Cyanamide Research Articles

Alternative products for breaking dormancy in ‘Reubennel’ plum in subtropical regions

Abstract Plum is a temperate fruit tree and thus shows abundant vegetative bud percentage and flowering following extended periods of low winter temperatures. When adequate periods of low temperatures do not occur, it is necessary to apply products to stimulate bud dormancy break and uniform leaf and flower appearance. This application is more frequently needed when plum trees are grown in the tropics. The objective of this study was to evaluate alternative products for breaking dormancy in ‘Reubennel’ plum in subtropical regions. The experiment was conducted at a site located at 22°22’S, 43°77’W and 1,173 m altitude, with a Cwa climate type. The following treatments were applied to eight-year-old ‘Reubennel’ plum trees in the 2018 and 2019 production cycles: 1) a negative standard composed of only water (control), a positive standard composed of 2) 1.5% hydrogen cyanamide (HC) (Dormex® commercial product) plus 4.5% mineral oil, 3) Erger G® organomineral fertilizer supplemented with 3% calcium nitrate, 4) 5% potassium nitrate and 5) 0.3% copper sulfate. Two liters of the treatment solutions were applied per plant with a sprayer. The effect of the tested products on vegetative bud percentage and flowering capacity, production cycle reduction and production and quality of ‘Reubennel’ plums was evaluated. It was concluded that the chemicals used to break dormancy affected only the phenology of plum trees in this subtropical region and that the application of copper sulfate can be used to break dormancy in these trees.

Soil Microorganism Interactions under Biological Fumigations Compared with Chemical Fumigation.

Biological fumigation, a potential alternative to chemical fumigation, shows a wide range of prospective applications. In this study, we carried out biological fumigation experiments to evaluate its effect on alleviating consecutive cropping problems (CRPs) when compared with chemical fumigation. We designed five treatments, namely, CR (no treatment), LN (chemical fumigation with lime nitrogen), Ta (fumigation with marigold), Ra (fumigation with radish), and Br (fumigation with mustard), for soils for replanting eggplant and measured the crop's growth status, soil bacterial and fungal communities, and soil physicochemical properties. The results showed that the Br and Ra treatments formed similar microbial communities, while the Ta treatment formed unique microbial communities. The genera Olpidiomycota and Rozellomycota could be used as indicator species for the transformation process of soil microbial communities after the Br and Ta treatments, respectively. When compared with the CR and LN treatments, the soil's physicochemical properties were optimized under the Br treatment, and the soil organic matter content increased by 64.26% and 79.22%, respectively. Moreover, under the Br treatment, the soil's biological properties enhanced the bacterial and fungal alpha diversity, and the saprotrophic fungi increased with the depletion of pathotrophic fungi, while some specific probiotic microorganisms (such as Olpidiomycota, Microascales, Bacillus, etc.) were significantly enriched. In contrast, under the Ta treatment, soil nutrient levels decreased and the soil's biological indices deteriorated, whereas the bacterial diversity decreased and the pathogenic fungi increased. Among these three biological fumigation methods, the Br pre-treatment was the best way to alleviate the crop's CRPs and may be a good substitute for chemical fumigation in some situations. However, the Ta treatment also had some risks, such as the loss of land quality and reduced productivity.

A study on the efficacy of hydrogen cyanamide and winter oil applications on male and female pistachio bloom and yield

A study on the efficacy of hydrogen cyanamide and winter oil applications on male and female pistachio bloom and yield

High-Yield Synthesis Route, Post-Synthesis Treatment, and Insights into the Photoluminescence and Magnetic Properties of Tricopper(I) Melaminate Cu3(C3N6H3).

A novel and more efficient synthesis of Cu3(C3N6H3) is presented through a salt-metathesis reaction using copper(I) chloride and sodium hydrogen cyanamide. This synthesis yields a melaminate trianion through the cyclotrimerization of (HNCN)- ions, offering an alternative route to the deprotonation of melamine for synthesizing melaminate. The reaction is analyzed via differential thermal analysis. After the unconventional formation of this MOF-like structure by solid-state reaction, this material still requires treatment via solvent exchange and vacuum drying due to the presence of a host molecule inside the channels of the structure. The process and the impact of the treatment of Cu3(C3N6H3) on its XRD pattern are thoroughly discussed. Additionally, results from stability, NMR and infrared spectroscopy, and thermogravimetric analysis. Finally, photoluminescence and magnetic studies are conducted to evaluate their potential as a functional material.

Rapid reconstruction of nickel iron hydrogen cyanamide with in-situ produced proton acceptor for efficient oxygen evolution

Metal oxyhydroxide (MOOH) through irreversible reconstructed fabrication from transition metal compounds are highly efficient oxygen evolution reaction (OER) electrocatalysts but face limits from adsorption energy scaling relationship and sluggish deprotonation kinetics. Herein, we present Fe-doped nickel hydrogen cyanamide (Ni0.8Fe0.2-HC), which is rapidly surface reconstructed into Ni0.8Fe0.2(OOH)-HC after OER. In-situ Raman spectroscopy and density functional theory (DFT) calculations, revealed that under OER conditions, -HNCN- converts into -NCN- ligand incorporating its abundant and uniform distribution across the active sites. DFT calculations further indicate that Fe predominantly acts as the active site, with -NCN- ligands contribute to the OER by facilitating the deprotonation of *OH in the rate-determining step (RDS), acting effectively as proton acceptor. The ensemble effect between Fe and -NCN- ligand forms the foundation of the exceptional electrocatalytic performance of Ni0.8Fe0.2(OOH)-HC (190 mV at 20 mA·cm−2). This discovery offers insights for designing innovative MOOH pre-catalysts to enhance OER efficiency.

PSV-14 The effects of calcium cyanamide on greenhouse gases, ammonia emissions, and the microbiome of dairy cattle lagoon water

PSV-14 The effects of calcium cyanamide on greenhouse gases, ammonia emissions, and the microbiome of dairy cattle lagoon water

Nutrient Preservation in Cattle Slurry via Emission Reduction during Storage with Calcium Cyanamide

Nutrient Preservation in Cattle Slurry via Emission Reduction during Storage with Calcium Cyanamide

Hydrogen Cyanamide: A Chemical to Prepone Natural Budburst Timing of Grapevine Cultivars in Nepalese Context

Grapes primarily belongs to mediterranean climate but overtime due to successful vine management practices, its cultivation has been extended to sub-tropics and tropics. In Nepal, grape cultivation has been started about 8 decades ago, and the demand of this crop has been increasing every year. However, the critical challenge of heavy rainfall coinciding with the berry harvest period has limited the production window, necessitating innovative solutions. This study explores the potential of grape cultivation in Nepal by assessing significance of hydrogen cyanamide (HC) application to ensure early and uniform budburst and therefore fruit maturity before monsoon. Winter pruning and HC application at 2-5% concentration has been found effective in preponing budburst and maturity in some grapes varieties ‘Steuben’ and ‘Cabernet Sauvignon’ in Nepal, but the results depend on date and dose of HC application in particular variety and specific growing condition. Application of HC at 2% concentration has resulted in earlier budburst by about 3 weeks in var. Cabernet Sauvignon in Dhading, Nepal. Also, the earlier treatment of HC and pruning in comparison to normal time of pruning (December 15 to January 15) has resulted in earlier and higher budburst and observed fruitfulness in varieties like ‘Steuben’ and ‘Cabernet Sauvignon’ in warm temperate belt of Nepal. Thus, the study concludes the prepone of natural budburst is a must need practice for successful viticulture in terai and mid-hills of Nepal. It also emphasizes the need of more research to optimize the application of HC and ensure its efficacy in advancing budburst and maturity specific to variety and locality. Overall, the findings aim to inspire growers, enhance commercial viability, and contribute valuable insights to the viticulture sector in Nepal.

Impacts of Calcium Cyanamide Application as a Nitrogen Source on Growth, Yield, Quality, and Storage Durability of Short-day Onion

Rapid leaching of soluble nitrogen (N) sources in soil poses a significant challenge in agricultural practices. Therefore, gaining a comprehensive understanding of crop responses to slow-release N application rates has become crucial to contributing valuable insights to optimize N management strategies in agriculture. A field study was conducted to investigate the influence of preplant calcium cyanamide fertilizer on the growth, yield, quality, and shelf life of short-day onion. Six levels of calcium cyanamide (CaCN2, 19.8% N), 0, 90, 120, 200, 400, and 600 kg⋅ha−1 CaCN2, which are equivalent to 0, 17.82, 23.76, 39.6, 79.2, and 118.8 kg⋅ha−1 N, respectively, replicated four times were broadcasted and incorporated into the top 5 to 10 cm of soil. Using 400 kg⋅ha−1 of CaCN2 yielded noteworthy improvements in various parameters of onion growth, such as plant height, leaf count, bulb weight per plant, bulb diameter, bulb length, and overall plant weight, as indicated by the study results. The application of different levels of CaCN2 as an N source exerted a significant influence on these growth factors. Moreover, the study revealed a direct correlation between CaCN2 application levels and the storage life of onions. Specifically, the findings demonstrated that the application of 400 kg⋅ha−1 CaCN2 resulted in enhanced yield and overall onion plant growth. However, the application of 600 kg⋅ha−1 CaCN2 increased the incidences of bulb weight loss, rots, and sprouting during the 8-week storage period at room temperature. These findings provide valuable insights for onion investors and farmers in the region and offer practical recommendations for optimizing fertilizer use and storage practices to improve onion production and minimize postharvest losses.

Low-concentration repeated exposure and high-concentration single exposure of cyanamide suppressed the growth of redroot pigweed in the alfalfa field

The inclination toward natural products has led to the onset of the discovery of new bioactive metabolites that could be targeted for specific therapeutic or agronomic applications. Despite increasing knowledge coming to light of plant-derived materials as leads for new herbicides, relatively little is known about the mode of action on herbicide-resistant weeds. Cyanamide (CA) is a naturally occurring herbicide synthesized by hairy vetch (Vicia villosa Roth.). However, it has not been experimentally verified whether CA suppresses target plants via sustained discharge at low concentrations, as is often the case with most plant-derived materials. This study aimed to detect the toxicity and the mode of action of CA to alfalfa (Medicago sativa L.) and redroot pigweed (Amaranthus retroflexus L.). The toxicity of CA toward the alfalfa and redroot pigweed by three different exposure patterns was compared: low-concentration repeated exposure with 0.3 g/L CA (LRE), high-concentration single exposure with 1.2 g/L CA (HSE), and distilled water spray as control. The results showed that CA had a stronger inhibitory effect on redroot pigweed growth compared to alfalfa under both LRE and HSE exposure modes, with leaves gradually turning yellow and finally wilting. Beyond that, field trials were conducted to corroborate the toxicity of CA to alfalfa and redroot pigweed. The results have also shown that CA could inhibit the growth of redroot pigweed without significant adverse effects on alfalfa. The outcomes concerning electrolyte permeability, root activity, and malondialdehyde (MDA) content indicated that CA suppressed the growth of redroot pigweed by interfering with the structure of the cell membrane and impacting cellular osmotic potential. CA could destroy the cell membrane structure to inhibit the growth of the redroot pigweed by both LRE and HSE exposure modes, which provides a theoretical basis for preventing and controlling redroot pigweed in alfalfa fields.

Enhancing soil health and strawberry disease resistance: the impact of calcium cyanamide treatment on soil microbiota and physicochemical properties.

Continuous strawberry cropping often causes soil-borne diseases, with 20 calcium cyanamide being an effective soil fumigant, pig manure can often be used as soil organic fertilizer. Its impact on soil microorganisms structure, however, remains unclear. This study investigated the effectiveness of calcium cyanamide and pig manure in treating strawberry soil, specifically against strawberry anthracnose. We examined the physical and chemical properties of the soil and the rhizosphere microbiome and performed a network analysis. Results showed that calcium cyanamide treatment significantly reduces the mortality rate of strawberry in seedling stage by reducing pathogen abundance, while increasing actinomycetes and Alphaproteobacteria during the harvest period. This treatment also enhanced bacterial network connectivity, measured by the average connectivity of each Operational Taxonomic Unit (OTU), surpassing other treatments. Moreover, calcium cyanamide notably raised the levels of organic matter, available potassium, and phosphorus in the soil-key factors for strawberry disease resistance and yield. Overall, applying calcium cyanamide to soil used for continuous strawberry cultivation can effectively decrease anthracnose incidence. It may be by changing soil physical and chemical properties and enhancing bacterial network stability, thereby reducing the copy of anthracnose. This study highlights the dual benefit of calcium cyanamide in both disease control and soil nutrient enhancement, suggesting its potential as a valuable tool in sustainable strawberry farming.

Enhancing Uniform Sprouting, Yield, and Quality in Grapevines: The Impact of Hydrogen Cyanamide (50% S.L) Treatment

Grape (Vitis vinifera L.) is considered as one of the most important commercial fruit crops in temperate, tropical and subtropical regions of the world. In India grape cultivation in tropical and subtropical regions assumes great significance, but one of the biggest issues preventing grapes from being produced in warm climates has been the lack of or insufficient winter chilling. Under these circumstances, there is uneven bud bursting, flowering, and delayed fruit development. The most crucial component of grape development is, consistent bud breaking is required to increase grape quality and maturity. Many plant growth regulators are used to promote bud burst and increase the proportion of bud break. Several locations across the world utilize plant growth regulators to intentionally cause bud break. The application of Hydrogen Cyanamide (H2CN2) during pruning time of grapes, helps to enhance growth uniformity, encourage earlier and more even bud break, raises the proportion of fruit buds, berry set, number of clusters per vine, weight of clusters, and dimensions of clusters. It also gives positive response to various metabolic activities; maximize yield and Maturity, Fruit quality, as well as production efficiency. In grape orchards, it is commonly used to promote consistent and improved bud burst, shortened flowering period, and boost output.

Heated scallop-shell powder and lime nitrogen effectively decrease the abundance of antimicrobial-resistant bacteria in aerobic compost

The emergence and dissemination of antibiotic-resistant bacteria (ARB) and antibiotic resistance genes (ARGs) are global public health concerns. Hence, measures should be implemented to reduce the abundance of ARB and prevent the spread of ARGs from livestock to the environment. In this study, to clarify the potential of reducing ARB abundance in livestock waste during aerobic composting, the effects of adding heated scallop-shell powder (HSSP) and lime nitrogen (LN) to manure compost on the abundance of several bacterial species were investigated. Several bacterial species (Escherichia coli, Pseudomonas aeruginosa, Salmonella enterica, Staphylococcus aureus, and Enterococcus faecalis), spores of Clostridioides difficile, and various concentrations of HSSP/LN were added to livestock manure. After 24 h, the tested bacteria and spores were eliminated using 2% (w/w) and 4% (w/w) HSSP/LN, respectively. Subsequently, field trials were conducted on a pig farm to investigate the effect of adding HSSP/LN to manure composts. Swine manure and rice husk were mixed with or without 4% (w/w) HSSP/LN, and aerobic composting was continued for 13 days. The results showed that all the tested bacteria were eliminated after adding HSSP/LN, but the abundance of antibiotic resistance genes was not significantly altered. Adding HSSP/LN significantly affected the bacterial diversity in the compost. In conclusion, using HSSP/LN as an additive in aerobic composting effectively reduced the abundance of ARB, including spore-forming bacteria.

VvSVP1 negatively regulates gibberellin accumulation before the dormant bud break of grapevine triggered by hydrogen cyanamide

In grapevine, previous studies have suggested that, gibberellin (GA) inhibits bud break before dormancy release while enhanced after dormancy release; the capacity of GA accumulation shows a trend of first inhibition and then upregulation. However, the regulatory mechanism of GA metabolism genes expression is as yet unclear during the process of dormancy release. In this study, we further validated the effect of GA3 and hydrogen cyanamide (HC) on bud break of ‘Red globe’ grape, confirmed inhibition and promotion effect, respectively. Restricted GA biosynthetic genes' expression and enhanced GA catabolic gene's expression were observed in the early stage after HC treatment, while opposite expression trend showed in the late stage. VvSVP1, a MADS-box transcription factor gene, was downregulated in the late stage, which might play an important role in regulating GA metabolism genes' expression. It was shown that, VvSVP1 could bind to the promoter regions of GA biosynthetic gene VvGA20ox6 and catabolic gene VvGA2ox3, negatively and positively regulated the corresponding genes' expression, respectively; the contents of GAs related to GA20ox were significantly reduced in the grape callus overexpressed VvSVP1, while the ratio of GAs related to GA2ox were significantly increased. Taken together, VvSVP1 can regulate the endogenous GAs level by manipulating the expression of GA metabolism genes before dormant bud break induced by HC. Our findings may provide some new theoretical insights for the study of bud dormancy regulation in the perennial woody fruit trees.

Integrated Management of Clubroot in Zhejiang Province, China

Clubroot, caused by Plasmodiophora brassicae, is a destructive soil-borne disease significantly harming global Brassica crop production. This study employed the Williams and European Clubroot Differential (ECD) and Williams systems to identify the pathotypes of P. brassicae collected from Hangzhou City, Yuhang District and Quzhou City, Kaihua County in Zhejiang Province. Greenhouse and field trials were conducted to evaluate the effects of plastic film covering and four chemical agents on the growth parameters and clubroot severity of the Chinese cabbage cultivar ‘Granaat’. Potential treatment mechanisms on clubroot were explored through a qPCR analysis of the resting spore density and pH measurement of the soil. Furthermore, treatment with 1-napthaleneacetic acid (NAA), a synthetic auxin, was also evaluated for its potential role in suppressing clubroot. The results indicate that the pathotypes of P. brassicae in the two districts were P1, ECD20/31/12, and P3, ECD20/15/4. While an individual application of plastic film covering could not effectively control clubroot, calcium cyanamid, dazomet and ammonium bicarbonate demonstrated significant efficacy in its management. These three agents significantly reduced the resting spore density in the soil, with calcium cyanamid and ammonium bicarbonate also increasing soil alkalinity. Additionally, ammonium bicarbonate promotes lateral root development in ‘Granaat,’ helping infected plants access adequate water and nutrients. However, NAA exhibited no efficacy in clubroot control. Therefore, sustained lateral root development is crucial for effectively resisting P. brassicae invasion. Considering application costs and environmental friendliness, we propose the field application of ammonium bicarbonate as the optimal method for clubroot disease management in Zhejiang Province.

Hepatotoxic Effect of Hydrogen Cyanamide (Dormex®) in Albino Rats and the Ameliorative Effect of Melatonin

Background: Hydrogen cyanamide (Dormex®) is used as a fertilizer sprayed on fruits, especially grapes to stimulate buds’ opening. It causes oxidative stress leading to hepatic, renal, and lung damage. Melatonin is derived primarily from the amino acid tryptophan, produced from the pineal gland, and has antioxidant effects. This study aimed to examine the effects of acute hydrogen cyanamide (Dormex®) exposure on the liver of albino rats and evaluate the biochemical and histological changes caused by Dormex® toxicity. Additionally, the study evaluated the potential ameliorative role of melatonin in these harmful effects. Methods: Forty adult male albino rats were divided into four groups; group I: Negative control, group II: Melatonin-treated (100 mg/kg/day), group III: Dormex®-treated (100 mg/kg) as a single dose, and group IV: Receiving melatonin (100 mg/kg/day)+Dormex® (100 mg/kg). After 24 hours, all animals were evaluated for liver enzymes (alanine aminotransferase, aspartate aminotransferase, alkaline phosphatase, and bilirubin), hepatic markers for oxidative stress (malondialdehyde (MDA), reduced glutathione (GSH), and superoxide dismutase (SOD)) and histopathological examination was done for hepatic tissues. Results: The Dormex®-treated group showed significantly elevated liver enzymes, elevated MDA, and decreased GSH and SOD. Histopathological examination revealed normal structure in groups 1 and 2 while group 3 showed several histopathological changes characterized by inflammation and hepatic necrosis. Administration of melatonin with Dormex® in group 4 caused a decrease in liver enzymes and MDA and an increase in GSH and SOD with improvement in liver histopathology. Conclusion: Melatonin showed an ameliorative effect and can be used as a protective agent against Dormex®-induced hepatic injury.

Biochemical Changes Induced by Hydrogen Cyanamide Foliar Application in the Buds of ‘Askari’ Grape

Biochemical Changes Induced by Hydrogen Cyanamide Foliar Application in the Buds of ‘Askari’ Grape

Response of Microbial Recovery Rate to Straw Return after Calcium Cyanamide Soil Disinfection

At present, returning vegetable straw in situ is an effective measure to solve environmental pollution and improve soil properties. However, the direct return of straw to the field can reduce the release rate of soil organic matter and cause serious soilborne diseases. The combined application of calcium cyanamide (CaCN2) and straw can solve this problem. The objective of this study was to determine the effect of CaCN2 combined with pepper straw return on cucumber yield, soil physicochemical properties, and soil microbial communities during 2020 to 2021 in Shandong Province, China. The treatments were designed as follows: (1) calcium cyanamide soil disinfection, CC; (2) fresh pepper straw return, LJ; (3) fresh pepper straw return combined with calcium cyanamide disinfection, LJ+CC; and (4) natural soil without straw return treatment, CK. Compared with CK, the LJ+CC treatment significantly improved cucumber production by 20%. The cultivable microbial community in the soil was temporarily inhibited during soil fumigation treatment, and the cultivable bacterial and actinomycete communities in the soil return to their initial levels after the film was removed (harvest period). The numbers of culturable bacteria and actinomycetes in the soil in the LJ+CC treatment were 4.68 × 107 CFU/g and 5.17 × 107 CFU/g, respectively, higher than those in the soil in the CC treatment. The contents of TN and OM in the LJ+CC treatment increased by 13.1% and 13.5%, respectively, compared with that in LJ. Therefore, the LJ+CC treatment enhanced soil fertility and cucumber yields. CaCN2 can promote straw decomposition and straw can promote soil microbial recovery, and their combined application is considered a feasible and sustainable technique for utilizing vegetable residues in the greenhouse. The combination of returning pepper straw to the field and calcium cyanamide technology achieves a win-win situation of resource circulation and economic circulation by converting agricultural waste into fertilizer before being put into production. Based on this, it is recommended that the straw returning technology receives strong policy support, stimulates researchers to explore the feasibility of different vegetable straw returning to the field, promotes the implementation of this technology achievement, and leverages the environmental benefits of the application of straw returning technology.

Hydrogen cyanamide exposure: a case series from Pavia Poison Control Centre.

Hydrogen cyanamide is a plant growth regulator introduced in Italy as Dormex in 2000, but recalled from the market in 2008. It's currently not authorized in Europe. Inhalation/dermal contact may cause irritation/caustic burns, ingestion of severe organ damage and concomitant alcohol consumption disulfiram-like reaction due to aldehyde-dehydrogenase inhibition by hydrogen cyanamide. To study all exposure cases referred to our centre, evaluating temporal and geographic distribution and analysing clinical manifestations, including the ones after alcohol consumption. We retrospectively evaluated all hydrogen cyanamide exposures referred to our Poison Control Centre (January 2007-December 2021). For each case, age, sex, exposure route/year, geographical location, intent of exposure, alcohol co-ingestion, emergency department-admission Poison Severity Score, signs/symptoms and treatment were analysed. Thirty subjects were included. Median case/year was 1 [1; 2]: 79% occurred after market withdrawal, 92% in Sicily. All exposures were unintentional and work related; 41% of patients also co-ingested alcohol. Mean poison severity score at emergency department admission was 1.54, more severe when ingestion occurred. The most common signs/symptoms were flushing, secondary to peripheral vasodilation (41%), hyperaemia/erythema (29%), dyspnoea (25%), nausea (20%), vomiting (12%), oedema (12%), II-III degrees burns (12%) and pharyngodynia (12%). All patients were treated symptomatically and fully recovered. Hydrogen cyanamide exposure can lead to severe clinical manifestations. Despite its withdrawal from the Italian market, hydrogen cyanamide is still used: through PCC's crucial role in monitoring exposure to agricultural products efforts should be made to contrast illegal trade and increase awareness of its potential toxicity in those countries in which it's still legal.

Effect of Calcium Cyanamide as an Alternative Nitrogen Source on Growth, Yield, and Nitrogen Use Efficiency of Short-Day Onion

Effective nitrogen (N) management in agriculture is vital to optimize crop growth and yield while minimizing environmental impact. Conventional nitrogen (N) sources, such as urea, have limitations in promoting growth and reducing N leaching. A two-year field experiment was carried out to investigate the effects of calcium cyanamide (CaCN2) as a slow-release N source on short-day onion growth, yield, and N use efficiency (NUE). Six types of N sources were administered: (i) an initial application of 80 kg ha−1 N in the form of CaCN2 before planting; (ii) an initial application of 80 kg ha−1 N in the form of CaCN2 before planting, followed by a topdressing of 50 kg ha−1 N in the form of limestone ammonium nitrate (LAN); (iii) an initial application of 80 kg ha−1 N in the form of CaCN2 before planting, followed by a topdressing of 50 kg ha−1 N in the form of urea; (iv) an initial application of 80 kg ha−1 N in the form of LAN before planting, followed by a topdressing of 50 kg ha−1 N in the form of LAN; (v) an initial application of 80 kg ha−1 N in the form of urea before planting, followed by a topdressing of 50 kg ha−1 N in the form of urea; and (vi) control (0 kg ha−1 N). Preplant CaCN2 (80 kg ha−1 N) outperformed the standard fertilizers used in onion as an N source (urea and LAN) by improving growth and yield, and reducing N leaching. Preplant CaCN2 topdressed with either LAN or urea led to a significant increase in plant growth and total yield compared to using LAN or urea alone. The application of CaCN2, followed by topdressing with either LAN or urea, decreased onion bolting by 1.6% and 1.83%, respectively, compared to the control. The study suggests that applying LAN or urea as a topdressing to preplant CaCN2 enhances N utilization efficiency, leading to increased onion bulb yield and quality while reducing N leaching. This approach can help mitigate farm-level environmental pollution and provide valuable insights for improving onion production and sustainable agriculture practices in South Africa.