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Review

Nitrous Oxide Production and Mitigation Through Nitrification Inhibitors in Agricultural Soils: A Mechanistic Understanding and Comprehensive Evaluation of Influencing Factors

by
Sandeep Kumar Malyan
1,*,
Damini Maithani
2 and
Vineet Kumar
3
1
Department of Environmental Studies, Dyal Singh Evening College, University of Delhi, New Delhi 110003, India
2
Department of Natural Resource Management-Plant Microbiology, College of Horticulture, Sadar Vallabhbhai Patel University of Agricultural and Technology, Meerut 250110, India
3
Department of Microbiology, School of Life Sciences, Central University of Rajasthan, Ajmer 305817, India
*
Author to whom correspondence should be addressed.
Nitrogen 2025, 6(1), 14; https://doi.org/10.3390/nitrogen6010014
Submission received: 5 November 2024 / Revised: 9 February 2025 / Accepted: 25 February 2025 / Published: 9 March 2025
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Abstract

:
Nitrous oxide (N2O) is a potent greenhouse gas, and agriculture represents more than fifty percent of total anthropogenic emissions. The production of N2O in soil is biogenic through nitrification, denitrification, chemonitrification, nitrifier denitrification, etc., which are processes influenced by the soil pH, temperature, moisture, oxygen concentration, organic carbon, and soil nitrogen. Higher N2O emissions from the soil result in lower nitrogen use efficiency and higher environmental pollution in terms of global warming. Therefore, an understanding of different pathways for N2O production in soil and the affecting factors is essential to mitigate N2O emissions from soil to the atmosphere. Nitrification inhibitor application has been reported in many studies, but the impact of nitrification inhibitors in different perennials (orchards) and biennials (rice, wheat, maize, etc.) is not lacking. In this study, we develop an understanding of different N2O production pathways and different influencing factors. The role of the different nitrification inhibitors was also developed to achieve low N2O emissions from soils to the atmosphere.

1. Introduction

Nitrous oxide (N2O) is a trace, colourless, non-flammable greenhouse gas that is commonly known as laughing gas or nitrous or dinitrogen monoxide, and it was discovered by English chemist Joseph Priestley in 1772. Tropospheric N2O presents two environmental concerns; first, the global warming potential (GWP) of N2O is 273 times higher compared to the unity (1) of carbon dioxide (CO2) on a 100-year scale [1]. Second, N2O is long-lived (lifetime of 114–120 years), is a highly stable gas in the stratosphere, and was found to be a potent stratospheric ozone scavenger [2]. In the field of medical sciences, N2O is widely used as an anesthetic gas. Although the concentration of N2O in the atmosphere is in trace amounts due to high GWP, it significantly contributes to global climate change.
Global climate change is the outcome of the enhanced greenhouse effect (GHE), and N2O plays a vital role in enhancing the process of the GHE. At the beginning of the 19th century, the atmospheric concentration of N2O was ~277 ppb (21.55% lower than in 2024) and has risen to above 336.7 ppb at present (Figure 1). The agricultural ecosystem contributes the most to anthropogenic atmospheric N2O emissions, and the main source of N2O emissions from agriculture is the application of nitrogen (N) fertilizers [1,3,4,5,6]. Reay et al. [7] stated that N2O emissions from soils after N fertilizer application accounts for ~60% of total global N2O emissions. The flux of N2O emissions from agricultural soil is affected by several factors, such as the types of N fertilizer applied, soil texture, soil pH, soil organic carbon (SOC), soil moisture, soil temperature, and microbial activity [1,8,9,10]. The biological activity of both nitrifying and denitrification microorganisms under aerobic/semi-anaerobic and anaerobic conditions, respectively, plays a key role in N2O production [1]. Globally, for the production of different crops, different types of N fertilizer are used, and the applied N fertilizer undergoes hydrolysis into plant-utilizable N species (nitrate and ammonia) and N2O gas [11]. The applied urea is completely hydrolyzed within two days in soil with a pH of 8 or higher [11]. The rate of hydrolysis can be reduced using nitrification inhibitors, which reduce the biological activity of nitrifying microorganisms. The mitigation of N2O emissions without affecting the production of the agricultural system is a global challenge. In a few previous studies, the mechanisms of N2O production in soil have been reviewed [8,12,13]; however, the production and mitigation of N2O from agricultural systems, especially through nitrification inhibitors, have not been reviewed in a comprehensive study. Therefore, in this study, we develop a better understanding of the different processes involved in N2O production and identify factors affecting N2O production and the role of nitrification inhibitors in mitigating atmospheric N2O emission in agricultural soil.

2. Methodology

This study gathered information about the nitrous oxide processes in soil, different affecting factors, nitrification inhibitors, and other mitigation options from Scopus, MDPI, PubMed, the Web of Sciences, Google Scholar, Science Direct, Springer, Wiley, etc. We used search terms related to nitrogen oxides, agricultural soil, nitrification inhibitors, and mitigation, and we applied inclusion and exclusion criteria to select relevant articles. After screening the abstracts and the titles of the identified articles, we further reviewed the full texts to extract relevant information. In total, 190 articles from each section/sub-section were collected, and data from this collection were used for analysis, interpretation, figure formation, and tabulation.

3. Nitrous Oxide Production Processes

N2O production involves biogenic processes in natural and artificial ecosystems, and a diverse range of microbes play a significant role in the emission of N2O from soil (Figure 2). Nitrification and denitrification are primary biological processes that utilize inorganic nitrogen compounds, and these two primary processes contribute approximately 70% to global N2O emissions [15]. Under aerobic and anaerobic soil conditions, N2O emissions from the soil are the result of the nitrification and denitrification processes that occur simultaneously [9,16]. Biotic (microbial population) and abiotic (oxygen percentage in pore space, fertilizer application, irrigation, soil pH, soil texture, etc.) factors determine whether to undertake the nitrification or denitrification process while dominating a net flux of N2O in the atmosphere [16]. Heterotrophic nitrification, codenitrification, and dissimilatory nitrate to ammonia are considered microbial processes that play a significant role in biological N2O production [9].

3.1. Nitrification

Nitrification is the aerobic biological oxidation of ammonia (NH3) to nitrate (NO3−) with nitrite (NO2−) and N2O as an intermediate and byproduct. Nitrification is the dominant biological process that governs N flow in agriculture. Like other biological processes, nitrification is also quite sensitive to environmental conditions such as soil temperature, pH, moisture, rainfall, type of N fertilizer applied, irrigation, crop, etc. [17,18,19]. The nitrification process is involved in environmental pollution by the leakage of highly reactive gaseous product N2O. The production of this reactive N species (N2O) by nitrifying microorganisms has been reported by Corbet [20]. Corbet [20] observed that NH4+ or NH2OH (hydroxylamine) was converted to nitrite by unidentified microorganisms and during this conversion, the N2O is produced. Bremner [21] quoted that, in 1962, the capacity of Nitrosomonas europaea bacteria for the production of N2O was published by Falcone et al. [22]. There are two distinct pathways of nitrification that were carried out by distinct types of microorganisms.

3.1.1. Autotrophic Nitrification

Ammonia Oxidation

The oxidation of ammonia (NH3) or ammonium ion (NH4+) to nitrite is the first step of autotrophic nitrification that is carried out by ammonia-oxidizing bacteria (AOB). The oxidation of ammonia is carried out by two different enzymes known as ammonia monooxygenase (amoABC) and hydroxylamine oxidoreductase (hao) [23]. The activity of AOB in low-N soil is higher as compared to the N-rich soil [23]. In autotrophic nitrification, the reactive gaseous spices (N2O) are produced at the intermediate step of hydroxylamine in the conversion of ammonia to nitrite.

Nitrifier Denitrification

Nitrifier denitrification is an alternative pathway of nitrification, and in this pathway, the oxidation of ammonia to nitrite is followed by the reduction of nitrite to nitrous oxide or molecular nitrogen. Nitrifier denitrification is considered a coupled nitrification–denitrification pathway that involves both oxidation (ammonia to nitrite) and reduction (nitrite to N2O or N2). The autotrophic ammonia oxidizer is the microorganism that carries out the sequences of nitrifier denitrification pathway in soil [23]. The completed reduction of nitrite to N2 is a rare phenomenon in nitrifier denitrification [24]; therefore, the emission of N2O is more common as a byproduct than N2 emissions. Soil with low organic carbon and high N content under low oxygen pressure contributes to a higher rate of N2O emission fluxes [25]. Poth and Focht [26] observed that N2O is produced by Nitrosomonas europaea cultures only under low-O2-concentration environments. Kool et al. [27] reported that the N2O fluxes through the nitrifier denitrification process significantly in arable and grassland soils.

3.1.2. Heterotrophic Nitrification

Heterotrophic nitrification is generally carried out by fungi in low-pH soil, and in this process, the heterotrophic nitrifier uses soil organic carbon as energy and carbon sources [28]. In both nitrifier denitrification and heterotrophic nitrification, the substrate, intermediate, and end products of both processes are the same, but the enzymes involved make these processes different. The amount of N2O flux emitted by the heterotrophic nitrification process is considered minor, but under low pH, high organic carbon, and abundant O2 concentration, the N2O fluxes are significantly higher. Forest soils generally have such an environment (low pH, high organic matter, and high O2 concentration); therefore, the heterotopic nitrification process is dominant in acidic forest soils [28].

3.2. Factors Affecting the Nitrification Process

The rate of nitrification in the soil is mainly influenced by soil pH, moisture, the concentration of ammonium, O2, carbon dioxide (CO2), fertilizers, and temperature [3,8,29,30]. Some of the important factors are explained below.

3.2.1. Soil pH

Soil pH is a crucial factor for the nitrification process, and it occurs in a wide range of soil pH [29,30], although the pH range from 6.5 to 8.5 is considered optimal [29]. Zebarth et al. [31] conducted a laboratory experiment to investigate nitrification under acidic conditions. The authors reported that the process of nitrification occurred in an acidic pH range from 3.97 to 5.29, but the activity of the nitrification enzyme was higher in the pH range of 4.5–5.2 [31]. In another four-year field experiment carried out by Kyverga et al. [32] in maize (Zea mays L.) soil, the authors found that 89% of total nitrification occurred in the soil with a pH less than 7.5. It was also found that urea fertilization influences both the soil pH and nitrification activity. In a paddy field experiment, Jiang et al. [33] found that a soil pH of 5.6 (acidic soil) and 8.2 (alkaline soil) shows high nitrification activity due to the dominant population of ammonia oxidation archaea (AOA) and ammonia oxidation bacteria (AOB), respectively. It is reported that the nitrification rate in high-pH soil (alkaline soil) is due to AOB rather than AOA [29,33,34,35].

3.2.2. Soil Temperature

Soil temperature is a key influencing factor in the nitrification process in agricultural soils [35,36,37,38]. However, there are contradictory findings about soil temperature and nitrification processes. Soil temperature affects the population of AOA and AOB, which regulate the nitrification process in soil. Gubry-Rangin et al. [35] conducted an incubation study to determine the influence of temperature range (20 °C, 30 °C, and 40 °C) on the nitrification process. The net rate of nitrification was higher at 20 °C or 30 °C, and no nitrification activity was observed at 40 °C [35]. Osborne et al. [38] conducted a laboratory experiment with three different temperature levels (4 °C, 12 °C, and 25 °C) and found that the nitrification process is not correlated with temperature. Maag and Vinther [30] observed a negative correlation between N2O produced through the nitrification process with soil temperature. N2O produced through the nitrification processes was 0.66% at 5 °C and it reduced to 0.23% at 20 °C, which shows a significant reduction. However, recently, in another incubation study, Lai et al. [37] found that nitrification and denitrification rise with an increase in soil temperature and the highest fluxes of N2O were observed between 35 and 40 °C. The ratio (N2O/N2) decreased from more than 4 at 35–40 °C to 0.5 at 45 °C [37], which shows that the activity of nitrification enzyme is suppressed around 45 °C soil temperature. Based on the above findings, it can be concluded that, in general, the process of nitrification has a positive correlation with temperature; however, temperatures higher than 40 °C have a negative correlation.

3.2.3. Soil Moisture and Oxygen Concentration

Soil moisture content significantly influences nitrification [36,39,40,41,42,43]. Usually increasing the soil moisture content results in decreased O2 concentration in soil. In agriculture, the pore spaces within the soil are occupied by water molecules just after irrigation or in the case of optimum rainfall. Therefore, the O2 concentration within the soil is reduced and it restricts the activity of nitrifier bacteria since O2 is essential for these bacteria. It was found that when the water-filled pore space (WFPS) is more than 60%, it suppressed nitrification [40]. The percentage contribution of heterotrophic nitrification and autotrophic nitrification has been measured in wheat acidic soil (pH-4.5, but high organic carbon-6.2%) by Liu et al. [42] in a laboratory study (Figure 3). The percentage contribution of heterotrophic nitrification at 50% and 70% WFPS at low temperatures (15 °C) was 69.2% and 49.9% (Figure 3) in gross nitrification processes. The rate of autotrophic nitrification increases exponentially at high temperatures (25 °C and 35 °C) as compared to low temperatures (15 °C), and the impact of moisture content on nitrification is comparatively reduced (Figure 4). The gross contribution of autotrophic nitrification at 50% WFPS (25 °C and 35 °C) and 70% WFPS (25 °C and 35 °C) is more than 92% of total nitrification (Figure 3). In another study, Maag and Vinter [30] investigated the impact of soil moisture on the N2O produced through the nitrification process. The rate of the nitrification process increased with soil moisture, and the percentage of N2O produced increased from 0.28% at 40% field capacity to 0.62% at 100% field capacity [30]. Based on the above findings, it can be concluded that soil moisture content has a positive correlation with nitrification processes.

3.3. Denitrification

Denitrification is an anaerobic process that sequentially reduces nitrate (NO3−) to nitrogen (N2) (Figure 4) via nitrite (NO2−) and the gases nitrous oxide (N2O) and nitric oxide (NO) [44]. The denitrification process plays a significant role in returning fixed soil nitrogen to the atmosphere in the form of nitrogen oxide. Out of all N the fertilizer applied in agricultural agroecosystems, up to 30% is lost by the denitrification process, therefore reducing nitrogen use efficiency (NUE) and thereby limiting the availability of nitrogen to plants [9,45]. Ammonium-based fertilizer instead of nitrate-based fertilizer reduces such losses as the nitrate produced by the nitrification of ammonium is often directly denitrified.
In complete denitrification, nitrate is reduced to N2 (Figure 4), while in incomplete denitrification greenhouses, N2O can be the product emitted from the soil to the atmosphere (Figure 4). The end product of denitrification processes depends on several biotic and abiotic factors.

3.3.1. Oxygen

Denitrification is an anoxic process, and the availability of O2 has a significant influence on the process. Oxygen concentration in soil depends upon soil water content to regulate the rate of O2 diffusion in soil. Higher water content in soil acts as a barrier to O2 diffusion [46]. Weier et al. [47] found that water-filled pore space (WFPS) enhanced the denitrification rates in soils. Several scientific reports [5,36] have observed that N2O emission is higher just after irrigation or rainfall. After irrigation or rainfall, the WFPS may be the most important abiotic factor that increases the rate of denitrification. The presence of O2 suppresses the activity of denitrification enzymes by regulating the flow of electrons [44]. N2O reductase is highly sensitive to O2 and it is suppressed under aerobic soil environment.

3.3.2. Soil pH

Nearly all biological processes are derived from soil pH, and it has been demonstrated that soil pH plays an important role in denitrification through enzyme activity [48,49,50]. A soil pH range of 7.0–8.0 is considered the optimum range for denitrification in soils [44,49,51]. Soil pH is the master variable factor that drives the emissions of the gaseous product (mainly N2 and N2O) from soils. Several studies demonstrated that under acid soil pH, N2O is a predominate gaseous product emitted from soil [52,53] due to the impairment of N2O reductase. Peterjohn [53] found that the activity of the denitrifying enzyme was highest at pH 7.0 in the desert soil of southwestern USA. The activity of the denitrifying enzyme is reduced by 50% if the pH of the soil rises above 8.0 and falls below 6.0 [53]. Soil pH affects the microbial community and the availability of organic carbon, mineral nitrogen, and other soil minerals [19,51]. Microbial groups are affected at proportional and community structural levels depending upon the prevailing soil pH condition of the region. Knowles et al. [51] quoted that in acid peat, low pH (below 3.5) was the only factor that suppressed the processes of denitrification. Soil with high O2 concentration (aerobic soil) with low pH prevented the complete denitrification and resulted in an increased proportion of N2O in the total gaseous product evolved from the soil [51].

3.3.3. Carbon

Soil organic carbon (SOC) is considered a major driving factor of denitrification [44,54,55]. The mineralization of SOC provides nitrate and reduces the soil redox (Eh) potential [55]. In denitrification (low-O2 environment), the availability of C is important, as C and nitrate act as electron donors and acceptors, respectively [56]. In several studies, it was demonstrated that C plays a significant role in denitrification in soil [57,58,59]. In the presence of a C-rich environment, the ratios of N2O: N2 gaseous product emission during denitrification are reduced [44,47,60], thus resulting in a lower emission of potent greenhouse gas (N2O) to the atmosphere. Both the quality and quantity of SOC regulate the denitrification directly or indirectly. Denitrification rates are usually higher in the rhizospheric zone of the plant as compared to bulk soil a few millimetres away from the plant [54]. A rhizospheric zone is a C-rich zone that supplies electrons for nitrate reduction, and it supports the denitrification microbial population as plant roots utilize O2 present in the soil pore space and create anoxic zones [54].

3.3.4. Nitrogen

During denitrification, appropriate nitrogen (NO3−) is used as a terminal electron acceptor under limited O2 conditions in soil. Several studies have been carried out that have demonstrated that the application of N fertilizers in soil enhanced the rate of denitrification [54,61,62,63,64,65]. N amendments affect the emission of both the N2O and dinitrogen (N2). A high soil nitrate (NO3−) concentration reduces the conversion of N2O to N2 and thus results in the higher emission of N2O to the atmosphere. The rhizosphere zone of plants emits less N2O and more N2 as compared to bulk soil. In the rhizospheric zone, there is competition between denitrifying microorganisms and plants for a similar substrate (NO3−), and, therefore, it results in lower N2O emissions and high N2 emissions.

3.3.5. Temperature

nDenitrification is an enzymatic process, and it is affected by temperature directly. Enzyme activity increases exponentially within the optimum range of temperature. O2 diffusion, solubility, and consumption by microbial respiration are completely temperature-dependent processes. Denitrifier microorganisms are active in a wide range of temperatures, namely 2.7 to 50 °C, but 30 °C is considered the optimum temperature for their activity [54].

3.4. Other Biological N2O Production Processes in Soil

3.4.1. Dissimilatory Nitrate Reduction to Ammonium (DNRA)

DNRA is also known as nitrate/nitrite ammonification, in which nitrate is reduced to ammonium by both the bacteria and fungi in the soil [66]. DNRA is the second most important biological nitrate-reducing process after denitrification. Microorganisms oxidize the SOM using nitrate as an electron acceptor instead of oxygen. In DNRA, the nitrate is reduced to nitrite and then to ammonium (NO3− → NO2− → NH4+) [55,67,68]. The nrfA gene is responsible for the reduction of nitrite to ammonium in DNRA [44]. In DNRA, at the nitrite reduction stage (Figure 5), N2O is produced as a byproduct [69] and is considered a detoxification mechanism of DNRA. N2O (potent GHGs) produced during DNRA cannot be further reduced to N2 and contribute to global warming (Figure 5). DNRA is a strictly anaerobic process and thus favours the denitrification process under a high C/N ratio [9,70,71]. Both denitrification and DNRA can occur simultaneously under an anaerobic soil environment, but tropical paddy soil environments favour DNRA [9,72]. Yin et al. [73] demonstrated that DNRA occurred significantly if the C/NO3− ratio was above 12. Silver et al. [71] reported that the DNRA rates in tropical upland soil were three times higher than rates of denitrification and that it accounted for up to 70% of total N pool turnover.
Environmental factors such as soil redox potential, nitrate availability, liable organic carbon, soil pH, microbial population, and temperature affect the rate of DNRA [54,69,72]. The DNRA process occurs in low- or no-O2 concentrations, but it is less sensitive to O2 dynamics unlike the denitrification process [44].

3.4.2. Codenitrification

The potential of certain organisms (mainly fungi and bacteria) to consume co-substrate denitrification is termed a codenitrification process [74,75,76]. In this process, they utilize totally different (product for denitrification pathway) nitrogen compounds such as amines, hydrazine (H2N-NH2), hydroxylamine (NH2OH) salicylhdroxamic acid (C7H7NO3), and NH4+ as co-metabolizers to produced gaseous (N2 and N2O) N product [75,76]. Codenitrification has been measured in agricultural and grassland soils and it accounts for up to 92% of N2 flux in grassland [75,76,77]. However, the main source of N2O flux in grassland is denitrification, which always has higher N2O than the N2 flux produced by codenitrification [9]. In this process, one N atom from NO (nitric oxide) or N2O and one N atom from another co-substrate combine to form dinitrogen (N≡N).
The process of codenitrification is influenced by environmental conditions, mainly oxygen availability, soil pH, and types of co-substrates. Since the codenitrification process involves the reduction of N compounds, the anaerobic environment is, therefore, considered the most favourable. Recently, a few studies have revealed that some bacterial and fungal species can also perform codenitrification even in low-O2 environments. The variability of O2 in soil affects the process of codenitrification, and the availability of O2 in the soil is inversely proportional, i.e., higher soil O2 concentration suppresses codenitrification and vice versa [74,75]. In their comprehensive review, Spott et al. [75] concluded that a soil pH that is weakly acidic (range of 6.0–7.0) or weakly alkaline (range of 7.0–9.0) is considered optimum for codenitrification.

3.4.3. Nitrate Assimilation

The fixing capacity of dinitrogen is limited to specific species of plants, fungi, and bacteria only. As all plants are unable to fix atmospheric N2, they assimilate nitrate or ammonia for their development, and the process of converting inorganic N to organic N is known as nitrogen assimilation [78]. Nitrate (NO3−) assimilation is a two-step process: assimilated NO3− reductase (ANR) followed by nitrite reductase to ammonium. Ammonium ions are directly assimilated by plants. Smart and Bloom reported that N2O is emitted from wheat leaves during nitrate assimilation. The photo assimilation of NO3− in the chloroplast of leaves produced N2O, and it does not have any correlation with soil microbial activity.

3.4.4. Chemodenitrification

There is different evidence that different N species (nitrite) are produced during the denitrification and nitrification process in soil [79,80]. The chemical reduction of this N species catalyzed by Fe (II) may produce N2O gas (Figure 6), and this process is termed chemodenitrification (cDNF) [79,80]. The process of cDNF occurs in acidic soil such as in forest (pH < 5) soil [70]. The production of N2O decreased with a reduction in soil pH [70,81]. Kesik et al. [81] report that the cDNF process contributed up to 62% of total gaseous nitrogen oxide production, but the contribution of N2O was negligible (0.8% only) in acidic soil (pH, 3.0).

4. Role of Nitrification Inhibitors (NIs) in Nitrous Oxide Emissions from Soil

Nitrification inhibitors (NIs) are the biological and artificial compounds that retard the functioning of bacteria through which ammonium is converted to nitrate. There are several reports that have suggested that the mixture of NO3− and NH4+ is essential for the ideal growth and development of the plants [3]. Therefore, if the application of NIs halts the nitrification process in the soil for some time, then the concentration of NH4+ will be increased for a longer duration in the soil, which may help in maintaining a mixture of NO3− and NH4+ in soil. The use of commercial NI compounds in the agricultural system increased dramatically in the scenario of global warming due to their better nitrogen use efficiency (NUE) and N2O emission mitigation potential [3]. The list of commonly used commercially or patently available NIs is shown in Table 1.
The application of NIs is beneficial globally in cereal, orchards, fodder, and horticulture crops [3,82,83,84,85,86,87,88]. NIs with nitrogen fertilizer basically increased NUE and crop yield and reduced N2O emission and NO3− leaching to groundwater as compared to nitrogen fertilizer alone. NIs affect the nitrification process, and they also affect biological, chemical, and physical processes of nitrogen transformation in soil (Table 2).
The efficacy of NIs depends on several factors such as soil texture, soil pH, soil organic matter, soil temperature, type of fertilizer applied, irrigation, etc. [89,90,91,92]. An NI is more effective in soil with little texture (such as sand) as compared to heavily textured soil (such as clay). In one incubation study, Barth et al. [91] found that the DMMP nitrification inhibitor has more efficacy in sandy soil than in loamy soil. The effectiveness of NIs in a cold climate is higher as compared to a warmer climate. Irigoyen et al. [93] studied the impact of soil temperature on the efficiency of two widely used NIs (DCD and DMMP). They conducted the 105-day incubation study at temperatures of 10 °C, 20 °C, and 30 °C and observed that the effectiveness of NIs decreased significantly with an increase in temperature [93]. The significance of NI application varies depending on the environment, crop, and soil properties. Roles and NI significance in some of the important agricultural and horticulture crops are discussed below:
Table 1. Different nitrification inhibitor compounds used in different studies.
Table 1. Different nitrification inhibitor compounds used in different studies.
S. NoNitrification InhibitorsType (Biological or Chemical)References
011,9-decanediolBiological Lu et al. [82]
02Polyaspartic acidPolymer materialYang et al. [94]
033,4-dimethylprazol phosphate (DMPP)ChemicalZhao et al. [95]; Taghizadeh-Toosi et al. [96]; Bozal-Leorri et al. [97]; Muller et al. [98]; Huerfano et al. [99]; Barrena et al. [100]
04DimethylphenylpiperaziniumChemicalPeixoto and Petersen [101]; Affendi et al. [102]
05PronitridineChemicalNelson, [103]
06NitrapyrinChemicalTariq et al. [104]; Tao et al. [105]; Khodabin et al. [106]; Mirkhani et al. [107]; Peixoto and Petersen [101]; Niu et al. [108]
07Dicyandiamide (DCD)ChemicalLi et al. [109]; Wang et al. [110]; Qu et al. [111]; Yaru et al. [112]; Ren et al. [113]
08Neem cakeBiologicalPathak and Bhatia [114]
09Neem oilBiologicalChakraborty et al. [115]; Pathak and Bhatia [114]
10NiminBiologicalDatta and Adhya [85]
11ThiosulphateChemicalPathak and Bhatia [114]
123,4-dimethyl pyrazole succinic (DMPSA)ChemicalHuérfano et al. [99]
13KaranjinBiologicalPaul et al. [84]; Datta and Adhya [85]
14Chlorinated pyridineChemicalMa et al. [25]
15S-benzylisothiouronium butanoate (SBT-butanoate)ChemicalBhatia et al. [116]
16S-benzylisothiouronium furoate (SBT-furoate)ChemicalBhatia et al. [116]
17Mentha spicata oilBiologicalPatra et al. [117]
18Calcium carbideChemicalMalla et al. [86]
19CarbofuranChemicalSahrawat [29]
20AminopurineChemicalBharati et al. [118]
21Ammonium thiosulphateChemicalBharati et al. [118]
22PyridineChemicalBharati et al. [118]
23Sodium azideChemicalBharati et al. [118]
24PyrazoleChemicalPeixoto and Petersen [101]
254-Methyl-1-(prop-2-yn-1-yl)-1H-1,2,3-triazole (MPT)ChemicalYildirim et al. [119]
26Phosphate rock and epoxy resin-coated ureaChemicalGe et al. [112]
27Methyl 3-(4-hydroxyphenyl) propionateBiologicalHuang et al. [120]; Lan et al. [121]
283-methylpyrazole 1,2,4-triazole (Piadin)ChemicalMuller et al. [98]
29eNtrenchChemicalWood et al. [122]
304-amino-l,2,4-triazoleChemicalAnwar et al. [123]
312-chloro-6-(trichloromethyl) pyridineChemicalLi et al. [124]
32Sugarcane root exudateBiologicalMawan and Kaewpradit [87]; Mawan and Kaewpradit [125]
33Oxalic acidBiologicalWang et al. [126]
34Protocatechuic aldehydeBiologicalWang et al. [126]
341,9-decanediolBiologicalDongwei et al. [127]
35Leymus chinensisBiologicalWang et al. [126]
36LimusChemicalPaul et al. [84]
37Moringa (Moringa oleifera Lam) seed extractBiologicalYang et al. [128]
38Sorghum roots releaseBiologicalZhang et al. [129]
Table 2. Processes affected by nitrification inhibitor application other than nitrification in soil (adapted and updated from Sahrawat [29]).
Table 2. Processes affected by nitrification inhibitor application other than nitrification in soil (adapted and updated from Sahrawat [29]).
Biological Processes
  • Denitrification.
  • Nitrous oxide production.
  • Immobilization and mineralization.
  • Urea hydrolysis.
Physical and chemical processes
  • Ammonia volatilization.
  • Ammonium fixation.
  • Nitrogen transport and movement in soil.

4.1. Mitigation of Nitrous Oxide Emissions Through Nitrification Inhibitors in Wheat

Globally, the area under wheat (Triticum spp.) cultivation is 218.54 M ha, with 771.72 million tonnes of production in 2017 [130]. Different countries follow different management practices for wheat cultivation. Wheat is a self-pollinating crop and therefore has many distinct regional and local varieties [131]. It is food for both humans (flour, bread, pasta, noodles, etc.) and livestock. Biofuel and alcoholic beverages are also produced from wheat through fermentation [131]. Wheat demand for food and fodder is increasing with time. For higher wheat production, several high-yielding cultivars have been developed around the world, and most of them are high-N fertilizers demanding. To fulfil the high demand of N of high-yielding cultivars, a high rate of N-based fertilizers is applied. Some portion of applied N fertilizers is lost in the form of N2O emissions through the nitrification process. The application of NIs in combination with N fertilizers has a worthy prospect for reducing N2O cumulative emissions as compared to N fertilizers, and it has been documented in several studies organized in Table 3.
N2O emission mitigation as compared to the conventional methods through NI application in wheat crops are reported globally (Table 3). Recently, Recio et al. [132] in Spain reported a 71.29% reduction in cumulative N2O emission as compared to control by applying DMPSA (Table 3). Products of a few plants such as neem (Azadirachta indica), Karanj (Pongamia glabra), Mint (Mentha spicata), Sweet wormwood (Artemisia annua), and tea (Camellia sinensis) have NI properties [133,134], and, therefore, they can be used as biological nitrification inhibitors (BNIs). India is using NOCU instead of simple urea, and the Government of India has banned the use and sale of uncoated urea in India. The efficiency of NOCU in the mitigation of N2O in wheat was in the range of ≈5–21% in India [86,114,135,136] (Table 3). Li et al. [137]) stated that the use of NI-NBPT-coated (0.045% w/w) urea had no impact on N2O emissions from Australian wheat soil (Table 3). The DMPP-coated (0.16% w/w) urea reduced the cumulative N2O emissions by 33.50% as compared to control (uncoated urea) in Australian wheat (Table 3). The application of NBPT and DMPSA in combination at the rate of 0.80% and 0.35% of total N applied efficiently reduced N2O emissions by 33.59% as compared to control (Table 3). Malla et al. [86] observed 21.21 and 27.27% reductions in total N2O emissions by the application of neem cake and thiosulphate at the rate of 10% of total N applied, respectively (Table 3). Biochar application at the rate of 7.5 and 15 t ha−1 increased the cumulative N2O emissions by 9.43 and 34.22%, respectively, as compared to control (Table 3). However, the application of biochar with NI showed a reduction in N2O emissions as compared to control [138]. Guardia et al. [139], recorded a reduction of N2O emissions by 37.52% by the application of urea and DMPSA mixture (urea-99.2% +0.8% DMPSA) over urea only (Table 3). Bhatia et al. [116] applied 10% N in the form of DCD, SBT-butanoate, and SBT-furoate nitrification inhibitory in wheat crops and observed 9.51%, 9.00% and 13.50% reduction in N2O emissions, respectively, as compared to control (Table 3). Malla et al. [86] studied the impact of two BNI (neem cake and neem oil) and four chemical NI (thiosulphate, hydroquinone, calcium carbide, and DCD) on N2O emission from wheat soils (Table 3). The reduction by BNI and chemical NI ranged from 15.15 to 21.21% and 0.6.06 to 28.79%, respectively [86]. Majumdar et al. [140] applied nimin- and neem oil-coated urea at the rate of 120 kg N ha−1 and recorded that N2O reduction by nimin-coated urea was 30.07% and neem-coated urea was 4.90% as compared to the same dose of urea applied as control (Table 3).
The efficacy of NIs is affected by management practices, soil texture, microbial populations, soil organic matter, etc. [101,141]. Tillage management has a significant impact on the efficiency of the NIs on N2O emission [101]. Peixoto and Petersen [101] investigated the efficacy of different NIs under tillage management and observed that the higher N2O emission under zero tillage is compared to ploughing management. A soil surface with zero tillage has more organic matter and residues that enhance the sorption of NIs and result in the lower availability of NIs in soil. On the other hand, in ploughed management practice, the applied NI (DMPP) reached the soil and halted the nitrification processes, resulting in lower N2O emissions [101]. Ribeiro et al. (2024) investigated the impact of different NIs (DCD, DMPP, and MP [3,4 Methypyrazo]) + TZ[Triazol]) on N2O under two soil textures (silt loam and loamy sand). The efficacy of NIs in loamy soil is higher than with the slit loam soil texture. The NIs DMPP, DCD, and MP + Triazol reduced total N2O-N emission by 80%, 56%, and 65%, respectively, in sandy soil texture, while the reduction in loamy soil texture was 70%, 46% and 59%, respectively [141].
Table 3. Mitigation of nitrous oxide emissions from wheat soil through nitrification inhibitors.
Table 3. Mitigation of nitrous oxide emissions from wheat soil through nitrification inhibitors.
Study LocationReferencesTreatment (Dose and Source)N2O EmissionMitigation (%)
ChinaZong et al. [142]Urea (U)977.6–1806.2 g N2O-N ha−1Control (C)
Urea (0.5% of urea-N by nitrapyrin) under elevated CO2-32.2–71.3
Urea (0.5% of urea-N by nitrapyrin) under elevated temperature-16.5–30.4
DenmarkPeixoto and Petersen [101]Pig slurry (PS) under ploughing0.15 kg N2O-N ha−1C
PS + DMPP under ploughing0.02 kg N2O-N ha−186.67
PS + DMPP under direct seeding0.08 kg N2O-N ha−146.67
PS + NP under ploughing0.07 kg N2O-N ha−153.33
PS + NP under seeding0.03 kg N2O-N ha−180.00
PS + Piadin under ploughing0.06 kg N2O-N ha−160.00
PS + Piadin under seeding0.05 kg N2O-N ha−166.67
GermanyNi et al. [143]Urea (U)710 g N ha−1C
U + DCD + 1H-1,2,4-Triazol (2% of Urea content m w/w)295 g N ha−158.45
Germany Guzman-Bustamante et al. [89]Calcium ammonium nitrate2.9 kg N2O ha−1Control
Calcium ammonium nitrate + DMPSA2.1 kg N2O ha−127.58
Pakistan Dawar et al. [144]Urea0.71 kg N2O ha−1Control
Biochar-6tons (B6)0.17 kg N2O ha−176.05
Biochar-12tons (B12)0.26 kg N2O ha−163.38
Urea + B60.54 kg N2O ha−123.94
Urea + B120.57 kg N2O ha−119.72
Urea + B6 + nitrapyrin (700 g ha−1)0.35 kg N2O ha−150.70
Urea + B12 + nitrapyrin (700 g ha−1)0.46 kg N2O ha−135.21
Canada An et al. [145]Urea–ammonium nitrate0.734 kg N2O-N ha−1Control
Urea–ammonium nitrate + DCD0.527 kg N2O-N ha−128.20
SpainRecio et al. [83]Control (120 kg N ha−1 by urea[U])498.8 g N ha−1Control
DMPSA (120 kg N ha−1, 99.2% by U, and 0.8% is DMPSA)143.2 g N ha−171.29
India Fagodiya et al. [135]Control (120 kg N ha−1 by U)0.98 kg N2O ha−1Control
DCD (120 kg N ha−1, 108 and 12 kg N ha−1 by U and DCD, respectively)0.7424.49
NOCU (120 kg N ha−1 by NOCU)0.7721.43
Australia Li et al. [137]Control (100 kg N ha−1 by Urea)80.9 g N2O-N ha−1Control
NBPT (100 kg N ha−1 U coated by 0.045% w/w NCPT)81.5 g N2O-N ha−1−0.74
DMPP (100 kg N ha−1 U coated by 0.16% w/w NCPT)53.9 g N2O-N ha−133.50
ChinaHe et al. [138]Optimal nitrogen (ON)- [125 kg N ha−1 by U] 1.59 kg N ha−1Control
ONB1-ON + Biochar (7.5 t ha−1)1.74 kg N ha−1−9.43
ONB2-ON + biochar (15 t ha−1)2.15 kg N ha−1−35.22
ONI-ON + DCD (0.5% w/w) + HQ (0.3% w/w)1.41 kg N ha−111.31
ONIB1-ONB1 + DCD (0.5% w/w) + HQ (0.3% w/w)0.80 kg N ha−149.69
ONIB2-DCD (0.5% w/w) + HQ (0.3% w/w)0.80 kg N ha−149.69
Spain Guardia et al. [139]Control (120 kg N ha−1 by U in one dose)421.65 g N ha−1Control
NBPT (120 kg N ha−1 by coated U in one dose)352 g N ha−117.69
DMPSA (120 kg N ha−1, 99.2% by U, and 0.8% is DMPSA)263.45 g N ha−137.52
NBPT + DMPSA (120 kg N ha−1, 98.15% by U, 0.8% is DMPSA, and 0.35% is DMPSA)280 g N ha−133.59
Nitrapyrin (120 kg N ha−1, 99.65% by U, and 0.35% by DMPSA)322.6 g N ha−123.49
Australia Jamali et al. [146]Control (172.5 kg N ha−1, 22.5 by DAP, and 150 by U)496 g N2O-N ha−1Control
DMPP (172.5 kg N ha−1, 22.5 by DAP, 150 by U + 17.6% dimethyl pyrazole solution in 1L of water and sprinkled on the soil surface)414 g N2O-N ha−116.53
China Ma et al. [147]CT-U (200 kg N ha−1)1.66C
CT-U + DCD (200 kg N ha−1, 97% by U, and 3% by DCD)1.1729.52
CT-U + CP (200 kg N ha−1, 99.76% by U, and 0.24% by CP)0.8548.80
NT-U (200 kg N ha−1)1.98C
NT-U + DCD (200 kg N ha−1, 97% by U, and 3% by DCD)1.3631.31
NT-U + CP (200 kg N ha−1, 99.76% by U, and 0.24% by CP)0.9253.54
China Liu et al. [43]Urea4.49 kg N ha−1C
DCD2.93 kg N ha−135
DMPP2.78 kg N ha−138
IndiaBhatia et al. [116]Control (120 kg N ha−1)778 g N2O-N ha−1Control
DCD (120 kg N ha−1, 90% by U and 10% by DCD)704 g N2O-N ha−19.51
SBT-butanoate (120 kg N ha−1, 90% by U and 10% by SBT-butanoate)708 g N2O-N ha−19.00
SBT-furoate (120 kg N ha−1, 90% by U, and 10% by SBT-furoate)673 g N2O-N ha−113.50
IndiaMalla et al. [86]U (120 kg N ha−1)0.66 kg N2O ha−1Control
U (120 kg N ha−1) + HQ (120 kg N ha−1)0.62 kg N2O ha−106.06
U (108 kg N ha−1) + neem cake (12 kg N ha−1)0.52 kg N2O ha−121.21
U (120 kg N ha−1) + thiosulphate (12 kg N ha−1)0.48 kg N2O ha−127.27
U coated with calcium carbide (120 kg N ha−1)0.58 kg N2O ha−112.12
NOCU (120 kg N ha−1)0.56 kg N2O ha−115.15
U (108 kg N ha−1) + DCD (12 kg N ha−1)0.47 kg N2O ha−128.79
China
(Pot experiment)		Boeckx et al. [148]U (345 kg N ha−1)2.11 mg N2O-N kg−1 soilC
U+ HQ (0.3% of applied U)1.87 mg N2O-N kg−1 soil11.37
U + DCD (0.5% of applied U)1.64 mg N2O-N kg−1 soil22.27
U + HQ (0.3% of applied U) + DCD (0.5% of applied U)1.58 mg N2O-N kg−1 soil25.12
IndiaMajumdar et al. [140]U (120 kg N ha−1)1.43 kg N2O-N ha−1C
U + DCD (120 kg N ha−1, 85% by U, and 15% by DCD)1.09 kg N2O-N ha−123.78
Nimin-coated U (120 kg N ha−1)1.00 kg N2O-N ha−130.07
NOCU (120 kg N ha−1)1.36 kg N2O-N ha−14.90
U + thiosulphate (120 kg N ha−1, 90% by U, and 10% by thiosulphate)1.19 kg N2O-N ha−116.78
Note: DCD—dicyandiamide; HQ—hydroquinone; DMPSA—2-(3,4-diemthyl-1H-pyrazol-1-yl); AS—ammonium sulphate; NBPT—N-(n-butyl)thiophosphoric triamide; NOCU–neem oil-coated urea; CT—conventional tillage; NT—no tillage; CP—chlorinated pyridine; DMPP—3,4-dimethyl-1H-pyrazole phosphate; PS—pig slurry.

4.2. Role of Nitrification Inhibitors (NIs) in Nitrous Oxide Mitigation in Maize

The application of NIs for reducing N2O emissions from maize has been explored globally, including in India, the United States of America (USA), Canada, China, Spain, Indonesia, Thailand, and others (Table 4). NIs reduce cumulative N2O emissions to the atmosphere by inhibiting nitrification and decreasing nitrate availability for denitrification. Several studies have reported that chemical NIs (nitrapyrin, DCD, Hydroquinol, and DMPSA) and biological NIs (neem oil) have a significant reduction potential for N2O emissions (Table 4). Urea is coated with plant-derived extract such as neem oil and used as a biological NI for reducing N2O emissions [135]. In maize crops, the application of NOCU reduced N2O emissions by 12.92% as compared to urea application without any neem oil coating [108,135]. Nui et al. [108] studied the influence of adding the NIs nitrapyrin and biochar on N2O emissions from maize soils in China (Table 4). The addition of the NI nitrapyrin at the rate of 0.26% of the total N applied reduced N2O emissions. The application of the NIs nitrapyrin and biochar at 3, 6, and 12 t ha−1 reduced the N2O emissions by 20, 16, and 25%, respectively (Table 4). In one study conducted by Guardia et al. [139] in Spain, the authors recorded 21.92, 50.15, and 66.97% reductions in total N2O emissions from maize soil by the application of calcium ammonium nitrate (CAN), urea + NI (DMPSA), and CAN + NI (DMPSA), respectively, as compared to urea in sprinkler irrigation (Table 4). Neem oil coated on N fertilizers at a higher rate has a non-significant impact on N2O emission reduction [149]. Increasing neem oil content from 5 to 10% in the coating of N fertilizer enhanced the N2O emissions (Table 4). Pengthamkeerati and Modtad [149] reported that the reduction in N2O emissions by 10% neem oil-coated N fertilizer is 9.88% as compared to control, which was slightly lower than the reduction in N2O emissions (10.48% as compared to control) using 5% neem oil-coated N fertilizer (Table 4). In the same study, Pengthamkeerati and Modtad [149] reported that raising the chemical NI DCD from 5% to 10% of the total N fertilizer increased N2O reduction from 16.67% to 25.51% as compared to the control (Table 4). This indicated that the biological nitrification inhibitor (BNI) shows N2O reduction by mixing it up to the optimal limit, while the N2O emission reduction by chemical nitrification inhibitors is directly related to the amount of NIs in the mixture. Hadi et al. [150] observed that the application of DCD reduced the N2O emissions by 96.95% in Indonesian maize. Some authors [135,151] report that the application of organic fertilizers such as FYM shows higher N2O emissions as compared to inorganic fertilizers. The application of organic fertilizers and NIs has a lower N2O mitigation potential as organic fertilizers provide sufficient C, which stimulates bacterial (nitrifying and denitrifying) N2O production [151]. Based on the above discussion, it can be concluded that N2O reduction through inorganic NIs such as DCD is significantly higher than organic NIs such as neem oil. However, the role of DCD on the quality of grain and overall soil health still requires more attention before their global acceptance in food grain crops.

4.3. Nitrous Oxide Mitigation Through Nitrification Inhibitors in Rice

Rice is predominately grown in tropical regions in irrigated and rain-fed lowland environments. Standing water after root establishment is required for optimal economic yield [161]. Nitrogen (N) is another limiting factor for optimal rice production. The nitrification–denitrification process affected the nitrogen use efficiency (NUE) and the amount of N2O emissions from rice [3,155]. NIs are used to reduce N2O emissions and simultaneously enhance NUE by retarding the nitrification process (oxidation of NH4+ to NO3−) in the rich soil. There are several types of biological and chemical NIs (Table 1). Neem cake, neem oil, nimin, moringa seed extract, and karanjin are the major biological NIs used by researchers for reducing N2O emissions in rice (Table 5). DCD, thiosulphate, hydroquinone, calcium carbide, and nitrapyrin are commonly used chemical NIs in rice (Table 5). Guo et al. [162] used the nitrapyrin (5% w/w)-coated urea in rice and recorded a 39.99% reduction in cumulative N2O emissions compared to urea (Table 6). The application of NIs slows down the nitrification process in soil; therefore, the NH4+ ion concentration in soil lasts longer. As the duration of NH4+ concentration is prolonged in rice soil, this results in more utilization of NH4+ ions by rice plants. Jumadi et al. [155] recorded the efficiency of a BNI (neem cake) and chemical NI (DCD) in reducing N2O emissions from rice soil under the same dose of N fertilizer (Table 5). First, 5% of N was applied by BNIs and chemical NIs, and it was observed that N2O reduction by neem cake is non-significant, while the N2O emission reduction under DCD is significant (Jumadi et al. [155]). Datta and Adhya [85] stated that the N2O reduction by the application of nimin, karanjin, and DCD was 85.37%, 48.78%, and 20.98%, respectively (Table 5). In this study, the N2O mitigation by BNIs (nimin and karanjin) was considerably greater than by the chemical NI (DCD) (Datta and Adhya, 2014) (Table 5). Some of the previous studies conducted by Majumdar et al. [140], Ghosh et al. [163], Boeckx et al. [148], Malla et al. [86], and Li et al. [164] have also concluded that DCD can significantly reduce N2O emissions from rice soil (Table 5). Ghosh et al. [163] concluded that DCD application with urea, ammonium sulphate, and potassium nitrate reduced N2O emissions by 52.56%, 45.90%, and 10.28%, respectively (Table 5). The flux of N2O emissions is directly controlled by the N fertilizer applied as the concentration of N in soil affects the processes of nitrification and denitrification. Therefore, the mitigation of N2O can be controlled by the method of application [165,166]. Pattanaik et al. [166] carried out field experiments in rice for the investigation of the NI reduction through different modes of application and observed that a reduced dose of N fertilizer with NIs reduced N2O emissions to the atmosphere (Table 5). Based on the above discussion, it can be concluded that mitigating N2O flux through NIs is affected by the type of NI, dose, and even by the method of application.

4.4. Nitrous Oxide Mitigation Through NIs in Orchards, Grasslands, and Others

In orchards and grasslands, NIs are usually used in two methods, mixed with irrigated water (Fertigation) or mixed with N fertilizer in optimum doses. The injection of fertilizers in irrigation water is termed as Fertigation. In most Asian countries, fertilizer is usually broadcast in orchards and grasslands. Also in Asia, agricultural technology-leading countries such as Israel commonly use the Fertigation method in agricultural production. NIs are used in both the Fertigation and broadcasting of fertilizers for reducing nitrogen losses and enhancing agricultural production. The use of NIs such as DCD, DMPP, etc., is an effective approach to mitigate N2O emissions, and related studies have been summarized in Table 6. In one recent experiment, Vilarrasa-Nogué et al. [172] applied three levels of N fertilizer (25, 50, and 100 kg N ha−1) with and without the NI DMPP (1% of N total dose) and recorded the impact on N2O emissions from a peach orchard in Spain (Table 6). The soil acted as N2O sinks in the treatment of N (25 N kg ha−1) and DMPP (1% w/w of N) (Table 6). N2O emission reduction at 25, 50, and 100 kg N ha−1 along with 1% (w/w of N) of the NI DMPP was 111.2%, 44.67%, and 24.94%, respectively (Table 6), which indicates that the efficiency of the NI reduced with the increase in N dose. Cardenas et al. [173] investigated the effect of DCD on N2O emissions from grasslands at three different places in the United Kingdom (UK) (Table 6). The uniform dose of urea + DCD (320 kg N ha−1) was applied at Crichton, Drayton, North Wyke, Hillsborough, and Pwllpeiran experimental sites in the UK, and the cumulative reductions in N2O fluxes of 23.11%, 55.35%, 34.21%,73.78%, and 77.72%, respectively, were recorded as compared to urea (320 kg N ha−1) (Table 6). The application of different NIs for the reduction in N2O fluxes from vegetables has been documented in several studies [39,174,175,176]. The combination of urease inhibitor (NBPT, 0.003% of N) + NI (DCD, 0.31% of N) along with urea reduced N2O emissions by 65.87% over urea [176]. Treweek et al. [177] studied the effect of a livestock urine, biochar, and DCD mixture application on N2O emissions from fodder crops (Brassica) in the Canterbury region of New Zealand (Table 6). DCD addition in urine and urine plus biochar at the rate of 20 kg ha−1 reduced the N2O fluxes significantly by 65.31% and 54.14%, respectively [177]. The use of NIs in grassland soils, tea plantations, vegetable soils, and other soils improves the nitrogen fertilizer use efficiency, which ultimately, nitrogen loses in the form of nitrate to groundwater and N2O to the atmosphere.
Table 6. Dynamics of nitrous oxide emission from orchard, grassland, and other soils under nitrification inhibitors.
Table 6. Dynamics of nitrous oxide emission from orchard, grassland, and other soils under nitrification inhibitors.
References and Location [Crop]TreatmentN2O EmissionMitigation (%)
Li et al. [124] Jiangsu Province (China), Vegetable SoilUrea (U)0.47 mg N2O-N kg−1 soilC
U + BC0.21 mg N2O-N kg−1 soil55.32
U + DMPP0.12 mg N2O-N kg−1 soil74.47
U + BC + DMPP0.09 mg N2O-N kg−1 soil80.85
Tea SoilUrea (U)0.24 mg N2O-N kg−1 soilC
U + BC0.21 mg N2O-N kg−1 soil12.50
U + DMPP0.10 mg N2O-N kg−1 soil58.33
U + BC + DMPP0.11 mg N2O-N kg−1 soil54.17
Peach Soil (1 Year)Urea (U)0.13 mg N2O-N kg−1 soilC
U + BC0.15 mg N2O-N kg−1 soil−15.38
U + DMPP0.05 mg N2O-N kg−1 soil61.54
U + BC + DMPP0.06 mg N2O-N kg−1 soil53.85
Peach Soil (7 Years)Urea (U)0.18 mg N2O-N kg−1 soilC
U + BC0.20 mg N2O-N kg−1 soil−11.11
U + DMPP0.07 mg N2O-N kg−1 soil61.11
U + BC + DMPP0.08 mg N2O-N kg−1 soil55.56
Vilarrasa-Nogué, et al. [172]Aitona (Spain)
[Peach]		N25 (25 kg N ha−1)0.45 kg N2O-N ha−1C
N25+ DMPP (1% w/w of N)−0.05 kg N2O-N ha−1111.2
N50 (25 kg N ha−1)0.99 kg N2O-N ha−1C
N50 + DMPP (1% w/w of N)0.55 kg N2O-N ha−144.67
N100 (25 kg N ha−1)4.47 kg N2O-N ha−1C
N100 + DMPP (1% w/w of N)3.36 kg N2O-N ha−124.94
Cardenas et al. [173]Crichton (UK)
[Grassland]		Urea (U) (320 kg N ha−1)4.24 kg N2O-N ha−1C
U + DCD (320 kg N ha−1)3.26 kg N2O-N ha−123.11
Drayton (UK)
[Grassland]		U (320 kg N ha−1)1.00 kg N2O-N ha−1C
U + DCD (320 kg N ha−1)0.49 kg N2O-N ha−155.35
North Wyke (UK)
[Grassland]		U (320 kg N ha−1)3.07 kg N2O-N ha−1C
U + DCD (320 kg N ha−1)2.02 kg N2O-N ha−134.21
Hillsborough (UK)
[Grassland]		U (320 kg N ha−1)1.18 kg N2O-N ha−1C
U + DCD (320 kg N ha−1)0.31 kg N2O-N ha−173.78
Pwllpeiran (UK)
[Grassland]		U (320 kg N ha−1)2.06 kg N2O-N ha−1C
U + DCD (320 kg N ha−1)0.46 kg N2O-N ha−177.72
Zhang et al. [39]Beijing (China)
[Tomato–Cabbage]		U (460 kg N ha−1 yr−1)9.58 kg N2O-N ha−1C
U (95%) + DCD (5%) (460 kg N ha−1 yr−1)7.11 kg N2O-N ha−125.78
Vinzeet et al. [178]Munich (Germany)
[Rapeseed]		Ammonium sulphate nitrate (200 kg N ha−1)0.43 kg N2O-N ha−1C
Urea (200 kg N ha−1)0.40 kg N2O-N ha−16.98
Urea + NI (200 kg N ha−1)0.33 kg N2O-N ha−123.26
Cantú et al. [179]Federal University of Santa Maria (Brazil)
[Lettuce]		Urea (175 kg N ha−1)6.71C
Urea + NBPT (0.003 w/w of urea) + DCD (0.031 w/w of urea)2.2965.87
PSC (500 kg N ha−1)1.4678.24
APSC (500 kg N ha−1)1.8173.03
Riches et al. [175]Melbourne (Australia)
[Lettuce]		Urea (125 kg N ha−1)337 g N2O-N ha−1C
DMPP urea (125 kg N ha−1)215 g N2O-N ha−136.80
Melbourne (Australia)
[Lettuce]		NP (121 kg N ha−1)296 g N2O-N ha−1C
DMPP NP (121 kg N ha−1)210 g N2O-N ha−129.05
DCD NP (121 kg N ha−1)292 g N2O-N ha−11.35
Treweek et al. [177]Canterbury Region (New Zealand)
[Fodder Crop—Brassica]		Urine (700 kg N ha−1)14.7 kg N2O-N ha−1C
UD-[Urine + DCD (20 kg ha−1)]5.1 kg N2O-N ha−165.31
UDB-[UD + biochar (5 t ha−1)]13.3 kg N2O-N ha−1C
UDB + DCD (20 kg ha−1)6.1 kg N2O-N ha−154.14
Zhang et al. [129]Gaoqiaomen Town, Jiangsu Province (China)
[Seven Different Vegetables in Two Years]		Urea (1112 kg N ha−1)32.1 kg N ha−1 yr−1C
DCD (5% of urea)30.1 kg N ha−1 yr−106.23
Nitrapyrin (0.24% of Urea)26.8 kg N ha−1 yr−116.51
Biological NI 21.1 kg N ha−1 yr−134.27
Scheer et al. [176]Queensland (Australia)
[Broccoli]		CONV (120 kg N ha−1, 54 by Nitrophoska®, and 66 by U)411.2 g N2O-N ha−1C
DMPP (120 kg N ha−1, 54 by Nitrophoska Entec®, and 66 by U)298.1 g N2O-N ha−127.50
DMPP-red (108 kg N ha−1, by 49 by Nitrophoska Entec®, and 59 by U)323.9 g N2O-N ha−121.23
Note: NP—Nitrophoska Special® (NP) (Incitec Pivot, Australia) containing 6.5% NH4+-N and 5.5% NO3−-N; PSC—pig slurry compost; APSC—acidified pig slurry compost.

5. Conclusions

Nitrous oxide is one of the most significant greenhouse gases in the atmosphere that enhances global warming. The atmospheric concentration of nitrous oxide prior to the agricultural revolution and industrialization was significantly lower compared to the present. In the modern agriculture system, the use of nitrogen-based fertilizer has gained special popularity among farmers for achieving higher production. Out of the total volume of applied nitrogen fertilizer, a significant amount is lost in the form of nitrous oxide and nitrate, which increases environmental population. Nitrous oxide emissions are affected by biotic (microbial population of soil) and abiotic factors (soil pH, temperature, organic matter content, oxygen concentration, water content, etc.). The nitrogen use efficiency of plants can be increased by retarding the process of nitrification in soil systems. The application of both biological and chemical nitrification inhibitors significantly reduced nitrous oxide fluxes without reducing the production of crops. Nitrification inhibitors can be used for a short duration on long-duration crops in the agricultural system globally. The reduction of nitrous oxide fluxes without reducing yield is an environmentally and farmer-friendly option that can be adopted globally.

Author Contributions

Conceptualization, formal analysis, investigation, writing—original draft preparation, writing—review editing, visualization, and supervision, S.K.M.; writing—review and editing and formal analysis—D.M.; writing—review and editing, V.K. All authors have read and agreed to the published version of the manuscript.

Funding

This research received no external funding.

Data Availability Statement

Data are available upon request.

Acknowledgments

The support to the author Sandeep Kumar Malyan, provided by the Principal of Dyal Singh Evening College, and the Governing Body of the College are highly acknowledged.

Conflicts of Interest

The authors declare no conflicts of interest.

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Figure 1. Changes in atmospheric nitrous oxide concentration at a global level (Source: https://www.n2olevels.org/ (accessed on 25 January 2025) [14]).
Figure 1. Changes in atmospheric nitrous oxide concentration at a global level (Source: https://www.n2olevels.org/ (accessed on 25 January 2025) [14]).
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Figure 2. Biological production of nitrous oxide in the soil.
Figure 2. Biological production of nitrous oxide in the soil.
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Figure 3. Contribution of heterotrophic and autotrophic nitrification to cumulative nitrification under different soil moistures and temperatures (source: Liu et al. [42]).
Figure 3. Contribution of heterotrophic and autotrophic nitrification to cumulative nitrification under different soil moistures and temperatures (source: Liu et al. [42]).
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Figure 4. General outline of denitrification pathway.
Figure 4. General outline of denitrification pathway.
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Figure 5. General pathway of dissimilatory nitrate reduction to ammonium.
Figure 5. General pathway of dissimilatory nitrate reduction to ammonium.
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Figure 6. General diagram of chemodenitrification (source: Chalk and Smith [80]).
Figure 6. General diagram of chemodenitrification (source: Chalk and Smith [80]).
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Table 4. Role of nitrification inhibitors compounds in the reduction of nitrous oxide in maize crops.
Table 4. Role of nitrification inhibitors compounds in the reduction of nitrous oxide in maize crops.
Location, ReferenceTreatmentN2O (Unit)Mitigation (%)Remarks
Spain, Guardia et al. [152]Ammonium sulphate (AS)415.15 g N2O-N ha−1Control (C)In this study, the effect of different nitrogen on N2O emissions was investigated.
AS + DMPSA228.5 g N2O-N ha−144.96
Calcium nitrate243.75 g N2O-N ha−141.29
Australia, Muller et al. [98]Recommended dose of NPK312.3 g N2O-N ha−1ControlThe effect of DMPP and Piadin on N2O was studied.
80% of NPK + DMPP152.2 g N2O-N ha−151.27
80% of NPK + Piadin154.6 g N2O-N ha−150.50
China, Dong et al. [153]Inorganic fertilizer + Manure1.06 kg N2O ha−1ControlThe impacts of manure and nitrification inhibitors were investigated.
Inorganic fertilizer + Manure + DMPP0.71 kg N2O ha−133.02
Iran, Borzouei et al. [154]CT1.62 kg N2O-N ha−1ControlIn this study, the effect of NIs on tillage practice was investigated.
CT + NI (0.35% of applied N)0.95 kg N2O-N ha−141.36
MT1.37 kg N2O-N ha−115.43
MT + NI (0.35% of applied N)0.93 kg N2O-N ha−142.59
Indonesia, Jumadi et al. [155]Urea4.67 kg N2O-N ha−1ControlIn this study, the impact of DCD and zeolite on N2O emission from maize soil was studied.
Urea + Neem3.96 kg N2O-N ha−115.20
Urea + zeolite2.07 kg N2O-N ha−155.68
Urea + zeolite + neem1.75 kg N2O-N ha−162.53
Urea + zeolite + DCD1.10 kg N2O-N ha−176.45
Urea + DCD0.89 kg N2O-N ha−180.94
USA, Omonode & Vyn [156]UAN (220 kg N ha−1 by urea ammonium nitrate)37.96 g N ha−1 d−1ControlThe study was conducted at Purdue University, West Lafayette, USA.
UAN + nitrapyrin (2.6 kg ha−1)36.01 g N ha−1 d−15.14
India, Fagodiya et al. [135]Control (120 kg N ha−1 by Urea)0.89 kg N2O ha−1ControlTwo years of studies were conducted in New Delhi, India.
DCD (120 kg N ha−1, 108 and 12 kg N ha−1 by U and DCD, respectively)0.7021.35
NOCU (120 kg N ha−1 by NOCU)0.77512.92
China, Song et al. [157]Deep fertilizer (242 kg N ha−1)113 ng N m−2 s−1ControlIn this study, deep fertilizer along with DCD reduces N2O emission significantly.
Deep fertilizer + DCD (7% of N)11.7 ng N m−2 s−189.65
China, Du et al. [158]Optimized N (160 kg N ha−1)1.41 kg N ha−1ControlThree years of studies were carried out to enhance the efficiency of nitrogen-based fertilizers.
Optimized N + DCD (10% of N)1.01 kg N ha−128.37
China, Niu et al. [108]N (120 kg N ha−1)1.00 kg N ha−1ControlIn this study, the impact of biochar and a nitrification inhibiter (nitrapyrin) was studied in combination and alone also.
NB3 (120 kg N ha−1 + BC 3 t ha−1)0.84 kg N ha−116
NB6 (120 kg N ha−1 + BC 6 t ha−1)0.85 kg N ha−115
NB12 (120 kg N ha−1 + BC 12 t ha−1)0.81 kg N ha−119
NI (120 kg N ha−1, 99.74% by urea + 0.26% by nitrapyrin)0.87 kg N ha−113
NIB3 (NI + BC 3 t ha−1)0.80 kg N ha−120
NIB6 (NI + BC 6 t ha−1)0.84 kg N ha−116
NIB12 (NI + BC 12 t ha−1)0.75 kg N ha−125
China, Dong et al. [41]Urea (U) (180 kg N ha−1)0.639 (kg N ha−1)ControlMean data of six years of maize growing seasons.
U + DCD (5.4 kg ha−1) + HQ (1.8 kg ha−1)0.528 (kg N ha−1)17.37
Spain, Guardia et al. [139]U-S (180 kg N ha−1)1.665ControlThe average data of two years of study conducted in Spain.
CAN-S (180 kg N ha−1)1.3021.92
U + NI-S (180 kg N ha−1)0.8350.15
CAN + NI-S (180 kg N ha−1)0.5566.97
Canada, Drury et al. [159]U (130 kg N ha−1)1.69 kg N ha−1ControlAverage data of two years of study.
U + NBPT + DCD (130 kg N ha−1)1.49 kg N ha−111.83
Thailand, Pengthamkeerati & Modtad [149]Chemical fertilizers (CF) 28.125 kg N ha−148.6 mg N2O-N m−2ControlAn experiment was conducted in the loamy sandy soil of Thailand.
CF + neem oil (5%)43.7 mg N2O-N m−210.48
CF + neem oil (10%)43.8 mg N2O-N m−29.88
CF + DCD (5%)40.5 mg N2O-N m−216.67
CF + DCD (10%)36.2 mg N2O-N m−225.51
Spain, Sanz-Cobena et al. [160]U (250 kg N ha−1)0.94 (kg N2O-N ha−1)ControlThe average data are taken from the study.
U + NBPT (0.4%) + DCD (3%)0.65 (kg N2O-N ha−1)30.85
U + NBPT (0.4%)0.59 (kg N2O-N ha−1)37.23
Indonesia, Hadi et al. [150]U (200 kg ha−1)691.7 mg N m−2ControlThe dose of each fertilizer is 90 kg N ha−1 in this experiment.
U (170 kg ha−1) + DCD (20 kg ha−1)21.1 mg N m−296.95
LP-30 (214 kg ha−1)57.3 mg N m−291.72
Indonesia, Jumadi et al. [150]U (90 kg N ha−1)1.87 kg N2O-N ha−1ControlIn this study, fertilizers are applied in two spilt (45 + 45 kg N ha−1).
CRF (90 kg N ha−1)1.70 kg N2O-N ha−19.09
DCD (90 kg N ha−1, 90% by U + 10% by DCD)1.06 kg N2O-N ha−143.32
Note: CT—conventional tillage; MT—minimum tillage; NI—nitrapyrin; BC—biochar; CRF—controlled-release nitrogen; U-S—urea applied by sprinkler irrigation; CAN-S—calcium ammonium nitrate by sprinkler irrigation; U + NI—urea + DMPSA by sprinkler irrigation; CAN + NI-S—CAN+ DMPSA by sprinkler irrigation.
Table 5. Effects of biological and chemical nitrification inhibitors on N2O emission from paddy soils.
Table 5. Effects of biological and chemical nitrification inhibitors on N2O emission from paddy soils.
References (Study Location)TreatmentN2O EmissionMitigation (%)
Paul et al. [84] (New Delhi, India)Prilled urea0.80 kg N2O-N ha−1Control (C)
Neem oil-coated urea (NCU)0.68 kg N2O-N ha−115
Karanj oil-coated urea0.67 kg N2O-N ha−116.25
Limus + NCU0.61 kg N2O-N ha−123.75
Huang et al. [120] (Anhui Province, China)Conventional fertilizer0.1028 mg N2O kg−1C
Methyl 3-(4-hydroxyphenyl) propionate0.0598 mg N2O kg−141.83
Ren et al. [113] (Shandong Province, China)Urea23.5 kg N2O ha−1 Control
Urea + DCD16.29 kg N2O ha−130.68
Urea + DCD + NBPT18.0 kg N2O ha−123.40
He et al. [167] (China)Conventional urea1.49 kg N2O ha−1C
Reduced N fertilizer (RN)1.14 kg N2O ha−123.49
RN + 7.5 t ha−1 biochar (B1)1.37 kg N2O ha−18.05
RN + 15 t ha−1 biochar (B2)1.49 kg N2O ha−10
RN + DCD + HQ (RNI)0.90 kg N2O ha−139.60
RNI + B10.97 kg N2O ha−134.90
RNI + B21.14 kg N2O ha−123.49
Cowan et al. [168] (India)Prilled urea and continuous flooding1.17 kg N2O-N ha−1C
Neem oil-coated urea and continuous flooding1.078.55
Prilled urea and intermitted irrigation1.45−23.93
Neem oil-coated urea and intermitted irrigation1.38−17.95
Gaihre et al. [169] (USA)Urea broadcast3010 g N2O-N/h m2C
Potassium nitrate1359 g N2O-N/h m254.85
Urea deep placement205 g N2O-N/h m293.19
Urea + DCD815 g N2O-N/h m272.93
Guo et al. [162]
(Hubei Province, China)		Farmer fertilizer practice (FFP) (195 kg N ha−1)3.33 kg N2O ha−1C
Polymer-coated controlled urea (195 kg N ha−1)2.10 kg N2O ha−136.99
Nitrapyrin-coated urea (nitrapyrin coating 5%) (195 kg N ha−1)2.00 kg N2O ha−139.99
Jumadi et al. [155]
(Maros District, Indonesia)		Urea granule (UG) (150 kg N ha−1)7.2 kg-N ha−1C
UGZ-UG + zeolite (10% (w/w) of U) (150 kg N ha−1)3.4 kg-N ha−152.78
UGZN-UGZ + neem cake (5% (w/w) of U) (150 kg N ha−1)7.0 kg-N ha−12.78
UGZD-UGZ + DCD (5% (w/w) of U) (150 kg N ha−1)4.7 kg-N ha−134.72
Li et al. [137]
(Jingzhou City, China)		Early riceU (165 kg N ha−1) + CI *1.3 kg N2O ha−1C
U (165 kg N ha−1) + SWD **1.9 kg N2O ha−1−46.15 !
CRU *** (165 kg N ha−1) + SWD1.4 kg N2O ha−1−7.69
NU +HQ (165 kg N ha−1) + CI1.1 kg N2O ha−17.69
Late riceU (165 kg N ha−1) + CI *1.7 kg N2O ha−1C
U (165 kg N ha−1) + SWD **2.5 kg N2O ha−1−47.06
CRU *** (165 kg N ha−1) + SWD2.2 kg N2O ha−1−29.41
NU + HQ (165 kg N ha−1) + CI1.8 kg N2O ha−1−5.88
Datta & Adhya [85]
(Cuttack, India)		Urea (90 kg N ha−1)2.05 kg N2O ha−1C
U (90 kg N ha−1) + DCD (5 kg ha−1)1.62 kg N2O ha−120.98
U (90 kg N ha−1) + nimin (0.9 kg N ha−1)0.30 kg N2O ha−185.37
U (90 kg N ha−1) + karanjin (0.9 kg N ha−1)1.05 kg N2O ha−148.78
Ali et al. [170] (Mymensingh, Bangladesh)Continues flooding (CF) + urea (200 kg ha−1)0.55 kg N2O ha−1Control
CF + Urea (200 kg ha−1) + calcium carbide (30 ppm)0.29 kg N2O ha−147.27
Intermittent irrigation (IR) + urea (200 kg ha−1)0.98 kg N2O ha−1Control
IR + urea (200 kg ha−1) + calcium carbide (30 ppm)0.69 kg N2O ha−129.59
Li et al. [164]
(Jurong City, China)		U (150 kg N ha−1)3.90 kg N2O-N ha−1C
U (150 kg N ha−1) + HQ (0.45 kg ha−1) + DCD (7.5 kg ha−1) HQ and DCD basal2.98 kg N2O-N ha−123.59
U (150 kg N ha−1) + HQ (0.45 kg ha−1) + DCD (7.5 kg ha−1) HQ and DCD at tillering 1.73 kg N2O-N ha−155.64
U (150 kg N ha−1) + HQ (0.45 kg ha−1) + DCD (7.5 kg ha−1) HQ and DCD at panicle initiation3.23 kg N2O-N ha−117.18
Malla et al. [86]
(New Delhi, India)		U (120 kg N ha−1)0.76 kg N2O-N ha−1C
U (120 kg N ha−1) + hydroquinone (12 kg ha−1)0.73 kg N2O-N ha−13.95
U (108 kg N ha−1) + neem cake (12 kg N ha−1)0.68 kg N2O-N ha−110.53
Calcium carbide-coated urea (120 kg N ha−1) 0.54 kg NO-N ha−128.95
Neem oil-coated urea (120 kg N ha−1)0.60 kg N22O-N ha−121.05
U (108 kg N ha−1) + DCD (12 kg N ha−1)0.63 kg N2O-N ha−117.11
U (120 kg N ha−1) + thiosulphate (12 kg ha−1)0.50 kg N2O-N ha−134.21
Boeckx et al. [148] (Pot experiment, China)U (345 kg N ha−1)8.62 mg N2O-N kg−1 soilC
U + HQ (0.3% of applied U)6.60 mg N2O-N kg−1 soil23.43
U + DCD (0.5% of applied U)4.57 mg N2O-N kg−1 soil46.98
U + HQ (0.3% of applied U) + DCD (0.5% of applied U)3.25 mg N2O-N kg−1 soil62.30
Ghosh et al. [163] (New Delhi, India)U (120 kg N ha−1)167.9 g N2O ha−1C
U (108 kg N ha−1) + DCD (12 kg N ha−1)79.5 g N2O ha−152.65
Ammonium sulphate (120 kg N ha−1)151.4 g N2O ha−1C
Ammonium sulphate (108 kg N ha−1) + DCD (12 kg N ha−1)81.9 g N2O ha−145.90
Potassium nitrate (120 kg N ha−1)186.7 g N2O ha−1C
Potassium nitrate (108 kg N ha−1) + DCD (12 kg N ha−1)167.5 g N2O ha−110.28
Kumar et al. [171] (New Delhi, India)U (140 kg N ha−1)0.16 kg N2O-N ha−1C
U (126 kg N ha−1) + DCD (14 kg N ha−1)0.142 kg N2O-N ha−111.25
U (126 kg N ha−1) + thiosulphate (14 kg N ha−1)0.147 kg N2O-N ha−18.13
(NH4)2SO4 (126 kg N ha−1) + thiosulphate (14 kg N ha−1)0.235 kg N2O-N ha−1−46.88
(NH4)2SO4 (126 kg N ha−1) + DCD (14 kg N ha−1)0.174 kg N2O-N ha−1−8.75
Majumdar et al. [140]
(New Delhi, India)		U (140 kg N ha−1)0.060 kg N2O-N ha−1C
U (119 kg N ha−1) + DCD (21 kg N ha−1)0.049 kg N2O-N ha−118.33
NOCU (140 kg N ha−1)0.053 kg N2O-N ha−111.67
Nimin-coated U (140 kg N ha−1)0.057 kg N2O-N ha−15.00
Pattanaik et al. [166] (Cuttack, India)Control (recommended dose through NCU)0.58 kg N2O ha−1Control
75% of the recommended dose through NCU0.55 kg N2O ha−15.17
50% of the recommended dose through NCU0.51 kg N2O ha−112.07
100% of the recommended dose through CLCC0.53 kg N2O ha−18.62
75% of the recommended dose through CLCC0.47 kg N2O ha−118.97
50% of the recommended dose through CLCC0.43 kg N2O ha−125.86
Note: !—emission is higher than control (C); * CI—conventional irrigation; ** SWD—shallow water depth with alternate wetting–drying; *** CRU—polymer-coated controlled-release urea; NCU—neem oil-coated urea; CLCC—conventional and customized leaf colour chart.
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Malyan, S.K.; Maithani, D.; Kumar, V. Nitrous Oxide Production and Mitigation Through Nitrification Inhibitors in Agricultural Soils: A Mechanistic Understanding and Comprehensive Evaluation of Influencing Factors. Nitrogen 2025, 6, 14. https://doi.org/10.3390/nitrogen6010014

AMA Style

Malyan SK, Maithani D, Kumar V. Nitrous Oxide Production and Mitigation Through Nitrification Inhibitors in Agricultural Soils: A Mechanistic Understanding and Comprehensive Evaluation of Influencing Factors. Nitrogen. 2025; 6(1):14. https://doi.org/10.3390/nitrogen6010014

Chicago/Turabian Style

Malyan, Sandeep Kumar, Damini Maithani, and Vineet Kumar. 2025. "Nitrous Oxide Production and Mitigation Through Nitrification Inhibitors in Agricultural Soils: A Mechanistic Understanding and Comprehensive Evaluation of Influencing Factors" Nitrogen 6, no. 1: 14. https://doi.org/10.3390/nitrogen6010014

APA Style

Malyan, S. K., Maithani, D., & Kumar, V. (2025). Nitrous Oxide Production and Mitigation Through Nitrification Inhibitors in Agricultural Soils: A Mechanistic Understanding and Comprehensive Evaluation of Influencing Factors. Nitrogen, 6(1), 14. https://doi.org/10.3390/nitrogen6010014

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