Nitrification Inhibitor Research Articles

Nitrogen removal capability and mechanism of a novel heterotrophic nitrifying-aerobic denitrifying strain H1 as a potential candidate in mariculture wastewater treatment.

The nitrogen removal performance and mechanisms of Bacillus subtilis H1 isolated from a mariculture environment were investigated. Strain H1 efficiently removed NH4+-N, NO2--N, and NO3--N in simulated wastewater with removal efficiencies of 85.61%, 90.58%, and 57.82%, respectively. Strain H1 also efficiently degraded mixed nitrogen (NH4+-N mixed with NO2--N and/or NO3--N) and had removal efficiencies ranging from 82.39 to 89.54%. Nitrogen balance analysis revealed that inorganic nitrogen was degraded by heterotrophic nitrification-aerobic denitrification (HN-AD) and assimilation. 15N isotope tracing indicated that N2O was the product of the HN-AD process, while N2 as the final product was only detected during the reduction of 15NO2--N. The nitrogen assimilation and dissimilation pathways by strain H1 were further clarified using complete genome sequencing, nitrification inhibitor addition, and enzymatic activity measurement, and the ammonium oxidation process was speculated as NH4+ → NH2OH → NO → N2O. These results showed the application prospect of B. subtilis H1 in treating mariculture wastewater.

Influence of seaweed extracts on the degradation and effectiveness of 3,4-dimethylpyrazole phosphate

3,4-Dimethylpyrazole phosphate (DMPP) is acknowledged as one of the most efficient nitrification inhibitors (NIs); however, researchers have suggested that its effectiveness needs to be further improved. The authors combined the biostimulant seaweed extract (SE) with DMPP and conducted an indoor incubation experiment to initially investigate the impact of the influence of SE on the degradation and effectiveness of DMPP. Meanwhile, a method for the extraction and determination of DMPP was developed. DMPP performed better, with a longer effective time in loess than black soil, and SE showed a delayed effect on DMPP degradation of DMPP at the beginning of the incubation and then accelerated the degradation process. This was attributed to the adsorption effect of SE on DMPP, consequently reducing its effectiveness. The SE delayed the hydrolysis of urea in various soils; however, no significant impact on urease activity was observed (P < 0.05) (P < 0.05). Furthermore, it also increased potential nitrification rate (PNR) from 10 to 21 days and promoting the rapid transformation of NH4+-N in black soil. The SE reduced PNR within 21 days and inhibited nitrification in loess. In addition, the SE appeared to mitigate the adverse effects of excessive nitrogen on microorganisms The combination of DMPP and SE was not conducive to the inhibition of soil nitrification, and this formulation in field applications requires further investigation.

Drug discovery-based approach identifies new nitrification inhibitors

Nitrogen (N) fertilization is crucial to sustain global food security, but fertilizer N production is energy-demanding and subsequent environmental N losses contribute to biodiversity loss and climate change. N losses can be mitigated be interfering with microbial nitrification, and therefore the use of nitrification inhibitors in enhanced efficiency fertilizers (EEFs) is an important N management strategy to increase N use efficiency and reduce N pollution. However, currently applied nitrification inhibitors have limitations and do not target all nitrifying microorganisms. Here, to identify broad-spectrum nitrification inhibitors, we adopted a drug discovery-based approach and screened 45,400 small molecules on different groups of nitrifying microorganisms. Although a high number of potential nitrification inhibitors were identified, none of them targeted all nitrifier groups. Moreover, a high number of new nitrification inhibitors were shown to be highly effective in culture but did not reduce ammonia consumption in soil. One archaea-targeting inhibitor was not only effective in soil, but even reduced - when co-applied with a bacteria-targeting inhibitor - ammonium consumption and greenhouse gas emissions beyond what is achieved with currently applied nitrification inhibitors. This advocates for combining different types of nitrification inhibitors in EEFs to optimize N management practices and make agriculture more sustainable.

The response of nitrifying activated sludge to chlorophenols: Insights from metabolism and redox homeostasis

The specialized wastewater treatment plants for the chemical industry are rapidly developed in China and many other countries. But there is a common bottleneck in that the toxic pollutants in chemical wastewater often cause shock impacts on biological nitrogen removal systems, which directly affects the stability and cost of operation. As the research on nitrification inhibition characteristics is not sufficient till now, there is a great lack of theoretical guidance on the control of the inhibition. This study investigated the response of nitrifying activated sludge to chlorophenols (CPs) inhibition in terms of metabolism disorder and oxidative stress. At the initial stage of reaction (i.e., 1 h), reactive oxygen species (ROS)-induced membrane damage which might account for declining nitrification performance. Simultaneously excessive extracellular polymeric substances (EPS) were secreted to alleviate oxidative stress injury and protected microorganisms to some extent. In particular tyrosine-like substances in LB-EPS with a Fmax increase of 242.30% were confirmed to efficiently resist phenols inhibition. Thus, as the inhibition proceeded, metabolism disorder replaced oxidative stress as the main cause of nitrification inhibition. The affected metabolic processes include weakened enzyme catalysis, restricted electron transport and lessened energy generation. At 4 h, nitrifying production of sludge amended with 5 mg/L chlorophenols was 89.27 ± 9.51%–98.15 ± 9.60% lower than blank, the inhibition could be attributed to comprehensively affected metabolism. The structural equation modeling indicated that phenols restricted nitrification enzymes and bacterial electron transport efficiency which was critical to nitrification performance. Moreover, the lessened energy generation weakens enzyme activity to further suppress nitrification. These findings enriched our knowledge of nitrifiers’ responses to CPs inhibition and provided the basis for addressing nitrification inhibition.

Adding nitrification inhibitors to N fertilisers induces rhizosphere acidification and enhances P acquisition: A meta-analysis

Ammonium (NH4+) absorption by crops enhances inorganic phosphate (Pi) acquisition efficiency mediated by rhizosphere acidification. The application of nitrification inhibitors (NIs) prolong NH4+ retention in soil by inhibiting ammonia oxidation and facilitating ammonium uptake by crops which may promote crop P utilisation. However, the efficacy of NIs on enhanced P-utilisation efficiency has not been comprehensively evaluated, and the mechanism underlying these effects remains unclear. Here, a meta-analysis of 92 peer-reviewed articles (1217 paired observations) was conducted to investigate soil pH and crop P absorption changes under NIs amendment, and boosted regression tree model was adopted to identify the primary factor regulating enhanced P-efficiency. The results showed that the addition of NIs reduced the rhizosphere soil pH by 12.37% and increased bulk soil pH by 2.38%, increased plant N and P uptake by 16.09% and 8.49%, respectively, and shoot N and P concentrations by 4.38% and 6.73%, respectively. NIs significantly decreased the crop N/P ratio and alleviated P limitation for crop production. Fertiliser (N and P) application method, NI product type, and soil properties (soil organic carbon, available P, total N content and soil texture) are major factors affecting crop P uptake. Using dicyandiamide (DCD) or 3,4-dimethylpyrazole phosphate (DMPP) as NIs combined with the application of ammonium-based fertiliser, adoption of subsurface or one-time N application, or application of these fertilisers to coarse-textured soils could significantly decrease rhizosphere soil pH while increasing crop P uptake. This study quantitatively demonstrated the positive impact of NIs on crop P acquisition using a meta-analysis approach, enhanced the knowledge on the incidental efficacy of N stabilisers and provide a strategy for the sustainable management of N and P in agriculture.

Emissions Reduction Strategies for the Orange and Cherry Industries in New South Wales.

The orange and cherry industries in New South Wales, Australia, are major horticulture industries with a high export value. Climate change has resulted in the carbon footprint of products being used by consumers to guide purchases meaning that products with a relatively high carbon footprint risk losing market access. The carbon footprint of cherry and orange production is unknown and there is no assessment of the success of climate change mitigation strategies to reduce the carbon footprint of their production and move production towards being carbon neutral. This study assesses the climate change mitigation potential of five management changes to on-farm cherry and orange production (revegetation, the use of nitrification inhibitors, renewable energy, green N fertilisers, and pyrolysis of orchard residues) over a 25-year period. for example, orchards in relevant growing regions. The results show that the carbon footprint of production can be reduced by 73 and 83% for cherries and oranges, respectively, when strategies that avoid emissions are included in their production. When strategies that sequester C from the atmosphere are also included, cherry and orange production becomes C negative in the first few years of the scenario. The economics of implementing these strategies are unfavourable, at present; however, our results indicate that the NSW cherry and orange industries can be confident in achieving emissions reductions in on-farm production to assure market access for their products.

Effects of combined natural synergists and chemical inhibitors on yield, nitrogen utilization and balance in wheat/maize rotation system.

Urease inhibitors and nitrification inhibitors can enhance nitrogen (N) fertilizer utilization efficiency and reducing N losses through regulating urea-N transformation. Common urease or nitrification inhibitors, however, are predominantly chemically synthesized and high-cost. Furthermore, their inhibitory effects are mediated by soil pro-perties, climatic conditions, and crop systems. In this study, we conducted a field experiment using natural synergists humic acid/zeolite, along with chemical nitrification inhibitor dicyandiamide (DCD) and their combination to elucidate the impacts of natural synergists combined with chemical inhibitors on annual yield, nitrogen utilization efficiency, soil nitrate-N accumulation, and nitrogen balance within the wheat/maize rotation system. The treatments included no nitrogen fertilizer application (CK), single application of urea (N), urea +DCD (ND), urea + humic acid (NH), urea + zeolite (NP), urea + urease inhibitor N-butylthiophosphoric triamide + DCD (NUD), urea + humic acid + DCD (NHD), and urea + zeolite + DCD (NPD). The results showed that, compared to the treatments NH and NP, the integration of humic acid or zeolite with DCD (NHD and NPD) significantly increased maize yield (11268 and 11397 kg·hm-2) and total annual yield (20494 and 20582 kg·hm-2), which were comparable to those of combined chemical urease and nitrification inhibitors (NUD). The NHD and NPD treatments had higher nitrogen utilization efficiency and lower soil nitrate-N accumulation in 80-100 cm soil layer across all seasons relative to the N treatment, which had no significant difference compared to the NUD treatment. Furthermore, a decline in soil nitrogen surplus by 10.7% and 13.9% was observed when comparing the NHD and NPD treatments with the NH and NP treatments, respectively. These findings suggested that combined humic acid or zeolite and chemical nitrification inhibitors could effectively enhance crop yield and N utilization efficiency and meet the requirements of the green and environmental preservation of modern agriculture.

Identification of nitrification inhibition in maize to mitigate soil nitrogen loss

Identification of nitrification inhibition in maize to mitigate soil nitrogen loss

Reduction of NH3 Emissions from Urea by Long-Term No-Tillage and Stover Mulching with Inhibitors: An Isotopic Field Study in Northeast China

Large nitrogen (N) losses during fertilization in agricultural production may result in energy wastage, soil and water contamination, and potentially influence crop development. Thus, with the help of a 15N-labeled tracer, we carried out a field monitoring analysis of NH3 emissions in a long-term (9-year) conservation tillage agroecosystem of Mollisols in northeast China, in order to determine whether a no-tillage regime and four levels of stover mulching (0%, 33%, 67%, and 100%), combined with urease and nitrification inhibitors, could improve fertilizer utilization efficiency in agricultural systems by reducing ammonia volatilization. Our results showed that in comparison with ridge tillage, no-tillage with stover mulching levels of 33%, 67%, and 100% significantly reduced NH3 emission rates and cumulative volatilization from 159.67 to 130.42 g N ha−1 and 15N-NH3 cumulative volatilization emission by 26% (on average). Furthermore, the application of urease and nitrification inhibitors significantly reduced 15N-NH3 volatilization levels from 1.19 to 0.98 g N ha−1. Our research results demonstrate that a long-term no-tillage regime and straw mulching can significantly reduce NH3 volatilization in fertilizers. Furthermore, when combined with the use of urease and nitrification inhibitors, these practices further enhance the reduction in NH3 volatilization. Although the volatilization of 15N-NH3 is minimally studied in Mollisols, these findings provide a solid foundation for improving fertilizer utilization efficiency, reducing crop production costs and mitigating subsequent environmental pollution.

Will crops with biological nitrification inhibition capacity be favored under future atmospheric CO2?

Will crops with biological nitrification inhibition capacity be favored under future atmospheric CO2?

The Effects of Long-Term Application of Stabilized and Coated Urea on Soil Chemical Properties, Microbial Community Structure, and Functional Genes in Paddy Fields

The addition of fertilizers is indispensable in agricultural production, and currently, there is a wide variety of new types of fertilizers available. For example, commonly used are stabilized fertilizers with inhibitors and coated slow-release fertilizers, among others. However, the long-term effects of these fertilizers, when applied continuously are still uncertain. This study will provide scientific and theoretical support for the development and promotion of these fertilizers. A 16-year paddy field with brown soil treated with different urease and nitrification inhibitors, sulfur-coated urea (SCU), and resin-coated urea (PCU) was studied. The study showed that long-term use of conventional urea nitrogen fertilizer resulted in a significant reduction in soil total phosphorus (TP). Long-term application of NBPT and conventional urea significantly increased soil organic matter (SOM). Moreover, except for HQ and NBPT+DMPP, the prolonged application of new urea fertilizers also significantly enhanced soil total potassium (TK). Application of SCU fertilizer in brown soil type paddy fields resulted in a significant decrease in soil pH over time. However, changes in pH had no effect on the abundance of ammonia-oxidizing bacteria (AOB), as AOB was mainly affected by soil-available N. DMPP, HQ+DCD, NBPT+DMPP, SCU, and PCU significantly reduced the 16S rRNA gene copy number of soil bacteria, with the greatest effect of coated urea fertilizer (SCU and PCU). Long-term application of stable urea fertilizer with HQ significantly reduced the bacterial community in paddy soil. Conversely, HQ+DCD-stabilizede urea fertilizer significantly increased the population structure and abundance of Basidiomycota fungi while decreasing the population structure and abundance of Rozellomycota fungi. DMPP-stabilized urea fertilizer notably increased the population structure and abundance of Ascomycota fungi while decreasing the population structure and abundance of Rozellomycota and Chytridiomycota fungi. Furthermore, HQ-stabilized urea fertilizer significantly reduced the population structure and abundance of Chytridiomycota fungi.

Genetic variation among elite inbred lines suggests potential to breed for BNI-capacity in maize

Biological nitrification inhibition (BNI) is a plant function where root systems release antibiotic compounds (BNIs) specifically aimed at suppressing nitrifiers to limit soil-nitrate formation in the root zone. Little is known about BNI-activity in maize (Zea mays L.), the most important food, feed, and energy crop. Two categories of BNIs are released from maize roots; hydrophobic and hydrophilic BNIs, that determine BNI-capacity in root systems. Zeanone is a recently discovered hydrophobic compound with BNI-activity, released from maize roots. The objectives of this study were to understand/quantify the relationship between zeanone activity and hydrophobic BNI-capacity. We assessed genetic variability among 250 CIMMYT maize lines (CMLs) characterized for hydrophobic BNI-capacity and zeanone activity, towards developing genetic markers linked to this trait in maize. CMLs with high BNI-capacity and ability to release zeanone from roots were identified. GWAS was performed using 27,085 SNPs (with unique positions on the B73v.4 reference genome, and false discovery rate = 10), and phenotypic information for BNI-capacity and zeanone production from root systems. Eighteen significant markers were identified; three associated with specific BNI-activity (SBNI), four with BNI-activity per plant (BNIPP), another ten were common between SBNI and BNIPP, and one with zeanone release. Further, 30 annotated genes were associated with the significant SNPs; most of these genes are involved in pathways of “biological process”, and one (AMT5) in ammonium regulation in maize roots. Although the inbred lines in this study were not developed for BNI-traits, the identification of markers associated with BNI-capacity suggests the possibility of using these genomic tools in marker-assisted selection to improve hydrophobic BNI-capacity in maize.

The influences of graphene oxide and nitrification inhibitor on vegetable growths and soil and endophytic bacterial communities: Double-edge sword effects and nitrate risk controls

Crop yield and quality are substantial indicators of evaluating agricultural nitrogen management practices, and the nitrate (NO3−-N) is one of the predominant factors affecting crop quality. The NO3−-N accumulation in vegetable crop affects plant growth and quality and human health. Therefore, it is necessary to stimulate vegetable yield but eliminate excessive NO3−-N in soils and plants with feasible management strategies. Graphene oxide (GO) is a novel carbon nanomaterial that has attracted great attention, but rare research has been conducted to quantify the effects of GO on plant NO3−-N accumulation and microbial communities. This study explored effects of the GO and nitrification inhibitors, dicyandiamide (DCD) and 3, 4-dimethylpyrazole phosphate (DMPP), on vegetable yields and NO3−-N contents and bacterial communities in soil-cabbage (Brassica rapa subsp. Chinensis) system. The soil NO3−-N content was significantly reduced with the single GO application. The cabbage NO3−-N content was increased by 60.4 % while the cabbage yield was significantly enhanced by 101.9 % with the single GO application. Meanwhile, the Invsimpson index of soil bacterial community and the ACE and Chao1 richness estimators of endophytic bacterial community were significantly decreased by the GO application. Cabbage NO3−-N content was significantly and negatively correlated with the soil Myxococcota, endophytic bacterial community co-occurrence network edge, cabbage soluble sugar and cabbage proline. The GO application generated double-edged sword effects of positively promoting yield but causing risks of NO3−-N accumulation and quality deterioration. However, these adverse effects could be mitigated by the extra nitrification inhibitor application. The potential ecological risks of GO application to the vegetable quality and endophytic community should be considered.

Activity of ammonia-oxidizing bacteria in enriched cultures exposed to 3,4-dimethyl-1H-pyrazole dihydrogen phosphate nitrification inhibitor

The use of nitrification inhibitors is an interesting tool to achieve a higher N efficiency in plants while decreasing the environmental impact of N fertilization. However, an integrated evaluation of the efficiency of nitrification inhibitors over time, understood as the period in which the nitrifying activity is inhibited or slows down, is necessary to assess whether their use is ecofriendly and sustainable.To test the direct efficiency of 3,4-dimethyl-1H-pyrazole dihydrogen phosphate (DMPP) on nitrification, a study has been carried out in two cultures enriched with ammonia-oxidizing bacteria (AOB) obtained from a soil with continuous N fertilization (80 kg N ha−1 year−1 as NH4NO3) and from soil without N fertilization. In addition, Cu has been evaluated as a cofactor of ammonia monoxygenase, a key enzyme in the nitrifying activity of AOBs. On the other hand, the stability of DMP has been studied both in the cultivation system enriched in AOBs and in soil to assess the efficiency of the inhibitor due to its persistence over time.Our work reveals that nitrification rates observed in cultures enriched in AOBs from genus Nitrosospira isolated from soils with continuous N fertilization were not higher than those of cultures without N fertilization. In AOB cultures, DMPP was a very efficient inhibitor of nitrification (> 50 % inhibition of integrated AMO activity), mainly due to the stability of DMP (3,4-dimethyl-1 H-pyrazole) in the cultures. However, DMP stability was significantly lower under soil conditions (> 90 % of DMP was degraded in the first 30 days of incubation). Other metals are suggested as cofactors of the enzyme ammonia monooxygenase alternatively to Cu.

Nitrogen dynamics after slurry application as affected by anaerobic digestion, biochar and a nitrification inhibitor

AbstractAnimal manures are valuable multi‐nutrient fertilizers, but their short‐term nitrogen (N) use efficiency (NUE) by plants is low, bearing the potential of harmful N losses to the environment, such as nitrate () leaching. To develop strategies to increase the NUE of cattle slurry, a comprehensive understanding of slurry N dynamics in the soil–plant system is needed. In a 57‐day microcosm experiment in the greenhouse, we assessed the effect of different slurry treatments on slurry N turnover in the soil and its uptake by ryegrass (Lolium multiflorum var. Westerwoldicum). Employing a two‐factorial design, 15N cattle slurry (SLU), 15N anaerobically digested cattle slurry (SLA), and 15N anaerobically digested cattle slurry plus biochar (SLA+) were combined with and without the nitrification inhibitor 3,4‐dimethyl‐1H‐pyrazole monophosphate (DMPP). As references, a mineral fertilizer (MIN) and an unfertilised treatment (N0) were included. The 15N recovery, hence NUE, in plant biomass was higher for SLA than for SLU, while recovery in soil at 55 days after set‐up showed an opposite trend, with over 45% of N from SLU still being recovered in soil. DMPP and biochar only marginally affected NUE and fertilizer N recovery in soil. Although 15N recovery in soil was highest for SLU, residual N leaching from SLU was low (<1% of added N). We attribute this to the limited presence of slurry N in mineral forms at this point of time, with the majority being stored in the non‐microbial organic soil N pool. Leaching of residual N from MIN was significantly higher for MIN than for SLU, while SLA and SLA+ ranged in between. Overall, anaerobic digestion appeared suitable for increasing NUE of cattle slurry, but further investigations under field conditions are necessary in order to assess its potential to reduce nitrate leaching in the long‐term.

Pollutants removal and connections among sludge properties, metabolism potential and microbial characteristics in aerobic granular sequencing batch reactor for petrochemical wastewater treatment

Petrochemical wastewater contains inhibitory compounds such as aromatics that are toxic to microorganisms during biological treatment. The compact and layered structure and the high amount of extracellular polymeric substances (EPS) in aerobic granular sludge (AGS) can contribute to protecting microorganisms from the harsh environment. This study evaluated the changes in the granule properties, pollutants removal, microbial metabolic potential and molecular microbial characteristics of the AGS process for petrochemical wastewater treatment. Granules treating petrochemical wastewater had a higher SVI30/SVI5 value (0.94) than that treating synthetic wastewater. An increase in bioactivity and EPS secretion with higher bio-polymer composition, specifically the functional groups such as hydroxyl, alkoxy and amino in protein, was observed, which promoted biomass aggregation. The granules also had more than 2-fold higher specific oxygen utilization rate. The AGS-SBR process obtained an average COD removal of 93% during petrochemical wastewater treatment and an effluent bCOD of below 1 mg L−1. No obvious inhibition of nitrification and denitrification activity was observed in the processes attributed to the layered structure of AGS. The average effluent NH4+-N of 5.0 mg L−1 was obtained and TN removal efficiencies of over 80.0% was achieved. Molecular microbial analysis showed that abundant functional genera Stenotrophomonas and Pseudoxanthomonas contributed to the degradation of aromatics and other petroleum organic pollutants. They were enriched with the variation of group behavior while metabolisms of amino acids and carboxylic acids by the relevant functional genera (e.g., Cytophagia) were significantly inhibited. The enrichment of Flavobacterium and Thermomonas promoted nitrification and denitrification, respectively. This research revealed the rapid start-up, enhanced granule structural strength, high inhibition resistance and considerable performance of AGS-SBR for petrochemical wastewater treatment.

Placement and nitrogen source effects on N2O emissions for canola production in Manitoba

AbstractThis study examined fertilizer nitrous oxide (N2O) emissions and canola (Brassica napus L.) grain yield for two granular urea sources (conventional and a dual urease and nitrification inhibitor [SuperU]) and three at‐planting placement methods (broadcast‐incorporated, shallow banded, and deep banded) on commercial fields in Manitoba. Nitrogen (N) rates were 100% and 70% of what was recommended based on soil test and target yield, with the 100% treatments having N2O emissions monitored. SuperU fertilizer consistently reduced N2O emissions (area‐, N‐applied‐, and yield‐based) compared to urea. Significant reductions in N2O emissions with SuperU occurred in four of six site‐years and coincided with delayed nitrification. Compared to broadcast‐incorporated, subsurface banding of conventional urea reduced N2O emissions in drier site‐years but increased emissions when rainfall was higher (especially in shallow banded urea). Across all six site‐years, shallow banding of urea resulted in significantly higher emission intensities than all other treatments. Nitrogen placement did not affect the emission reduction benefit of SuperU. N source or placement did not greatly affect canola yield within either 100% or 70% N rates. Fertilizer N recovery efficiency was also not greatly impacted by either N source or placement. The results demonstrate that dual inhibited granular urea fairly consistently reduces N2O emissions in canola production in southern Manitoba, whereas nitrogen placement had variable effects depending on growing season rainfall. However, with little agronomic benefit, the added cost of enhanced efficiency fertilizers must be overcome for widespread adoption and to achieve greenhouse gas reduction targets for the Canadian agriculture sector.

Changes in soil pore structure generated by the root systems of maize, sorghum and switchgrass affect in situ N2O emissions and bacterial denitrification

AbstractDue to the heterogeneous nature of soil pore structure, processes such as nitrification and denitrification can occur simultaneously at microscopic levels, making prediction of small-scale nitrous oxide (N2O) emissions in the field notoriously difficult. We assessed N2O+N2 emissions from soils under maize (Zea mays L.), switchgrass (Panicum virgatum L.), and energy sorghum (Sorghum bicolor L.), three potential bioenergy crops in order to identify the importance of different N2O sources to microsite production, and relate N2O source differences to crop-associated differences in pore structure formation. The combination of isotopic surveys of N2O in the field during one growing season and X-ray computed tomography (CT) enabled us to link results from isotopic mappings to soil structural properties. Further, our methodology allowed us to evaluate the potential for in situ N2O suppression by biological nitrification inhibition (BNI) in energy sorghum. Our results demonstrated that the fraction of N2O originating from bacterial denitrification and reduction of N2O to N2 is largely determined by the volume of particulate organic matter occluded within the soil matrix and the anaerobic soil volume. Bacterial denitrification was greater in switchgrass than in the annual crops, related to changes in pore structure caused by the coarse root system. This led to high N-loses through N2 emissions in the switchgrass system throughout the season a novel finding given the lack of data in the literature for total denitrification. Isotopic mapping indicated no differences in N2O-fluxes or their source processes between maize and energy sorghum that could be associated with the release of BNI by the investigated sorghum variety. The results of this research show how differences in soil pore structures among cropping systems can determine both N2O production via denitrification and total denitrification N losses in situ.

An In Silico Analysis of Synthetic and Natural Compounds as Inhibitors of Nitrous Oxide Reductase (N2OR) and Nitrite Reductase (NIR).

Nitrification inhibitors are recognized as a key approach that decreases the denitrification process to inhibit the loss of nitrogen to the atmosphere in the form of N2O. Targeting denitrification microbes directly could be one of the mitigation approaches. However, minimal attempts have been devoted towards the development of denitrification inhibitors. In this study, we aimed to investigate the molecular docking behavior of the nitrous oxide reductase (N2OR) and nitrite reductase (NIR) involved in the microbial denitrification pathway. Specifically, in silico screening was performed to detect the inhibitors of nitrous oxide reductase (N2OR) and nitrite reductase (NIR) using the PatchDock tool. Additionally, a toxicity analysis based on insecticide-likeness, Bee-Tox screening, and a STITCH analysis were performed using the SwissADME, Bee-Tox, and pkCSM free online servers, respectively. Among the twenty-two compounds tested, nine ligands were predicted to comply well with the TICE rule. Furthermore, the Bee-Tox screening revealed that none of the selected 22 ligands exhibited toxicity on honey bees. The STITCH analysis showed that two ligands, namely procyanidin B2 and thiocyanate, have interactions with both the Paracoccus denitrificans and Hyphomicrobium denitrificans microbial proteins. The molecular docking results indicated that ammonia exhibited the second least atomic contact energy (ACE) of -15.83 kcal/mol with Paracoccus denitrificans nitrous oxide reductase (N2OR) and an ACE of -15.20 kcal/mol with Hyphomicrobium denitrificans nitrite reductase (NIR). The inhibition of both the target enzymes (N2OR and NIR) supports the view of a low denitrification property and suggests the potential future applications of natural/synthetic compounds as significant nitrification inhibitors.

Relationship between yield and tree growth in almond as influenced by nitrogen nutrition

Understanding the relationship between nitrogen (N), tree growth and yield, can maximize productivity and sustainability. This study analyzed the effect of N on canopy development and its relation with yield in a super-intensive almond orchard in Spain over two seasons. The treatments included 50 kg N ha−1, 100 kg N ha−1, 150 kg N ha−1, and 100 kg N ha−1 applied between 3.1 and 7.7 Growth Stages, and their combinations with a nitrification inhibitor, DMPSA. The canopy was measured using LiDAR technology after pruning in spring and before harvest. Differences were found in canopy parameters comparing early N (Nstop) against N applied along the season. The treatments N50, N100 and N150 resulted in higher cross sections and widths, less porosity and higher yield, fruit set and hull weights. In contrast, Nstop gave higher porosity and higher flower density. DMPSA produced more homogeneous canopies and improved N use efficiency, combined with N100 or N150. These findings provide evidence to support the management of N in super-intensive orchards.