to 10–14 Tg CO2e yr−1 in the 2010s, with much higher growth in Mediterranean than in temperate areas. Direct N2O EFs of N fertilizers doubled due to the expansion of irrigation, synthetic fertilizers and liquid manure, associated with livestock industrialization. Synthetic N production dominated the emissions balance (55%–60% of GHGe in the 21st century). Large energy efficiency gains of industrial fertilizer production were largely offset by the changes in the fertilizer mix. Downstream N2O emissions associated with NH3 volatilization and NO3 − leaching increased tenfold. The yield-scaled carbon footprint of N use in Spanish agriculture increased fourfold, from 4 and 5 Mg CO2e Mg N−1 to 16–18 Mg CO2e Mg N−1. Therefore, the results reported herein indicate that increased productivity could not offset the growth in manufacture and soil emissions related to N use, suggesting that mitigation efforts should not only aim to increase N use efficiency but also consider water management, fertilizer type and fertilizer manufacture as key drivers of emissions.

Application of Zeolites in Agriculture and Other Potential Uses: A Review

Excessive use of nitrogen fertilizer and inappropriate fertilization designs have negative results in agricultural ecosystems, such as considerable nitrogen losses through nitrogen dioxide (NO2) soil leaching and ammonia NH3 volatilization. In addition, climate change, with rising summer temperatures and reduced precipitation, leads to production declines and water shortages in the soil. This review aims to highlight the characteristics of natural zeolite and focus on their multiple uses in agriculture. These minerals are tectosilicates showing an open three-dimensional structure involving the cations required to balance the framework electrostatic charge of aluminum and silicon tetrahedral units. Different research groups reported more than fifty natural zeolites; chabazite, clinoptilolite, phillipsite, erionite, stilbite, heulandite, and mordenite are the most well-known. Zeolites are great tools to help the farmer and agronomist cope with several issues, such as soil or water pollution, contamination by heavy metals, loss of nutrients, and loss of water-use efficiency (WUE) of drylands. These natural crystalline aluminosilicates are considered soil conditioners to improve soil chemical and physical properties, such as saturated hydraulic conductivity (Ks), infiltration rate, cation exchange capacity (CEC), and water-holding capacity (WHC). Owing to their properties, these materials are able to reduce nitrate leaching and ammonia volatilization. Zeolites are also known for their carrying capacity of slow-release macronutrients, micronutrients, and fertilizers. However, the potential of these materials in agricultural areas is apparent, and zeolites show the promise of contributing directly to improve agricultural ecosystems as a sustainable product.