Article

Evaluation of effectiveness of enhanced-efficiency fertilizers as mitigation options for N2O and NO emissions from agricultural soils: Meta-analysis

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Abstract

Agricultural fields are an important anthropogenic source of atmospheric nitrous oxide (N2O) and nitric oxide (NO). Although many field studies have tested the effectiveness of possible mitigation options on N2O and NO emissions, the effectiveness of each option varies across sites due to environmental factors and field management. To combine these results and evaluate the overall effectiveness of enhanced-efficiency fertilizers [i.e., nitrification inhibitors (NIs), polymer-coated fertilizers (PCFs), and urease inhibitors (UIs)] on N2O and NO emissions, we performed a meta-analysis using field experiment data (113 datasets from 35 studies) published in peer-reviewed journals through 2008. The results indicated that NIs significantly reduced N2O emissions (mean: −38%, 95% confidential interval: −44% to −31%) compared with those of conventional fertilizers. PCFs also significantly reduced N2O emissions (−35%, −58% to −14%), whereas UIs were not effective in reducing N2O. NIs and PCFs also significantly reduced NO (−46%, −65% to −35%; −40%, −76% to −10%, respectively). The effectiveness of NIs was relatively consistent across the various types of inhibitors and land uses. However, the effect of PCFs showed contrasting results across soil and land-use type: they were significantly effective for imperfectly drained Gleysol grassland (−77%, −88% to −58%), but were ineffective for well-drained Andosol upland fields. Because available data for PCFs were dominated by certain regions and soil types, additional data are needed to evaluate their effectiveness more reliably. NIs were effective in reducing N2O emission from both chemical and organic fertilizers. Moreover, the consistent effect of NIs indicates that they are potent mitigation options for N2O and NO emissions.

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... Inhibitors are the major constituents of EEF products and they generally improve NUE by impeding microbial N transformation to better synchronize N supply with crop demand (Zhang et al., 2012). Three strategies for inhibitor application include: using urease inhibitors (UI) to decrease NH3 volatiliza tio n by delaying urea hydrolysis; using nitrification inhibitor (NI) to reduce N2O emissio ns by suppressing the oxidation of NH4 + by nitrifiers in soil; and a combined applicatio n of UI and NI (UINI) to lower both NH3 and N2O emission potentials (Akiyama et al., 2010;Cantarella et al., 2018;Ni et al., 2018;Woodley et al., 2020). ...
... In this study, all reviewed inhibitors were effective in mitigating N2O despite inhibitor type and product, and the N2O emissions were significantly decreased by 13%, 49% and 31% under UI, NI and UINI, respectively, with NI being the most effective in N2O mitigation and UI the least (Fig. 2c). Similar results have been observed in previous studies (Martins et al., 2017;Volpi et al., 2017;Xia et al., 2017) and are as expected, given that NI directly hinder the production of N2O by inhibiting nitrifica t io n and NO3formation which is a precursor to N2O (Akiyama et al., 2010). This metaanalysis demonstrated a significant effect of UI on N2O mitigation, possibly because UI could indirectly limit the N2O emission potential by improving the efficiency of N uptake in plants (Singh et al., 2013). ...
... Cropping system was a significant explanatory variable controlling the inhib itor impacts on N loss reduction with a medium level of relative importance (Table 4 and Fig. 7). Irrespective of target variable (i.e., NH3 or N2O loss), grass was more responsive to inhibitor application than cereal crops (Fig. 3), falling in line with the findings of Akiyama et al. (2010) and Abalos et al. (2014). The increased root density of grasses, particularly in the early growth stage when inhibitor action is most pronounced, could facilitate the immobilization of N for a more efficient inhibition of N losses via inhibitors than cereal crops (Di & Cameron, 2005). ...
Article
Inhibitors are widely considered an efficient tool for reducing nitrogen (N) loss and improving N use efficiency, but their effectiveness is highly variable across agroecosystems. In this study, we synthesized 182 studies (222 sites) worldwide to evaluate the impacts of inhibitors (urease inhibitors [UI], nitrification inhibitors [NI] and combined inhibitors [UINI]) on crop yields and gaseous N loss (ammonia [NH3] and nitrous oxide [N2O] emissions) and explored their responses to different management and environmental factors including inhibitor application timing, fertilization regime, cropping system, water management, soil properties and climatic conditions using subgroup meta‐analysis, meta‐regression and multivariate analyses, including multiple linear regression and random forest regression. The UI were most effective in enhancing crop yields (by 5%) and reducing NH3 volatilization (by 51%) whereas NI were most effective at reducing N2O emissions (by 49%). The application of UI mitigates NH3 loss and increases crop yields especially in high NH3‐N loss scenarios, whereas NI application would minimize the net N2O emissions and the resultant environmental impacts especially in low NH3‐N loss scenarios. Alternatively, the combined application of UI and NI enables producers to balance crop production and environmental conservation goals without pollution tradeoffs. The inhibitor efficacy for decreasing gaseous N loss was dependent upon soil and climatic conditions and management practices. Notably, both meta‐regression and multivariate analyses suggest that inhibitors provide a greater opportunity for reducing fertilizer N inputs in high‐N‐surplus systems and presumably favor crop yield enhancement under soil N deficiency situations. The pursuit of an improved understanding of the interactions between plant‐soil‐climate‐management systems and different types of inhibitors should continue to optimize the effectiveness of inhibitors for reducing environmental losses while increasing productivity.
... The application of nitrogen fertilizer increases N 2 O emission by increasing mineral N levels (Akiyama et al. 2010;Qiu et al. 2015;Adviento-Borbe and Linquist 2016;Breuillin-Sessoms et al. 2017), among which urea is the main nitrogen fertilizer used in paddy fields . However, fertilizer application is essential to providing food for approximately 50% of the world's population (Denk et al. 2017), and it is difficult to reduce N 2 O emissions only by reducing the amount of nitrogen fertilizer applied. ...
... Therefore, other methods to reduce atmospheric N 2 O concentration without compromising food security are urgently needed (Bell et al. 2015;Raheem et al. 2019). In order to reduce N 2 O emission from agriculture soil, many measures have been explored, such as using inhibitors to limit the decomposition and conversion rate of nitrogen fertilizer (Akiyama et al. 2010;Wu et al. 2019). Among them, urease inhibitors PPD and NBPT can delay the hydrolysis of urea in rice fields, with combined application providing the best results (Phongpan et al. 1995;Wu et al. 2019). ...
... As expected, additions of mixed inhibitors with urea reduced N 2 O production by 26.69% (Figs. 1A and 2), which is in Fig. 2 The contribution of four pathways (NN, nitrification; ND, nitrifier denitrification; NCD, nitrification-coupled denitrification; HD, heterotrophic denitrification) under two treatments (U and U + I) to N 2 O produced in paddy soil line with other similar studies (Akiyama et al. 2010;Wu et al. 2019;Dong et al. 2021). The NH 4 + -N produced by the hydrolysis of urea provides the substrate for ammonia oxidation and N 2 O production. ...
Article
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Purpose In flooded paddy soils, quantifying and discerning nitrous oxide (N2O) production by four biological pathways (nitrifier nitrification (NN), nitrifier denitrification (ND), nitrification-coupled denitrification (NCD), and heterotrophic denitrification (HD)) are essential for developing innovative strategies to mitigate the greenhouse effect. Materials and methods Soils were collected from Shenyang Experimental Station of the Institute of Applied Ecology, Liaoning Province, China, and were sealed and incubated in the dark at 25 °C and submerged for 48 h. The amount of N2O produced by each of the four pathways and the abundance of corresponding functional genes were determined by dual-isotope (¹⁵N-¹⁸O) labeling technique combined with quantitative PCR (qPCR). Results and discussion In our incubation experiment, ¹⁵N isotope tracing showed that not urea but paddy soil was the largest contributor of N2O within 48 h after urea application. Combined application of urea and mixed inhibitors (N-(n-butyl) thiophosphoric triamide (NBPT) + phenylphosphorodiamidate (PPD) + 3,4-dimethylpyrazole phosphate (DMPP)) could reduce total N2O production by 26.69%. Through dual-isotope (¹⁸O-¹⁵N) labeling technology, it was found that N2O production mainly came from HD pathway, accounting for 77% of total N2O production, and N2O produced by ammonia oxidation (NN, ND, and NCD) after urea application accounted for 23% of total N2O production. The largest proportion of N2O production among the ammonia oxidation pathways was the ND pathway (0–23.00%), followed by the NN pathway (0–19.21%) and NCD pathway (0–3.79%). Application of mixed inhibitors significantly reduced the N2O produced by the HD pathway by more than 15%; reduced the N2O produced by the ammonia oxidation pathway from 23.00 to 10.39%; and reduced the N2O produced by the NN, ND, and NCD pathways by more than 50%. This is probably caused by the decreased ammonium level and reduced gene copies of AOB amoA, narG, and nirK, which are key N2O producing genes. Conclusions Incubation experiment showed that ammonia oxidation pathway is also an important pathway for N2O production in flooded paddy soil. Mixed inhibitors have inhibitory effects on N2O produced by NN, ND, NCD, and HD pathways. The future development of mixed inhibitor application strategies suitable for paddy fields is of great significance for mitigating the global greenhouse effect.
... NI application can decrease nitrification rates and N losses, thereby improving N fertiliser efficiency and increasing rice yield . N 2 O emissions were significantly reduced by NI application since NI application effectively constrains NH 4 + oxidation by reducing the abundance of ammonia-oxidising archaea and bacteria (Akiyama et al., 2010;Wang et al., 2021b). Furthermore, the decrease in nitrification rates limits substrate availability and thus reduces the abundance of nirS and nirK in the subsequent denitrification pathway (Meng et al., 2020). ...
... Furthermore, the decrease in nitrification rates limits substrate availability and thus reduces the abundance of nirS and nirK in the subsequent denitrification pathway (Meng et al., 2020). Thus, reduced nitrification and denitrification rates may both contribute to the decrease in N 2 O emissions under NI application (Akiyama et al., 2010). In addition, NI application can promote the reduction of N 2 O to N 2 by increasing nosZ abundance . ...
Article
Rice agriculture faces the dual challenge of increasing grain production while reducing global warming potential (GWP). Yield-scaled GWP, a commonly employed indicator, is not sufficient to identify smart agronomic practices that can address this dual challenge. Thus, practices that can increase yield while simultaneously reducing GWP in rice paddies have not yet been clearly defined. In this study, we synthesised independent experiments by meta-analyses to identify agronomic management practices with higher rice yield and lower GWP. The results showed that the application of nitrification inhibitors (NI) and biochar significantly increased rice yield by an average of 9.5% and 9.1%, and simultaneously reduced GWP by 24% and 14%, respectively. Overall, controlled-release nitrogen (N) fertilisers did not affect GWP despite increasing rice yield (+9.2%). In contrast, conventional N application enhanced both rice yield (+44%) and GWP (+27%). No-tillage reduced GWP (˗23%) but did not significantly affect rice yield. Non-continuous flooding in rice paddies significantly reduced GWP (˗48%) but also reduced the yield (˗4.2%). The rice yield and GWP outcomes were similar for rice-animal co-culture and rice monoculture systems. In conclusion, both NI and biochar application are promising practices for increasing yield while simultaneously reducing GWP in rice paddies. In addition, we suggest that individual agronomic practices should be combined to increase rice yield while mitigating climate warming.
... Dicyandiamide (DCD) and 3,4-dimethylpyrazole phosphate (DMPP) are highly effective inhibitors of nitrification (NIs) and have been used to increase efficiency of NH + 4 -based fertilizers and productivity of agricultural systems, and reduce the environmental impacts of nitrate leaching and nitrous oxide emissions [56]. However, natural heterogeneity in soil physicochemical properties impacts the efficacy of DMPP and DCD, resulting in its uncertainty and therefore hesitancy in use [1,20,47,58,65]. Significant progress has been made towards unravelling the complex interactions among abiotic (e.g. ...
... Taken together, these results indicated the distinct effects of DCD and DMPP in soils with contrasting properties, a finding strongly supported by previous metaanalyses [1,20,32]. This could be attributed to the lower mobility of DCD than of DMPP in soil (DCD > NH + 4 ≈ DMPP), and higher degradation rate of DCD than of DMPP [42,45,56]. ...
Article
Full-text available
The efficacy of nitrification inhibitors (NIs) dicyandiamide (DCD) and 3,4-dimethylpyrazole phosphate (DMPP) varies with soil types. Understanding the microbial mechanisms for this variation may lead to better modelling of NI efficacy and therefore on-farm adoption. This study addressed the response patterns of mineral nitrogen, nitrous oxide (N2O) emission, abundances of N-cycling functional guilds and soil microbiota characteristics, in relation to urea application with or without DCD or DMPP in two arable soils (an alkaline and an acid soil). The inhibition of nitrification rate and N2O emission by NI application occurred by suppressing ammonia-oxidizing bacteria (AOB) abundances and increasing the abundances of nosZI-N2O reducers; however, abundances of ammonia-oxidizing archaea (AOA) were also stimulated with NIs-added in these two arable soils. DMPP generally had stronger inhibition efficiency than DCD, and both NIs’ addition decreased Nitrobacter, while increased Nitrospira abundance only in alkaline soil. N2O emissions were positively correlated with AOB and negatively correlated with nosZI in both soils and AOA only in acid soil. Moreover, N2O emissions were also positively correlated with nirK-type denitrifiers in alkaline soil, and clade A comammox in acid soil. Amendment with DCD or DMPP altered soil microbiota community structure, but had minor effect on community composition. These results highlight a crucial role of the niche differentiation among canonical ammonia oxidizers (AOA/AOB), Nitrobacter and Nitrospira, as well as nosZI- and nosZII-N2O reducers in determining the varying efficacies of DCD and DMPP in different arable soils.
... Figure 1 reports a schematic representation of the processes acting in the unsaturated and saturated zones. Among all biogeochemical processes, DNT is considered the predominant factor responsible for NO3 − attenuation in agricultural soil [45], representing an important pathway for Nr losses. Nevertheless, DNT also has a serious adverse environmental effect, Among all biogeochemical processes, DNT is considered the predominant factor responsible for NO 3 − attenuation in agricultural soil [45], representing an important pathway for Nr losses. ...
... Among all biogeochemical processes, DNT is considered the predominant factor responsible for NO3 − attenuation in agricultural soil [45], representing an important pathway for Nr losses. Nevertheless, DNT also has a serious adverse environmental effect, Among all biogeochemical processes, DNT is considered the predominant factor responsible for NO 3 − attenuation in agricultural soil [45], representing an important pathway for Nr losses. Nevertheless, DNT also has a serious adverse environmental effect, being the principal source of N 2 O and NO, accounting for 70% of the N 2 O emitted annually from the biosphere into the atmosphere [46]. ...
Article
Full-text available
Several groundwater vulnerability methodologies have been implemented throughout the years to face the increasing worldwide groundwater pollution, ranging from simple rating methodologies to complex numerical, statistical, and hybrid methods. Most of these methods have been used to evaluate groundwater vulnerability to nitrate, which is considered the major groundwater contaminant worldwide. Together with dilution, the degradation of nitrate via denitrification has been acknowledged as a process that can reduce reactive nitrogen mass loading rates in both deep and shallow aquifers. Thus, denitrification should be included in groundwater vulnerability studies and integrated into the various methodologies. This work reviewed the way in which denitrification has been considered within the vulnerability assessment methods and how it could increase the reliability of the overall results. Rating and statistical methods often disregard or indirectly incorporate denitrification, while numerical models make use of kinetic reactions that are able to quantify the spatial and temporal variations of denitrification rates. Nevertheless, the rating methods are still the most utilized, due to their linear structures, especially in watershed studies. More efforts should be paid in future studies to implement, calibrate, and validate user-friendly vulnerability assessment methods that are able to deal with denitrification capacity and rates at large spatial and temporal scales.
... Nitrification inhibitors, which are the most effective nitrification control method, directly inhibit the conversion of ammonium to nitrite by AOB by suppressing AMO activity and reducing the risk of nitrate leaching and N 2 O emissions (Subbarao et al. 2006;Beeckman, Motte, and Beeckman 2018). Meta-analyses have reported that the application of nitrification inhibitors significantly reduces dissolved inorganic N leaching and N 2 O emission (Akiyama, Yan, and Yagi 2010;Qiao et al. 2015;Xia et al. 2017). The N 2 O mitigation effects of 2-chloro-6-(trichloromethyl) pyridine (nitrapyrin), dicyandiamide (DCD), and 3,4-dimethylepyrazole phosphate (DMPP), which are widely used in agriculture, were evaluated as 50%, 30%, and 50%, respectively (Akiyama, Yan, and Yagi 2010). ...
... Meta-analyses have reported that the application of nitrification inhibitors significantly reduces dissolved inorganic N leaching and N 2 O emission (Akiyama, Yan, and Yagi 2010;Qiao et al. 2015;Xia et al. 2017). The N 2 O mitigation effects of 2-chloro-6-(trichloromethyl) pyridine (nitrapyrin), dicyandiamide (DCD), and 3,4-dimethylepyrazole phosphate (DMPP), which are widely used in agriculture, were evaluated as 50%, 30%, and 50%, respectively (Akiyama, Yan, and Yagi 2010). On the other hand, the application of nitrification inhibitors with nitrogen fertilizer or animal urine could potentially increase NH 3 emission in some soils (Qiao et al. 2015). ...
Article
Nitrogen cycle, a most important elemental cycle in earth ecosystem, is carried out by three major microbial processes including nitrogen fixation, nitrification and denitrification. Nitrification is particularly important in agricultural soil ecosystems because it is involved in nitrogen loss, groundwater pollution by nitrogen leaching, and greenhouse gas nitrous oxide emission. Recent genomic, metagenomic and physiological analysis of nitrifying microorganisms gives new insights into their ecology and functions in soils. In the last decade, there have been a number of important findings regarding nitrification. The discovery of nitrifying archaea and complete nitrifying bacteria has overturned the conventional theory that nitrification is driven by ammonia-oxidizing and nitrite-oxidizing bacteria. Each of the newly discovered nitrifying microorganisms has unique properties, for example, a different affinity for ammonia. These nitrifying microorganisms have been shown to actually play important roles in nitrification in agricultural soils. Soil conditions and agricultural practices such as fertilization and tillage have been shown to influence the contribution of each nitrifying microorganism to the activity of nitrification. In addition, nitrification inhibition technologies have been developed to prevent the loss of nitrogen fertilizer and the of nitrous oxide emission. This review provides an overview of recent researches on the diversity and characteristics of nitrifying microorganisms, soil factors affecting their ecology in soil, their involvement in nitrous oxide emissions, and nitrification control technologies.
... For example, ammonium nitrate-based fertilizers have reduced N losses by ammonia (NH 3 ) volatilization when compared with urea-based fertilizers, since nitrate does not volatilize (Meyer et al., 1961;Ti et al., 2019). On the other hand, nitrification inhibitors were used to decrease N 2 O emissions as they delay the transformation of ammonium into nitrate, therefore reducing the denitrification rate, which is the main process involved in N 2 O emission (Akiyama et al., 2010;Chen et al., 2008;Qiao et al., 2015). However, their efficiency is influenced by soil type and climate regime (Akiyama et al., 2010;Menéndez et al., 2006;Merino et al., 2006;Weiske et al., 2001) and management (Woodley et al.2020). ...
... On the other hand, nitrification inhibitors were used to decrease N 2 O emissions as they delay the transformation of ammonium into nitrate, therefore reducing the denitrification rate, which is the main process involved in N 2 O emission (Akiyama et al., 2010;Chen et al., 2008;Qiao et al., 2015). However, their efficiency is influenced by soil type and climate regime (Akiyama et al., 2010;Menéndez et al., 2006;Merino et al., 2006;Weiske et al., 2001) and management (Woodley et al.2020). ...
Article
About half of the applied nitrogen (N) is not consumed by crops, causing environmental and economic costs. This N can be lost as ammonia (NH3) volatilization, nitrous oxide (N2O) emission or leaching, among others. This work aimed to compare the amount of gaseous N losses using three different fertilizers on two consecutive experiments: one summer crop (maize) and one winter crop (wheat) in the Rolling Pampa, Argentina. The fertilizers used were: UAN (Urea Ammonium Nitrate); CAN (Calcium Ammonium Nitrate) and AN+DMPP (Ammonium Nitrate‐based NPK fertilizer with DMPP nitrification inhibitor). NH3 emissions were estimated using a semi open‐static absorption system during the first month after fertilization for each experiment. N2O emissions were estimated using vented static chambers during the growing season of each crop. Results show that CAN or AN+DMPP fertilizers used instead of UAN helped to reduce NH3 volatilization by 45‐50% and 62‐63% on maize and wheat experiments respectively, but failed to reduce N2O emissions. In addition, contrary to the expected, AN+DMPP increased N2O emissions during the maize experiment. The majority of the gaseous N losses occurred at specific moments of the crop cycle (after N fertilization and around leaf senescence). Losses as NH3 volatilization were higher than N2O emissions in the maize experiment, as expected because of the warmer temperature during this summer crop. However, N2O emissions were higher during the wheat crop, emphasizing the importance of factors such as meteorological conditions, previous land‐use, residual soil nitrate and stubble quality on the soil.
... The application of traditional fertilizers causes adverse environmental consequences, although they increase the quality and quantity of crop [12]. The indiscriminate use of nitrogen fertilizers induces serious environmental problems, including nitrification, denitrification, downstream degradation of water quality, loss via runoff, volatilization, etc. [13,14]. The excess nutrients released by traditional fertilizers deteriorate subsurface and surface water [6,12,[14][15][16]. ...
... The indiscriminate use of nitrogen fertilizers induces serious environmental problems, including nitrification, denitrification, downstream degradation of water quality, loss via runoff, volatilization, etc. [13,14]. The excess nutrients released by traditional fertilizers deteriorate subsurface and surface water [6,12,[14][15][16]. The development of fertilizers with controlled nutrient release properties is a solution to this problem [5,6,17,18]. ...
Article
Full-text available
This research presents the mechanical creation of smart fertilizers from a mixture of smectite and urea in a 3:2 ratio by using the planetary milling technique. The smectite–urea composites show intercalation between urea and mineral, which increases steadily with increasing activation time. A shift of X-Ray Diffraction basal reflections, intensities of Fourier transform infrared spectroscopy (FTIR) peaks, and weight losses in thermogravimetric analysis (TG) document the systematic crystallo-chemical changes of the composites related to nitrogen interaction with activation. Observations of the nanocomposites by scanning electron microscopy (SEM) and transmission electron microscopy (TEM) corroborate the inference. Nitrogen intercalates with smectite in the interlayer space and remains absorbed either within micro-aggregates or on the surface of activated smectites. Soil leaching tests reveal a slower rate of nitrogen than that of traditional urea fertilizers. Different forms of nitrogen within the composites cause their differential release rates to the soil. The formulated nanocomposite fertilizer enhances the quality and quantity of oat yield.
... Applying nitrification inhibitors is the other mitigation strategy with a significant potential, with an average reduction in N 2 O emissions from fertilizers of 38% (Akiyama et al., 2010). However, these have only been successfully tested for immature crop residues. ...
... Number of observations used in the meta-analysis: grain or seed crop, n = 102; vegetable, n = 40; cover crops, n = 91. * Acceptability (%) is derived from the questionnaire of our study; ** based on (Akiyama et al., 2010). ...
Article
Full-text available
Crop residues represent a climate change dilemma: they can promote carbon (C) sequestration, but they may also stimulate emissions of the powerful greenhouse gas nitrous oxide (N2O). Although there are crop residue management measures to reduce N2O emissions, N2O reductions achieved at national scale with these measures have been seldom studied, and how farmers' willingness to accept the measures constrains their potential remains largely unknown. Using Denmark as a case study, we combined a survey (completed by 592 farmers) and national data to assess the practical potential and obstacles for the successful implementation of management strategies to reduce N2O emissions from crop residues. Crop residue removal (particularly from vegetables and cover crops) and nitrification inhibitors were identified as effective in reducing N2O emissions from a biophysical perspective. If all aboveground crop residues from vegetables and cover crops were removed, N2O emissions could be reduced by 0.181 Gg N2ON, corresponding to 11% of the total N2O emissions from crop residues nationally. However, a low percentage of farmers would be willing to remove crop residues from the field, especially for vegetables and cover crops (25%), in connection to the possible short- to medium-term reduction in C sequestration. Similarly, use of nitrification inhibitors would reduce emissions by 0.247 Gg N2ON, corresponding to 15% of the total residue N2O emissions, and only 37% of all farmers would accept their use. Our results highlight that farmer’ preferences for the adoption of measures can constrain the use of the few available effective mitigation options. Better knowledge dissemination and advisory services are crucial to address this challenge; farmers may be motivated to remove aboveground crop residues by highlighting the proportionally more important contribution of belowground residues to C sequestration, and that aboveground residues may have commercial value (biorefining, biogas, biofuel), although these options need further development.
... Figure 1 reports a schematic representation of the processes acting in the unsaturated and saturated zones. Among all biogeochemical processes, DNT is considered the predominant factor responsible for NO3 − attenuation in agricultural soil [45], representing an important pathway for Nr losses. Nevertheless, DNT also has a serious adverse environmental effect, Among all biogeochemical processes, DNT is considered the predominant factor responsible for NO 3 − attenuation in agricultural soil [45], representing an important pathway for Nr losses. ...
... Among all biogeochemical processes, DNT is considered the predominant factor responsible for NO3 − attenuation in agricultural soil [45], representing an important pathway for Nr losses. Nevertheless, DNT also has a serious adverse environmental effect, Among all biogeochemical processes, DNT is considered the predominant factor responsible for NO 3 − attenuation in agricultural soil [45], representing an important pathway for Nr losses. Nevertheless, DNT also has a serious adverse environmental effect, being the principal source of N 2 O and NO, accounting for 70% of the N 2 O emitted annually from the biosphere into the atmosphere [46]. ...
Article
Full-text available
Several groundwater vulnerability methodologies have been implemented throughout the years to face the increasing worldwide groundwater pollution, ranging from simple rating methodologies to complex numerical, statistical, and hybrid methods. Most of these methods have been used to evaluate groundwater vulnerability to nitrate, which is considered the major groundwater contaminant worldwide. Together with dilution, the degradation of nitrate via denitrification has been acknowledged as a process that can reduce reactive nitrogen mass loading rates in both deep and shallow aquifers. Thus, denitrification should be included in groundwater vulnerability studies and integrated into the various methodologies. This work reviewed the way in which denitrification has been considered within the vulnerability assessment methods and how it could increase the reliability of the overall results. Rating and statistical methods often disregard or indirectly incorporate denitrification, while numerical models make use of kinetic reactions that are able to quantify the spatial and temporal variations of denitrification rates. Nevertheless, the rating methods are still the most utilized, due to their linear structures, especially in watershed studies. More efforts should be paid in future studies to implement, calibrate, and validate user-friendly vulnerability assessment methods that are able to deal with denitrification capacity and rates at large spatial and temporal scales.
... Of the 30 meta-analyses, 11 meta-analyses used nonmanipulative observations and 17 used manipulative experiments, while 2 used both non-manipulative observations and manipulative experiments. We followed the original database in defining the categories of environmental stressors; namely, acidification (Acid, k = 62; Nagelkerken & Connell, 2015), biodiversity loss (BD loss, k = 942;Cardinale et al., 2006;Griffin et al., 2013;Östman et al., 2016), fertilization (Fert, k = 811;Akiyama et al., 2010;Elser et al., 2007;Liang et al., 2016;Treseder, 2008), bush fire (Fire, k = 179;Dijkstra & Adams, 2015;Dooley & Treseder, 2012), plant invasion(Inv, k = 316;Gaertner et al., 2014;Gallardo et al., 2016;Vilà et al., 2011), land use change (LUC, k = 612;Gibson et al., 2011; Van Lent et al., 2014), precipitation (Precip, k = 138;Liu et al., 2016), and global warming (Warm, k = 790;Ateweberhan & McClanahan, 2010;Lin et al., 2010;Lu et al., 2013). ...
Article
Field studies are essential to reliably quantify ecological responses to global change because they are exposed to realistic climate manipulations. Yet such studies are limited in replicates, resulting in less power and, therefore, unreliable effect estimates. Further, while manipulative field experiments are assumed to be more powerful than non‐manipulative observations, it has rarely been scrutinized using extensive data. Here, using 3,847 field experiments that were designed to estimate the effect of environmental stressors on ecosystems, we systematically quantified their statistical power and magnitude (Type M) and sign (Type S) errors. Our investigations focused upon the reliability of field experiments to assess the effect of stressors on both ecosystem’s response magnitude and variability. When controlling for publication bias, single experiments were underpowered to detect response magnitude (median power: 18% – 38% depending on effect sizes). Single experiments also had much lower power to detect response variability (6% – 12% depending on effect sizes) than response magnitude. Such underpowered studies could exaggerate estimates of response magnitude by 2 – 3 times (Type M errors) and variability by 4 – 10 times. Type S errors were comparatively rare. These observations indicate that low power, coupled with publication bias, inflates the estimates of anthropogenic impacts. Importantly, we found that meta‐analyses largely mitigated the issues of low power and exaggerated effect size estimates. Rather surprisingly, manipulative experiments and non‐manipulative observations had very similar results in terms of their power, Type M and S errors. Therefore, the previous assumption about the superiority of manipulative experiments in terms of power is overstated. These results call for highly powered field studies to reliably inform theory building and policymaking, via more collaboration and team science, and large‐scale ecosystem facilities. Future studies also require transparent reporting and open science practices to approach reproducible and reliable empirical work and evidence synthesis.
... Of the 30 meta-analyses, 11 meta-analyses used nonmanipulative observations and 17 used manipulative experiments, while 2 used both non-manipulative observations and manipulative experiments. We followed the original database in defining the categories of environmental stressors; namely, acidification (Acid, k = 62; Nagelkerken & Connell, 2015), biodiversity loss (BD loss, k = 942;Cardinale et al., 2006;Griffin et al., 2013;Östman et al., 2016), fertilization (Fert, k = 811;Akiyama et al., 2010;Elser et al., 2007;Liang et al., 2016;Treseder, 2008), bush fire (Fire, k = 179;Dijkstra & Adams, 2015;Dooley & Treseder, 2012), plant invasion(Inv, k = 316;Gaertner et al., 2014;Gallardo et al., 2016;Vilà et al., 2011), land use change (LUC, k = 612;Gibson et al., 2011; Van Lent et al., 2014), precipitation (Precip, k = 138;Liu et al., 2016), and global warming (Warm, k = 790;Ateweberhan & McClanahan, 2010;Lin et al., 2010;Lu et al., 2013). ...
Preprint
Field studies are essential to reliably quantify ecological responses to global change because they are exposed to realistic climate manipulations. Yet such studies are limited in replicates, resulting in less power and, therefore, unreliable effect estimates. Further, while manipulative field experiments are assumed to be more powerful than non-manipulative observations, it has rarely been scrutinized using extensive data. Here, using 3,847 field experiments that were designed to estimate the effect of environmental stressors on ecosystems, we systematically quantified their statistical power and magnitude (Type M) and sign (Type S) errors. Our investigations focused upon the reliability of field experiments to assess the effect of stressors on both ecosystem’s response magnitude and variability. When controlling for publication bias, single experiments were underpowered to detect response magnitude (median power: 18% – 38% depending on mean difference metrics). Single experiments also had much lower power to detect response variability (6% – 12% depending on variance difference metrics) than response magnitude. Such underpowered studies could exaggerate estimates of response magnitude by 2 – 3 times (Type M errors) and variability by 4 – 10 times. Type S errors were comparatively rare. These observations indicate that low power, coupled with publication bias, inflates the estimates of anthropogenic impacts. Importantly, we found that meta-analyses largely mitigated the issues of low power and exaggerated effect size estimates. Rather surprisingly, manipulative experiments and non-manipulative observations had very similar results in terms of their power, Type M and S errors. Therefore, the previous assumption about the superiority of manipulative experiments in terms of power is overstated. These results call for highly powered field studies to reliably inform theory building and policymaking, via more collaboration and team science, and large-scale ecosystem facilities. Future studies also require transparent reporting and open science practices to approach reproducible and reliable empirical work and evidence synthesis.
... Ammonia losses can be minimized through management choices, such as the incorporation of urea (Woodley et al, 2020), injection of urea-ammonium nitrate compared with surface application (Woodley et al., 2018), or using non-urea fertilizer sources (Pan et al, 2016). In addition to farming best management practices, there have been many studies evaluating the effectiveness of treating urea to prevent volatilization through inhibition of the urease enzymes in soil (Akiyama et al., 2010). The most commercially sold urease inhibitor is N-(n-butyl) thiophosphoric triamide (nBTPT or NBPT) (IPNI, 2018). ...
Article
Surface application of urea can result in high nitrogen (N) losses through ammonia (NH3) volatilization. While management practices aim to increase the efficiency of nutrient cycling and prevent N loss, it is unknown whether the combination of multiple practices will have a synergistic or antagonistic effect. Therefore, laboratory volatilization studies were conducted to determine the effect of five cover crop treatments (surface clover [Trifolium incarnatum L.] and rye [Secale cereale L.], incorporated clover and rye, and bare soil), three N application timings (2, 4, and 8 wk after cover crop addition), and two N sources (untreated and treated urea) on the effectiveness of a urease inhibitor. Soils were incubated according to N application timing treatment, amended with the appropriate N source, and placed in chambers which captured NH3 over 7 d. There were significant interactions between cover crop treatment and N source and N source and N application timing on cumulative NH3 loss, ranging from 29 to 174 kg N ha−1. Losses were highest from treated urea when applied 2 wk after residue addition (75.9 kg N ha−1) or on top of surface residues (85.8 kg N ha−1). There was no significant effect of application timing on cumulative NH3 loss from untreated urea. However, inhibitor effectiveness did increase when residue was applied eight weeks after residue addition (77%) as compared with 2 wk after residue addition (45%). Future research should focus on alternate dosing or application timing to overcome high residue scenarios in these systems. The urease inhibitor reduced ammonia volatilization by 45–77% over 7 d. Surface cover crop residue significantly reduced urease inhibitor efficacy. Nitrogen application timing had a significant effect on efficacy of the urease inhibitor.
... The use of NIs has been shown to effectively reduce N 2 O emissions and NO 3 − leaching following application of mineral fertilizers to soil (Meijide et al., 2007). Akiyama et al. (2010) found a 31-44% reduction in N 2 O emissions following the application of different NIs to grasslands and arable fields alongside different N fertilizers. Based upon these results, it could be concluded that use of NIs has considerable mitigation potential for reducing N 2 O emissions. ...
Article
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Background Nitrification inhibitors (NI) may be used to inhibit nitrous oxide (N2O) emissions from agricultural soils, but their efficacy could be strongly affected by soil temperature and moisture. Aims This study investigated how different NI behave in a sandy soil under variable temperature and moisture levels, which currently remains unclear. Methods Efficacies of four NI [dicyandiamide (DCD), 3,4-dimethylpyrazole phosphate (DMPP), nitrogenous mineral fertilizers containing the DMPP ammonium stabilizer (ENTEC) and active ingredients: 3.00%–3.25% 1,2,4-triazole and 1.50%–1.65% 3-methylpyrazole (PIADIN)] were investigated in an incubation experiment under two soil temperatures (15 and 25°C) and two moisture levels [60% and 80% water-holding capacity (WH)] for 60 days in a sandy soil. The soil received 0.5 g NH4⁺-N kg⁻¹ soil and the inhibitors were applied at 5% of applied N. Total N2O emissions were calculated based on gas samples collected throughout the incubation period. Results Increasing soil temperature from 15 to 25°C decreased N2O emissions by 73%–191% while increasing soil moisture from 60% to 80% WHC caused a 109%–251% increase in the emissions. ENTEC followed by DCD were the least effective inhibitors to reduce N2O emissions under all temperature and moisture combinations. Depending upon temperature and soil moisture, DMPP and PIADIN inhibited 85%–100% of N2O emissions. At 15°C, both DMPP and PIADIN almost completely inhibited N2O emissions. At 25°C, the efficacy of PIADIN decreased to 88%, while that of DMPP ranged from 86% to 98%. Increased soil moisture content improved the efficacy of all the NI. Conclusions Overall, DMPP and PIADIN were more effective than DCD in a sandy soil under both the soil moisture levels and temperatures. DMPP was the most effective inhibitor, completely inhibiting N2O emissions at 15–25°C and up to 80% WHC in this soil, and is therefore recommended for use in agricultural lands. The concentration of the NI contained in ENTEC was insufficient to affect nitrification at the both soil moisture levels and temperatures.
... In Brazil, slow-release N fertilizer maintained lower production of N 2 O as compared to calcium nitrate, urea, ammonium nitrate, and ammonium sulfate fertilizers . Similarly, use of NIs has great potential in mitigating N 2 O emissions with a mean reduction of 38% compared with conventional fertilizers (Akiyama et al., 2010). ...
Chapter
Nitrogenous fertilizers are fundamental to crop production, and the global consumption of these fertilizers is increasing to meet the demand of growing population at the cost of environmental footprints. Nitrogen use efficiency (NUE) of crops is low due to excessive use of nitrogen (N) in soil–plant system that results in greenhouse gases (GHGs) emissions and cause global warming. This chapter discusses possible reasons for GHGs emissions and its mitigation potential through soil, plant, and sensors-based approaches. Potential of split N application, different nitrification inhibitors, green manure crops, and biological nitrogen fixation including the use of legumes as cover crops have also been highlighted. Furthermore, the significance of promotion of innovative on-farm technologies has also been discussed. Integrated strategies including site-specific N management, crop residues management, higher plant densities, weed and pest control, and balanced fertilization with other nutrients can help reduce N losses. Food waste, manure, and sewage can be used to improve NUE for achieving UN Sustainable Development Goals.
... In contrast, NIs inhibit conversion of ammonium (NH 4 + ) to nitrate (NO 3 − ) and result in higher NH 3 accumulation/ volatilization Lam et al. 2017;Qiao et al. 2015). Although, the inhibitors control gaseous N loss and improve NUE (Abalos et al. 2014), their economic return is still debatable (Akiyama et al. 2010). ...
Article
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Low wheat production is linked to soil degradation, low organic matter, temperature variation, and nutrient depletion in soils of semiarid regions. Nitrogen is mostly applied as urea to meet crop requirements; however, excessive N application may pollute the environment and contaminate groundwater. The current studies explored possible ways for decreasing N losses (NH3 volatilization and NO3 leaching) and improving N availability for wheat production in alkaline soil. The ZnO was coated on urea (1% Zn coating) to get zinc-coated urea (ZnU), and both urea and ZnU were incubated in laboratory at recommended rate (RR), i.e., 150 kg N ha⁻¹ and 80% (N of RR), after further coating with inhibitors [N-(n-butyl) thiophosphoric triamide (NBPT) at 1% of urea and 4-amino-1,2,4-triazole (ATC) at 2% of urea], thus creating six treatments. The results showed higher NH3–N loss at day 4 and thereafter a decreasing trend reaching to minimum at day 14. The cumulative NH3–N volatilization from urea alone was found higher (28.99%), except ATC treatments producing statistically similar losses due to restriction in nitrification process. In greenhouse, the treatments were tested in wheat cultivars (Faisalabad 2008 and Lasani) for crop growth, nutrient (N, P, K, and Zn) uptake, and yield parameters, where 80% of RR treatment, i.e., NBPT + ZnU80, was found at par with full RR as commercial products, especially comparable to ZnU (at RR) that produced the highest chlorophyll (53.65unit value), net leaf photosynthetic rate (19.64 μmol CO2 m⁻² s⁻¹), plant biomass (208.13 g/pot), grain yield (63.65 g/pot), and nutrient (NPK and Zn) accumulation in grain of Fsd-2008 cultivar. In field trial, NBPT + ZnU80 also outperformed and produced the highest physiological efficiency (PE), agronomic efficiency (AE), and nitrogen recovery efficiency (REN); the treatment also found statistically similar with ZnU (at RR) that produced the maximum plant height (95.4 cm), plant biomass (11.58 t/ha), grain yield (4.69 t/ha), and 1000-grain weight (42.55 g). The relative NO3 leaching was found lower in 80% N treatments, yet leaching was not significant from either treatment at the three stages of crop growth. Overall, current studies revealed the effectiveness of NBPT-amended urea (followed by ZnU) with 20% saving of N inputs through higher N availability for plant uptake that could benefit growers as well as conserve environment.
... NIs slow down nitrification in soil by deactivating the ammonia mono-oxygenase enzyme responsible for ammonium oxidation. Thus, NIs help retain soil N in the ammonium form for longer periods which allows more time for plant uptake of ammonium and limit N losses via leaching and N 2 O emissions (Subbarao et al., 2006;Akiyama et al., 2010). As outlined in Adhikari et al. (2021b) an ideal NI for use in agriculture should specifically block ammonium oxidation to nitrite, remain effective in the soil for several weeks after N input, and not have any adverse effect on soil organisms, plants, animals, humans and the surrounding environment at the application rates used to effectively inhibit nitrification. ...
Article
Information on the comparative effectiveness of the nitrification inhibitors (NIs), 3,4-dimethylpyrazole phosphate (DMPP) and 2-chloro-6-(trichloromethyl) pyridine (nitrapyrin) on New Zealand (NZ) urine-amended pasture soils is lacking. Therefore, laboratory incubation experiments were conducted to test the half-life and efficacy of these NIs to reduce nitrous oxide (N2O) emissions from two urine-amended pasture soils varying in clay and organic matter content. Two application rates of each NI were tested as follows: 2.5 and 5 mg DMPP kg⁻¹ soil, and 3 and 6 mg nitrapyrin kg⁻¹ soil. Dicyandiamide (DCD) was used as a reference NI, at the recommended application rate (10 mg DCD kg⁻¹ soil). The half-life values (at 15°C) of the NIs varied with clay and organic matter. These were 12–17 days for DMPP and 18–29 days for nitrapyrin compared with 20–33 days for DCD. All the NIs reduced N2O emissions, but their efficacy differed with the amount of NI and soil type. The reductions in N2O emissions were 19–46% with DMPP and 45–59% with nitrapyrin relative to 43–47% with DCD. The higher rate of nitrapyrin achieved significantly (p < 0.05) greater reductions under lower clay and organic matter content. The NIs did not affect the levels of soil microbial biomass carbon and nitrogen (MBC and MBN) during the study period.
... Although limited data makes us unable to examine the general impact of prevailing knowledge-based management practices on N 2 O emissions from orchards, some information should be considered for future research. Like in other agricultural fields (Akiyama et al., 2010), the effectiveness of nitrification inhibitors in orchards has been sporadically studied and consistently showed decreased N 2 O emissions (Maris et al., 2015;Zhu et al., 2015;Vilarrasa-Nogué et al., 2020). However, biochar amendment had either a stimulatory or no impact on soil N 2 O emissions from orchards as reported previously (Verhoeven and Six, 2014;Oo et al., 2018). ...
Article
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The fruit has become the third-largest agricultural planting industry after cereals and vegetables in China. Fertilization regimes (e.g., application rate and method) in fruit orchards typically differ from cereal croplands, which would incur a pronounced difference in fertilizer-induced nitrous oxide (N2O) emissions between them. However, fertilizer-induced direct N2O emissions from orchard fields remain poorly understood. We conducted a field experiment in a peach orchard and a global meta-analysis of N2O emissions from fruit orchards. The emission factor (EF) of fertilizer N for N2O averaged 0.81%, with a background N2O emission of 3.4 kg N ha–1 yr⁻¹ in our field study. A global meta-analysis suggested that the linear regression model was the best to fit N2O emissions by fertilizer N input for most fruit types compared to the nonlinear models. When averaging all global data, the linear model projected the EF of N2O from orchards to be 0.84%, with the background emission of 1.96 kg N ha–1. The estimate of direct N2O derived from the orchard-specific nonlinear model was substantially lower than those from the nonlinear model with global cropland measurements. The fertilizer-induced direct N2O emission from Chinese orchards during the 2000s was estimated to be 32–49 Gg N yr–1, equivalent to about 14% of total direct N2O emissions from Chinese uplands. Therefore, orchard cultivation constitutes a hotspot of N2O emissions in the agricultural sector, and priority should be given to emissions reduction to achieve the transition to climate-smart agriculture.
... Improved fertilisation management can also increase fertiliser NUE and reduce GHG emissions . Split N fertiliser applications, adjusted ratios of basal-N to top-dressed N, and the application of controlled-release fertiliser (CRF) have been proposed as means to decrease N 2 O emissions (Smith et al. 1998;Akiyama et al. 2010;Ye et al. 2013). Specifically, for a given total N rate, when the rate of N fertiliser application is kept low through split application, lower cumulative CO 2 emissions would be expected relative to a single application. ...
Article
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Over the last century, anthropogenic greenhouse-gas (GHG) emissions have changed the global climate, and agriculture plays an important role in the global flux of GHG. Agricultural management practices, such as split N applications and the use of controlled-release fertilisers have significantly increased the crop yield and N-use efficiency by balancing the N demand of crops and the N availability of soils. However, the impacts of these practices on GHG emissions (in particular in wheat–peanut relay intercropping systems) have not been evaluated in detail. In this study, a common compound fertiliser and a controlled release compound fertiliser (CRF) were used the day prior to sowing, at the jointing stage of wheat and at the peanut anthesis stage in ratios of 50-50-0% (JCF100), 35-35-30% (JCF70) and 35-35-30% (JCRF70), with a control treatment of 0 kg ha−1. The findings demonstrated that treatment JCF70 achieved increases in yields of 9.7% and 14.6% for wheat grain and peanut pod, respectively, compared to treatment JCF100; however, this treatment also significantly increased soil emissions of CO2 and N2O. In addition, cumulative emissions of CO2 and N2O were higher in the peanut growing season by 74.4 and 31.7%, respectively, than in the wheat growing season owing to the relatively higher soil temperature during the former season. Fertilisation combined with irrigation, was found to be the main cause of GHG emissions. Under the same fertiliser rate and N-management style, JCRF70 further increased the yield of peanut pods and the total combined yield of peanut and wheat by 10.3% and 8.9%, respectively, compared to treatment JCF70. The cumulative CO2 and N2O emissions in treatment JCRF70 were 20.4–45.4% less than those in treatment JCF70. The total global warming potentials of CO2 and N2O were lowest in treatment JCRF70 owing to it providing the highest grain yield. Therefore, N application with three splits, together with the use of a slow-release fertiliser, may be a simple and effective approach to enhance the grain yield whilst reducing the GHG emissions.
... These efficient fertilizers frequently contain inhibitors of urease and/or nitrification (Abalos et al., 2014). Urease inhibitors are compounds that delay the hydrolysis of urea, whereas nitrification inhibitors are compounds that delay bacterial oxidation of ammonium by depressing the activities of nitrifiers in the soil (Akiyama et al., 2010). N-(n-butyl) thiophosphoric triamide (NBPT), which is a structural analogue of urea, is one of the most studied urease inhibitors (Krol et al., 2020). ...
Thesis
La France est le premier producteur européen de blé tendre (Triticum aestivum L.), une céréale majeure pour la filière semences et les secteurs agro-alimentaire et industriel. Cependant, il reste des marges d’amélioration du bilan agro-environnemental de cette culture céréalière vis-à-vis de ses besoins en azote (N) pour optimiser les rendements de manière durable et sans altérer la qualité de la farine conduisant par exemple à des intolérances au gluten. Dans ce contexte, ces travaux de thèse ont consisté (i) à étudier les effets d’un apport de formulations innovantes d’engrais azotés combinés à des biostimulants sur l’efficience d’usage de l’azote (EUA), le rendement et la qualité grainière (notamment le ionome et le protéome) sur le blé tendre en conditions contrôlées et de plein champ et (ii) à calibrer plusieurs outils de diagnostic (SPAD, XRF et NIRS) qui évaluent l’impact des biostimulants sur le statut nutritionnel de la culture et des traits de qualité de la graine.Cette étude a mis en évidence l’effet bénéfique des biostimulants à base de Glutacétine® sur l’EUA, le rendement et ses composantes notamment le nombre de grains grâce à une meilleure fertilité des épis. L’optimisation de l’EUA a permis d’accroitre l’azote total dans les grains en serre et au champ notamment pour VNT4 et la Glutacétine®. La qualité grainière a aussi été fortement modifiée par les formulations testées notamment avec la baisse de la teneur en phytates, des changements au niveau du ionome (Mn, Mo, B et Se) et du protéome (protéines impliquées dans la régulation de la synthèse des protéines, la réponse aux stress biotiques et abiotiques, les fonctions de stockage et les processus de germination). D’un point de vue agro-économique, VNT4 et la Glutacétine® ont permis de générer des revenus complémentaires et sur le plan agro-environnemental, VNT4 a évité la fuite de 55 unités d’azote au champ. En parallèle, les calibrations d’outils de diagnostic portables utilisables au champ ont permis de déterminer les teneurs en éléments des feuilles (N), de la farine (N, P, K, Mg, S, Ca, Fe, Zn et Mn) et des pailles (P, K, Mg, S, Ca, Fe, Mn et Ni). Plus particulièrement, le développement de la technologie NIRS portable a permis d’établir les équations de prédiction du rendement, du PS, du PMG et de la teneur en N du grain à partir de spectres de réflectance obtenus sur les feuilles drapeaux au stade floraison.
... The BR-NCU and BR-U + KTS treatments recorded 9.4 and 7.55% lower emissions than BR-U due to the nitrogen inhibitors and fertilizer. It retards the oxidation process of NH 4 + because of the presence of coating and resulting in lower N 2 O emission (Akiyama et al., 2010). ...
Article
The impacts of nitrous oxide (N2O) released from the fertilized agro-ecosystems are of increasing concern. Governing fertilizer requirements and utilizing nitrification inhibitors (NI) are effective methodologies to increase nitrogen retention and reduce N2O emissions from soil. Therefore, the effect of potassium thiosulfate (KTS) and neem-coated urea (NCU) on N2O efflux under irrigated tomato cultivation was assessed. Soil Test Crop Response (STCR) based recommendation of NPK with normal Urea and KTS at 1% of applied N (183:160:125 kg ha⁻¹) (STCR-U-KTS) recorded the least N2O emission and high efficiency in suppressing the nitrate reductase activity. STCR-NCU was on par with STCR-U-KTS, reporting a higher reduction of N2O (21.1, 31.2, and 34.4% during the basal application, 1st, and 2nd top dressing, respectively) compared to the blanket recommendation of nutrients. Similarly, STCR-U + KTS recorded the highest reduction (26.2, 25.6, and 30.9% during the basal application, 1st, and 2nd top dressing, respectively) after fertilizer application. Besides, the yield of tomatoes is increased in the STCR-NCU (14.08%) and STCR-U-KTS (12.48%) with good quality fruit along (AA, Lycopene, and TSS contents) with low N2O emissions. The DeNitrification-DeComposition (DNDC) model further revealed that the simulated data and assessed findings were in good accord, proving the model's reliability and use as a tool for predicting the efficiency of fertilizer application.
... The labor cost saving was approximately U$72.5 per ha ( Gao et al., 2021 ). Additionally, Akiyama et al. (2010) reported a 35 % reduction of N 2 O emissions with application of controlled release fertilizers. However, the overall manufacturing cost of controlled-release fertilizer is still higher than conventional fertilizers ( Lawrencia et al., 2021 ;Fertahi et al., 2021 ). ...
Article
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The hydrolysis of conventional urea fertilizer accounts for a 50 % loss in the field, which results in atmospheric and water stream contamination due to the volatilization of greenhouse and ozone scavenger gases, and nitrate leaching, respectively. Fertilizer granule structural design can be a potential solution to minimize the field losses. Nonetheless, quantitative analysis of urea dissolution as affected by formulation and process design remains underexplored. In this study, urea and a binder in powder form were mixed at a fixed binder-solid ratio of 5 % (w/w) and compacted at different loads using a punch-die set on a standard material testing system. The binders tested to produce the binary mixtures were hydroxypropyl methylcellulose grade E5- HPMC, high molecular weight hydroxypropyl cellulose- HPC, gluten from wheat, and a mixture of xanthan and konjac gums. The total porosity, apparent diffusion, and dynamic contact angle profiles of the compacts were measured at ambient conditions. The hydrophilicity of the formulations with gums, attributable to their lower contact angle when compared with control samples, helps explain the fast in-matrix mass transfer. Based on Weibull distribution model analysis, all the dissolution curves followed either sigmoidal or exponential shape profiles. Within the formulations evaluated in this study, the synergism between densification and higher hydration capacity of formulations with gums ensured binder mobility and gelation at the solid-liquid interface. The results indicate that gel formation reduced solvation and dissolution, resulting in a delay of nutrient release. These findings will aid in the optimization of controlled-release fertilizer formulations for field crops and help understand the effect of binder physicochemical characteristics on the microstructure of granular fertilizers.
... Trade-offs in the form of NH3 emissions, odors, enhanced denitrification rates due to coexistence of high soil water contents and organic carbon suitable for denitrifiers, must be considered together with the application technology used to fertilize with liquid manures. Nitrification and urease inhibitors (NI) are used in a wide range of agro-climatic regions (Akiyama et al. 2010;Gilsanz et al. 2016). In Mediterranean soils, NIs have shown high mitigation efficiency in rain-fed and irrigated fields, with a likely indirect effect on denitrification in the latter systems . ...
... However, Di and Cameron [35] reported that the application of DCD has been reported as being beneficial in enhancing N fertilizer efficiency and crop yields. It may be that DCD can reduce N loss in various ways [20,36]. ...
Article
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This study researched the effects of using various nitrogen (N) conservation measures on the residual characteristics of nitrate and ammonium N in soil and the associated N uptake by cotton plants. A field experiment with six treatments was conducted, as follows, no N application (DT1), conventional N application (DT2), 60% conventional N application combined with DCD (DT3), 60% conventional N application combined with NBPT (DT4), 60% conventional N application combined with cotton straw returning (DT5), and 60% conventional N application combined with DCD, NBPT, and cotton straw returning (DT6). The results showed that the cotton straws in the DT5 treatment were beneficial for the vegetative growth of cotton seedlings. However, it was observed that the later performance of the plants in this sample was poor in terms of height, biomass, and yield of cotton. The plant height in the DT6 sample increased by 15 cm compared with those in DT1, and the soil and plant analyzer development (SPAD) values of the fourth leaf from the top of the DT6 plants were higher than those in the DT1 and DT4 samples. The DT6 plants (60% Urea + DCD + NBPT + cotton straw) increased N use efficiency by up to 47%, and no significant decrease in biomass and cotton yield was observed compared to the DT2 sample. The residual content of nitrate N in the tillage layer increased gradually over time between two rounds of drip irrigation treatment applications. Compared with the DT2 treatment, the other treatments resulted in lower residual nitrate N contents. In summary, the application of N fertilizers at a reduced rate combined with N conservation measures may increase N use efficiency and decrease the risk of non-point source N fertilizer pollution, while maintaining the cotton yield.
... Although few studies have focused on DMPP performance on soil NH 4 + -N nitrification and crop performance under tropical soil conditions (Barth et al. 2019;Souza et al. 2020), most of the studies with nitrification inhibitors have focused on and widely suggested that nitrification inhibitors can reduce N 2 O emissions by over 30% (Akiyama et al. 2010;Gilsanz et al. 2016;Padilla et al. 2018;Rose et al. 2018;Huérfano et al. 2019). Therefore, the effect of DMPP application on inorganic N-leaching losses and N recovery is less noticeable. ...
Article
Nitrification inhibitors applied to soil could reduce nitrogen (N) fertilizer leaching losses by delaying the nitrification process via enhanced N fertilizer management. Thus, we investigated the agronomic efficiency of the nitrification inhibitor 3,4-dimethylpyrazole phosphate (DMPP) applied in three tropical soils (Typic Quartzipsamment, Typic Hapludox and Rhodic Hapludox) cultivated with cotton plants, evaluating the fate of N (NH 4 +-N, NO 3 −-N, and total N in leached water and soil), N accumulation and N use efficiencies (agronomic, physiological, and recovery efficiencies). Five treatments were tested with each treatment consisting of two N sources applied, urea (U) and ammonium sulfate nitrate (ASN), either with or without DMPP application; an additional control treatment (absence of N application) was also tested. Leaching columns were used to assess NH 4 +-N and NO 3 −-N losses. DMPP improved the recovery efficiency from applied U and ASN fertilizers by reducing NO 3 −-N and NH 4 +-N leaching, leading to enhanced N acquisition from fertilizer and augmenting plant N accumulation and biomass. We found that agronomic efficiency in cotton plants increased from 4 to 52% with the DMPP + ASN source relative to ASN along the soil types. In addition, DMPP use increased agronomic efficiency from urea application from 32 to 91% relative to conventional urea. The use of DMPP would benefit from more urea than ASN mainly in sandy-textured soils, where the leaching losses were observed to be increased. The reduction in NO 3 −-N and NH 4 +-N losses highlights the potential of DMPP to mitigate the impact of N-based fertilizer application on N leaching, thereby improving agronomic efficiency, N uptake, and cotton growth-related responses under tropical soil conditions.
... Compared with normal urea, CRU can significantly reduce N losses (e.g. nitrogen leaching, ammonia volatilization) and improve the NUEs and yield of rice (Akiyama et al. 2010;Tian et al. 2018;Zhang et al. 2019;Sun et al. 2020;Kenawy et al. 2021). However, the nitrogen release rate of CRU is lower than that of normal urea, and the one-time basal application of CRU will lead to nutrient deficiency in the early growth stage of rice, thus affecting yield (Farmaha and Sims 2013). ...
Article
Full-text available
Controlled-release urea (CRU) and normal urea have been shown to improve yield and nitrogen use efficiency (NUE) in rice. However, the effects of combined fertilizers (CRU and normal urea, at different N ratios) on rice yield, temperature and solar radiation utilization efficiency (TSRUE) and NUEs remain unclear. In this study, CRU with release periods of 60 days and 100 days were mixed with urea at N ratios of 7:3, 6:4, 5:5, 4:6 and 3:7 and applied during the rice-growing season in a rice-wheat cropping system. Rice yield, dry matter accumulation (DMA), TSRUE and NUEs were investigated. The yields under one-time fertilization mode 2 (OFM2) and OFM8 were 5.36%-9.70% higher than that of farmer fertilization practices (FFP) on average across 2018 and 2019. The NUEs under OFM2 and OFM8 was 3.87%-35.56% and 6.26%-58.56% higher than that under FFP, respectively, across 2018 and 2019. Correlation analysis showed that TSRUE were significantly positively correlated with yield, DMA and NUEs. The higher TSRUE under OFM2 and OFM8 contributed to the synergistic improvement of yield and NUEs. Both OFM2 and OFM8 improved rice yields and NUEs compared to FFP while having lower fertilizer and labor costs; therefore, these treatments are worthy of promotion and application. ARTICLE HISTORY
... However, the production of N 2 O may still be limited with WFPS around 50-60% as a result of dissimilatory nitrate reduction to ammonia [101]. For instance, continuous flooding in rice releases less N 2 O to the atmosphere [102,103], owing to water saturated conditions favoring ultimate NO 3 − reduction to N 2 by denitrifiers [51]. Conversely, AWD may be responsible for increased N 2 O emission when it determines soil cracks; stronger aeration at deeper layers increases NF and provides substrate for N 2 O emission [104,105]. ...
Article
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The concentration of greenhouse gases (GHGs) in the atmosphere has been increasing since the beginning of the industrial revolution. Nitrous oxide (N2O) is one of the mightiest GHGs, and agriculture is one of the main sources of N2O emissions. In this paper, we reviewed the mechanisms triggering N2O emissions and the role of agricultural practices in their mitigation. The amount of N2O produced from the soil through the combined processes of nitrification and denitrification is profoundly influenced by temperature, moisture, carbon, nitrogen and oxygen contents. These factors can be manipulated to a significant extent through field management practices, influencing N2O emission. The relationships between N2O occurrence and factors regulating it are an important premise for devising mitigation strategies. Here, we evaluated various options in the literature and found that N2O emissions can be effectively reduced by intervening on time and through the method of N supply (30–40%, with peaks up to 80%), tillage and irrigation practices (both in non-univocal way), use of amendments, such as biochar and lime (up to 80%), use of slow-release fertilizers and/or nitrification inhibitors (up to 50%), plant treatment with arbuscular mycorrhizal fungi (up to 75%), appropriate crop rotations and schemes (up to 50%), and integrated nutrient management (in a non-univocal way). In conclusion, acting on N supply (fertilizer type, dose, time, method, etc.) is the most straightforward way to achieve significant N2O reductions without compromising crop yields. However, tuning the rest of crop management (tillage, irrigation, rotation, etc.) to principles of good agricultural practices is also advisable, as it can fetch significant N2O abatement vs. the risk of unexpected rise, which can be incurred by unwary management. View Full-Text
... With urea point placement, the N movement distance (about 70 mm) was highly limited by the fertilizer placement. The RON consistently maintained a higher soil-available N content than the SN, which stimulated root proliferation and enlarged field (Akiyama et al. 2010;Linquist et al. 2013; Noordwijk and Brussaard 2014), regional (Gu et al. 2012;Chen et al. 2014;Hofmeier et al. 2015), and global scales (Galloway 1998;Tilman et al. 2011). Furthermore, the costs of fertilizer application have increased because of the labour shortage in rural areas associated with increasing urbanization. ...
Article
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Split nitrogen (N) management is a primary strategy for reducing N loss using the conventional broadcasting method in high-yield maize systems, while increasing labour costs with the progression of labour transfer. This study examined whether localized, one-time urea-N fertilization can achieve high yield for rainfed and irrigated maize in the Huang-Huai-Hai Plain, China. We first identified the critical N placement depth (120 mm) that ensures a high yield and N uptake for the two types of maize in a field experiment. A 2-year field experiment was conducted to validate the root zone one-time N management (RON) strategy based on an optimal placement with seven N levels compared with split N management (SN). With urea point placement, the N movement distance (about 70 mm) was highly limited by the fertilizer placement. The RON consistently maintained a higher soil-available N content than the SN, which stimulated root proliferation and enlarged root surface area, especially for rainfed maize. Hence, the RON, based on placement regulation, increased the yield plateau by 8% while reducing the optimal N rate by 22% for rainfed maize compared with the SN and archived a similar yield plateau while decreasing the optimal N rate by 25% for irrigated maize. Compared with SN, the apparent recovery efficiency of N under the RON treatment increased from 41 to 48%, and from 43 to 54% for irrigated and rainfed maize, respectively. In conclusion, one-time urea-N fertilization based on placement regulation could be an efficient nutrient management strategy for intensive maize systems.
... We must improve our ability to reduce net N 2 O fluxes from agricultural soils because they are the largest anthropogenic emission source of this potent greenhouse gas (Dalal et al., 2003;Fowler et al., 2009). Efforts to improve the efficiency of agricultural N use require the identification and reward of management practices that reduce N 2 O emissions from soils (Akiyama et al., 2010;Halvorson et al., 2014). Quantifying soil N 2 O flux at the field scale is crucial for identifying effective N management but is challenging because N 2 O emissions vary widely in both space and time (Mathieu et al., 2006;Desjardins et al., 2010;Hénault et al., 2012). ...
Article
Accurate estimation of field‐scale nitrous oxide (N2O) fluxes is hindered by their considerable variability and the fact that soils can be both sources and sinks for N2O. This is particularly challenging for organic systems that have complex rotations and inputs. This study used digital soil mapping and survey datasets to explore spatial controls of N2O ‘hot moments’ induced by precipitation with strategic sampling designed to identify covariates that influence N2O emission patterns. Soil N2O fluxes after rain events were measured within three management zones (MZs, ‘High’, ‘Medium’, ‘Low’) delineated by crop productivity, soil fertility, and hydrological features in eight organic fields during the 2018 and 2019 corn growing seasons. Hot moments typically occurring one day after rain events included both positive and negative N2O fluxes. The MZ‐based design identified regions with different patterns in positive and negative flux, with hotspots for both being co‐located with areas of poorer drainage and higher soil fertility. Covariates that best explained hot moments included corn growth stage, soil moisture, slope, texture, and soil organic matter. Negative fluxes were large enough to offset positive fluxes so that averaged net N2O fluxes were only significantly different between the ‘High’ and ‘Low’ MZs. Had negative fluxes been omitted, averaged N2O fluxes would have increased estimates by 37%. Processes that lead to N2O consumptions must be better quantified to improve the estimation of management‐associated net N2O flux. Use of strategic sampling can efficiently capture needed information, but spatial and temporal weighting is needed to scale up results. This article is protected by copyright. All rights reserved Inherent soil properties identified management zones that differ in temporal N2O flux Dynamic properties improved prediction of N2O flux from organically managed fields Strategic sampling following rain captured spatial and temporal N2O flux patterns N2O hotspots occur where substrate abundance and O2 limitations are greatest Post‐rain N2O loss is overestimated when negative N2O hotspots are not considered
... Mitigating negative global climate change caused by greenhouse gas (GHG) emissions is one of the major challenges in sustainable development [1,2]. Nitrous oxide (N2O) is the third largest greenhouse gas [3], with a greenhouse effect 298 times greater than that of CO2 on a 100-year scale [4], and a significant contributor to the destruction of the stratospheric ozone [5][6][7]. Agricultural soil is the main source of N2O [8] and contributes approximately 60% of global anthropogenic N2O emissions [9]. Therefore, a comprehensive understanding of N2O emission from agricultural soils is crucial for the formulation of reasonable emission reduction strategies. ...
Article
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Returning corn stalks to the field is an important and widely used soil management practice which is conducive to the sustainable development of agriculture. In this study, the effects of corn stalks and urea on N2O production in corn field soil were investigated through a 21-day incubation experiment. This study showed that increasing amounts of urea added to soil with a history of corn cultivation leads to increasing overall N2O emissions, by increasing both the intensity and the duration of emissions. Although N2O production was affected primarily by urea-derived NH4+-N and NO3--N, its main source was native soil nitrogen, which accounted for 78.5 to 94.5% of N2O. Returning corn stalk residue to the field reduced the production of N2O, and the more urea was applied, the stronger the effect of corn residue on reducing N2O emissions. Combining the application of corn stalks and urea could reduce the concentration of NH4+-N and NO3--N derived from urea, and then reduce the substrate required for N2O production in nitrification and denitrification processes. In addition, the combined application of corn stalks and urea could effectively inhibit the abundance of key N2O-producing genes AOA amoA, nirS and nirK.
... The increased vegetable yield and improved NUE of NI and CRF were due to the nitrification inhibitor effectively inhibiting ammonium N nitrification compared to urea, reducing N loss, and maintaining a high ammonium N concentration in the root zone for a long time. The CRF treatment could effectively control the rate of N release and maintain a higher N supply, both of which can better synchronize N supply with pepper demand at temporal and spatial scales [42], promote middle and late pepper growth, and increase the proportion of N distributed from stems and leaves to fruits after flowering and fruiting. Thus, compared to the conventional urea application, NI and CRF further improved the vegetable N uptake, yield, and N fertilizer use efficiency. ...
Article
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Excessive nitrogen (N) fertilizer application is a serious issue in intensive vegetable production and can negatively affect vegetable productivity and N use efficiency (NUE). The optimization of the N fertilizer rate and application of enhanced efficiency N fertilizers (EENFs), including nitrification inhibitors (Nis) and controlled-release fertilizer (CRF), are widely recognized as feasible N management strategies to resolve the problem of unreasonable N fertilizer input. Therefore, we conducted a 2-year field experiment (2019–2020) in an open-field vegetable system (pepper, Capsicum annuum L.) in southwest China to investigate the effects of an optimized N application rate and EENFs on vegetable yield, NUE, and crop N uptake. The following N management treatments were established: control without N fertilizer input (CK); optimized N fertilizer rate as urea (OPT); farmers’ fertilizer practice (FP); application of a nitrification inhibitor (NI) within the optimized N fertilizer rate; and application of controlled-release fertilizer (CRF) within the optimized N fertilizer rate. The results showed that the OPT treatment based on root zone N management achieved a 37.5% reduction in the N application rate without compromising vegetable yield and increased the recovery efficiency of N (REN) by 31.5% compared to the FP treatment. Furthermore, the combined application of the NI or CRF treatments with the OPT treatment resulted in greater vegetable yields, fruit N uptake, and REN (9.54%, 26.8%, and 27.6%, respectively, for NI; 10.5%, 28.7%, and 28.8%, respectively, for CRF) than the OPT treatment alone. The absorption ratio of fruit N uptake to total crop N uptake was also increased. Our results clearly showed that the combined application of EENFs with the OPT treatment could achieve the win–win benefits of a yield increase and improved REN in Chinese vegetable production.
... We utilize the values given per fertilizer type i in the technical CFT documentation according to the mapping in Table 31. The CFT models uses the reduction factors from the meta-analysis of Akiyama et al. (2010) in order to model the influence of nitrification inhibitors and polymer-coated fertilizer. Since the meta-analysis deals with total emissions and does not attempt to differentiate between background emissions and fertilizer induced emissions, the CFT has taken the conservative approach of applying emissions to the fertilizer-induced part only. ...
Technical Report
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... Recent reviews have concluded that the use of nitrification inhibitors can significantly decrease soil N 2 O emissions in upland (i.e., non-flooded) crops compared to conventional N fertilizer sources (Ruser and Schulz 2015;Padilla et al. 2018;Rose et al. 2018;Huérfano et al. 2019). Meta-analysis studies concluded that DMPP application could decrease N 2 O emissions by 38 to 42% (Akiyama et al. 2010;Gilsanz et al. 2016). ...
Article
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PurposeThe use of nitrification inhibitors could be an interesting alternative when applied to enhance nitrogen (N) fertilizer use efficiency in annual crops such as cotton under tropical soil conditions. Thus, our aim was to evaluate the efficiency of the nitrification inhibitor 3,4-Dimethylpyrazole phosphate (DMPP) in a typical tropical soil by evaluating the fate of nitrogen (N-NO3−, N-NH4+ and total N in soil and leached water), N accumulation and N recovery by cotton plants and soil.Methods Leaching columns with cotton plants were used to assess N-NO3− and N-NH4+ losses in drainage water. The treatments consisted of three N levels applied in side-dressing (corresponding to 50, 100 and 150 kg N ha−1) as 15N-urea with and without DMPP application. An additional treatment (absence of N application in side-dressing) was used as a control.Results3,4-Dimethylpyrazole phosphate efficiently improved N recovery after urea fertilizer was applied to plants and in the soil by reducing NO3− leaching, leading to enhanced N acquisition from fertilizer and soil and augmenting N accumulation in plants, mainly when high N levels above 100 kg N ha−1 were applied. We found that total N recovery increased 31% when 150 kg N ha−1 was applied as a urea + DMPP source compared to the application of conventional urea. In addition, DMPP application reduced NO3− leaching losses (by approximately 11 to 20%), although it had no significant effect on the shoot or root dry matter yields.Conclusion The reduction in NO3− leaching losses obtained herein highlights the potential of DMPP to mitigate the impact of increased urea inputs on leaching losses, thereby improving N use efficiency and N uptake in cotton crops.
... One of the highly effective mitigation technologies in controlling nitrification process and improving NUE and yields is using nitrification inhibitors (NIs) (Moir et al. 2012). NIs greatly suppress the oxidation of NH 4 + to NO 3 − (nitrification process) in the soil (Fig. 4) and subsequent denitrification of NO 3 − as compared with conventional fertilizers (Akiyama et al. 2010). Specifically, the synthetic NIs inhibit the ammonia monooxygenase (AMO) pathway ( Fig. 4) within nitrification (Subbarao et al. 2008). ...
Article
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Reactive nitrogen (N) plays a pivotal role in supplying N to plants and soil microbes, but it has negative environmental impacts through influencing the quality of water and air, which in turn influences human health. Thus, there is an urgent necessity to maximize N benefits while reducing the negative impacts on the environment. Improving crop N use efficiency (NUE) is required for environmental conservation and agricultural sustainability. Thus, the pivotal objective of this article is to introduce the modern developments and imminent prospects of improving crops NUE using various complementary methods. Here, the approaches of site-specific N management, use of synthetic and biological nitrification inhibitors, microbial nitrate (NO3−) immobilization stimulation, and stimulation of the dissimilatory nitrate reduction to ammonium (DNRA), adopting agroforestry system, breeding techniques, quantitative trait loci (QTL) mapping, omics approaches, and potential new targets and overexpression of N-related genes were presented as effective approaches to improving NUE. Optimal rate, time, application methods, using specially formulated forms of fertilizer, and using nitrification inhibitors are the most agricultural practices linked with improving NUE. The fertilizer recommendations could be often justified across the field rather than a uniform application using spatial variability of nutrient content. Restoring soil NO3− retention capacity and adopting agroforestry system can also be promising ways to improve NUE. Furthermore, the use of genetic modification or the development of new cultivars that use N more efficiently is critical. In addition, omics data, including transcriptomics and metabolomics, not only advance our current understanding of N reactions but also help us move towards strategies, which are more effective in improving NUE and enhancing crop production. In conclusion, this article strongly advocates the use of integrated approaches with a private insight of genetics and agricultural management when managing N.
... Urea breakdown can begin as soon as it is applied to the soil. In the presence of the urease enzyme and a small amount of soil moisture, urea hydrolysis occurs and nitrogen is lost due to ammonia volatilization [1][2][3][4][5]. ...
... Urea, CAN and AN are the most commonly used straight fertilizers in the UK and Ireland [14][15][16][35][36][37]. A detailed meta-analysis done by Cowan et al. [13] reported that urea fertilizer had a lower N2O-EF value (EF = average 0.6%; range 0.5-0.7%) ...
Article
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Emissions of nitrous oxide (N2O), a potent greenhouse gas, are a challenge associated with application of nitrogen (N) fertilizers to soil. However, N source selection can play a role in reducing these emissions. Nitrous oxide emissions were measured from ammonium (ammonium sulfate) and nitrate (calcium nitrate) fertilizers over one year in temperate grassland using the closed static chamber method. Nitrogen was applied at a system representative rate of 220 kg ha −1 y −1 in six split applications. Cumulative annual N2O-N emissions were 0.29 kg ha −1 for the control, 1.07 kg ha −1 for the ammonium fertilizer and significantly higher at 2.54 kg ha −1 for the nitrate fertilizer. The annual emission factor (EF) for the ammonium fertilizer was 0.35% vs 1.02% for the nitrate fertilizer, a 66% reduction in the EF for ammonium vs nitrate and a 2.9 times higher EF for nitrate compared with ammonium. No difference in grass yield or N uptake was detected between fertilizers. This study shows that an ammonium fertilizer produces the same yield and N efficiency as a nitrate fertilizer with lower N2O emissions. The results also demonstrate that the nitrate portion of fertilizers is a key factor in N2O emissions in temperate grassland. This work is the first of its kind detailing the annual EF of both a solely ammonium-N and a solely nitrate-N fertilizer we could find.
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To meet the food demand of an increasing population, hybrid rice varieties with high yields were selected, including indica-japonica hybrids. However, information about growth characteristics under the utilization of coated urea was limited. In this study, growth performance and yield of two indica-japonica hybrid varieties under five coated urea rates (0, 150, 225, 300 and 375 kg N ha⁻¹) were investigated, while two conventional late japonica were used as controls. Consequently, yield of indica-japonica hybrids was obviously higher than that of late japonica under a single application of coated urea, due to larger grain number per panicle. The relationship of yield and N rate was an open downward conic curve, while polymer coated urea for the maximum yield of the four varieties was about 225 kg N ha⁻¹. The dry matter accumulation of indica-japonica hybrids was significantly higher than that of the late japonica. Nitrogen use efficiencies were higher under lower nitrogen rate.
Article
Increasing concentrations of greenhouse gases such as carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O) in the atmosphere and the consequent climate change have irreversible effects on the environment and human health. Greenhouse gases in the soil are produced by microbial activity, root respiration, chemical decomposition, and heterotrophic respiration of organisms; the carbon flux from the soil in the form of carbon dioxide is caused by respiration and other activities of soil organisms, nitrous oxide is produced by nitrification and denitrification processes, and methane is produced by microbial methanogenesis under anaerobic conditions. This is while various environmental and managerial factors might affect their concentrations in the soil. Proper management of agricultural soils offers a significant potential to reduce greenhouse emissions. For instance, crop rotation, cover crop farming, conservation tillage, crop residues retention, and avoiding plant residue burning or removal serve as appropriate management practices to reduce carbon dioxide emission. Strategies employed to mitigate nitrous oxide emission include better nitrogen management, well-planned application of nitrogen fertilizers only to meet crop requirements in a timely manner, reduced application of nitrogen fertilizers tailored to the different stages of plant growth, using Legume plants in crop rotation, proper crop residue management, use of slow-release fertilizers, and application of nitrification and denitrification inhibitors. Methane emissions may be reduced through drainage of rice paddies to provide adequate ventilation for methane oxidation and tillage or composting to decompose crop residues before flooding.
Chapter
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The trends in human population growth suggest that population will be a primary driver to produce more with limiting resources. Here, we discuss the correlation between population growth and the projected changes in various sectors and the resultant increase in nitrogen (N) use in Pakistan. Main drivers for increasing N use are (i) population; (ii) food and feed production; (iii) livestock population; (iv) land use; (v) dietary patterns; (vi) power generation; (vii) industry; and (viii) transport. As N use increases, it adds into N emissions, impacts biodiversity, and increases air and water pollution and eutrophication, which raise concerns about human health and socioecological sustainability and abatement costs. Given the important role of N in economy, food security, human health, and environment, a detailed discussion on critical N drivers is essential to improve our understanding about N cycling/dynamics. In Pakistan, a steadily increasing N consumption calls for optimizing N demand and use. Development and enforcement of regulatory measures are needed to reduce N footprints both for the industrial and agriculture sector in Pakistan. Recognizing the cross-related sectors and interrelated drivers, a holistic approach is required to be adopted for regular assessment of N dynamics.
Chapter
Globally, the advances in agricultural science have helped increase crop production and crop diversification, which, in turn, has resulted in the diversification of sources used for fertilizers. With the Green Revolution, farmers progressively shifted from irregular application of organic fertilizers to regular applications of synthetic fertilizers. The use of nitrogenous (N) fertilizers in Pakistan has more or less followed the global trend. However, developed countries are shifting toward more balanced nutrient applications and integration of organic and inorganic fertilizers. N fertilizer application in Pakistan is quite high as compared to the balanced NPK application. This chapter covers the conventional viz. organic, synthetic, and non conventional sources of nitrogen mainly being used for crop production in Pakistan. The discussion is based on publicly available published information. Pakistan heavily relies on synthetic N, i.e., urea and very little to none information is available on the extent of organic sources of N consumption in the country. New novel sources of N, which are efficient and environment friendly, are being investigated but farm level use is very low.
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Die Landwirtschaft trägt zu einem großen Teil der Stickstoffüberschüsse und -emissionen in Deutschland bei. Dieser Beitrag untersucht, welche von der Wissenschaft diskutierten Strategien zur Minderung von Stickstoff aus Gülle in landwirtschaftlichen Fachzeitschriften thematisiert werden. Ein Literaturreview und eine Text Mining-Analyse zeigen Unterschiede zwischen den Medien und im Untersuchungszeitraum 2010 bis 2020. Die Ergebnisse können dazu beitragen, Diskrepanzen zu identifizieren und potenziell geeignete Minderungstechniken verstärkt zu kommunizieren.
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This study aimed to investigate the effects of using controlled release fertilizers with reduced application rates on nitrous oxide (N2O) gas emissions. For this, we monitored the N2O emissions released from soybean fields converted from rice paddies in Japan for three years, i.e., from 2017 to 2020, under six nitrogen fertilizer treatments: conventional (AC: ammonium chloride, 20 kg N ha⁻¹), controlled release coated urea (CRCU: ammonium chloride, 5 kg N ha⁻¹, coated urea, 15 kg N ha⁻¹, total 20 kg N ha⁻¹), controlled release coated nitrate (CRCN: coated calcium nitrate, 20 kg N ha⁻¹), CRCU at a reduced rate (CRCU-R: 10 kg N ha⁻¹), CRCN at a reduced rate (CRCN-R: 10 kg N ha⁻¹), and no nitrogen fertilizer (NF: 0 kg N ha⁻¹). The soil of the field was classified as Gleyic Fluvisol. The annual N2O emissions of the CRCN treatment were significantly lower than those of the AC in the first and second years (p < 0.05) and were not significantly different in the third year, with reductions of 17–32%, while the same yield was maintained. The annual N2O emissions of the CRCU treatment tended to be lower than those of the AC for the three years, with reductions of 14–19%, although not statistically significant. This suggests that coated nitrate fertilizers were more effective in reducing N2O emissions, since nitrate produces this gas via denitrification only. In addition, the N2O emissions of the CRCU-R and CRCN-R treatments were 22–37% and 24–41% lower than that of the AC treatment, respectively. Although not statistically significant, these reductions were slightly greater than those obtained for the N2O emissions of CRCU and CRCN, suggesting the effect of further mitigation of N2O emissions through the reduction of application rate. Furthermore, the N2O emissions per yield tended to decrease due to the use of controlled release fertilizers for the three years, and further decrease due to the reduction of application rate. In conclusion, the use of controlled release fertilizers with reduced application rates can be regarded as an improved climate-smart soil management in soybean fields converted from rice paddies.
Book
Nitrogen Assessment: Pakistan as a Case-Study provides a detailed overview of issues and challenges related to nitrogen use and overuse, thus serving as a reference for researchers in Pakistan and providing important insights for other geographic regions. Excess and inefficient nitrogen use in crops and livestock sectors is polluting our rivers, seas, atmosphere, and ecosystems, contributing to climate change, hampering biodiversity, and contributing to stratospheric ozone depletion. This book covers the importance of nitrogen in relation to food security, human health, and economic stability in South Asia. It also discusses nitrogen status, sources, sinks, and drivers of nitrogen use in Pakistan, focusing on current nitrogen measures and policies. Nitrogen pollution is one of the biggest challenges of 21st Century, and the international scientific community is beginning to recognize the significance of nitrogen pollution and to explore how to combat it. The editors’ institution, University of Agriculture, Faisalabad, partners with South Asia Nitrogen Hub, which includes about 30 organizations from South Asia and UK working on nitrogen assessment, budgeting, awareness, and policy guidance, as well as possible measures to reduce nitrogen pollution. Nitrogen Assessment: Pakistan as a Case-Study provides an important guide to this work and is written in a way that is accessible to an audience with a wide range of experience from advanced students to seasoned researchers.
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Soil cadmium (Cd) contamination is one of the most serious environmental problems on a global scale. Biochar has a great potential to reduce Cd bioavailability in contaminated soils even though biochar effects on soil Cd bioavailability has been inconsistent among studies. In this meta-analysis, we used 802 paired observations from 84 peer-reviewed articles to evaluate the effect of biochar application on Cd bioavailability among different soil types and to elucidate the factors governing that effect. Our key findings are: 1) biochar application reduced Cd bioavailability across various biochar and soil types, with the greatest reduction (70%) in urban/anthropogenically contaminated soils, and reductions of 41.1, 42.3 and 30.2% were found in acidic soils (pH < 6.5), and in coarse- and medium-textured soils, respectively. However, biochar increased Cd bioavailability in fine-textured soils by 16.2%; 2) in acidic soils, biochars produced from rice straw, pyrolyzed at 450–550 °C, with a heating rate of 1–5 °C min⁻¹ and a residence time of <60 min were most effective; whereas in alkaline soils, biochars produced from sewage sludge, pyrolyzed at <350 °C, with a residence time >60 min were more effective in reducing Cd bioavailability; and 3) the effect of biochar on soil Cd bioavailability was mainly governed by the induced changes in soil pH and dissolved organic C, and by the surface area, ash content, H/C and abundance of O-containing functional groups of biochars. We conclude that biochar application to acidic or coarse- and medium-textured soils is effective for remediating Cd contamination, but application to fine-textured soils should be avoided.
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With the rising popularity of the concept of “carbon neutralization,” low-carbon products are likely to gain more advantages. Related to this, green tea—as an important beverage that is widely consumed in China—along with emissions from planting, processing, and use phase should be given attention. Meanwhile, quantifying the carbon footprint (CF) of green tea is an essential task in developing the pathway to carbon neutrality. In this study, we quantified the CF and mitigation potential of green tea through life cycle assessment, after which we investigated the pathway toward carbon neutrality in 16 major tea-producing regions (except Hainan and Taiwan) in China. The system boundary was divided into six subsystems from cradle to grave: cultivation, processing, transport, packaging, consumption, and disposal. The results showed that the total carbon emissions of green tea, reached 44.13 Mt CO2eq in 2019, of which 43% came from consumption and 28% from cultivation. There were 18.78 Mt CO2eq emissions from fertilizer production and application, while there was a 7.71 Mt CO2eq carbon sink of tea trees. The average carbon intensity was 24.30 kg CO2eq kg⁻¹ tea, while Shandong and Guizhou ranked as the top two provinces. Sichuan, Hubei, and Yunnan Provinces had the largest amounts of carbon emissions at 6.79, 6.14, and 5.96 Mt CO2eq, respectively. by 2030, 2050 and 2060, total carbon emissions would be reduced by 46%, 63%, and 86%, respectively, under carbon neutrality assumption. A small amount of 6.14 Mt CO2eq carbon emissions was retained to be offset by carbon trading or zero-carbon cultivation. Finally, the results indicate that adopting low-carbon fertilizers and clean energies will be a key entry point for carbon-neutral green tea.
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Ammonia (NH3) and nitrous oxide (N2O) are two important air pollutants that have major impacts on climate change and biodiversity losses. Agriculture represents their largest source and effective mitigation measures of individual gases have been well studied. However, the interactions and trade-offs between NH3 and N2O emissions remain uncertain. Here we report the results of a two-year field experiment in a wheat-maize rotation in the North China Plain (NCP), a global hotspot of reactive N emissions. Our analysis is supported by a literature synthesis of global croplands, to understand the interactions between NH3 and N2O emissions, and to develop the most effective approaches to jointly mitigate NH3 and N2O emissions. Field results indicated that deep placement of urea with nitrification inhibitors (NIs) reduced both emissions of NH3 by 67% to 90% and N2O by 73% to 100%, respectively, in comparison with surface broadcast urea which is the common farmers’ practice. But deep placement of urea, surface broadcast urea with NIs and application of urea with urease inhibitors probably led to trade-offs between the two gases, with a mitigation potential of -201% to 101% for NH3 and -112% to 89% for N2O. The literature synthesis showed that deep placement of urea with NIs had an emission factor of 1.53%-4.02% for NH3 and 0.22%-0.36% for N2O, which were much lower than other fertilization regimes and the default values recommended by IPCC guidelines. This would translate to a reduction of 3.86-5.47 Tg N yr-1 of NH3 and 0.41-0.50 Tg N yr-1 of N2O emissions, respectively, when adopting deep placement of urea with NIs (relative to current practice) in global croplands. We conclude that the combination of NIs and deep placement of urea can successfully tackle the trade-offs between NH3 and N2O emissions, therefore avoiding N pollution swapping in global croplands.
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The present study aimed to identify and characterize prevailing dairy production systems in Ghana and compare production costs and profitability of identified production systems using the TIPI_CAL (Technology Impact, Policy Impact Calculation) model. Three typical farms were determined to represent each production system: intensive (GH-03), semiextensive (GH-35), and extensive production system (GH-27). The cost of milk production for GH-03, GH-35, and GH-27 were €53.79/100kg Energy Corrected Milk (ECM), €25.16/100kg ECM, and €32.13/100kg ECM, respectively. All three typical farms had a positive entrepreneur's profit and covered their total production costs from dairying and finished cattle in the short-term and medium-term. However, the extensive system GH-27 is economically unviable in the long-term because of the high opportunity cost of labour. Low milk yield, shortage of forage, absence of artificial insemination, lack of cooling and storage facility, lack of organized marketing facility were the major constraints faced by dairy farmers in Ghana.
Article
Oxamide is a potential slow-release nitrogen (N) fertilizer, especially under waterlogged conditions, due to its low solubility in water and the slow-release of ammonium by soil amidases. To investigate the effects of oxamide granules (2.00–2.38 mm in diameter) after a single basal fertilization on rice growth, soil properties, and N use efficiency in terms of N recovery efficiency (NRE), we conducted field experiments in two different types of paddy soils over two rice-growing seasons. Results showed that the fertilization effects of oxamide granules varied in the two types of paddy soil. In the red clayey paddy soil, the grain yields for both rice-growing seasons were high with a significantly higher NRE in the oxamide treatment than in the urea treatment. However, in the alluvial sandy paddy soil, the grain yield in the oxamide treatment was slightly lower than in the urea treatment. Furthermore, oxamide produced little improvement in NRE in the alluvial sandy paddy soil. Soil incubation experiments over 98 d were also carried out to evaluate the factors affecting the N release behavior of oxamide granules in the two types of paddy soil. We found that the amidase activities were higher and, therefore, the oxamide hydrolysis rates were faster in the alluvial sandy paddy soil, which had a higher soil pH value and organic matter content. The faster N release and the longer growth period resulted in a mismatch between N supply by oxamide and rice demand, which, in turn, led to little improvement in NRE and a decreased grain yield in the alluvial sandy paddy soil, especially in the reduced oxamide treatment. These results could help select the appropriate size of oxamide granules for use as a slow-release N fertilizer depending on the soil properties and growth period of rice.
Article
Application of coated controlled‐release urea (CRU) has been widely recognized as an effective measure to improve crop yield while alleviating nitrogen (N) fertilizer‐induced environmental consequences. However, the overall effect of CRU on crop yield across field sites remains uncertain, especially for CRU applied at a reduced rate and frequency or blended with urea. Here, we applied a meta‐analysis approach to address these issues. Our results indicated that applying CRU at an equal N rate significantly increased crop yield by 9.2% compared to conventional urea. The increase in crop yield was positively correlated with soil organic matter content and N release period of CRU but negatively correlated with mean annual temperature. However, reducing CRU application times brought a smaller yield increase (7.0%), although it could save labor and mechanical cost. Moreover, lowering CRU‐N application rate had no significant impact on crop yield, mainly due to the reduced application frequency. This effect can be further weakened with the decreasing CRU‐N application rate. In contrast, one‐time application of CRU‐urea blend still exhibited superior efficiency with a 9.8% increase in crop yield. Our findings showed that there existed a trade‐off between the saving of CRU input cost and crop yield gain. However, a win‐win scenario that attains more yield increase while saving input cost can be achieved through one‐time application of CRU‐urea blend. This article is protected by copyright. All rights reserved CRU at an equal N rate significantly increased crop yield by 9.2% compared to conventional urea. Reducing CRU application times brought a smaller yield increase of 6.9%. Lowering CRU‐N input rate did not significantly alter crop yield. One‐time application of CRU‐urea blend exhibited superior efficiency with a 9.8% yield increase.
Article
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Nitrous oxide (N2O) emissions were measured over two years from an intensively managed grassland site in the UK. Emissions from ammonium nitrate (AN) and urea (UR) were compared to those from urea modified by various inhibitors (a nitrification inhibitor, UR(N), a urease inhibitor, UR(U), and both inhibitors together, SU), as well as a controlled release urea (CR). N2O fluxes varied through time and between treatments. The differences between the treatments were not consistent throughout the year. After the spring and early summer fertilizer applications, fluxes from AN plots were greater than fluxes from UR plots, e.g. the cumulative fluxes for one month after N application in June 1999 were 5.2 ± 1.1 kg N2O-N ha-1 from the AN plots, compared to 1.4 ± 1.0 kg N2O-N ha-1 from the UR plots. However, after the late summer application, there was no difference between the two treatments, e.g. cumulative fluxes for the month following N application in August 2000 were 3.3 ± 0.7 kg N2O-N ha-1 from the AN plots and 2.9 ± 1.1 kg N2O-N ha-1 from the UR plots. After all N applications, fluxes from the UR(N) plots were much less than those from either the AN or the UR plots, e.g. 0.2 ± 0.1 kg N2O-N ha-1 in June 1999 and 1.1 ± 0.3 kg N2O-N ha-1 in August 2000. Combining the results of this experiment with earlier work showed that there was a greater N2O emission response to rainfall around the time of fertilizer application in the AN plots than in the UR plots. It was concluded that there is scope for reducing N2O emissions from N-fertilized grassland by applying UR instead of AN to wet soils in cool conditions, e.g. when grass growth begins in spring. Applying UR with a nitrification inhibitor could cut emissions further.
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Agricultural practices, soil characteristics and meteorological conditions are responsible for eventual nitrate accumulation in the subsoil. There is a lot of evidence that denitrification occurs in the subsoil and rates up to 60–70 kg ha-1 yr-1 might be possible. It has also been shown that in the presence of Fe2+ (formed through weathering of minerals) and an alkaline pH, nitrate can be chemically reduced. Another possible pathway of disappearance is through the formation of nitrite, which is unstable in acid conditions. With regard to the emission of N2O and N2, it can be stated that all conditions whereby the denitrification process becomes marginal are favourable for N2O formation rather than for N2. Because of its high solubility, however, an important amount of N2O might be transported with drainage water.
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Should international protocols be ratified, New Zealand will become legally committed to limit its greenhouse gas emissions The three major greenhouse gases are carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O) Agricultural soils are generally considered to be the main source of N2O emissions in New Zealand, but production estimates to date are surrounded by great uncertainty This paper reviews our current understanding of agricultural N2O emissions, and suggests directions for future research needs by evaluating the default emission factors of the 1996 Revised Guidelines for National Greenhouse Gas Inventories of the Intergovernmental Panel on Climate Change (IPCC) for the New Zealand situation The emission factors calculated for New Zealand agricultural soils are generally within the range of the 1996 IPCC default values, but the limited amount of research data available hampers a full evaluation of the appropriateness of these factors for New Zealand More long‐term studies are needed to refine our emission factors, particularly those for animal urine and dung returned to pasture Application of the IPCC methodology to New Zealand identifies herbivore excrement as the single largest potential source of anthropogenic N2O emissions (about 50% of the total emission) In addition, research is also required for indirect sources of N2O, because only limited overseas data, and none from New Zealand, are available The 1996 IPCC methodology does not account for variations in climatic and soil physical conditions, which are known to affect N2O emissions In the longer term, development of robust process‐based models, coupled with spatial and temporal data sets of the major drivers of N2O emissions, may therefore be a useful approach for obtaining national emission estimates for New Zealand This will require long‐term monitoring of N2O emissions, under various land uses and on a national network of sites
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A field experiment was conducted in an Andosol in Tsukuba, Japan to study the effect of banded fertilizer applications or reduced rate of fertilizer N (20% less) on emissions of nitrous oxide (N2O) and nitric oxide (NO), and also crop yields of Chinese cabbage during the growing season in 2000. Six treatments were applied by randomized design with three replications, which were; no N fertilizer (CK); broadcast application of urea (BC); band application of urea (B); band application of urea at a rate 20% lower than B (BL); band application of controlled-release urea (CB) and band application of controlled-release urea at a rate 20% lower than CB (CBL). The results showed that reduced application rates, applied in bands, of both urea (BL) and controlled-release urea fertilizer (CBL) produced yields that were not significantly lower than yields from the full rate of broadcast urea (BC). The emissions of N2O and NO from the reduced fertilizer treatments (BL, CBL) were lower than that of normal fertilizer rates (B, CB). N2O and NO emissions from controlled-release urea applied in band mode (CB, CBL) were less than those from urea applied in band mode (B, BL). The total emissions of N2O and NO indicated that applying fertilizers in band mode mitigated NO emission from soils, but N2O emissions from banded urea (B) were no lower than from broadcast urea (BC).
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Increases in the concentrations of greenhouse gases, carbon dioxide (CO 2), methane (CH 4), nitrous oxide (N 2 O), and halocarbons in the atmosphere due to human activities are associated with global climate change. The concentration of N 2 O has increased by 16% since 1750. Although the atmospheric concentration of N 2 O is much smaller (314 ppb in 1998) than of CO 2 (365 ppm), its global warming potential (cumulative radiative forcing) is 296 times that of the latter in a 100-year time horizon. Currently, it contributes about 6% of the overall global warming effect but its contribution from the agricultural sector is about 16%. Of that, almost 80% of N 2 O is emitted from Australian agricultural lands, originating from N fertilisers (32%), soil disturbance (38%), and animal waste (30%). Nitrous oxide is primarily produced in soil by the activities of microorganisms during nitrification, and denitrification processes. The ratio of N 2 O to N 2 production depends on oxygen supply or water-filled pore space, decomposable organic carbon, N substrate supply, temperature, and pH and salinity. N 2 O production from soil is sporadic both in time and space, and therefore, it is a challenge to scale up the measurements of N 2 O emission from a given location and time to regional and national levels. Estimates of N 2 O emissions from various agricultural systems vary widely. For example, in flooded rice in the Riverina Plains, N 2 O emissions ranged from 0.02% to 1.4% of fertiliser N applied, whereas in irrigated sugarcane crops, 15.4% of fertiliser was lost over a 4-day period. Nitrous oxide emissions from fertilised dairy pasture soils in Victoria range from 6 to 11 kg N 2 O-N/ha, whereas in arable cereal cropping, N 2 O emissions range from <0.01% to 9.9% of N fertiliser applications. Nitrous oxide emissions from soil nitrite and nitrates resulting from residual fertiliser and legumes are rarely studied but probably exceed those from fertilisers, due to frequent wetting and drying cycles over a longer period and larger area. In ley cropping systems, significant N 2 O losses could occur, from the accumulation of mainly nitrate-N, following mineralisation of organic N from legume-based pastures. Extensive grazed pastures and rangelands contribute annually about 0.2 kg N/ha as N 2 O (93 kg/ha per year CO 2 -equivalent). Tropical savannas probably contribute an order of magnitude more, including that from frequent fires. Unfertilised forestry systems may emit less but the fertilised plantations emit more N 2 O than the extensive grazed pastures. However, currently there are limited data to quantify N 2 O losses in systems under ley cropping, tropical savannas, and forestry in Australia. Overall, there is a need to examine the emission factors used in estimating national N 2 O emissions; for example, 1.25% of fertiliser or animal-excreted N appearing as N 2 O (IPCC 1996). The primary consideration for mitigating N 2 O emissions from agricultural lands is to match the supply of mineral N (from fertiliser applications, legume-fixed N, organic matter, or manures) to its spatial and temporal needs by crops/pastures/trees. Thus, when appropriate, mineral N supply should be regulated through slow-release (urease and/or nitrification inhibitors, physical coatings, or high C/N ratio materials) or split fertiliser application. Also, N use could be maximised by balancing other nutrient supplies to plants. Moreover, non-legume cover crops could be used to take up residual mineral N following N-fertilised main crops or mineral N accumulated following legume leys. For manure management, the most effective practice is the early application and immediate incorporation of manure into soil to reduce direct N 2 O emissions as well as secondary emissions from deposition of ammonia volatilised from manure and urine. Current models such as DNDC and DAYCENT can be used to simulate N 2 O production from soil after parameterisation with the local data, and appropriate modification and verification against the measured N 2 O emissions under different management practices.
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Field experiments were designed to quantify N2O emissions from corn fields after the application of different types of nitrogen fertilizers. Plots were established in South Kalimantan, Indonesia, and given either urea (200 kg ha−1), urea (170 kg ha−1) + dicyandiamide ([DCD] 20 kg ha−1) or controlled-release fertilizer LP-30 (214 kg ha−1) prior to the plantation of corn seeds (variety BISI 2). Each fertilizer treatment was equivalent to 90 kg N ha−1. Plots without chemical N fertilizer were also prepared as a control. The field was designed to have three replicates for each treatment with a randomized block design. Nitrous oxide fluxes were measured at 4, 8, 12, 21, 31, 41, 51, 72 and 92 days after fertilizer application (DAFA). Total N2O emission was the highest from the urea plots, followed by the LP-30 plots. The emissions from the urea + DCD plots did not differ from those from the control plots. The N2O emission from the urea + DCD plots was approximately one thirtieth of that from the urea treatment. However, fertilizer type had no effect on grain yield. Thus, the use of urea + DCD is considered to be the best mitigation option among the tested fertilizer applications for N2O emission from corn fields in Kalimantan, Indonesia.
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The objective of this study was to examine the effect of soil water content, and other physical and chemical factors, on the abiotic component of nitric oxide (NO) production in laboratory studies using soils from agricultural fields in Minnesota, California, and Connecticut. In all soils, gross NO production decreased with increasing gravimetric water content (ϑ) in nitrite (NO 2−)-amended sterilized soils. The rate coefficient describing nitrous acid (HNO2)-mediated NO production (k p) also decreased with increasing ϑ in both gamma-irradiated and autoclaved soils. Significant correlations were found between ln k p and several soil properties including: content of silt, clay, total carbon, total N, and extractable iron, and an estimate of the cation exchange capacity of the clay fraction. Multiple regression models incorporating these variables explained 85–93% of the variance in ln k p. The relationships obtained suggest that the mechanism of abiotic NO production is primarily mediated at the soil solution–surface interface. These findings provide consistent evidence of a previously unrecognized mechanism by which soil water content can affect NO production by mediating a chemical process. Application of a dynamic process model indicated that the simulated variation in NO emissions as a consequence of this effect is comparable to the variation observed in previous studies of NO emissions. Comparison of soils from two different long-term tillage studies also indicated that reduced pH in no-till systems may lead to greater NO emissions for a given level of NO 2− accumulation. Overall, these results suggest that current views of controls over N oxide gas emissions may need to be revised to include abiotic reactions, in addition to microbial and physical processes, as yet another category of factors that is highly sensitive to soil water content.
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The effectiveness of nitrification inhibitors for abatement of N loss from the agroecosystem is difficult to measure at typical agronomic scales, since performance varies at the research-field scale due to complex interactions among crop management, soil properties, length of the trial, and environmental factors. The environmental impact of the nitrification inhibitor nitrapyrin on N losses from agronomic ecosystems was considered with emphasis on the Midwestern USA. A meta-evaluation approach considered the integrated responses to nitrification inhibition found across research trials conducted in diverse environments over many years as measured in side-by-side comparisons of fertilizer N or manure applied with and without nitrapyrin. The resulting distributions of response indices were evaluated with respect to the magnitude and variance of the agronomic and environmental effects that may be achieved when nitrification inhibitors are used regionally over time. The indices considered (1) crop yield, (2) annual or season-long maintenance of inorganic N within the crop root zone, (3) NO3-N leached past the crop root zone, and (4) greenhouse gas emission from soil. Results showed that on average, the crop yield increased (relative to N fertilization without nitrapyrin) 7% and soil N retention increased by 28%, while N leaching decreased by 16% and greenhouse gas emissions decreased by 51%. In more than 75% of individual comparisons, use of a nitrification inhibitor increased soil N retention and crop yield, and decreased N leaching and volatilization. The potential of nitrification inhibitors for reducing N loss needs to be considered at the scale of a sensitive region, such as a watershed, over a prolonged period of use as well as within the context of overall goals for abatement of N losses from the agroecosystem to the environment.
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In this study we review recent studies where dicyandiamide was used as a nitrification inhibitor to reduce both N2O emissions from urine patches and nitrate leaching from pasture systems, and which led to the development of a commercial product for use on farmland. On average, emissions of N2O and nitrate leaching were reduced by 72% and 61%, respectively. This study then demonstrates how a mitigation tool can be accounted for in the Intergovernmental Panel on Climate Change’s inventory methodology when constructing an inventory of New Zealand’s agricultural soil N2O emissions. The current New Zealand specific emission factors for EF1 (0.01), EF3PRP (0.01) and FracLEACH (0.07) are amended to values of 0.0058, 0.0058 and 0.0455. Examples are also given, based on overseer™ models, of the implications of farm management scenarios on N2O inventories and total greenhouse gas production when using a N2O mitigation tool; CO2 equivalents kg−1 milk solid decreased from 14.2 to as little as 11.7, depending on the management scenario modelled.
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Nitrification, a microbial process, is a key component and integral part of the nitrogen (N) cycle. Soil N is in a constant state of flux, moving and changing chemical forms. During nitrification, a relatively immobile N-form (NH4 ) is converted into highly mobile nitrate-N (NO3 ). The nitrate formed is susceptible to losses via leaching and conversion to gaseous forms via denitrification. Often less than 30% of the applied N fertilizer is recovered in intensive agricultural systems, largely due to losses associated with and following nitrification. Nitrogen-use efficiency (NUE) is defined as the biomass produced per unit of assimilated N and is a conservative function in most biological systems. A better alternative is to define NUE as the dry matter produced per unit N applied and strive for improvements in agronomic yields through N recovery. Suppressing nitrification along with its associated N losses is potentially a key part in any strategy to improve N recovery and agronomic NUE. In many mature N-limited ecosystems, nitrification is reduced to a relatively minor flux. In such systems there is a high degree of internal N cycling with minimal loss of N. In contrast, in most high-production agricultural systems nitrification is a major process in N cycling with the resulting N losses and inefficiencies. This review presents the current state of knowledge on nitrification and associated N losses, and discusses strategies for controlling nitrification in agricultural systems. Limitations of the currently available nitrification inhibitors are highlighted. The concept of biological nitrification inhibition (BNI) is proposed for controlling nitrification in agricultural systems utilizing traits found in natural ecosystems. It is emphasized that suppression of nitrification in agricultural systems is a critical step required for improving agronomic NUE and maintaining environmental quality.
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The steady increase in population growth and food demand and the continuous reduction in cultivated land per capita induce steady intensification of fertilizer application worldwide. Despite improvements in the practices of nutrient application, the use efficiency (UE) of essential elements such as N and P is not satisfactory, resulting in an increase of environmental problems. The use of controlled-release fertilizers (CRFs) starts to evolve as a promising direction offering an excellent means to improve management of nutrient application and by this reducing significantly environmental threats while maintaining high crop yields of good quality. Low cost effectiveness and limited recognition of the potential benefits to be gained from the CRFs were so far the main reasons for their limited consumption. A systematic classification of the slow- and controlled-release fertilizers (SRF/CRFs) and details about the production and action mechanisms of the more common products is given in this chapter. The difference between slow and controlled release is emphasized, stressing the importance of proper synchronization of nutrient supply with plant demand as crucial for achieving the expected benefits from SRF/CRFs. Fertilizers based on polymer coating are singled out as the CRFs offering the best control over release. These are also the ones with the largest growth rate among the SRF/CRFs. Special attention is devoted to the description of release mechanisms and recent developments in modeling release which are essential for predicting nutrient release under real conditions and which can provide the technologists with tools for better design of CRFs. The use of SRF/CRFs in agriculture and nonfarm applications is described, stressing the need to better assess the agronomic and the environmental benefits to be gained. This, together with technological improvements in production of CRFs, is believed to significantly promote the future use of SRF/CRFs in practice. Finally, the efforts to improve the characterization of CRFs are described and a scheme for a systematic evaluation and classification of CRFs is offered. These efforts are likely to promote standardization of the different SR/CR products. By proper labeling, they will also assist legislators and producers in educating consumers about the relevant features of CRFs (e.g., release pattern and duration, and content of available forms).
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Intensively managed grasslands are potentially a large source of NH3, N2O, and NO emissions because of the large input of nitrogen (N) in fertilizers. Addition of nitrification inhibitors (NI) to fertilizers maintains soil N in ammonium form. Consequently, N2O and NO losses are less likely to occur and the potential for N utilization is increased, and NH3 volatilization may be increased. In the present study, we evaluated the effectiveness of the nitrification inhibitor 3,4-dimethylpyrazol phosphate (DMPP) on NH3, N2O, NO, and CO2 emissions following the application of 97 kg N ha(-1) as ammonium sulfate nitrate (ASN) and 97 kg NH4+ -N ha(-1) as cattle slurry to a mixed clover-ryegrass sward in the Basque Country (northern Spain). After slurry application, 16.0 and 0.7% of the NH4+ -N applied was lost in the form of N2O and NO, respectively. The application of DMPP induced a decrease of 29 and 25% in N2O and NO emissions, respectively. After ASN application 4.6 and 2.8% of the N applied was lost as N2O and NO, respectively. The application of DMPP with ASN (as ENTEC 26; COMPO, Münster, Germany) unexpectedly did not significantly reduce N2O emissions, but induced a decrease of 44% in NO emissions. The amount of NH4+ -N lost in the form of NH3 following slurry and slurry + DMPP applications was 7.8 and 11.0%, respectively, the increase induced by DMPP not being statistically significant. Levels of CO2 emissions were unaffected in all cases by the use of DMPP. We conclude that DMPP is an efficient nitrification inhibitor to be used to reduce N2O and NO emissions from grasslands.
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Slow-release nitrogen (N) fertilizers offer many potential benefits for vegetable production. In sandy soils, their use may lessen N leaching. If the slowrelease fertilizer has a release pattern that matches crop needs, N uptake by the growing crop may become more efficient. Additionally, if slow-release fertilizers can be applied as a preplant application, production costs could be lessened, eliminating the need for multiple applications of soluble N fertilizer. Synthetic slow-release fertilizers can be separated into two general groups: those that are slow release as a byproduct of a chemical reaction (such as urea-formaldehyde), and those that are slow release via a sulfur, wax, or resin coating around the fertilizer prill. In vegetable crop research, much of the available literature has focused on use of sulfur coat urea and urea-formaldehyde, as they have been in the fertilizer market for 40 years. Newer research has evaluated resin-coated products. In most studies, use of slowreleaseNfertilizers a a preplant treatment did not decrease crop yield, but yield was rarely increased when compared with standard split applications of soluble N. Based on available research, the benefits of using slow-release N fertilizers in vegetable crop production will come from reduced environmental risk and savings in production costs.
Article
N2O, NO and NO2 fluxes from an Andosol soil in Japan after fertilization were measured 6 times per day for 10 months from June 1997 to April 1998 with a fully automated flux monitoring system in lysimeters. Three nitrogen chemical fertilizers were applied to the soil–calcium nitrate (NI), controlled-release urea (CU), and controlled-release calcium nitrate (CN), and also no nitrogen fertilizer (NN). The total amount of nitrogen applied was 15 g N m−2 in the first and the second cultivation period of Chinese vegetable. In the first measuremnt period of 89 days, the total N2O emissions from NI, CN, CU, and NN were 18.4, 16.3, 48.7, and 9.60 mgN m−2, respectively. The total NO emissions from NI, CN, CU, and NN were 48.4, 33.7, 149, and 13.7 mgN m−2, respectively. In the second measurement period of 53 days, the total N2O emissions from NI, CN, and CU were 9.66, 7.23, and 20.6 mgN m−2, respectively. The total NO emissions from NI, CN, and CU were 24.7, 2.60 and 34.2 mgN m−2, respectively. The total N2O emission from CU was significantly higher than CN. In the third cultivation period, all plots were applied with 10 g N m−2 of ammonium phosphate (AP) and winter barley was cultivated. In the third measurement period of 155 days, the total N2O and NO emissions were 9.02 mgN m−2 and 10.2 mgN m−2, respectively. N2O and NO peaks were observed just after the fertilization for 30 days and 15 days, respectively. N2O, NO and NO2 fluxes for the year were estimated to be 38.6 ∼ 81.5, 48.2 ∼ 181, and −24.8 to −39.3 mgN m−2, respectively. NO2 was absorbed in all the plots, and a negative correlation was found between NO2 flux and the NO2 concentration just after the chamber closed. NO was absorbed in the winter period, and a negative correlation was found between NO flux and the NO concentration just after the chamber closed. A diurnal pattern was observed in N2O and NO fluxes in the summer, similar to air and soil temperature. We could find a negative relationship between flux ratio of NO-N to N2O-N and water-filled pore space (WFPS), and a positive relationship between NO-N and N2O-N fluxes and temperature. Q10 values were 3.1 for N2O and 8.7 for NO between 5∼30 °C.
Article
Field studies using a chamber technique to measure emissions of nitrous oxide (N2O) showed that the N2O emissions induced by fertilization of soil with anhydrous ammonia (180 kg N ha-1) were markedly reduced by addition of nitrapyrin [2-chloro-6- (trichloromethl)-pyridinel] to this fertilizer. The emission of N2O induced by application of anhydrous ammonia in the fall was reduced 63% by addition of nitrapyrin at the rate of 0.56 kg ha-1. The corresponding reduction when nitrapyrin was added to anhydrous ammonia applied in the spring was 87%. These observations indicate that nitrapyrin has potential value for reduction of the N2O emissions induced by nitrogen fertilization of soils and the possible adverse effects of these emissions on our climate.
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The Cochrane Handbook for Systematic Reviews of Interventions (the Handbook) has undergone a substantial update, and Version 5 of the Handbook is now available online at www.cochrane-handbook.org and in RevMan 5. In addition, for the first time, the Handbook will soon be available as a printed volume, published by Wiley-Blackwell. We are anticipating release of this at the Colloquium in Freiburg. Version 5 of the Handbook describes the new methods available in RevMan 5, as well as containing extensive guidance on all aspects of Cochrane review methodology. It has a new structure, with 22 chapters divided into three parts. Part 1, relevant to all reviews, introduces Cochrane reviews, covering their planning and preparation, and their maintenance and updating, and ends with a guide to the contents of a Cochrane protocol and review. Part 2, relevant to all reviews, provides general methodological guidance on preparing reviews, covering question development, eligibility criteria, searching, collecting data, within-study bias (including completion of the Risk of Bias table), analysing data, reporting bias, presenting and interpreting results (including Summary of Findings tables). Part 3 addresses special topics that will be relevant to some, but not all, reviews, including particular considerations in addressing adverse effects, meta-analysis with non-standard study designs and using individual participant data. This part has new chapters on incorporating economic evaluations, non-randomized studies, qualitative research, patient-reported outcomes in reviews, prospective meta-analysis, reviews in health promotion and public health, and the new review type of overviews of reviews.
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Agricultural fields are significant sources of anthropogenic atmospheric nitrous oxide (N2O). We compiled and analyzed data on N2O emissions from Japanese agricultural fields (246 measurements from 36 sites) reported in peer-reviewed journals and research reports. Agricultural fields were classified into three categories: upland fields, tea fields and rice paddy fields. In this analysis, data measured over a period of more than 90 days for upland fields and 209 days for tea fields were used to estimate annual fertilizer-induced emission factors (EF) because of limitations in the available data. The EF is defined as the emission from fertilized plots minus the background emission (emission from a zero-N control plot), and is expressed as a percentage of the N applied. The mean of N2O emissions from upland fields with well-drained soils was significantly lower than that from poorly drained soils. Mean (± standard deviation) N2O emissions measured over a period of more than 90 days from fertilized upland fields were 1.03 ± 1.14 kg N ha−1 and 4.78 ± 5.36 kg N ha−1 for well-drained and poorly drained soils, respectively. Because the ratio of the total areas of well-drained soils and poorly drained soils was different from the ratio of the number of available EF data for each soil category, we used a weighted mean to estimate EF for all upland fields. The EF was estimated to be 0.62 ± 0.48% for all fertilized upland fields. Mean N2O emissions and the estimated EF for fertilized tea fields measured over a period of more than 209 days were 24.3 ± 16.3 kg N ha−1 and 2.82 ± 1.80%, respectively. The mean N2O emission and estimated EF from Japanese rice paddy fields were 0.36 kg N ha−1 and 0.31 ± 0.31% for the cropping season, respectively. Significant uncertainties remain in these results because of limitations in the available data.
Article
Grassland is a major source of nitrous oxide (N2O) and methane (CH4) emissions in the UK, resulting from high rates of fertilizer application. We studied the effects of substituting mineral fertilizer by organic manures and a slow-release fertilizer in silage grass production on greenhouse gas emissions and soil mineral N content in a three-year field experiment. The organic manures investigated were sewage sludge pellets and composted sewage sludge (dry materials), and digested sewage sludge and cattle slurry (liquid materials). The organic manures produced N2O and carbon dioxide (CO2) consistently from time of application up to harvest. However, they mitigated N2O emissions by around 90% when aggregate emissions of 15.7 kg N ha−1 from NPK fertilizer were caused by a flux of up to 4.9 kg N ha−1 d−1 during the first 4 days after heavy rainfall subsequent to the NPK fertilizer application. CH4 was emitted only for 2 or 3 days after application of the liquid manures. CH4 and CO2 fluxes were not significantly mitigated. Composting and dried pellets were useful methods of conserving nutrients in organic wastes, enabling slow and sustained release of nitrogen. NPK slow-release fertilizer also maintained grass yields and was the most effective substitute for the conventional NPK fertilizer for mitigation of N2O fluxes.
Article
Increases in the atmospheric concentrations of nitrous oxide (N2O) contribute to global warming and to ozone depletion in the stratosphere. Nitric oxide (NO) is a cause of acid rain and tropospheric ozone. The use of N fertilizers in agriculture has direct and indirect effects on the emissions of both these gases, which are the result of microbial nitrification and denitrification in the soil, and which are controlled principally by soil water and mineral N contents, temperature and labile organic matter.
Article
Two experiments were conducted to evaluate the inhibitory effects of 2-chloro-6 (trichloromethyl) pyridine (nitrapyrin) and dicyandiamide on nitrous oxide (N2O), a greenhouse gas, emission from soils amended with ammonium sulfate. In the two experiments, samples of an Andosol and a Gray Lowland soil were kept in glass vessels sealed with a butyl rubber cap and incubated at 25°C. In the first experiment, nitrapyrin (1 µg g−1 dry soil) and dicyandiamide (10 µg g−1 dry soil) were applied to samples of a water-saturated Andosol and a Gray Lowland soil to which ammonium sulfate had been applied at a rate of 0.1 mg N g−1 dry soil. Nitrapyrin decreased N2O emissions from the Andosol and the Gray Lowland soil by 71% and 24%, respectively. Dicyandiamide decreased N2O emissions from the Andosol and Gray Lowland soil by 31% and 18%, respectively. In the second experiment, nitrapyrin (1 µg g−1 dry soil) was applied to samples of an Andosol at 51% water-filled pore space to which ammonium sulfate had been applied at rates of 0.01, 0.1 and 0.5 mg N g−1 dry soil. Nitrapyrin decreased N2O emissions by 62%, 83% and 74%, respectively. Changes in the and + concentrations in soil showed that nitrapyrin and dicyandiamide slowed down the nitrification process, but did not completely stop the process at any time. The results reveal the potential of nitrification inhibitors to decrease N2O emission from fertilized soil in a wide range of moisture conditions and nitrogen levels.
Article
The study was carried out at the experimental station of the Japan International Research Center for Agricultural Sciences to investigate gas fluxes from a Japanese Andisol under different N fertilizer managements: CD, a deep application (8 cm) of the controlled release urea; UD, a deep application (8 cm) of the conventional urea; US, a surface application of the conventional urea; and a control, without any N application. NO, N2O, CH4 and CO2 fluxes were measured simultaneously in a winter barley field under the maize/barley rotation. The fluxes of NO and N2O from the control were very low, and N fertilization increased the emissions of NO and N2O. NO and N2O from N fertilization treatments showed different emission patterns: significant NO emissions but low N2O emissions in the winter season, and low NO emissions but significant N2O emissions during the short period of barley growth in the spring season. The controlled release of the N fertilizer decreased the total NO emissions, while a deep application increased the total N2O emissions. Fertilizer-derived NO–N and N2O–N from the treatments CD, UD and US accounted for 0.20±0.07%, 0.71±0.15%, 0.62±0.04%, and 0.52±0.04%, 0.50±0.09%, 0.35±0.03%, of the applied N, respectively, during the barley season. CH4 fluxes from the control were negative on most sampling dates, and its net soil uptake was 33±7.1 mg m−2 during the barley season. The application of the N fertilizer decreased the uptake of atmospheric CH4 and resulted in positive emissions from the soil. CO2 fluxes were very low in the early period of crop growth while higher emissions were observed in the spring season. The N fertilization generally increased the direct CO2 emissions from the soil. N2O, CH4 and CO2 fluxes were positively correlated (P<0.01) with each other, whereas NO and CO2 fluxes were negatively correlated (P<0.05). The N fertilization increased soil-derived global warming potential (GWP) significantly in the barley season. The net GWP was calculated by subtracting the plant-fixed atmospheric CO2 stored in its aboveground parts from the soil-derived GWP in CO2 equivalent. The net GWP from the CD, UD, US and the control were all negative at −243±30.7, −257±28.4, −227±6.6 and −143±9.7 g C m−2 in CO2 equivalent, respectively, in the barley season.
Article
Microorganisms play important roles in the nitrogen cycles of various ecosystems. Research has revealed that a greater diversity of microorganisms is involved in the nitrogen cycle than previously understood. It is becoming clear that denitrifying fungi, nitrifying archaea, anammox bacteria, aerobic denitrifying bacteria and heterotrophic nitrifying microorganisms are key players in the nitrogen cycle. Studies have revealed a major contribution by fungi in the production of N2O and N2 in grasslands, semiarid regions and forest soils. Some fungi can grow under various O2 conditions by using three types of energy-yielding metabolism: O2 respiration, denitrification (nitrite respiration) and ammonia fermentation. The amoA-like gene copies of Crenarchaeota were shown to be more abundant in soils than in autotrophic ammonia-oxidizing bacteria, and the gene was expressed at higher levels in soil to which ammonia was added. There are some contradictory findings, however, regarding archaeal and bacterial nitrification. Anammox bacteria have been shown to be widely distributed and to play an important role in both artificial and natural environments. The contribution of heterotrophic microorganisms to nitrification has been recognized in soil, and the biochemical mechanisms of several bacteria are becoming clear. A wide variety of bacteria have been found to be able to carry out aerobic denitrification and to be distributed across diverse environments. Using molecular biological techniques for soil bacteria, Nitrosospira species of clusters 2, 3 and 4 have been shown to be the dominant group in soils. Genome analyses of autotrophic nitrifying bacteria are providing new insights into their ecology and functions in soils.
Article
Nitrous oxide emission from three soils was measured using a chamber technique. Treatments sampled were unfertilized soil, and soil fertilized with 60 or 80 kg N ha-1 of band-applied anhydrous ammonia ± nitrapyrin. The flux of nitrous oxide from unfertilized soil was very low (1.1 to 1.6 g N ha-1 day-1). Application of anhydrous ammonia caused a significant increase in the cumulative emission of nitrous oxide in two soils over 27 or 29 days compared with unfertilized soil. Fertilizer-induced loss of nitrous oxide was highest in a calcareous clay soil which had the highest nitrification rate and accumulated the highest concentration of nitrite within the fertilizer bands. Fertilizer-induced losses of nitrous oxide were < 0.05% of the applied fertilizer. Addition of nitrapyrin inhibited nitrification in all soils and reduced nitrite accumulation in the fertilizer bands. Nitrapyrin addition significantly reduced fertilizer-induced loss of nitrous oxide only in the calcareous clay soil. In the other soil, nitrapyrin had a lower bioactivity (relative inhibition of nitrification) which may have been due to its higher organic matter content.
Article
Agricultural activities greatly contribute to the global net flux of CH4, N2O and CO2 from the terrestrial biosphere into the atmosphere. For CH4 and N2O, the net contribution is in the order of 40%. Because of this relatively large contribution, there is an urgent need for the implementation of effective strategies to decrease the net flux of CH4, N2O and CO2 from agriculture. The objectives of this paper are to review the various measures that have been proposed so far and to discuss the constraints and challenges. A large number of suggestions for decreasing emissions of CH4, N2O and CO2 from agriculture can be found in literature. Common to most of these abatement measures is that the suggested potentials to decrease the emissions of CO2, CH4 and N2O from agriculture are large. Common to most of the measures is also the `single gas' and `source-oriented' approach. In most papers it has been implicitly assumed that farmers are able and willing to implement the proposed measures. So far, none of the measures has been consciously implemented and tested at farm scale. The major challenge of policy makers is to formulate effective and efficient policies and measures, using the potentials of the abatement measures proposed so far, and in an international setting with still highly uncertain cause–effect relationships. Major constraints for policy makers follow from the complexities and possible feed back and side effects of abatement measures, from the many stakeholders involved, often with contrasting views, and from the unfamiliarity of farmers with the problem of climate change. Because of the many complexities and interactions involved, policy makers should follow two tracks. Priority should be given to chain-oriented measures, i.e. measures that aim at an increased carbon, nitrogen and water use efficiencies in the whole food chain, above source-oriented measures, i.e. measures that aim at decreased emission from specific sources. Chain-oriented measures should fit in with other environmental policies that aim at increasing resource use efficiency, to be effective and efficient.
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In most countries, nitrous oxide (N2O) emissions typically contribute less than 10% of the CO2 equivalent greenhouse gas (GHG) emissions. In New Zealand, however, this gas contributes 17% of the nation’s total GHG emissions due to the dominance of the agricultural sector. New Zealand’s target under the Kyoto Protocol is to reduce GHG emissions to 1990 levels. Currently total GHG emissions are 17% above 1990 levels. The single largest source of N2O emission in New Zealand is animal excreta deposited during grazing (80% of agricultural N2O emissions), while N fertilizer use currently contributes only 14% of agricultural emissions. Nitrogen fertilizer use has, however, increased 4-fold since 1990. Mitigation strategies for reducing N2O emissions in New Zealand focus on (i) reducing the amount of N excreted to pasture, e.g. through diet manipulation; (ii) increasing the N use efficiency of excreta or fertilizer, e.g. through grazing management or use of nitrification inhibitors; or (iii) avoiding soil conditions that favour denitrification e.g. improving drainage and reducing soil compaction. Current estimates suggest that, if fully implemented, these individual measures can reduce agricultural N2O emissions by 7–20%. The highest reduction potentials are obtained from measures that reduce the amount of excreta N, or increase the N use efficiency of excreta or fertilizer. However, New Zealand’s currently used N2O inventory methodology will require refinement to ensure that a reduction in N2O emissions achieved through implementation of any of these mitigation strategies can be fully accounted for. Furthermore, as many of these mitigation strategies also affect other greenhouse gas emissions or other environmental losses, it is crucial that both the economic and total environmental impacts of N2O mitigation strategies are evaluated at a farm system’s level.
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Fertilizer type and application mode may influence nitrous oxide(N2O) and nitric oxide (NO) emissions as well as crop yield. Using astatic chamber method, fluxes of both gases from a Chinese cabbage field inJapan were measured in situ following the application of easily decomposableurea by broadcasting (U-BC) and banding (U-B) and coated urea by banding(CU-B),respectively, at an application rate of 250 kg Nha–1. The measurements were made throughout the growingseason and continued 3 more months after harvest to determine the effect ofcropresidues on the emissions. Large N2O fluxes from U-BC occurredwithinabout 2 weeks after the application of the N fertilizer, while that from bothU-B and CU-B was prolonged by about 2 weeks, and significant emissions lasted alonger time but with a smaller emission size. Substantial N2O fluxesderived from crop residues were observed in the late growing season (especiallyfollowing rainfall) as well as after harvest, at all treatments including thecontrol plots (CK). Large NO fluxes occurred only at U-BC within the first 2weeks through the measurements. Total emissions were estimated to be 38.1,78.3,77.8, and 100.4 mg N2O-N m–2 and 0.7,194.9, 8.5, and 11.4 mg NO-N m–2 at CK, U-BC,U-B,and CU-B, respectively. Statistical analyses indicate that neither the bandmodenor the coated urea was able to significantly reduce the total N2Oemission through the season, but the band mode substantially reduced the NOemission. However, the application of urea by the band mode presented a 22.8%increase in crop yield as compared with urea applied by broadcasting.Therefore,by improving fertilizer use efficiency to decrease the amount of N needed tobetter meet the crop growing demand, the band mode may be a good agriculturalpractice to also reduce N2O emission. In addition, the experimentdemonstrated that crop residue is a large source of N2O emission.
Article
N2O and NO emissions from an Andisol maize field were studied. The experimental treatments were incorporation of urea into the plough layer at 250 kg N ha-1 by two applications (UI250), band application of urea at a depth of 8 cm at 75 kg N ha-1 plus incorporation of urea into the plough layer at 75 kg N ha-1 (UB150), band application of polyolefin-coated urea at a depth of 5 cm at 150 kg N ha-1 (CB150), and a control (without N application). N2O fluxes from UI250 and UB150 peaked following the incorporation of supplementary fertilizer, and declined to the background level after that, while the N2O flux from CB150 was relatively low but remained at a constant level until shortly after harvest. Accordingly, the total N2O emissions during the whole cultivation period from the three treatments were not significantly different. The fertilizer-derived N2O-N losses from UI250, UB150 and CB150 were 0.15%, 0.27% and 0.28% of the applied N, respectively. However, it was suggested that, due to the low plant N recovery, UI250 had a significantly larger potential for indirect N2O emission than the other treatments. On the other hand, NO emissions from UI250 and UB150 were 12 times higher than that from CB150, and the fertilizer-derived NO-N losses from the three treatments were 0.16%, 0.27% and 0.026% of the applied N, respectively. Significant NO fluxes were detected only when urea-N fertilizer was surface-applied and incorporated into plough-layer soil.