Dicyandiamide Research Articles

In-vitro assessment of 3,5-diaryl-1h-pyrazoles for nitrification inhibition in soil

Nitrification process involves conversion of nitrogen into nitrates by soil microbes which are then taken up by plants. But due to denitrification, ammonia volatilization, nitrous oxide emission, leaching, run off, etc., the plant available nitrogen is lost from the soil. Pyrazoles are good nitrification inhibitors and DMPP (3,4-dimethylpyrazole phosphate) is a known commercial nitrification inhibitor in agricultural crops. The study explores the potential of a group of diarylpyrazoles for their nitrification inhibitory properties under in-vitro conditions. The test pyrazole compounds were applied at recommended dose of 1% of urea nitrogen-N. Four of the pyrazole compounds showed promising results with several compounds having more than 50% nitrification inhibition. Some compounds showed better performance than the standard DCD (dicyandiamide) at 1% and 5%. There were few compounds which showed no inhibition. Results suggest that some of the compounds proved to be good inhibitors of nitrification under laboratory conditions.

Promotional effects of trace Ni on its dual-functional electrocatalysis of Co/N-doped carbon nanotube catalysts for ORR and OER

It is still a great challenge for developing efficient dual-functional electrocatalysts for oxygen reduction reaction (ORR) and oxygen evolution reaction (OER). The electrocatalysts are critical to enhance the efficiency of metal-air cells and fuel cells. In this study, a one-pot vapor deposition method was used to realize the synchronously dope of N and Ni (trace) into Co/C to form Co–Ni (trace)/N-doped carbon nanotubes (Co–Ni (trace)/NCNTs). An interesting result is that injecting dicyandiamide (DCD) into Ni foam as a precursor led to the in situ formation of NCNTs, with synchronous doping of trace Ni into Co species. The cooperative effects of the Co–Ni (trace) and N-doped carbon nanotubes resulted in superior dual-functional electrocatalytic performance of Co–Ni (trace)/NCNTs for the ORR (half-wave potential E1/2 vs. RHE: 0.83 V, electron transfer number n: 3.97) and OER (overpotential vs. RHE: 337 mV at 10 mA cm−2, Tafel slope: 94.0 mV dec−1). Moreover, the Co–Ni (trace)/NCNTs catalyst showed excellent stability during 20,000 s of durability testing for both ORR and OER. This study provides a feasible strategy for designing efficient nonnoble metal-catalysts for renewable energy conversion devices.

Field Quantification of Ammonia Emission following Fertilization of Golf Course Turfgrass in Sub/Urban Areas

Low cost and favorable handling characteristics make urea (46-0-0) a leading nitrogen source for frequent, foliar N fertilization of golf course putting greens in season. Yet few field investigations of resulting NH3 volatilization from putting greens have been directed. Meanwhile, NH3 emissions degrade air and surface water quality. Our objective was to quantify NH3 volatilization following practical, low-N rate, and foliar application of commercial urea-N fertilizers. Over the 2019 and 2020 growing seasons in University Park, PA, USA, an industrial vacuum pump, H3BO3 scrubbing flasks, and sixteen dynamic flux chambers were employed in four unique experiments to measure NH3 volatilization from creeping bentgrass putting greens (Agrostis stolonifera L. ‘Penn G2’) in the 24 h period ensuing foliar application of urea based-N at a 7.32 or 9.76 kg/ha rate. Simultaneous and replicated flux chamber trapping efficiency trials showing 35% mean NH3 recovery were used to adjust NH3 volatilization rates from treated plots. Under the duration and conditions described, 3.1 to 8.0% of conventional urea N volatilized from the putting greens as NH3. Conversely, 0.7 to 1.1% of methylol urea liquid fertilizer (60% short-chain methylene urea) or 0.7 to 2.2% of urea complimented with dicyandiamide (DCD) and N-(n-butyl) thiophosphoric triamide (NBPT) volatilized as NH3.

Factors Influencing Local Branded Fresh Milk Purchase Intention among Consumers: A Case from Kurunegala District of Sri Lanka

Disputable information released through the mass media related to the imported powder milk incorporated with melamine, dicyandiamide (DCD) and animal fat has made a negative influence on powder milk consumption in Sri Lanka. This study was focused to analyze how consumers’ perceived knowledge, processed knowledge, health consciousness, attitudes, certification and subjective norms influence the purchase intention of local branded fresh milk among consumers in Kurunegala District in Sri Lanka. Data were collected from 200 consumers in selected supermarkets and other sales centers covering five Divisional Secretariats in Kurunegala district by means of face to face interview. Super markets were selected randomly and respondents were selected by systematic sampling. A Confirmatory Factor Analysis was carried out to find the relationships between selected seven Constructs. The results revealed that consumers’ health consciousness was the main Construct that influenced the purchasing intention of locally produced branded fresh milk. Findings of this study provide new information about the purchasing behaviour of consumers. Keywords: Confirmatory factor analysis, Locally produced branded fresh milk, Purchase intention, Recent trends

Green chromatographic methods for simultaneous micro-determination of empagliflozin, linagliptin with metformin and its pharmacopoeial impurities in pure form and triple combination tablets: A comparative study

Green analytical chemistry (GAC) is gaining great interest with the respect of global environmental pollution control (EPC). Consequently, we have developed two green chromatographic methods for the simultaneous precise and selective estimation of empagliflozin (EMP), linagliptin (LNA) with Metformin (MET) and its pharmacopoeial impurities cyanoguanidine (CGN) and melamine (MLN). The scientific database lacks any analytical reports tackling such concurrent estimation of the five cited analytes. The first developed method is a reversed phase HPLC-DAD employing Agilent C18 column (4.6 × 250 mm, 5 μm p.s.) and a mobile phase composed of methanol and 0.01 M sodium dihydrogen orthophosphate buffer of pH 2.55 (adjusted with orthophosphoric acid) eluted in a gradient mode with detection at 218 and 224 nm.The second method is HPTLC using Merk TLC plates precoated with 60 F 254 silica gel on aluminium sheet as the stationary phase developed with ethanol: ethylacetate: water (3.5: 3:1, v/v/v, respectively) as mobile phase and scanned at 216 and 224 nm. The proposed methods offered neat separation and quantitation of the five analytes in their pure form and in the triple combination tablets. Both methods were validated as per the ICH guidelines in terms of linearity, range, accuracy, precision, specificity and robustness. Moreover, Greenness assessment of the developed methods was carried out using the Analytical Eco-Scale. Further evaluation of the methods’ ecofriendliness and comparison with previously reported methods was performed using NEMI, GAPI and the novel AGREE tool.

Correction to: Effects of N Application Rate and Dicyandiamide on the Fate of 15N Fertilizer and the Abundance of Microbial Genes in a Sandy Soil Amended with Sugarcane Litter

Renewable energy produced from sugarcane (Saccharum spp.) has clear advantages over fossil fuels in mitigating climate change. However, N2O emissions and NO3− leaching from fertilizer nitrogen (N) addition can jeopardize the sustainability of sugarcane production worldwide. One of the possible approaches to mitigating these N-loss pathways is the use of nitrification inhibitors such as dicyandiamide (DCD). However, the effects of DCD on the fate of fertilizer-derived N in soil pools and functional N genes (e.g., nitrifiers and denitrifiers) remain unclear. We performed a laboratory incubation study for 54 days to evaluate the influence of DCD and fertilizer N rate ((15NH4)2SO4 applied at 40, 80, 120, and 160 µg N g−1) on 15N transformation and abundance of total prokaryotes (16S rRNA), nitrifiers (ammonia-oxidizing archaea (AOA) and bacteria (AOB)), and denitrifiers (nirK and nosZ) in a tropical sandy soil amended with sugarcane residues. Especially for high N rates (120 and 160 µg N g−1), DCD not only increased the NH4+-15N recovery by inhibiting nitrification but also stimulated microbial immobilization. However, the nitrification inhibitor decreased N losses (i.e., unrecovered 15N). The abundance of total archaea and bacteria was unaffected by both the fertilizer N rate and DCD. While the abundance of AOB and nirK was suppressed by DCD, AOA and nosZ abundance increased, with the latter gene being the highest at 160 µg g−1. We conclude that DCD mitigates N losses from ammonium-based fertilizer by inhibiting NO3− production and changing nitrifying and denitrifying microorganisms in sandy acidic soil.

Effects of different nitrification inhibitors on nitrification, maize yield, and nitrogen use efficiency in red soil.

We examined the effects of nitrification inhibitors (NIs) on soil nitrification, maize yield and nitrogen use efficiency (NUE), aiming to screen out high efficiency stabilized ammonium chloride fertilizer in red soil. Nitrification inhibitors 2-chloro-6-trimethyl-pyridine (CP), 3, 4-dimethyl-pyrazolate phosphate (DMPP), and dicyandiamide (DCD) and their combinations were added into ammonium chloride (NH4Cl) to make six stabilized nitrogen fertilizers. With blank (CK) and NH4Cl (N) as the controls, we conducted a maize pot experiment with the same amount of nitrogen addition. The results showed that compared with the treatment of N, soil ammonium content in CP+DMPP and DMPP+DCD increased by 56%-62%, which was significantly higher than that in CP, DMPP, and DCD, while the apparent nitrification rate of red soil was significantly reduced by 33%-34%. All the six treatments with nitrification inhibitors and their combinations significantly improved biomass and nitrogen absorption efficiency of maize. Compared with the N treatment, the application of adding NIs alone was significantly higher than that of the treatments of NIs combinations, with an average of 1.3 times increase. DCD was the most efficient one in improving maize yield, nitrogen uptake, and nitrogen adsorption efficiency, which increased by 4.1, 6.3 and 4.4 times, respectively. Comprehensively, DCD performed the best in reducing cost and improving yield and nitrogen use efficiency in red soil.

Screen superior ultra-thin g-C3N4 material for photocatalytic in-situ H2O2 production to remove tetracycline

Photocatalytic in-situ hydrogen peroxide (H2O2) preparation for cascade reactions is a novel and promising application strategy, especially for environmental remediation. Graphitic carbon nitride (g-C3N4) has been proven to be one of the most effective catalysts. However, the H2O2 yields on g-C3N4 materials fabricated by different precursors varied greatly, so that the reasons need to be explored urgently for the later using. In this work, a series of different ultra-thin g-C3N4 nanosheets catalysts are synthesized, on which the H2O2 generation and tetracycline removal abilities are evaluated comprehensively. Among these, the g-C3N4 nanosheets prepared by dicyandiamide (DCN) is demonstrated the excellent one with the maximum H2O2 production efficiency of 665.4 μmol h−1 g−1, and its apparent quantum yield (AQY) arrives to 9.3% when illuminated at 400 nm. The superior photocatalytic performance of DCN is attributed to its nearly two-electron (2e-) oxygen reduction reaction (ORR) process, numerous unpaired electrons, suitable band structure, rapid charge separation and transfer efficiency. This work provides an effective strategy for wastewater purification without adding H2O2, which has screened an excellent ultra-thin g-C3N4 catalyst, for the further photocatalysis research.

Efficacy of four nitrification inhibitors for the mitigation of nitrous oxide emissions under different soil temperature and moisture#

AbstractBackgroundNitrification 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.AimsThis study investigated how different NI behave in a sandy soil under variable temperature and moisture levels, which currently remains unclear.MethodsEfficacies 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.ResultsIncreasing 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.ConclusionsOverall, 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.

Evaluating the nitrification inhibition potential of selected botanicals and their non-target effects

Nitrification inhibitors (NI) are aimed at improving N-fertilizer use efficiency in cropping systems. This study aimed to assess the nitrification inhibition potential and non-target effects of dry leaf powders (botanicals) of 10 plant species (neem (Azadirachta indica), lantana (Lantana camara), karanda (Pongamia pinnata), Brachiaria (Brachiaria humidicola), cinnamon (Cinnamomum verum), clove (Syzygium aromaticum), wild-sunflower (Tithonia diversifolia), mee (Madhuca longifolia), nutmeg (Myristica fragrans), and pepper (Piper nigram)). The effect of botanicals on the growth of three ammonia oxidizing bacteria isolates (M4, M5, and M7) and NO3− formation in soil were tested in laboratory experiments. In a pot-experiment, botanicals were applied with urea to assess their effect on vegetative-growth of tomato and capsicum. The non-target effects of botanicals on soil bacteria and fungi, and seed germination were assessed separately. Dicyandiamide (DCD) was used as the positive control in all experiments. Only the growth of M7 was significantly suppressed by all botanicals except neem, Brachiaria, and pepper. The highest shoot-biomass of tomato was obtained when urea was applied with pepper. Nitrate leaching from pots was significantly reduced (P < 0.05) when urea was added with botanicals except for clove and wild-sunflower at basal-dressing. The abundance of culturable fungi and bacteria were not affected significantly by botanicals while seed germination was reduced significantly and consistently by clove only. From the 10 botanicals tested leaf powders of nutmeg, lantana, cinnamon, mee, and pepper were identified as materials with better potential to suppress nitrification with minimum non-target effects.

Freeze-dried dicyandiamide-derived g-C3N4 as an effective photocatalyst for H2 generation

BackgroundHydrogen (H2) is viewed as a clean, green, and sustainable energy source. The photocatalytic H2 evolution using light-activated photocatalyst under light irradiation is attractive to convert light into chemical energy in a feasible way. In the present work, photocatalysis of H2 generation was explored, using graphitic carbon nitride (g-C3N4) synthesized from freeze-dried dicyandiamide (DICY). MethodsThe DICY underwent rapid dissolution-recrystallization during the freeze-drying process, enabling more complete polymerization of the heptazine units of g-C3N4 than occurred in the same compound synthesized from untreated DICY. After loading with Pt as a cocatalyst, and under light irradiation (metal halide lamp) in the presence of triethanolamine, g-C3N4 synthesized from freeze-dried DICY (DCN) showed an increased H2 evolution rate (∼20 μmol h‒1) compared with that using g-C3N4 derived from untreated DICY (CN) (12 μmol h‒1). In addition, DCN had a higher H2 generation rate than CN under light of different wavelengths (400, 450, and 550 nm). Significant FindingsThe improved activity of DCN could be attributed to inhibition of charge recombination (evidenced by photoluminescence), fast charge transfer (evidenced by electrochemical impedance spectra and photocurrent measurements), and a suitable energy bandgap (evidenced by Mott-Schottky and UV–vis measurements) resulting from better-polymerized heptazine rings (evidenced by nuclear magnetic resonance spectroscopy). In summary, DCN prepared in this study could be used as a visible-light activated and effective metal-free material for photocatalytic H2 generation.

Fast curing unidirectional carbon epoxy prepregs based on a semi-latent hardener: The influence of ambient aging on the prepregs Tg0, processing behavior and thus derived interlaminar performance of the composite

The aging behavior of a fast-curing epoxy resin (EP) was examined over three months in unidirectional carbon fiber prepregs for the first time. The semi-latent, 120 °C curing one-pot formulation was developed based on industry-grade diglycidyl ether of bisphenol A (DGEBA) resins without the necessity of B-staging, to fully monitor the property change by aging without any post-processing influence. To extend the shelf-life compared to standard wet EP systems, the latent dicyandiamide (DICY) and a semi-latent urea-based catalyst were used, leading to full conversion within 15 min. The conversion was monitored by increasing Tg0 and rheology. High quality unidirectional carbon prepregs were manufactured and then investigated over three months regarding tackiness and resin flow. In parallel, laminates were autoclave-manufactured to evaluate the aging influence on the interlaminar properties. Thus, a correlation between decreasing gel-time, interlaminar adhesion and resulting multiple crack growth was observed via GIC and interlaminar shear strength (ILSS) testing. The investigations show a clear influence of the consolidation quality of the prepregs based on ILSS values and GIC values. A decrease of 19% in ILSS and combined with an erroneous increase of 63% of the GIC due to multiple delamination was observed in the worst case.

Bifunctional-based small molecule as multifunctional additive for improved performance of perovskite solar cells

Hybrid perovskites have great potential as light-absorbing materials, while its degradation of poor crystallization and ion migration have been the major obstacle in perovskite solar cells (PSCs). Herein, the bifunctional-based small molecule dicyandiamide (DCD) was applied as additive in the PSCs. The amino and cyano group of DCD could effectively control crystallization and passivating grain defects, resulting in the high-quality perovskite films with large grain size. In addition, the adding of DCD increases the film conductivity of perovskite active layer, which is beneficial for charge transport in perovskite film. The DCD added PSCs shows an optimal power conversion efficiency (PCE) of 19.08% with negligible hysteresis. Furthermore, the long-term stability of PSCs is significantly enhanced. The results indicate that the device's integrative performance could be efficiently improved by the synergistic effect of amino and cyano functional groups, meaning that the addition of DCD into perovskite precursor could enable this optimization.

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

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

CoNi nanoalloys embedded in N-doped carbon nanofibers derived from layered bimetal-organic framework and as efficient oxygen electrocatalyst

Developing efficient and low-cost bifunctional catalysts towards oxygen evolution reaction (OER) and oxygen reduction reaction (ORR) is a significant scientific issue in establishing renewable energy systems. Herein, we propose a bifunctional oxygen electrocatalyst derived from a bimetal-organic framework. Two-dimensional (2-D) CoNi-BDC (BDC = benzenedicarboxylic acid) was synthesized via an bottom-up approach (improved inter-diffusion route). Lamellar CoNi nanoalloys embedded in N-doped carbon nanofibers (CoNi-N-CNFs) were obtained by electrospinning CoNi-BDC and dicyandiamide (DCD) into a polyacrylonitrile (PAN) polymer and subsequent post-calcination treatment. By taking advantage of the synergetic interactions between CoNi nanoalloys and N-doped carbon, the as-synthesized CoNi-N-CNFs catalysts exhibited outstanding catalytic performance with respect to the OER and ORR. CoNi-N-CNFs-60 exhibited a low overpotential of 229 mV at 10 mA cm−2 and a half-wave potential of 0.823 V in 1 M KOH, making it a promising candidate as an efficient air electrode in Zn-air battery. The hierarchical 1-D/2-D composite structure and porous morphology play a key role in improving electrocatalytic performance by exposing a greater number of active CoNi-N sites.

Measuring Responses of Dicyandiamide-, 3,4-Dimethylpyrazole Phosphate-, and Allylthiourea-Induced Nitrification Inhibition to Soil Abiotic and Biotic Factors.

Nitrification inhibitors (NIs) such as dicyandiamide (DCD), 3,4-dimethylpyrazole phosphate (DMPP), and allylthiourea (AT) are commonly used to suppress ammonia oxidization at different time scales varying from a few hours to several months. Although the responses of NIs to edaphic and temperature conditions have been studied, the influence of the aforementioned factors on their inhibitory effect remains unknown. In this study, laboratory-scale experiments were conducted to assess the short-term (24 h) influence of eight abiotic and biotic factors on the inhibitory effects of DCD, DMPP, and AT across six cropped and non-cropped soils at two temperature conditions with three covariates of soil texture. Simultaneously, the dominant contributions of ammonia-oxidizing archaea (AOA) and bacteria (AOB) to potential ammonia oxidization (PAO) were distinguished using the specific inhibitor 2 phenyl-4,4,5,5-tetramethylimidazoline-1-oxyl 3-oxide (PTIO). Our results revealed that AT demonstrated a considerably greater inhibitory effect (up to 94.9% for an application rate of 75 mg of NI/kg of dry soil) than DCD and DMPP. The inhibitory effect of AT was considerably affected by the relative proportions of silt, sand, and clay in the soil and total PAO. In contrast to previous studies, the inhibitory effects of all three NIs remained largely unaffected by the landcover type and temperature conditions for the incubation period of 24 h. Furthermore, the efficacy of all three tested NIs was not affected by the differential contributions of AOA and AOB to PAO. Collectively, our results suggested a limited influence of temperature on the inhibitory effects of all three NIs but a moderate dependence of AT on the soil texture and PAO. Our findings can enhance the estimation of the inhibitory effect in soil, and pure cultures targeting the AOA and AOB supported ammonia oxidization and, hence, nitrogen dynamics under NI applications.

Temperature alters dicyandiamide (DCD) efficacy for multiple reactive nitrogen species in urea-amended soils: Experiments and modeling

Dicyandiamide (DCD) is a nitrification inhibitor (NI) used to reduce reactive nitrogen (N) losses from soils. While commonly used, its effectiveness varies widely. Few studies have measured DCD and temperature effects on a complete set of soil N variables, including nitrite (NO2−) measured separately from nitrate (NO3−). Here the DCD reduction efficiencies (RE) for nine N availability metrics were quantified in two soils (a loam and silt loam) using aerobic laboratory microcosms at 5–30 °C. Both regression analysis and process modeling were used to characterize the responses. Four metrics accounted for NO3− production and included total mobilized N, net nitrification, maximum nitrification rate, and cumulative NO3− (cNO3-). The REs for these NO3−-associated production variables decreased linearly with temperature, and in all cases were below 60% at temperatures ≥22 °C, except for cNO3- in one soil. In contrast, REs for NO2− and nitric oxide (NO) gas production were less sensitive to temperature, ranging from 80 to 99% at 22 °C and 50–95% at 30 °C. Addition of DCD suppressed nitrous oxide (N2O) production in both soils by 20–80%, but increased ammonia volatilization by 36–210%. The time at which the maximum reduction efficiency occurred decreased exponentially with increasing temperature for most variables. The two-step nitrification process model (2SN) was modified to include competitive inhibition coupled to first-order DCD decomposition. Model versus data comparisons suggested that DCD had indirect effects on NO2− kinetics that contributed to the greater suppression of NO2− and NO relative to NO3−. This study also points to the need for NIs that are more stable under increased temperature. The methods used here could help to assess the efficacy and temperature sensitivity of other NIs as well as new microbial inhibitors that may be developed.

Global analysis of nitrification inhibitors on grasslands nitrous oxide emission rates

Field studies have tested the effectiveness of nitrification inhibitors in reducing grassland soil nitrous oxide (N2O) emissions. However, the magnitude of the effects on N2O emission rates across global grasslands remains unclear owing to its spatial heterogeneity. In this study, we synthesized 40 datasets from 23 published studies. The meta-analysis revealed that effect size of nitrification inhibitors was −0.59 ± 0.07 (95% confidence interval: −0.73 to −0.46). The mitigation effect on global grassland N2O emission rates was approximately 44.56%. Meanwhile, dicyandiamide (DCD) and 3,4-dimethylpyrazole phosphate (DMPP) decreased grassland N2O emission rates by 48.31% and 32.97%, respectively (P < 0.05). The mixed effects models indicated that total nitrogen, soil bulk and air temperature were the main controlling factors, which explained 42.79%, 40.70%, and 18.59% of the variation in effect size, respectively. Considering global warming, there is considerable potential benefit from mitigating grassland N2O emissions through the application of DCD and DMPP.

Effects of soil moisture on microbial processes of soil nitrogen gases production under anaerobic conditions

Gaseous nitrogen (N) emission [nitric oxide (NO), nitrous oxide (N2O), and nitrogen (N2)] is an important pathway of soil N loss. Nitrification and denitrification are the main processes of gaseous N production in soil. However, the contribution of heterotrophic nitrification, co-denitrification, and anammox to gaseous N production remains uncertain. In a laboratory soil incubation experiment, we used the 15N labelling and pairing technique, combining the nitrification inhibitor dicyandiamide (DCD), to quantify the contribution of different microbial processes to soil NO, N2O and N2 production under anaerobic conditions. The results showed that after 24 h anaerobic incubation, the highest total 15N recovery of three gases occurred at 65% water filled pore space (WFPS), accounting for 20.0% of total added 15N. Denitrification contributed 49.9%-94.1%, 29.0%-84.7%, and 58.2%-85.8% to the production of NO, N2O and N2 respectively, suggesting that denitrification was the predominant process of those three N gases emission. Heterotrophic nitrification was an important pathway of NO and N2O production, particularly at conditions with low soil water content (10% WFPS), with its contribution to those two N gases production being 50.1% and 42.8%, respectively. Co-denitrification contributed 10.6%-30.7% of N2O production. For N2 production, the total contribution of co-denitrification and anammox was 14.2%-41.8%. The role of co-denitrification can not be ignored for N2O and N2 production. Our results demonstrated that the 15N labelling and pairing technique is a promising tool to quantify the contribution of different microbial processes to gaseous N loss.

The proportion of deposited urine patch intercepted by a delayed inhibitor application

ABSTRACT Nitrification inhibitors can reduce nitrous oxide (N2O) emissions and nitrate leaching losses from agricultural soils. Technologies have been developed to detect and target urine patches for inhibitor application, thereby reducing the total amount of inhibitor used. However, in practice there will be a time delay between the urine deposition and inhibitor application, potentially leading to physical separation of the inhibitor and urine that could reduce the effectiveness of the inhibitor compared to when the inhibitor and urine are well mixed. In this study, 2L of cattle urine was applied on two soil types in New Zealand. Twenty-four hours later the inhibitor dicyandiamide (DCD) was applied. The soil was sampled within 18 h and again after a rainfall event. DCD concentrations were measured in the 0–20 mm, 20–50 mm, and 50–100 mm depth ranges. The movement of the urine in the soil was simulated using the HYDRUS model. Before the rain most of the DCD was within the top 20 mm and intercepted 21–29% of the urine. After the rainfall event the DCD concentration decreased in the 0–20 mm layer and increased in the 20–50 mm layer. 18–55% or 63-79% of the urine was intercepted by DCD at a concentration of >4 ppm using the measured and modelled DCD concentrations, respectively. However, only 0–27% or 0-53% of the urine was intercepted at a DCD concentration >10 ppm.