Nitrification Inhibitor Nitrapyrin Research Articles

Impact of nitrapyrin on urea‐based fertilizers in a Mediterranean calcareous soil: Nitrogen and microbial dynamics

AbstractNitrification inhibitors, such as nitrapyrin (NI), are increasingly co‐applied with nitrogen (N) fertilizers as part of sustainable agricultural practice. Several studies in temperate regions have documented the effectiveness of NI in retaining soil ammonium (NH4+), minimizing N loss and increasing crop yields. However, less is known about the effects of NI in Mediterranean regions, where agricultural production is challenging and requires intensive irrigation and fertilization. We investigated the short‐term impact of the nitrification inhibitor nitrapyrin (2‐chloro‐6‐(trichloromethyl)pyridine) in a two‐factor mesocosm experiment, using a typical Mediterranean soil, where NI was co‐applied with a selection of urea‐based fertilizers: urea (U), U with urease inhibitors (U + UI), methylene urea (MU) and zeolite‐coated urea (ZU). NI co‐applied with urea fertilizers resulted in higher availability of soil NH4+ and a concurrent increase in NH3 volatilization. Net cumulative soil NH4+ availability was 1.5–3.3 fold greater when NI was applied. Concurrently, net cumulative nitrate (NO3−) and nitrite (NO2−) availability was reduced by 10%–60%; this was found for all the tested fertilizer types except MU fertilizer, where the net cumulative soil NO3− and NO2− doubled. Nitrous oxide (N2O) emissions from urea fertilization were reduced by 40% with UI, 50% with NI and 66% with NI + UI. Interestingly, after 28 d, the composition of soil microbial communities was distinctly different, due to NI application. Specifically, NI application dramatically reduced the abundance of ammonia‐oxidizing and denitrifying bacterial functional groups. NI was effective in reducing N2O emissions in this calcareous soil; however, NH3 emissions were remarkably enhanced. These findings have important implications for the large‐scale adoption of inhibitor technologies in Mediterranean agroecosystems and for the reduction of greenhouse gas emissions.

Effects of the nitrification inhibitor nitrapyrin on N2O emissions under elevated CO2 and rising temperature in a wheat cropping system

Nitrogen (N) fertilizer input will likely increase to meet the food demands of a growing population under climate change conditions, characterized by increasing atmospheric CO2 concentration and temperature. Nitrification inhibitors have the potential to reduce N2O emissions from N fertilized croplands. However, it remains unclear whether future climate change scenarios could affect the effectiveness of nitrification inhibitors. In a two-year study, winter wheat (Triticum aestivum L.) was cultivated in climate-controlled growth chambers with an elevated CO2 concentration (ambient +200 μmol mol−1) and increased temperature (ambient +2 °C). Urea was applied with or without nitrapyrin (0.5 % of urea-N). In this study, we measured nitrous oxide (N2O) fluxes, soil ammonium and nitrate levels, and the abundance of five nitrogen-cycling genes related to nitrification (amoA of ammonia-oxidizing bacteria (AOB) and ammonia-oxidizing archaea (AOA)) and denitrification (nirS, nirK and nosZ). Key findings included the following: 1) without nitrapyrin, cumulative N2O emissions were not significantly altered by increased temperature, but decreased 24.9 % by the combination of elevated CO2 and temperature treatment and 17.5 % by the elevated CO2 alone. NO3−-N accumulation occurred in soils under increased CO2 and temperature, both individual and in combination; 2) nitrapyrin effectively reduced AOB abundance, inhibiting NO3−-N accumulation and N2O emission, irrespective of CO2 concentrations and temperature. However, under the combination of elevated CO2 and temperature conditions, the efficiency of nitrapyrin in reducing N2O emission was lower (−13 % to −49 %) than that in the control (−28 % to −65 %) and elevated CO2 (−32 % to −71 %) conditions. This reduced effectiveness of the combined treatment can be attributed to the inability of nitrapyrin to inhibit the AOA, nirS and nirK genes. Thus, nitrapyrin is expected to reduce N2O emissions under future climate change scenarios, but the efficacy may be lower than previously expected when CO2 concentration and temperature increase simultaneously. The indirect effects of nitrapyrin on denitrifiers under climate change scenarios should be considered in future research.

Winter wheat responses to enhanced efficiency liquid nitrogen fertilizers in the Canadian Prairies

To evaluate how enhanced efficiency liquid nitrogen (N) fertilizers affect winter wheat ( Triticum aestivum L.) production under irrigated and rain-fed environments, experiments were conducted at two irrigated and five rain-fed sites across the Canadian Prairies from 2013 to 2018 (22 site-years). The N fertilizers included urea ammonium nitrate (UAN) treated with ( i) urease inhibitor N-(n-butyl) thiophosphoric triamide (NBPT), ( ii) NBPT plus nitrification inhibitor dicyandiamide, and ( iii) nitrification inhibitor nitrapyrin (Nitrapyrin), as well as untreated UAN and urea, and polymer-coated urea (PCU). All fertilizers were applied by banding 50% at planting and 50% in-crop in early-spring, except PCU, where PCU was applied at planting and urea was applied in early-spring. Nitrous oxide (N2O) emissions and methane (CH4) uptake were measured at one rain-fed site from 2014 to 2017. NBPT increased grain yield by 1.2%–14% and 2.8%–4% under irrigated and rain-fed environments, respectively, relative to all the other N sources except untreated urea in the rain-fed environment. Total N uptake with NBPT was between 0% and 12% higher than the other N sources across irrigated and rain-fed environments. The results suggested that both grain yield and N use efficiency were optimized when UAN contained a urease inhibitor. All liquid enhanced efficiency fertilizers produced grain protein content greater than 11%, except Nitrapyrin under irrigated environments. Data from three site-years indicated that greenhouse gas emissions were unaffected by N source under rain-fed conditions. Liquid UAN with a urease inhibitor may have the most potential to optimize winter wheat production and N use efficiency in the Canadian Prairies.

Winter wheat responses to enhanced efficiency granular nitrogen fertilizer in the Canadian Prairies

Optimizing the timing of nitrogen (N) enhanced efficiency fertilizers (EEFs) may maximize winter wheat ( Triticum aestivum L.) grain yield, protein content, and N-use efficiency (NUE). From 2013 to 2018, experiments were conducted at two irrigated and six rain-fed sites across the Canadian Prairies (24 site-years) to evaluate winter wheat responses to N source and timing/placement effects of EEFs. Nitrogen sources included untreated urea, nitrification inhibitor nitrapyrin treated urea, urease inhibitor N-( n-butyl) thiophosphoric triamide (NBPT) plus nitrification inhibitor dicyandiamide (DCD)-treated urea (NBPT + DCD), and polymer-coated urea (PCU). The N sources were all side-banded at planting, 30% side-banded at planting plus 70% broadcast in-crop late-fall (averaged 38 days after planting; split-applied late-fall), or 30% side-banded at planting plus 70% broadcast in-crop early-spring (averaged 224 days after planting; split-applied early-spring). Nitrous oxide and methane emissions were measured at one rain-fed site to test whether N source and timing/placement influenced CO2-equivalents (CO2-eq; nitrous oxide + methane). Under irrigation, NBPT + DCD consistently produced the highest yields regardless of timing/placement; however, the 80% of the recommended rate caused suboptimal protein responses (≤11%) unless split-application of N was adopted. Untreated urea produced the highest net CO2-eq and yield-scaled CO2-eq emissions, with the highest emissions when urea was split-applied early-spring. To optimize winter wheat production and NUE, we conclude that NBPT + DCD all-banded during seeding operations or split-applied early-spring provided similar and often superior results to other sources, including a more typical system of urea side-banded at the time of seeding.

Effect of straw incorporation and nitrification inhibitor on nitrous oxide emission in three cropland soils

AbstractIntroductionNitrification inhibitors and straw incorporation are used to reduce microbial mediated nitrogen (N) losses, thereby increasing N use efficiency (NUE) in cropland soil, but their effects on nitrous oxide (N2O) emission across different soil types and the underlying molecular mechanisms remain less understood.Materials and MethodsIn this study, we investigated how nitrification inhibitor nitrapyrin and straw incorporation affected soil N balance, N2O emission, nitrifiers and denitrifiers in three cropland soils (black, fluvo‐aquic and red soils).ResultsCompared with fertilization‐only treatment (N), nitrapyrin addition increased ammonium, while it decreased nitrate concentration in all soils; however, the performance of straw incorporation was less significant. Nitrapyrin decreased N2O emission only in the fluvo‐aquic soil, while straw incorporation strongly increased N2O emission in the red soil. Terminal restriction fragment length polymorphism analysis revealed that the denitrifier community was distinct across the three soils, but not strongly structured by nitrapyrin or straw incorporation. Compared with the N treatment, straw incorporation and nitrapyrin increased nosZ gene abundance only in the black soil. Structural equational modelling further confirmed that, after accounting for different soil properties, straw incorporation significantly increased N2O emission from black and red soils, and a decrease in nosZ gene abundance was the main biological factor for increased N2O emission in red soil.ConclusionTaken together, our work provides new knowledge that the performance of nitrification inhibitor and straw incorporation on N2O emission is soil type‐dependent, and management practices should be used as per soil type to balance NUE and N2O emission.

Response and recovery of nosZ abundant and rare subcommunities to organic amendment and nitrification inhibitor disturbances, with implications for N2O emissions

Clarifying the mechanisms underpinning the responses of abundant and rare taxa of the nitrous oxide reductase (nosZ) gene to fertilization disturbances is beneficial for understanding the relationships between N2O reduction and the nosZ community. Here, we compared the species richness, composition, and abundance of rare and abundant nosZ taxa and their community resistance and resilience within 85 days after different fertilization disturbances, i.e., chemical N anole (CF), chemical N + cattle manure (CM), and cattle manure + nitrification inhibitor nitrapyrin (CP). Our results showed that CM and CP disturbances significantly increased the species richness and α-diversity of the whole nosZ community (P < 0.05), which was mainly attributed to the changes in rare taxa rather than in the abundant taxa. The Bray–Curtis dissimilarity of community composition (average 0.56) of nosZ rare taxa was significantly greater than that of abundant taxa (average 0.26) after disturbances. The rare subcommunity was sensitive to CM and CP disturbances but was resistant to CF disturbance. The α-diversity and abundance of the nosZ community almost recovered at 85 days after disturbance, more so under CM amendment, while its community composition hardly recovered. The nosZ co-occurrence networks indicated that CM and CP disturbances substantially increased the strength of the connections and degrees and strengthened the co-occurrence relationships among modules compared to the CF disturbance. Furthermore, our results confirmed that the resistance or resilience of rare subcommunity compositions contributed more to the mitigation of N2O caused by CM and CF disturbances, and these were mainly derived by edaphic factors, including SOC, NO3−, pH, and CEC. Our findings suggested that rare taxa played a dominant role in mediating the resistance and resilience of nosZ communities in agro-soil under environmental disturbances and could significantly influence N2O emissions.

The nitrification inhibitor nitrapyrin has non-target effects on the soil microbial community structure, composition, and functions

Nitrapyrin is a nitrification inhibitor used to retain ammonia-N in soil to improve crop yields and quality. Nitrapyrin targets specifically the ammonia oxidizers, but it is not known if it has non-target effects on the soil microbial communities. Here, we tested the hypothesis that nitrapyrin also leads to large shifts in soil microbial community structure, composition, diversity and functions. To test this hypothesis, we set-up a field experiment where wheat (Triticum aestivum cv. AC Walton) was fertilized with ammonium nitrate (NH4NO3) and supplemented or not with nitrapyrin. Rhizosphere and bulk soils were sampled twice (at grain filling and harvest), the 16S rRNA gene and ITS region were amplified and sequenced to follow the changes in archaeal, bacterial and fungal community structure, composition and diversity. To assess microbial functions, several genes involved in the nitrogen cycle were quantified by real-time qPCR, and volatile organic compounds (VOCs) were trapped in the rhizosphere at the moment of sampling. Sampling dates and soil compartments had overwhelming effects on the microbial communities. However, nitrapyrin still significantly affected the relative abundance of Thaumarchaeota, Proteobacteria, Nitrospirae and Basidiomycota, and several genera. Nitrapyrin also significantly affected bacterial and fungal community structure, and the abundance of all the N-cycle gene tested, but always in interaction with the sampling date. In contrast, nitrapyrin had no significant effect on the emission of VOCs, where only sampling dates significantly influenced the profiles observed. Our results show that nitrapyrin influences non-target soil- and plant-associated microbial communities. In the longer term, these shifts might counteract the positive effect of nitrapyrin on crop nutrition and greenhouse gas emissions.

Biochar decreases the efficacy of the nitrification inhibitor nitrapyrin in mitigating nitrous oxide emissions at different soil moisture levels

Unprecedented increases in agricultural nitrous oxide (N2O) emissions in recent years have caused substantial environmental pollution that leads to ozone depletion and global warming. Application of biochar and/or nitrification inhibitors (NIs) has the potential to reduce N2O emissions; however, it is not clear how biochar application may affect the efficacy of NI in reducing nitrification rates, soil enzyme activities, and N2O emissions under different soil moisture regimes. We conducted a 60-day laboratory incubation experiment to study the effects of manure biochar and nitrapyrin (as a NI) on N2O emissions from a urea fertilized soil with either 60 (low) or 80% (high) water-filled pore space (WFPS). Nitrification rates were significantly affected by biochar × NI × WFPS and biochar × WFPS interactions. Biochar initially increased and then decreased the rates, resulting in 45.2 and 26.6% (P < 0.001 for both) overall reductions in low and high WFPS, respectively while NI reduced the rates only in the first 10 days at 60% WFPS. Biochar decreased (P < 0.001) and NI increased (P = 0.007) β-1,4-N-acetyl glucosaminidase activities while urease activities were increased (P < 0.001) by biochar across WFPS. Biochar had significant interaction with NI in cumulative N2O emissions with the efficacy of NI being reduced when co-applied with biochar. Cumulative N2O emissions were greater at high than at low WFPS; the emissions were decreased by biochar at 60% WFPS and NI at both 60 and 80% WFPS. We conclude that biochar reduces efficacy of nitrapyrin in mitigating N2O emissions and their effects on net nitrification rates, enzyme activities and N2O emissions are dependent on soil moisture level.

Using the Nitrification Inhibitor Nitrapyrin in Dairy Farm Effluents Does Not Improve Yield-Scaled Nitrous Oxide and Ammonia Emissions but Reduces Methane Flux

The application of dairy farm effluents (DFE) without previous treatment in paddocks was intensified due to the approval of this practice in Costa Rican legislation since 2012. Applying DFE instead of synthetic N fertilizer in grasslands is an opportunity to reach a circular economy; however, this practice increases the risk of emissions of nitrous oxide (N2O), methane (CH4), and ammonia (NH3), which contribute to global warming. A field experiment was carried out using a permanent grassland (90% Star grass and 10% Kikuyo grass) to simultaneously assess the effect of nitrapyrin on yield-scaled emissions of NH3, CH4, and N2O. The experiment lasted for 5 months in 2017, based on a randomized complete block design, including three treatments of control (CK) without N application, surface application of DFE with nitrapyrin (SNI), and without nitrapyrin (S). Total N applied was 149 ± 12 kg N ha−1 for both S and SNI treatments split into five applications. CH4 emissions from S, SNI, and CK showed a high temporal variation. Daily fluxes of CH4 from SNI were significantly lower than those of S in August (P &amp;lt; 0.05). Cumulative emissions of CH4, the majority produced in the soil, ranged from 4 to 168 g ha−1 for S, and from −13 to 88 g ha−1 for SNI. The ratio between the N2O cumulative emissions and the N applied as DFE were 1.6 ± 0.5 and 1.7 ± 0.2% for S and SNI, respectively. NH3 volatilization potential was very low (i.e., 0.6 ± 0.2% of the N applied). Under the prevailing experimental conditions, no significant difference between yield-scaled NH3 and N2O emissions were found between S and SNI, suggesting that nitrapyrin may not be a viable mitigation option for gaseous N losses from DFE application in Costa Rican grasslands in rainy season.

Widespread Use of the Nitrification Inhibitor Nitrapyrin: Assessing Benefits and Costs to Agriculture, Ecosystems, and Environmental Health.

Agricultural production and associated applications of nitrogen (N) fertilizers have increased dramatically in the last century, and current projections to 2050 show that demands will continue to increase as the human population grows. Applied in both organic and inorganic fertilizer forms, N is an essential nutrient in crop productivity. Increased fertilizer applications, however, create the potential for more N loss before plant uptake. One strategy for minimizing N loss is the use of enhanced efficiency fertilizers, fortified with a nitrification inhibitor, such as nitrapyrin. In soils and water, nitrapyrin inhibits the activity of ammonia monooxygenase, a microbial enzyme that catalyzes the first step of nitrification from ammonium to nitrite. Potential benefits of using nitrification inhibitors range from reduced nitrate leaching and nitrous oxide emissions to increased crop yield. The extent of these benefits, however, depends on environmental conditions and management practices. Thus, such benefits are not always realized. Additionally, nitrapyrin has been shown to transport off-field, and it is unknown what effects environmental nitrapyrin could have on nontarget organisms and the ecological nitrogen cycle. Here, we review the agronomic and environmental benefits and costs of nitrapyrin use and present a series of research questions and considerations to be addressed with future nitrification inhibitor research.

Nitrification inhibitor nitrapyrin does not affect yield-scaled nitrous oxide emissions in a tropical grassland

Urea is the most common nitrogen (N) fertilizer used in the tropics but it has the risk of high gaseous nitrogen (N) losses. Use of nitrification inhibitor has been suggested as a potential mitigation measure for gaseous N losses in N fertilizer-applied fields. In a field trial on a tropical Andosol pastureland in Costa Rica, gaseous emissions of ammonia (NH3) and nitrous oxide (N2O) and grass yield were quantified from plots treated with urea (U; 41.7 kg N ha–1 application–1) and urea plus the nitrification inhibitor nitrapyrin (U + NI; 41.7 kg N ha–1 application–1 and 350 g of nitrapyrin for each 100 kg of N applied) and control plots (without U and NI) over a six-month period (rainy season). Volatilization of NH3 (August to November) in U (7.4% ± 1.3% of N applied) and U + NI (8.1% ± 0.9% of N applied) were not significantly different (P > 0.05). Emissions of N2O in U and U + NI from June to November were significantly different (P < 0.05) only in October, when N2O emission in U + NI was higher than that in U. Yield and crude protein production of grass were significantly higher (P < 0.05) in U and U + NI than in the control plots, but they were not significantly different between U and U + NI. There was no significant difference in yield-scaled N2O emission between U (0.31 ± 0.10 g N kg–1 dry matter) and U + NI (0.47 ± 0.10 g N kg–1 dry matter). The results suggest that nitrapyrin is not a viable mitigation option for gaseous N losses under typical N fertilizer application practices of pasturelands at the study site.

Effects of the nitrification inhibitor nitrapyrin and tillage practices on yield-scaled nitrous oxide emission from a maize field in Iran

Nitrification inhibitors can effectively decrease nitrification rates and nitrous oxide (N2O) emission while increasing crop yield under certain conditions. However, there is no information available on the effects of nitrification inhibitors and tillage practices on N2O emissions from maize cropping in Iran. To study how tillage practices and nitrapyrin (a nitrification inhibitor) affect N2O emission, a split factorial experiment using a completely randomized block design with three replications was carried out in Northeast Iran, which has a cold semiarid climate. Two main plots were created with conventional tillage and minimum tillage levels, and two nitrogen (N) fertilizer (urea) management systems (with and without nitrapyrin application) were created as subplots. Tillage level did not have any significant effect on soil ammonium (NH4+) and nitrate (NO3–) concentrations, cumulative amount and yield-scaled N2O emission, and aboveground biomass of maize, whereas nitrapyrin application showed significant effect. Nitrapyrin application significantly reduced the cumulative amount of N2O emission by 41% and 32% in conventional tillage and minimum tillage practices, respectively. A reduction in soil NO3– concentration by nitrapyrin was also observed. The average yield-scaled N2O emission was 13.6 g N2O-N kg–1 N uptake in both tillage systems without nitrapyrin application and was significantly reduced to 7.9 and 8.2 g N2O-N kg–1 N uptake upon the application of nitrapyrin in minimum tillage and conventional tillage practices, respectively. Additionally, nitrapyrin application increased maize biomass yield by 4% and 13% in the minimum tillage and conventional tillage systems, respectively. Our results indicate that nitrapyrin has a potential role in reducing N2O emission from agricultural systems where urea fertilizers are broadcasted, which is common in Iran due to the practice of traditional farming.

Effects of the nitrification inhibitor nitrapyrin and the plant growth regulator gibberellic acid on yield-scale nitrous oxide emission in maize fields under hot climatic conditions

Nitrification inhibitors are widely used in agriculture to mitigate nitrous oxide (N2O) emission and increase crop yield. However, no concrete information on their mitigation of N2O emission is available under soil and environmental conditions as in Pakistan. A field experiment was established using a silt clay loam soil from Peshawar, Pakistan, to study the effect of urea applied in combination with a nitrification inhibitor, nitrapyrin (2-chloro-6-tri-chloromethyl pyridine), and/or a plant growth regulator, gibberellic acid (GA3), on N2O emission and the nitrogen (N) uptake efficiency of maize. The experimental design was a randomized complete block with five treatments in four replicates: control with no N (CK), urea (200 kg N ha–1) alone, urea in combination with nitrapyrin (700 g ha–1), urea in combination with GA3 (60 g ha–1), and urea in combination with nitrapyrin and GA3. The N2O emission, yield, N response efficiency, and total N uptake were measured during the experimental period. The treatment with urea and nitrapyrin reduced total N2O emission by 39%–43% and decreased yield-scaled N2O emission by 47%–52%, relative to the treatment with urea alone. The maize plant biomass, grain yield, and total N uptake increased significantly by 23%, 17%, and 15%, respectively, in the treatment with urea and nitrapyrin, relative to the treatment with urea alone, which was possibly due to N saving, lower N loss, and increased N uptake in the form of ammonium; they were further enhanced in the treatment with urea, nitrapyrin, and GA3 by 27%, 36%, and 25%, respectively, probably because of the stimulating effect of GA3 on plant growth and development and the reduction in biotic and abiotic stresses. These results suggest that applying urea in combination with nitrapyrin and GA3 has the potential to mitigate N2O emission, improve N response efficiency, and increase maize yield.

Adsorption of nitrification inhibitor nitrapyrin by humic acid and fulvic acid in black soil: characteristics and mechanism.

The compound nitrapyrin is easily adsorbed by soil organic matter in high-organic matter soils, and this results in its effectiveness reducing significantly. In this study, the adsorption characteristics and mechanisms of nitrapyrin as an adsorptive on humic acid (HA) and fulvic acid (FA) as adsorbents were investigated. The results showed that the kinetics of adsorption of nitrapyrin on both HA and FA followed pseudo-second-order kinetic models (R2 ≥ 0.925, P < 0.05) and the adsorption process included an initial fast-adsorption stage and a slow-adsorption stage thereafter. The adsorption efficiencies of nitrapyrin on HA + FA were higher than that on HA or FA alone, and that of HA was higher than that of FA. The adsorption isotherms of nitrapyrin on HA and FA could be optimally fitted with the Langmuir equation (R2 ≥ 0.982, P < 0.05). The maximum adsorption capacities of nitrapyrin on HA, FA and HA + FA were 4896.49, 3173.70 and 4925.56 mg kg−1, respectively. Synergistic adsorption of nitrapyrin in co-existing systems of HA and FA was also observed. The adsorption mechanism of nitrapyrin on both HA and FA involved hydrogen bonding and hydrophobic interaction. Therefore, HA and FA in the soil environment can adsorb a large amount of nitrapyrin and reduce its effectiveness, and they have a positive synergistic effect.

Effects of the nitrification inhibitor nitrapyrin and mulch on N2O emission and fertilizer use efficiency using 15N tracing techniques

Nitrous oxide (N2O), is a potent greenhouse gas (GHG) that shares 7% of global warming around the world. Among different sources, agricultural systems account for approx. 60% of global anthropogenic N2O emissions. These N2O emissions are associated with the activity of nitrifiers and denitrifiers that contribute to >4 Tg (teragrams) N2O-N emission per year. Application of nitrogen (N) fertilizers and manures in agricultural fields plays an imperative role in this regard. On the other hand nitrification inhibitors are an effective approach to minimize N2O-N emissions from agricultural fields. Here we examined the effects of applying urea with a nitrification inhibitor (Ni) nitrapyrin and mulch (Mu) on urea transformation, nitrous oxide (N2O) emissions, grain yield and nitrogen (N) uptake efficiency. The treatments include a control (zero N), urea (U) applied at 200 kg N ha−1, U + Ni (Ni applied at 700 g ha−1), U+ Mu (Mu applied at 4 t ha−1) and U + Ni + Mu. The N2O emission factor (EF) was 66% and 75% when U and Mu were applied, respectively. Yield-scaled N2O emissions were lower in U and Mu by 45% and 55%, respectively. The Ni coupled with Mu enhanced urea-15N recovery by 58% and wheat grain yield by 23% and total N uptake by 30% compared with U alone. In conclusion, Ni usage is an effective strategy to mitigate N2O emissions under field conditions.

The adsorption and mechanism of the nitrification inhibitor nitrapyrin in different types of soils.

The nitrapyrin was easily adsorbed by soil, but most current studies have focused on comparing the effects of nitrapyrin application at different soil organic matter levels and in different soil types. The adsorption kinetics and isotherm adsorption of the nitrification inhibitor nitrapyrin in black soil, chernozem and planosol were studied in this paper. The adsorption kinetics were fitted by quasi-second-order kinetic equation (R2 ≥ 0.8907, p < 0.05) with a lower acting energy of adsorption (Ea < 8.0 kJ mol−1). The isotherm was fitted by the Langmuir equation (R2 ≥ 0.9400*, p < 0.05). The adsorption mechanism was determined to involve a spontaneous endothermic reaction accompanied mainly by physical adsorption to the surface that belonged to the ‘L’ isotherm curve (n > 1). Temperature promoted the adsorption of nitrapyrin in these three soils, and the maximum adsorption occurring at different temperatures following the order of black soil > planosol > chernozem. The adsorption capacity and rate decreased with decreasing soil organic matter. For the black soil, the nitrapyrin EC adsorption rate was more than seven times higher than that of nitrapyrin CS. The result would determine the dose of nitrapyrin required for availability in different types of soils and to provide a theoretical basis for elucidating the adsorption of nitrapyrin in the soil environment.

Effect of Soil Organic Matter on Adsorption of Nitrification Inhibitor Nitrapyrin in Black Soil

ABSTRACTExperiments were conducted to study the adsorption kinetics and isothermal adsorption mechanism of nitrification inhibitor nitrapyrin onto the black soil of northeastern China. The nitrapyrin adsorption kinetics of the black soil were fitted with a quasi-second-order kinetics equation before and after organic matter removal (R2 ≥ 0.8320, p < .05). The adsorption isotherm was obtained by the Langmuir equation (R2 ≥ 0.9400, p < .05). Isothermal adsorption requires less energy and is a spontaneous endothermic reaction with an L-type isothermal curve (n > 1), dominated by surface physical adsorption. With the decrease of organic matter content in black soil, the adsorption mechanism of nitrapyin changed from distribution mechanism to surface adsorption. The black soil’s organic matter content exhibited a quadratic relation with the maximum adsorption capacity and adsorption constant (Kf) at the different temperatures, reaching significant levels (R2 ≥ 0.6484, p < .05).

Effects of enhanced efficiency nitrogen fertilizers on NH3 losses in a calcareous fluvo-aquic soil: a laboratory study

Excessive ammonia (NH3) emission to the atmosphere can cause a series of environmental problems and further cost to human health. Enhanced efficiency nitrogen (N) fertilizers (EENFs) were designed to reduce N losses to the environment and thus to improve fertilizer N use efficiency. The aim of the present study was to test the effectiveness of EENFs on NH3 emissions from surface-broadcast urea (dominant N application method for the studied region) in a fluvo-aquic soil under laboratory conditions. The study consisted of five treatments: (1) UREA: common urea; (2) UREA + NP: urea with incorporated nitrification inhibitor nitrapyrin; (3) UREA + DCD: urea with incorporated nitrification inhibitor dicyandiamide; (4) UREA + NBPT: urea with incorporated urease inhibitor NBPT [N-(n-butyl) thiophosphoric triamide]; (5) PCU, a polymer-coated urea. Urea with or without NP, DCD, and NBPT was dissolved in deionized water and was then carefully broadcast to the soil surface. The polymer-coated urea was surface-broadcast uniformly, and thereafter, deionized water was carefully dripped onto the soil surface. A forced-draft system with a volatilization chamber was employed to measure the NH3 flux. After the main experiment, the upper and lower soil layer was separately homogenized for analysis of soil ammonium N (NH4+-N) and nitrate N (NO3−-N) contents. The NH3 flux peak for UREA + NP, UREA + DCD, and UREA + NBPT treatment occurred on 5–8 days after fertilizer application, which were 1.04, 1.16, and 0.36 μg N cm−2 h−1, respectively, while NH3 flux for PCU treatment was very low (0.02–0.19 μg N cm−2 h−1) and no obvious NH3 flux peak emerged during the whole experiment. Urea with incorporated NP and DCD increased cumulative NH3 losses by 59% and 202% compared to urea only, respectively, while urea incorporated with NBPT and PCU reduced cumulative NH3 losses by 59% and 82% compared to urea only, respectively, Our results suggested that NH3 losses were greatly increased by applying the nitrification inhibitors nitrapyrin and dicyandiamide to urea, and nitrification inhibitors need to be carefully used in the fluvo-aquic soil. As surface-broadcast urea is nowadays still the dominant N application method in the NCP, surface application of NBPT-amended urea or PCU would be good options to reduce NH3 losses without having to change farmers’ fertilizer application method.

Nitrapyrin affects the abundance of ammonia oxidizers rather than community structure in a yellow clay paddy soil

PURPOSE: Yellow clay paddy soil (Oxisols) is a low-yield soil with low nitrogen use efficiency (NUE) in southern China. The nitrification inhibitor nitrapyrin (2-chloro-6- (tricholoromethyl)-pyridine, CP) has been applied to improve NUE and reduce environmental pollution in paddy soil. However, the effects of nitrapyrin combined with nitrogen fertilizers on ammonia oxidizers in yellow clay paddy soil have not been examined. MATERIALS AND METHODS: A randomized complete block design was set with three treatments: (1) without nitrogen fertilizer (CK), (2) common prilled urea (PU), and (3) prilled urea with nitrapyrin (NPU). Soil samples were collected from three treatments where CK, PU, and NPU had been repeatedly applied over 5 years. Soil samples were analyzed by quantitative PCR and 454 high-throughput pyrosequencing of the amoA gene to investigate the influence of nitrapyrin combined with nitrogen on the abundance and community structure of ammonia oxidizers in yellow clay paddy soil. RESULTS AND DISCUSSION: The potential nitrification rate (PNR) of the soil was significantly correlated with the abundances of both ammonia-oxidizing archaea (AOA) and ammonia-oxidizing bacteria (AOB). Application of urea significantly stimulated AOA and AOB growth, whereas nitrapyrin exhibited inhibitory effects on AOA. Phylogenetic analysis showed that the most dominant operational taxonomic units (OTUs) of AOA and AOB were affiliated with the Nitrosotalea cluster and Nitrosospira cluster 12, respectively. AOA and AOB community structures were not altered by urea and nitrapyrin application. CONCLUSIONS: Nitrogen fertilization stimulated nitrification and increased the population sizes of AOA and AOB. Nitrapyrin affected the abundance, but not community structure of ammonia oxidizers in yellow clay soil. Our results suggested that nitrapyrin improving NUE and inhibiting PNR was attributable to the inhibition of AOA growth.

Nutrient Uptake and Leaching from Soil Amended with Cattle Manure and Nitrapyrin

ABSTRACTWe investigated whether nitrification inhibitor nitrapyrin can reduce nutrient leaching and increase nutrient uptake by corn (Zea mays L.) in cattle manure amended soil. Amendments included non-amended check (CK), urea (Urea), REG (manure from cattle fed barley grain), and DDGS (manure from cattle fed 60% dried distillers grains with solubles), co-applied with or without nitrapyrin and leached or unleached with water. Nitrapyrin reduced (P < 0.01) leaching of nitrate by 56, 32, and 24% from DDGS, REG, and Urea treatments, respectively, and also reduced (P < 0.05) leaching of phosphate (58%), potassium (39%), calcium (39%), and magnesium (39%) from DDGS treatment. While nitrapyrin reduces the rate of ammonium conversion to nitrate, higher magnesium and phosphate levels in DDGS-amended soil favor struvite formation and reduce their leaching. Corn biomass and nutrient uptake were higher (P < 0.01) in DDGS and Urea than CK and REG treatments, but remained unaffected by nitrapyrin. The benefits of nitrapyrin should be further investigated under field conditions.Abbreviations: DCD, dicyandiamide; DDGS, dried distillers grains with solubles; NI, nitrification inhibitor; TP, total P; TN, total N.