Soil Nitrification Inhibitors Research Articles

Dissipation of AM Nitrification Inhibitor in Soil Supplemented with Organic Amendments

ABSTRACT To examine the effect of organic amendments on the dissipation and nitrification inhibition activity of 2-amino 4-chloro 6-methyl pyrimidine (AM), a laboratory study was conducted on a sandy loam soil (Typic Hapludoll) receiving no organic amendments (Control) or application of farmyard manure (FYM) or pine needles biochar (PNB) @ 5 t ha−1. Dissipation of AM was initially faster during the first 7 d, and then it slowed down. Dissipation kinetics of AM conformed to the first-order model (R2 values = 0.973 to 0.981, significant at p ≤ .01). The conventionally estimated time for the dissipation of half the amount of initially detected AM (half-life) was 15.9, 23.6, and 12.1 d for the control, FYM, and PNB treatments, respectively. All treatments receiving AM had numerically lower NO3 −–N concentrations compared to no AM but significantly lower NO3 −–N concentrations were recorded under, especially the PNB + AM treatment at 15, 30, 45, 60 and 90 d. The higher effectiveness of AM under PNB could be attributed to the sorption of AM in the micro-pores of PNB with slower release. Percent distribution of sorbed AM onto FYM and PNB revealed that desorption of sorbed AM from PNB was comparatively very limited. FTIR spectra revealed that both FYM and PNB strongly retained AM. Application of AM @1 mg kg−1 soil (equivalent to 2.24 kg ha−1) seems to effectively retard the nitrification of urea in soil amended with PNB and help reduce the leaching losses of NO3 −–N in agriculture.

Quantification of 3,4-Dimethyl-1H-Pyrazole Using Ion-Pair LC-MS/MS on a Reversed-Phase Column.

Few methods exist for the analysis of the soil nitrification inhibitor 3,4-dimethyl-1H-pyrazole (3,4-DMP), which is a pesticide with the ability to reduce the production of nitrogenous greenhouse gases in soils as a result of fertilizer application. Due to its small size and polar nature, 3,4-DMP can be difficult to retain on an LC column, which makes diversion of a co-extracted soil matrix away from the MS/MS impossible. The current study aims to better control the retention time (RT) of 3,4-DMP. Additionally, 3,4-DMP-15N2 was synthesized and used as an internal standard for the soil extraction of 3,4-DMP. Perfluoroalkanoic acids were used as ion-pair reagents and were compared for their abilities to improve peak shape and RT, to better separate 3,4-DMP from the soil matrix without the need for cleanup during soil extraction. RTs increased with both the carbon number and the concentration of the perfluoroalkanoic acid, and this improved peak shape and height. Perfluorooctanoic acid performed best, and improved peak height (PH) and shape were obtained by increasing the flow rate, resulting in a better S/N than from formic acid. The method provided a 10-fold improvement limit of quantitation on the most sensitive existing method and the use of 3,4-DMP-15N2 as an internal standard resulted in recoveries of 101-107%. Ion-pair reagents drastically increased the retention of 3,4-DMP and allowed the re-use of old LC columns that may otherwise be discarded. Improved separation of 3,4-DMP from the soil matrix allowed much of the matrix to be diverted from the MS/MS spray chamber. Greater control of 3,4-DMP retention by the LC column resulting in the ability to separate 3,4-DMP from the soil matrix. The inclusion of ion-pair reagents only in the aqueous phase reduced ionization suppression of the analytes in the MS source.

Evidences towards deciphering the mode of action of dimethylpyrazole-based nitrification inhibitors in soil and pure cultures of Nitrosomonas europaea

BackgroundAgriculture relies on the intensive use of synthetic nitrogen (N) fertilizers to maximize crop yields, which has led to the transformation of agricultural soils into high-nitrifying environments. Nevertheless, nitrification inhibitors (NIs) have been developed to suppress soil-nitrifier activity and decrease N losses. The NIs 3,4-dimethylpyrazole phosphate (DMPP) and 2-(3,4-dimethyl-1H-pyrazol-1-yl) succinic acid isomeric mixture (DMPSA) are able to reduce N2O emissions and maintain soil NH4+ for a longer time. Although both NIs have been proven to be effective to inhibit soil nitrification, their exact mode of action has not been confirmed. We aimed to provide novel insights to further understand the mode of action of DMP-based NIs. We evaluated the performance of DMPP and DMPSA in soil and pure cultures of nitrifying bacteria Nitrosomonas europaea.ResultsDMPSA did not inhibit nitrification in pure cultures of N. europaea. In the soil, we evidenced that DMPSA needs to be broken into DMP to achieve the inhibition of nitrification, which is mediated by a soil biological process that remains to be identified. Moreover, both DMPP and DMPSA are thought to inhibit nitrification due to their ability to chelate the Cu2+ cations that the ammonia monooxygenase enzyme (AMO) needs to carry on the first step of NH4+ oxidation. However, the efficiency of DMPP was not altered regardless the Cu2+ concentration in the medium. In addition, we also showed that DMPP targets AMO but not hydroxylamine oxidoreductase enzyme (HAO).ConclusionsThe inability of DMPSA to inhibit nitrification in pure cultures together with the high efficiency of DMPP to inhibit nitrification even in presence of toxic Cu2+ concentration in the medium, suggest that the mode of action of DMP-based NIs does not rely on their capacity as metal chelators.Graphical

A novel amended nitrification inhibitor confers an enhanced suppression role in the nitrification of ammonium in soil

PurposeNitrification inhibitor plays an important regulatory role in inhibiting the nitrification of ammonium in soils. However, most of nitrification inhibitors lack the sustainable effects in suppressing the nitrification of ammonium. In this study, a novel DMS nitrification inhibitor was prepared and tested to explore its lasting effect of nitrification suppression in black soil.Materials and methodsBoth culture experiments and field trial were performed in black soils. Three kinds of nitrification inhibitors (NIs), dicyandiamide (DCD) with low bioactivity, 3,4-dimethylpyrazole phosphate (DMPP) with high bioactivity, and a novel 3,4-dimethylpyrazole sulfate zinc (DMS) with long half-life, were applied into soils, respectively, and the abundance changes of ammonia-oxidizing archaea (AOA) and ammonia-oxidizing bacteria (AOB) were investigated; then, the accumulation changes of inorganic nitrogen, nitrogen use efficiency, and crop yields were furtherly evaluated.Results and discussionsA novel DMS nitrification inhibitor with high activity and long half-life maintained a persistent effect of nitrification suppression, and remarkably increased the accumulation of ammonium nitrogen in soil, thus improving nitrogen use efficiency and crop yields. This study implies that lowering the nitrogen loss of nitrification-triggered in soil is of great importance for improving nitrogen use efficiency.ConclusionsThis study provided an insight into the sustainable nitrification suppression of a novel DMS nitrification inhibitor under excessive application of nitrogen fertilizer in black soils. Compared with improving the activity, reasonably prolonging the validity of nitrification inhibitors in soil is a more important strategy increasing the sustainable effects of nitrification inhibition, and the survival period of nitrification inhibitors in soil should be a crucial factor improving nitrogen use efficiency.

Effects of rhizosphere soil nitrification on the compensatory growth of Italian ryegrass (Lolium multiflorum Lam) based on root‐produced cytokinin

AbstractCompensatory growth of forage grass can determine its optimal biomass, which is beneficial for increasing its production. The effect of rhizosphere soil nitrification on Italian ryegrass (Lolium multiflorum Lam) regrowth was investigated on the basis of root‐produced cytokinin concentration in leaves to reveal the forage grass compensatory growth mechanism. The nitrification inhibitor 3,4‐dimethylpyrazole phosphate was added to inhibit soil nitrification. Without soil nitrification being inhibited, compared with no clipping one defoliation cycle increased the leaf photosynthetic rate by 43.82%–53.79%, increased the leaf cytokinin content by 33.48%–34.73%, and increased the cytokinin transport from roots to leaves by 28.88%–39.47%. Nitrification inhibitor decreased soil nitrification rates by 23.33%–84.17% in the rhizosphere and by 42.71%–68.29% in the bulk soil during regrowth. In the rhizosphere micro‐environment, nitrification increased soil nitrate concentration that played an important role in the transport of cytokinin from roots to leaves during regrowth, increasing the leaf cytokinin concentration. However, bulk soil nitrification rate and nitrate content had little influence on leaf cytokinin concentration during regrowth. An increase in leaf cytokinin improved the photosynthesis and the regrowth. Without soil nitrification being inhibited, total biomass at the end of regrowth period was 1.09 times higher in plants that were defoliated once than in non‐clipped plants. However, soil nitrification inhibitor and two defoliation cycles decreased Italian ryegrass regrowth. Super compensatory growth occurred in the one defoliation cycle Italian ryegrasses without adding soil nitrification inhibitor. Compensatory growth occurred in once‐defoliated Italian ryegrass with adding soil nitrification inhibitor and in twice‐defoliated Italian ryegrass without adding soil nitrification inhibitor. In conclusion, rhizosphere soil nitrification is the key factor that regulates the compensatory growth of Italian ryegrass.

Methyl 3-(4-hydroxyphenyl) propionate modulates plant growth and secondary metabolite accumulation by inducing metabolic changes in Perilla frutescens

As one of the components of root exudates, methyl 3-(4-hydroxyphenyl) propionate (MHPP) not only functions as a nitrification inhibitor in soil but also modulates plant growth and root system architecture (RSA); however, the physiological and molecular mechanisms underlying MHPP-mediated plant growth remain largely unclear. Here, we investigated the effects of MHPP treatment on growth and secondary metabolite accumulation by integrating physiology, transcriptome and metabolome analyses using perilla (Perilla frutescens), a type of medicinal and edible plant. MHPP reduces primary root growth but markedly induces lateral root formation in perilla seedlings. The full-length transcript sequencing combined with the comparative transcriptomic analysis revealed that the differential expression of genes involved in carbon/nitrogen metabolism and secondary metabolism contributed to the MHPP-mediated plant growth. An investigation of the differentially expressed genes showed that MHPP modulates the growth and metabolism of leaves and roots in distinct pathways. The genes involved in the phenylpropanoid metabolism pathway showed opposite expression patterns between the roots and leaves, thereby resulting in the differential accumulation of secondary metabolites in the roots and leaves. Furthermore, the differential expression of PER genes and elevated peroxidase activity in the MHPP-treated roots were responsible for modulating the equilibrium of ROS and the components of lignin and phenolic compounds, thereby affecting plant growth and secondary metabolite accumulation. MHPP modulates RSA and metabolite profiles and improves the contents of medicinal ingredients in perilla plants. These results suggested that the application of MHPP may represent a useful strategy for the medicinal plant cultivation.

Degradation of AM Nitrification Inhibitor in Soil of Subtropical Region

ABSTRACTThe aim of the study was to evaluate the degradation and persistence of 2-amino 4-chloro 6-methyl pyrimidine (AM), nitrification inhibitor at 1 and 2 µg g−1 application rates in soil. The extraction of AM was done by QuEChER’s (Quick, Easy. Cheap. Rugged and Safe) method and the quantitative analysis by high-performance liquid chromatography (HPLC). AM decreased with time at both the levels of application with the decline being faster in the beginning up to 7 d. Dissipation of AM occurred in a single phase with the persistence data fitting well to the first-order kinetics. Half-lives of AM were determined to be 14.33 and 16.7 d at 1 and 2 µg g–1 levels application rates. Since AM remains effective for an adequate period of time, it can be used for increasing efficiency of nitrogenous fertilizers in rice–wheat cropping systems as well as a safeguard for controlling environmental pollution in subtropical soils.

Some plant extracts retarde nitrification in soil

An incubation experiment was conducted to evaluate the effect of aqueous extracts of 17 plant materials on nitrification inhibition of urea- N in soil as compared with chemical inhibitor Dicyandiamide (DCD). Plant materials used in study were collected from different areas of Basrah province, south of Iraq. Aqueous extracts were prepared at ratio of 1:10 (plant material: water) and added at conc. of 0.05, 0.10 and 0.20 ml g– 1 soil to loamy sand soil. DCD was added to soil at rate of 50 µg g-1 soil . Soil received urea at rate of 1000 µg N g-1 soil. Treated soils were incubated at 30 OC for 40 days. Results showed that application of all plant extracts, except those of casuarina, date palm and eucalyptus to soil retarded nitrification in soil. Caper, Sowthistle ,bladygrass and pomegranate extracts showed highest inhibition percentage (51, 42, 40 and 40 %, respectively) and were found to be more effective than DCD (33 %). Highest inhibition was achieved by using those extracts at conc. of 0.1 ml g-1 soil after 10 days of incubation . Data also revealed that treated soil with these plant extracts significantly increased amount of NH4+–N and decreased amount of NO3-–N accumulation in soil compared with DCD and control treatments. Results of the study suggested a possibility of using aqueous extracts of some studied plants as potent nitrification inhibitor in soil.

Research on nitrogen circulation and management of bamboo: a review

As one of forest resources, bamboo forest not only has important economic values but also provides important ecosystem services including soil conservation, water conservation, carbon fixation and oxygen release. Bamboo cultivation has been a focus of research in recent years. Fertilizing is an important measure to improve bamboo cultivation. As one of the major factors affecting the growth of bamboo, nitrogen has great influences on the growth and development of bamboo. In order to provide scientific theoretical basis for bamboo nitrogen input, this paper summarized nutrient diagnosis of bamboo, nitrogen balance of bamboo, nitrogen absorption and utilization of bamboo, environmental impacts on bamboo nitrogen, and put forward the following focus areas for further research on bamboo nitrogen: nitrogen cycling of bamboo, the influence of nitrogen forms on bamboo growth, bamboo soil nitrification inhibitors based on the quality assurance of the bamboo shoots, environmental safety based nitrogen input, and development and application of exclusive controlled-release fertilizer of bamboo nitrogen. ［Ch, 52 ref.］

Can nitrogen fertiliser and nitrification inhibitor management influence N2O losses from high rainfall cropping systems in South Eastern Australia?

Nitrous oxide (N2O) is a potent greenhouse gas released from high rainfall cropping soils, but the role of management in its abatement remains unclear in these environments. To quantify the relative influence of management, nitrogen (N) fertiliser and soil nitrification inhibitor was applied to separate but paired raised bed and conventionally flat field experiments in south west Victoria, to measure emissions and income from wheat and canola planted 2 and 3 years after conversion from a long-term pasture. Management included four different rates of N fertiliser, top-dressed with and without the nitrification inhibitor Dicyandiamide (DCD), which was applied in solution to the soil in the second year of experimentation. Crop biomass, grain yield, soil mineral N, soil temperature and soil water and N2O flux were measured. Static chamber methodology was used to identify relative differences in N2O loss between management. In the second crop (wheat) following conversion, N2O losses were up to 72 % lower (P < 0.05) in the furrows, receiving the lower rate of N fertiliser compared with the highest rate, with less frequent reductions observed in the third crop (canola); losses of N2O from the beds was unaffected by N rate, perhaps from nitrate leakage into the adjacent furrow of the raised bed experiment. On the nearby flat experiment, nitrate leaching may have diminished the effects of N rate and DCD on N2O flux. Furthermore the extra N did not significantly increase grain yield in either the wheat or canola crops on both experiments. The application of DCD in the canola crop temporarily reduced (P < 0.05) N2O production by up to 84 % from the beds, 83 % in the adjacent furrows and 75 % on the flat experiment. Grain yield was not significantly (P < 0.001) affected however, canola income was reduced by $1407/ha and $1252/ha, compared with no addition of inhibitor on the respective bed and flat experiments. Although N2O fluxes are driven by environmental episodic events, management will play a role in N2O abatement. However, DCD currently appears economically unfeasible and matching N fertiliser supply to meet crop demand appears a better option for minimising N2O losses from high rainfall cropping systems.

Which cropland greenhouse gas mitigation options give the greatest benefits in different world regions? Climate and soil‐specific predictions from integrated empirical models

AbstractMajor sources of greenhouse gas (GHG) emissions from agricultural crop production are nitrous oxide (N2O) emissions resulting from the application of mineral and organic fertilizer, and carbon dioxide (CO2) emissions from soil carbon losses. Consequently, choice of fertilizer type, optimizing fertilizer application rates and timing, reducing microbial denitrification and improving soil carbon management are focus areas for mitigation. We have integrated separate models derived from global data on fertilizer‐induced soil N2O emissions, soil nitrification inhibitors, and the effects of tillage and soil inputs of soil C stocks into a single model to determine optimal mitigation options as a function of soil type, climate, and fertilization rates. After Monte Carlo sampling of input variables, we aggregated the outputs according to climate, soil and fertilizer factors to consider the benefits of several possible emissions mitigation strategies, and identified the most beneficial option for each factor class on a per‐hectare basis. The optimal mitigation for each soil‐climate‐region was then mapped to propose geographically specific optimal GHG mitigation strategies for crops with varying N requirements. The use of empirical models reduces the requirements for validation (as they are calibrated on globally or continentally observed phenomena). However, as they are relatively simple in structure, they may not be applicable for accurate site‐specific prediction of GHG emissions. The value of this modelling approach is for initial screening and ranking of potential agricultural mitigation options and to explore the potential impact of regional agricultural GHG abatement policies. Given the clear association between management practice and crop productivity, it is essential to incorporate characterization of the yield effect on a given crop before recommending any mitigation practice.

Nitrosomonas europaea ATCC25978 Is the Right Ammonia-Oxidizing Bacterium for Screening Nitrification Inhibitors

To determine whether Nitrosomonas europaea is adequate to assay nitrification inhibitors as representative of ammonia-oxidizing bacteria or not, the inhibitory activity exhibited by known nitrification inhibitors in soil and the susceptibility of recently isolated ammonia-oxidizing bacteria to the inhibitors in cell suspension were compared. Nitrapyrin, MAST and Br-MAST completely inhibited nitrification in soil at 15 ppm for 15 days, whereas dicyanodiamide and thiourea were weak inhibitors. In order of effectiveness, the inhibitors ranked as follows; Br-MAST>MAST>nitrapyrin>>dicyanodiamide ≥ thiourea. Ammonia-oxidation by ammonia-oxidizing bacteria in cell suspension was strongly inhibited by nitrapyrin, MAST and Br-MAST, whereas dicyanodiamide and thiourea were weak inhibitors. N. europaea is adequate to assay nitrification inhibitors as representative of ammonia-oxidizing bacteria.

Evaluation of XDE‐474 as a soil nitrification inhibitor

Abstract This study was conducted to evaluate the effectiveness of XDE‐474 as a nitrification inhibitor in two soils that differed significantly in organic carbon (C) and texture. The results were compared with those obtained by using nitrapyrin [N‐Serve: 2‐chloro‐6‐(trichloromethyl)pyridine]. In the first experiment, a 10 g sample of surface soil treated with 1 mL ammonium sulfate [(NH4)2SO4] solution containing 2 mg nitrogen (N) and increasing concentrations of 0.05, 0.10, 0.20, or 0.40 μg active ingredient (AI)/g of the inhibitors was incubated at 20°C for 14 days. In the second experiment, the soil sample treated with (NH4)2SO4 and 0.40 μg AI/g inhibitor was incubated at 10, 20, or 30°C for 14 days. The results showed that application of XDE‐474 to soils induced nitrification of indigenous soil organic N. Nitrification rate decreased significantly as inhibitor concentrations increased. The superiority of XDE‐474 over nitrapyrin in controlling nitrification of (NH4)2SO4 added to soils was clearly demon...

Efficacy of Dicyandiamide as a Soil Nitrification Inhibitor in Citrus Production

AbstractNitrification inhibitors such as dicyandiamide (DCD) help reduce leaching losses by retaining applied N in the ammoniacal form. Research objectives were to evaluate dicyandiamide added to ammonium sulphate nitrate (ASN) as a nitrification inhibitor in cultivated soils (Xeropsamments) and its effect on N uptake by citrus (Citrus sinensis (L.) Osbeck). In a greenhouse experiment, 10 g N as ASN either with or without 2% of DCD‐N were applied to plants grown in 50‐L pots filled with peat and sand (2:1). Addition of DCD to ASN resulted in significantly higher levels of NH+4‐N in the substrate than the ASN treatment, for at least 100 d. Drainage water from the ASN‐DCD treated pots was lower in NO−3‐N concentration during the first 60 d. Inclusion of DCD with ASN resulted in greater uptake of the fertilizer N by citrus plants. Under field conditions, fertilization of adult trees with ASN (600 g N tree−1) either with or without DCD (2% DCD‐N) was compared. In the ASN‐amended soil, nitrification was much more rapid than when DCD was added to the ASN. Fertilization with ASN + DCD maintained relatively high levels of NO−3‐N in soil longer than ASN alone. In another experiment, 60 g N as ASN either with or without DCD (2% DCD‐N) were applied to 3‐yr‐old citrus plants grown individually outdoors in containers and the distribution of NH+4‐N and NO−3‐N in the soil profile after consecutive flood irrigations was monitored. After the third irrigation, 68% of applied N was leached below 0.45 m in ASN amended soils, whereas only a very small amount of the applied N was retained above this depth. When DCD was added, only 20% of the applied N was lost by leaching at this time. The DCD nitrification inhibitor improved the N fertilizer efficiency and decreased NO−3 losses so as to minimize the economic and environmental risks that are inherent in irrigated production of citrus.

Evaluation of 2‐Ethynylpyridine as a Soil Nitrification Inhibitor

AbstractRecent work in our laboratory showed that 2‐ethynylpyridine is a potent inhibitor of nitrification in soil. To further evaluate this compound as a soil nitrification inhibitor, we compared the effects of 2‐ethynylpyridine and 16 compounds patented or proposed as fertilizer amendments for inhibition of nitrification in soil. We measured production of NO2 and NO3 in soils incubated under aerobic conditions at 20, 25, or 30 °C after treatment with (NH4)2SO4 or urea. The data obtained showed that 2‐ethynylpyridine compared favorably with nitrapyrin [N‐Serve; 2‐chloro‐6‐(trichloromethyl)pyridine] and etridiazole [Dwell; 5‐ethoxy‐3‐trichloromethyl‐1,2,4‐thiadiazole] for inhibition of nitrification in soil and was considerably more effective than the other nitrification inhibitors tested (dicyandiamide [DCD], thiourea [Tu], guanylthiourea [ASU], potassium azide, 4‐amino‐1,2,4‐triazole [ATC], 2‐amino‐4‐chloro‐6‐methylpyridine [AM], 2‐mercaptobenzothiazole [MBT], 2,4‐diamino‐6‐trichloromethyltriazine, sulfathiazole [ST], sodium thiocarbonate [Na2CS3], N‐2,5‐dichlorophenylsuccinamide [DCS], 4‐nitrobenzotrichloride, 4‐mesylbenzotrichloride, and ammonium thiosulfate [(NH4)2S2O3]). Other studies showed that 2‐ethynylpyridine is more effective for inhibiting nitrification of NH4‐N than of urea‐N, that it has very little, if any, effect on hydrolysis of urea or denitrification of NO3 in soil, and that its effectiveness as a soil nitrification inhibitor is markedly affected by soil type and temperature. These findings and other work reported indicate that 2‐ethynylpyridine deserves consideration as a fertilizer amendment for retarding nitrification of fertilizer N in soil.

Evaluation of 3-methylpyrazole-1-carboxamide as a soil nitrification inhibitor

Laboratory studies to evaluate 3-methylpyrazole-1-carboxamide (MPC) as a soil nitrification inhibitor showed that it was comparable to nitrapyrin (N-Serve) for inhibiting nitrification of ammonium in soil, but was not as effective as etridiazole (Dwell) or 2-ethynylpyridine. They also showed that the effectiveness of MPC as a soil nitrification inhibitor is markedly affected by soil type and soil temperature, that MPC is more effective for inhibiting nitrification of ammonium-N than of urea-N, and that MPC has little, if any, effect on hydrolysis of urea or denitrification of nitrate in soil. These observations and other work discussed indicate that MPC is one of the most promising compounds so far proposed for inhibition of nitrification in soil.

Laboratory evaluation of dicyandiamide as a soil nitrification inhibitor

Abstract Laboratory studies to evaluate dicyandiamide (DCD) as a soil nitrification inhibitor showed that it is considerably more effective than several compounds that have been patented or proposed as fertilizer amendments for retarding nitrification of fertilizer nitrogen (N) in soil, but is considerably less effective than 2‐ethynylpyridine, nitrapyrin (N‐Serve), etridiazole (Dwell), 3‐methylpyrazole‐l‐carboxamide (MPC), or 4‐amino‐l,2,4‐triazole (ATC). Other findings in studies reported were as follows: a) DCD is more effective for inhibiting nitrification of ammonium‐N than of urea‐N; b) the effectiveness of DCD as a nitrification inhibitor is markedly affected by soil temperature and soil type and is limited by the susceptibility of DCD to leaching; c) DCD has very little, if any, effect on urea hydrolysis, denitrification, or seed germination in soil; d) products of DCD decomposition in soil (guanylurea and guanidine) have little, if any, effect on nitrification compared with DCD; e) in the absence...

A method of selective inhibition to distinguish between nitrification and denitrification as sources of nitrous oxide in soil

Nitrapyrin and C2H2 were evaluated as nitrification inhibitors in soil to determine the relative contributions of denitrification and nitrification to total N2O production. In laboratory experiments nitrapyrin, or its solvent xylene, stimulated denitrification directly or indirectly and was therefore considered unsuitable. Low partial pressures of C2H2 (2.5–5.0 Pa) inhibited nitrification and had only a small effect on denitrification, which made it possible to estimate the contribution of denitrification. The contribution of nitrification was estimated by subtracting the denitrification value from total N2O production (samples without C2H2). The critical C2H2 concentrations needed to achieve inhibition of nitrification, without affecting the N2O reductase in denitrifiers, must be individually determined for each set of experimental conditions.

Inhibition of Nitrification in Soil by Acetylenic Compounds

AbstractRecent work has shown that acetylene (ethyne) is a potent inhibitor of nitrification in soil. To discover if substituted acetylenes inhibit nitrification in soil, we determined the effects of seventeen monosubstituted (HC ≡ CR) acetylenes (propyne, 1‐butyne, 2‐ethynylpyridine, phenylacetylene, 3‐butyn‐2‐one, 1‐phenyl‐2‐propyn‐1‐ol, 1‐pentyne, 4‐phenyl‐1‐butyne, 5‐phenyl‐1‐pentyne, 1‐ethynylcycloh‐examine, 2‐propyn‐1‐ol, 2‐propyn‐1‐amine, 1‐hexyne, 3‐butyn‐1‐ol, 1‐heptyne, 1‐octyne, acetylene monocarboxylic acid) and of seven disubstituted (RC ≡ CR′) acetylenes (2‐butyne, 3‐phenyl‐2‐propyn‐1‐ol, diphenylacetylene, 2‐butyn‐1‐ol, 2‐butyn‐1,4‐diol, acetylene dicarboxylic acid, 2‐butynoic acid) on production of (NO‐3 + NO‐2)‐N in soils treated with (NH4)2SO4. The data obtained showed that most of the substituted acetylenes tested inhibited nitrification in soil and that some were potent inhibitors of nitrification. The results with the four gaseous compounds tested showed that acetylene, propyne, and 1‐butyne inhibited nitrification in soils at partial pressures as low as 0.1 or 1.0 Pa, whereas 2‐butyne had little or no effect on nitrification at partial pressures as high as 10 Pa. The data obtained with the 21 nongaseous compounds tested showed that 2‐ethynylpyridine, phenylacetylene, and 3‐butyn‐2‐one had the greatest inhibitory effect on nitrification and that acetylene monocarboxylic acid, acetylene dicarboxylic acid, and 2‐butynoic acid had the least effect. Studies to measure production of C2H2 in soils treated with the nongaseous compounds showed that the inhibition of nitrification observed with these compounds was not due to C2H2 formed by their decomposition in soil. Experiments reported indicate that 2‐ethynylpyridine and phenylacetylene compare favorably with nitrapyrin (N‐Serve) and etridiazole (Dwell) as soil nitrification inhibitors and have potential practical value for retarding nitrification of fertilizer N in soil.

Effects of urease inhibitors on nitrification in soils

The effects of 10 urease inhibitors on nitrification in soils were studied by determining the effects of 10 and 50 parts/10 6 (soil basis) of each inhibitor on the amounts of nitrate and nitrite produced when soils treated with ammonium sulfate (200 μg of ammonium N/g of soil) were incubated (30°C) under aerobic conditions for 14 days. The urease inhibitors used (catechol. hydroquinone, p-benzoquinone, 2,3-dimethyl- p-benzoquinone, 2,5-dimethyl- p-benzoquinone. 2,6-dimethyl- p-benzoquinone. 2,5-dichloro- p-benzoquinone, 2,6-dichloro- p-benzoquinone. sodium p-chloromercuribenzoate, and phenylmercuric acetate) were those found most effective in previous work to evaluate more than 130 compounds as soil urease inhibitors. Their effects on nitrification were compared with those of three compounds patented as soil nitrification inhibitors (N-Serve. AM. and ST). Most of the urease inhibitors studied had little effect on nitrification when applied at the rate of 10 μg/g of soil. but had marked inhibitory effects when applied at the rate of 50 μg/g of soil. None inhibited nitrification as effectively as N-Serve. but phenylmercuric acetate inhibited nitrification more effectively than did AM or ST when applied at the rate of 10 μg/g of soil. Phenylmercuric acetate, 2,5-dimethyl- p-benzoquinone, and 2,6-dimethyl- p-benzoquinone had very marked effects on nitrification when applied at the rate of 50 μg/g of soil.