1 New era of demand for stabilized fertilizer
1.1 Enhancing fertilizer efficiency is a critical aspect of China’s green agricultural development
Improving nitrogen fertilizer efficiency is a key challenge for both food security and ecological sustainability in China. Nitrogen fertilizer accounts for about 45% of the increase in China’s grain production and contributes to about 60% of the protein supply in the food chain, providing a vital means of sustaining China’s 1.4 billion people
[1]. However, the intensive use of nitrogen fertilizer depends on high energy consumption, particularly through coal combustion during production, leading to about 400 Mt of CO
2 emissions annually
[2]. Also, N
2O produced during the application of nitrogen fertilizer accounts for 70% of the total global emissions and is an important source of greenhouse gas emissions
[3]. NH
3 emissions represent 50% of total emissions and contribute about 30% to haze formation
[4]. Additionally, ammonia deposition is a major contributor to water eutrophication, accounting for about 25% of total nitrogen input in surface waters.
Low nitrogen use efficiency is a primary driver of these environmental issues. Although China’s nitrogen fertilizer consumption declined from 30 Mt in 2015 to 24 Mt in 2024, with use efficiency rising to nearly 43%
[5], a significant gap remains compared to the green development target of 60% (Tab.1)
[7]. Several factors contribute to low nitrogen fertilizer utilization rates. First, nitrogen fertilizer formulations are relatively limited, primarily consisting of urea and ammonium-based fertilizers. These fertilizers dissolve and transform rapidly, and are prone to volatilization and loss, and do not align well with crop nutrient uptake patterns. Second, nitrogen fertilizer application technology remains underdeveloped and mechanized infrastructure insufficient, making precise and targeted application challenging. Additionally, farmers have limited awareness and expertise in precision fertilizer application, hindering the full utilization of existing nitrogen fertilizer products. Consequently, excessive fertilizer application is often used as a risk mitigation strategy. Adapting to modern agricultural production is key to advancing nitrogen fertilizer product innovation and application technology.
The primary objective of agricultural nutrient management technology development in China is to further reduce and improve the efficiency of nitrogen fertilizer use. In recent years, China has actively promoted technologies for fertilizer reduction and efficiency enhancement. In February 2015, the Ministry of Agriculture and Rural Affairs issued the Action Plan for Zero Growth of Fertilizer Use by 2020, aiming to achieve zero growth of fertilizer use of major crops by 2020 through the establishment of a scientific fertilizer management and technology system. The annual growth rate of fertilizer use was capped at 1% from 2015 to 2019. In 2022, the Ministry of Agriculture and Rural Affairs, along with relevant departments, issued several policies: In May, the National Development and Reform Commission jointly issued the Implementation Plan for Carbon Emission Reduction and Sequestration in Agriculture and Rural Areas, emphasizing the promotion of nitrogen fertilizer reduction and efficiency in key areas such as major grain-producing areas. In September, the five departments jointly issued the Implementation Plan for Building National Agricultural Green Development Pilot Zones and Promoting Comprehensive Green Transformation in Agricultural Modernization Demonstration Zones guiding pilot and demonstration zones to formulate carbon emission reduction and sequestration plans, and promoting such emission reduction technologies as water management in rice fields, and nitrogen fertilizer reduction and efficiency improvement in farmland. In October, they issued the Guiding Opinions on Promoting the High-quality Development of Rice-fishery Comprehensive Farming Industry emphasizing the ecological cycle, green and low-carbon characteristics of rice-fishery comprehensive farming, and reducing the use of pesticides and fertilizers. In November, the Chemical Fertilizer Reduction Action Plan by 2025 was released, with the goal of achieving a stable decline in the application of agricultural mineral fertilizers across China by 2025 and a more appropriate crop nutrition regime.
In February 2023, the Ministry of Agriculture and Rural Affairs issued the Implementation Opinions on the Implementation of the Key Work Deployment of the CPC Central Committee and The State Council in 2023 to comprehensively promote rural revitalization, once again emphasizing the reduction of fertilizers and pesticides, along with efficiency improvements. This included the implementation of fertilizer reduction actions, the development of novel fertilizer application technologies, innovation products, creation of machinery and the establishment of integrated supporting model areas. Additionally, the application of intelligent fertilizer recommendation systems was highlighted. These policies reflect China’s sustained efforts and firm determination in the green development of agriculture, and in the reduction and the enhancement of fertilizer efficiency. In recent years, the amount of nitrogen fertilizer application in China has dropped to about 24 Mt. In line with current policy directions and technological advancements, there is still potential for further reduction in nitrogen fertilizer application, with a target range of 18–21 Mt, aligning with crop absorption needs.
1.2 Stabilized fertilizer is the main way to decrease nitrogen loss and increase efficiency
To optimize the structure of fertilizer products, improve their utilization rate, and ensure food security, China’s fertilizer industry continues to focus on developing more efficient fertilizer products. Currently, the enhanced fertilizer products that have achieved large-scale industrialization primarily include slow- or controlled-release fertilizers (e.g., polymer coatings and polymer sulfur coatings), biofertilizers (e.g.,
Azotobacter, mycorrhizal fungi, phospholysaccharides and rhizobia), value-added fertilizers (e.g., amino acids, fulvic acid, humic acid, protein hydrolysates and seaweed extracts), and stabilized fertilizers (e.g., with nitrification or urease inhibitors). Among them, stabilized fertilizers have attracted widespread attention due to their clear function, high safety and ease of application. In June 2019
[8], the European Union introduced a new regulation on fertilizers, classifying products containing inhibitors into separate categories and establishing fertilizer standards. Since February 2020, the use of standard urea has been banned in Germany
[9], with urease inhibitors required or deep application methods mandatory.
According to a report by Industry ARC, the global nitrification and urease inhibitors market has been growing at a compound annual growth rate of 3.26% from 2018 to 2023. According to the International Fertilizer Association, global consumption of stabilized fertilizers in 2022 was about 10 Mt, with stabilized nitrogen fertilizers containing nitrification and urease inhibitors accounting for about 7.3 and 2.6 Mt, respectively. The primary markets for these products are expected to be concentrated in the EU and USA. Leading global enterprise clusters have been formed, including companies such as Compo and BASF in Germany, Solvay in Belgium, Corteva in USA and Koch Agronomic Services in USA. Global consumption of stabilized fertilizers is projected to reach nearly 13 Mt by 2030
[10].
According to statistics from the China National Chemical Information Center Co., Ltd., in 2023, China’s stabilized fertilizer production reached 2.6 Mt
[11], all of which was used domestically. It is expected that by 2030, the consumption of stabilized fertilizer in China will reach 3.14 Mt (Tab.2). Although the full potential for stabilized fertilizer application has not yet been realized, its rapid growth in recent years clearly indicates that China is accelerating toward a global leadership position.
2 Rapid development of stabilized fertilizers in China
2.1 China has emerged as the leading global producer of inhibitors
The core technology behind stabilized fertilizers primarily focuses on the application of nitrification and urease inhibitors. As attention on stabilized fertilizers increases, both domestic and international research, and development efforts in inhibitor technology are accelerating. Commercial nitrification inhibitors remain limited, with dicyandiamide (DCD), nitrapyrin and 3,4-dimethylpyrazole phosphate (DMPP) being the primary inhibitors still widely applied. DCD was first identified for its nitrification-inhibiting properties in 1918, although it only gained widespread use in US agriculture in the 1980s (Tab.3)
[13]. Advancements in technology have led to DCD becoming a widely used nitrification inhibitor. The nitrification-inhibiting properties of nitrapyrin were first identified by Goring in 1962
[16], leading to the development of N-Server by Dow Chemical in the 1970s, which was approved for agricultural use by the US Environmental Protection Agency in 1975
[17]. DMPP was developed and commercialized by BASF in Germany in the 1990s. Compared to the earlier nitrification inhibitors, such as DCD and nitrapyrin, DMPP offers higher efficiency, lower toxicity and environmental friendliness, making it widely used in agricultural production across Asia, Australia, Europe and South America
[14].
The commercially available urease inhibitors primarily include HQ (hydroquinone), NBPT (N-(n-butyl) thiophosphoric triamide) and NPPT (N-(n-propyl) thiophosphoric triamide). In the 1970s, Bremner & Douglas
[18] screened over 130 compounds and identified benzoquinone and HQ derivatives as effective urease inhibitors. Of these, HQ gained widespread international recognition as one of the earliest and most cost-efficient urease inhibitors, leading to extensive research and practical application (Tab.4)
[19]. Today, NBPT is one of the most widely used and effective urease inhibitors. Research and development began in the late 1980s, and in 1996, IMC-Agrotain, based in the USA, developed and launched the commercial product
[22]. NPPT, a new inhibitor developed by BASF in Germany, is based on NBPT. Its representative product, LIMUS, enhances the ammonia volatilization inhibition rate and duration by combining NBPT and NPPT, while significantly improving storage stability. Domestic research and application of NPPT are in the early stages, with large-scale production yet to be established, and the product is primarily imported
[23]. In addition to chemical nitrification inhibitors, biogenic inhibitors have also seen significant advancements (Tab.5). Current research has identified several biogenic nitrification inhibitors from plant root exudates, including methyl p-hydroxyphenyl propionate, sakuranetin, sorghum ketone, brachialactone and 1,9-decanediol from various plants such as sorghum and rice
[35]. Biologically derived nitrification inhibitors are advantageous for their long-lasting, effective and natural properties, making them an ideal strategy for sustainable nitrogen management. Denitrification inhibitors, which suppress the activity of denitrifying bacteria and decrease the conversion of nitrate to dinitrogen or nitrogen oxides, have become a focal point of ongoing research.
China began researching inhibitors in the 1970s. The Shenyang Institute of Ecology, Chinese Academy of Sciences, successfully developed long-acting urea and ammonium carbide products containing DCD. Since the 1990s, the combined use of nitrification and urease inhibitors has been promoted
[19]. In recent decades, Chinese research on pyrazoles and phospho-polysaccharides has made significant advancements
[19]. Currently, inhibitor products in China are continuously being optimized for higher efficiency, lower cost and environmental friendliness, which has laid a solid foundation for the agricultural green development and the popularization of nitrogen fertilizer efficiency enhancement technologies.
China is the main global producer of current inhibitor products. According to the data provided by Wuwei Jincang Biotechnology Co., Ltd., in 2024, the production of DCD, 2-chloro-6-(trichloromethyl) pyridine (CP) and DMPP in China has reached 3, 0.5, 2 kt, respectively, accounting for 80%, 90% and 50% of the global total production, and more than 10 enterprises have participated in the production of nitrification inhibitor (Tab.6). As far as urease inhibitors are concerned, the common urease inhibitor HQ limits the scale of its industrial application due to the risk of biological toxicity, and the global production is about 210 t·yr−1, and China’s production is 200 t·yr−1. The most widely used NBPT has an annual output of 6 kt in China, accounting for 90% of global production. On the consumption side, the a total of 1.6 kt nitrification inhibitors was used in China in 2023. Specifically, the consumption of DMPP was 800 t, of which 400 t was consumed as the active ingredient and the remaining 400 t was consumed as a formulated product (totaling 1.4 kt). The consumption of DCD was 500 t, of which 100 t was consumed as the active ingredient and the remaining 400 t was consumed in the form as a formulated product (totaling 1.3 kt). The consumption of CP is 300 t, of which 150 t are consumed as the active ingredient and the remaining 150 t are consumed as a formulated product (totaling 500 t). In addition, the total consumption of urease inhibitor NBPT in China in 2023 was 300 t, of which 60 t was consumed as the active ingredient, and the remaining 240 t are consumed as a formulated product (totaling 800 t).
2.2 Technological innovation in stabilized fertilizer: breakthroughs and practices in inhibitor addition process
The key feature of stabilized fertilizers lies in the application of scientifically designed and appropriate inhibitor addition technologies. These technologies, when integrated with fertilizer products, enhance the nutrient use efficiency of crops and decrease environmental pollution. However, due to the chemical characteristics of inhibitors and the complexity of the fertilizer production process, the technology for their addition has long had numerous technical challenges (Tab.7). In European and American countries, where terminal fertilizer dispensing technologies and equipment are relatively advanced, the strategy of mixing and using inhibitors has been predominantly adopted, with minimal demand on inhibitor addition technology. In contrast, China’s current fertilizer technology and equipment are still under development. Consequently, there has been a strong focus on the addition of inhibitors during upstream fertilizer production, which has presented technical challenges, including inhibitor stability, equipment safety, safe production and uniformity of addition
[17]. In recent years, through technological innovation, China has made significant breakthroughs in inhibitor addition technology for stabilized fertilizers, laying an important foundation for their industrialization. For example, Sinofert Holdings Limited developed a patented protection plus efficiency enhancement technology for DMPP. By optimizing and coating the molecular structure of DMPP, the retention rate of DMPP in the fertilizer system (over 6 months) was improved from a range of 20%–40% reaching 60%–70%, nitrogen use efficiency was boosted by 15%–20%, and a one-time fertilizer application approach for crops, such as maize, was achieved. This approach reduces mineral fertilizer usage by 10%–20%, while simultaneously increasing crop yield by 5%–15%.
In the production of stabilized fertilizers, the inhibitor addition technology is critical for ensuring the production of high-quality products. For example, nitrapyrin is prone to both decomposition and volatilization under high-temperature and high-light conditions, NBPT tends to be inactivated under conditions of high temperature, high humidity and acidity, and the chloride ions present in NBPT need to be strictly controlled to prevent corrosion of processing equipment. These factors limit the application of these inhibitors in urea-based products. In response to these challenges, domestic enterprises have adopted solvent carrier and biochemical inhibitor composite technologies, which enable complete miscibility and uniform distribution of the inhibitor with a urea slurry. Additionally, optimizing the instant addition process has allowed for the integration of inhibitors into the urea production process, significantly improving both production efficiency and product stability
[19].
Also, the instant addition system, developed based on rotary centrifugal separation technology, effectively addresses the issue of inhibitor decomposition during the addition process and significantly reduces the risk of equipment corrosion
[36]. This innovative technology has enhanced the production process of stable large-particle urea and provided technical support for the large-scale production of urea-based stabilized fertilizers.
2.3 Diversification of downstream products
To meet the diverse agricultural demands, the types and functions of stabilized fertilizers in China have become increasingly varied and comprehensive. Stabilized fertilizer technology has been extensively applied across a range of fertilizer categories, including standard compound fertilizers, nitrogen fertilizers, water-soluble fertilizers and others (Tab.8). For example, stabilized nitrogen fertilizers containing urease inhibitors have seen significant application. The Pu Zilan, stabilized nitrogen fertilizer launched by Nanning Harworld Biological Technology, Inc. and the Chao Kongshi stabilized fertilizer produced by Henan Xinlianxin Chemical Industry Group Co., Ltd., both incorporate Limus technology (Tab.9). These products are suitable for fertilizer application in large fields, fruit tree cultivation and horticultural crops. Additionally, the nitrification inhibitor DMPP has been successfully used in the Wistom stabilized fertilizer by Sichuan Jinxiang Chemical Co., Ltd and the Meizile stabilized compound fertilizer by Yunnan Yuntianhua Co., Ltd, among numerous other applications.
The diversified development of stabilized fertilizers is not only reflected in the expansion of product types but also in their ability to precisely meet the specific demands of different soils, climates and crops. For example, spring fertilizer application in winter wheat often poses significant ammonia volatilization risks. In regions characterized by frequent rainfall and alkaline soils, strong nitrification can lead to a substantial emission of greenhouse gases, such as N
2O, and cause the loss of nitrate through leaching. The application of fertilizers containing nitrification inhibitors and urease inhibitors offers an effective solution to these challenges
[37,
38]. This technology has also been successfully applied in the fertilizer application of fruit trees and other horticultural crops. For example, in perennial fruit trees, such as citrus and apples, long-lasting and stabilized fertilizers with slow-release characteristics are used to extend nutrient release over time, meeting the nutritional needs of the trees during their fruit expansion period and the stage of nutrient accumulation.
The diversification of stabilized fertilizers can be attributed to their ability to mitigate environmental pollution, such as ammonia volatilization and nitrate leaching, while significantly improving fertilizer use efficiency. This, in turn, promotes the sustainable development of agriculture. Urease inhibitors and nitrification inhibitors are crucial to achieving these outcomes. For example, Limus technology effectively decreases ammonia volatilization by inhibiting the activity of urease during urea decomposition
[39]. This not only decreases ammonia loss but also ensures better nitrogen absorption by crops, thereby increasing yields and reducing the overall use of nitrogen fertilizers. Also, nitrification inhibitors such as DMPP help mitigate the leaching and loss of nitrogen when using nitrate fertilizers. These inhibitors also decrease nitrogen loss caused by soil nitrification by lowering the nitrification rate, making them particularly suitable for regions with strong nitrification, high humidity and abundant rainfall
[14].
3 Stabilized fertilizers facilitating agricultural green development in China
Over the past 50 years, significant advancements have been made in the development of stabilized fertilizers, supported by numerous field experiments conducted both in China and internationally, as well as extensive meta-analyses. The effects of urease inhibitors, such as NBPT, on reducing ammonia emissions have been largely clarified. However, uncertainties remain for the mitigation of N2O emissions and nitrate leaching. Similarly, while the functions of nitrification inhibitors, such as DMPP, in lowering N2O emissions and nitrate leaching have been well-established, there are still questions about their effectiveness in mitigating NH3 emissions.
Despite these advancements, a common challenge with both nitrification and urease inhibitors in previous trials has been their limited impact on increasing yield and improving efficiency. This results in insufficient benefits for farmers, diminishing their enthusiasm for adopting these technologies and affecting the willingness of enterprises to invest. To address these challenges, collaborative efforts involving institutions, such as China Agricultural University, Wuwei Jincang Bioscience Co., Ltd. and CNSIG Anhui Hongsifang Co., Ltd. with support from the Laboratory of Stabilized Fertilizers and the Research Institute of Green Intelligent Compound Fertilizers, have led to experimental demonstrations across 23 locations in China, covering 14 different crop species (Tab.10). In addition, these efforts have involved the extensive collection of relevant scientific data from both domestic and international sources.
Through systematic analysis of this data, it has become evident that stabilized fertilizers not only offer reliable environmental emission reduction benefits but also hold significant potential for improving crop yields and enhancing efficiency. The key to maximizing these benefits lies in their appropriate application. To further elucidate the advantages of stabilized fertilizers, case studies have been conducted, which explore their effects across eight key areas: (1) increasing yield and quality, (2) extending fertilizer effect period, (3) lowering nitrogen loss and emissions, (4) improving fertilizer use efficiency, (5) enhancing crop stress resistance, (6) promoting root development, (7) improving element availability, and (8) reducing soil acidification and salinization.
3.1 Increase in yield and quality
Stabilized fertilizers, with their long-lasting nature and ammonium-nitrate nutrient regulation characteristics, provide crops with a balanced nutrient supply throughout their growth stages. This ensures that crops can effectively absorb and use the nutrients, preventing issues of both nutrient deficiency and excess. As a result, the overall yield and quality of crops is enhanced. Numerous experiments and studies have been conducted across various regions, including northern, north-western and eastern China, focusing on a variety of crops. For example, in the major apple-producing areas of northern and north-western China, the application of stabilized fertilizers containing nitrification inhibitors has demonstrated significant improvements in both yield and quality. During the apple fruit expansion period, the inclusion of a nitrification inhibitor with a nitrogen content of 1% enables slow nitrogen release. This approach has led to an average yield increase of 18.6% and an average improvement of 20.9% in the acid-to-sugar ratio of the fruit (Fig.1).
Similar results were also obtained in a vegetable system in northern China. For example, when applied to loose-leaf lettuce and head lettuce, a single application of stabilized fertilizer containing a nitrification inhibitor (with 1% nitrogen content), compared with multiple applications of standard fertilizer, the yields increased by 48.8% and 17.3% respectively, and the nitrate content decreased by 38.2% and 49.8% respectively (Fig.2)
[40].
In addition to economic crops, stabilized fertilizers also significantly increase the yield of food crops. A study conducted in eastern China on maize, rice and wheat showed that the average yield increase from stabilized fertilizers was 8.68%. Also, in the practice of rice production in eastern China, a fertilizer application management model combining rice-specific fertilizers with urease inhibitors further clarified that applying stabilized fertilizers can significantly increase the number of grains per spike, thereby increasing rice yield by 24%–30% (Fig.3)
[41].
In addition to field trials, large-scale demonstrations and applications of stabilized fertilizers have consistently resulted in stable yield increases. In 2024, the cumulative demonstration area for stabilized fertilizers in Northwest China reached nearly 2.4 kha, with varying degrees of yield enhancement across eight crop systems, including maize, wheat, potato, cotton, seed-producing zucchini, pepper, sunflower, and Isatis root. For example, maize yields increased by 5.9%–24%, wheat by 16%–25%, and potato by 6.5%–37% (Tab.11). These demonstration results clearly illustrate the positive role of stabilized fertilizers in enhancing crop productivity.
3.2 Extension of the duration of fertilizer effectiveness
Standard fertilizers typically have a short effective period, with nutrients being rapidly released after application. Under conditions of heavy rainfall or intensive irrigation, nutrients are prone to leach beyond the root zone, reducing their availability to crops and leading to low fertilizer use efficiency. In contrast, stabilized fertilizers use controlled nutrient hydrolysis and transformation mechanisms to ensure a more uniform and prolonged nutrient release. This approach extends the effective duration of fertilizers, maintaining continuous nutrient availability throughout the crop growth cycle. Previous studies using inhibition rate analysis have demonstrated that NBPT remains effective for more than 20 days, while DMPP sustains efficacy for 50–60 days.
Practical agricultural applications have shown that this sustained and stable nutrient supply not only significantly enhances crop growth potential but also reduces fertilizer application frequency and costs for farmers. For example, field trials in apple orchards in Yantai (Shandong Province), Sanmenxia (Henan Province), Luannan (Hebei Province) and Luochuan (Shaanxi Province) indicate that applying stabilized fertilizers containing DMPP twice, once in late June and again in early August during the fruit expansion stage, significantly increased yield by ensuring a continuous nutrient supply for 60 days (Tab.12). Similarly, a trial conducted on lettuce in Tangshan, Hebei Province demonstrated that incorporating DMPP into fertilizers allows a single application to meet the nitrogen demands and high-yield requirements of lettuce throughout its growth period while extending the fertilizer effectiveness to 50 days.
Also, comparable benefits have been observed in grain crop systems. For example, in the maize production system in Quzhou County, Hebei Province, applying DMPP-stabilized fertilizer at sowing eliminates the need for supplementary fertilizer application later. Based on calculations from sowing to the large ear stage, the fertilizer effectiveness period is expected to extend to 60 days.
Extensive field trials with stabilized fertilizers containing NBPT have demonstrated even more pronounced effects in enhancing fertilizer efficiency when applied as panicle fertilizer. For example, in the rice production system in Chongming, Shanghai, the addition of NBPT to panicle fertilizer, applied from the young panicle differentiation stage to harvest, ensured a sustained nutrient supply for about 90 days. In wheat production, multisite studies conducted at experimental locations in Shunyi (Beijing), Luannan (Hebei Province), Quzhou (Hebei Province), Jinan (Shandong Province), and Yuzhou (Henan Province) revealed that NBPT application enables early fertilizer application with delayed nutrient release. Specifically, applying NBPT-stabilized fertilizer at the regreening and tillering stages ensures nutrient availability during the jointing stage, thereby optimizing crop population structure and extending fertilizer efficacy by an estimated 30–40 days.
3.3 Improvement in fertilizer use efficiency
In standard fertilizer application, the low use efficiency of fertilizers has long been a critical issue demanding immediate resolution. Due to factors such as nutrient volatilization, leaching and transformation, the utilization rate of standard fertilizers commonly ranges from 30% to 40%. In contrast, stabilized fertilizers significantly enhance fertilizer use efficiency by controlling release and mitigating nutrient losses. In numerous cases, the nitrogen use efficiency can be increased to over 50% through the application of stabilized fertilizers (Tab.13). This not only reduces fertilizer input costs but also alleviates environmental burdens.
A comprehensive meta-analysis of extensive research has revealed that the application of both nitrification inhibitors and urease inhibitors significantly enhances nitrogen use efficiency
[42]. For example, in wheat-maize cropping systems, the use of nitrification inhibitors and urease inhibitors increased nitrogen use efficiency by 12.7% and 14.3%–17.5%, respectively. In grassland management, the application of these inhibitors resulted in nitrogen use efficiency improvements of 48.4% and 17.9%, while in paddies, nitrogen use efficiency was enhanced by 11.1% and 28.7%
[43]. In spring maize trials conducted in the Hexi region in Gansu Province, results demonstrated that when nitrogen application was maintained at 180 kg·ha
−1, the addition of DMPP (a nitrification inhibitor applied at 1% of the fertilizer nitrogen content) and NBPT (a urease inhibitor applied at 0.2% of the fertilizer nitrogen content) to urea increased nitrogen use efficiency from 53% to around 73%
[44]. In the wheat cropping system of Quzhou, Hebei Province, a two-year trial revealed that the use of stabilized nitrogen fertilizer containing NBPT (urease inhibitor applied at 0.2% of the fertilizer nitrogen content) significantly improved nitrogen fertilizer efficiency from 27.5% to 51.5%
[45]. In rice production in Chongming, Shanghai, the application of stable urea-ammonium nitrogen fertilizer (containing 19% urea nitrogen and 12% ammonium nitrogen) effectively leveraged the rapid efficacy of ammonium nitrogen and the slow-release characteristics of stabilized urea nitrogen, increasing nitrogen fertilizer efficiency from 32.0% to 49.5%. Among economic crops, the stabilized fertilizers have a more significant effect on improving nitrogen use efficiency. For example, in apple planting experiments conducted in Sanmenxia (Henan Province), Luannan (Hebei Province), Luochuan (Shaanxi Province) and Yantai (Shandong Province), the results showed that applying DMPP during the fruit expansion period could significantly enhance nitrogen use efficiency, increasing it from an average of 40.0%–83.1%. In the lettuce planting system of Luannan, Hebei Province, the application of stabilized fertilizers could increase nitrogen use efficiency to 70.0%–73.2%
[40].
Nitrogenous inhibitors decrease the rate of conversion of ammonium to nitrate by inhibiting the activities of nitrifying bacteria in the soil, thereby slowing the accumulation and loss of nitrate. This leads to a slower and more stable release of nitrogen in the soil, allowing crops to more effectively absorb nitrogen from these sources during the growing season and thereby improving nitrogen use efficiency. Under the action of urease inhibitors, the rate of nitrogen transformation slows down, enabling nitrogen to remain in the soil for a longer time. This helps stabilize the supply of nitrogen sources and enables crops to have continuous and uniform access to nitrogen from these sources throughout the growing season, thereby enhancing the fertilizer use efficiency. In summary, the use of inhibitors can achieve balanced release of nitrogen. By regulating the rate of nitrogen transformation, inhibitors delay the supply process of nitrogen from fertilizers to crops, allowing nitrogen to be released continuously and uniformly during the crop growth process, thereby significantly improving nitrogen use efficiency.
3.4 Enhance the stress resistance of crops
In recent years, as climate change becomes increasingly severe, achieving green development in agriculture faces numerous challenges. The application of stabilized fertilizers provides a potential pathway to enhance crop stress resistance. Taking the Hetao Irrigation District in 2022 as an example, the annual rainfall in this region was only 68 mm. If standard nitrogen loss minimization measures were adopted, it could lead to a 12.8% risk of yield reduction. Conversely, adding inhibitors while decreasing nitrogen loss can strengthen ammonium nitrogen supply, promote nutrient uptake and avoid yield reduction. Similarly, under low-temperature conditions, the use of inhibitors can enhance crop resistance. For example, in the fruit trees of Luannan, Hebei Province, frequent low temperatures during the bud burst period can limit flowering. However, the use of inhibitors can increase ammonium nitrogen supply, balance the ammonium-to-nitrate ratio, and thereby promote nutrient absorption, mitigating the impact of low-temperature damage. Also, the continuous supply of nutrients can alleviate growth suppression caused by nutrient deficiency, thereby improving crop resilience and yield under adverse conditions. For example, in Quzhou, Hebei Province, when waterlogging occurs, it is difficult for maize to apply timely fertilizer supplementation. The application of stabilized nitrogen fertilizers can effectively extend the fertilizer efficiency period, thereby reducing the risk of yield reduction due to insufficient nutrients in the later growth stages.
In addition to adverse conditions caused by climatic factors, the excessive input of nutrients also imposes stress on the normal growth and development of crops by affecting soil pH and salinity. This is particularly evident in enclosed production of vegetables and fruit trees, where the over-application of fertilizers significantly exacerbates soil salinization, thereby restricting the normal growth of crops. The application of stabilized fertilizers, through efficient nutrient uptake and the regulation and absorption of ammonium and nitrate, alleviates the salinity stress induced by high nutrient input, improves soil fertility, and substantially enhances crop yield. In the enclosed vegetable production system in Luannan, Hebei Province, the soil EC value reached as high as 1470 µS·cm−1, far exceeding the normal range of 200–1000 µS·cm−1. Under high salinity stress, the application of stabilized fertilizers containing DMPP significantly increased the ammonium content in the soil while decreasing nitrate content. This improved nutrient absorption through the synergistic effect of the ammonium and nitrate forms as well as further reducing the risk of aggravated salt damage. Also, experiments with leafy vegetables revealed that when the DMPP addition accounted for 1% of the nitrogen content, the maximum leaf area increased by 44.9%, the number of leaves increased by 32.4%, the fresh weight per plant increased by 51.5% and the yield increased by 48.8%. Additionally, the nitrate content in leafy lettuce decreased by 61.9%. These findings fully demonstrate that the application of stabilized fertilizers under high salinity stress conditions helps enhance crop stress resistance.
3.5 Promote the healthy development of root systems
Stabilized fertilizers promote the healthy development of root systems by regulating the release of nutrients. A stable supply of nutrients can promote the expansion and distribution of root systems, increase the absorption area of roots, and thereby enhance the water and nutrient absorption capacity of roots. In the growth and development process of many crops, the healthy development of root systems is crucial for final yield and quality. For example, when crops suffer from nutrient deficiency or excessive application, the growth of root systems is often inhibited, leading to the small and shallow root systems, which further affects the absorption of water and nutrients. Stabilized fertilizers, by providing a continuous supply of nutrients, can effectively avoid nutrient deficiency, promote the deep development of root systems, and enable roots to better adapt to complex soil environments.
Currently, the mechanisms by which stabilized fertilizers influence root system development are primarily focused on three aspects. First, this is by regulating of nutrient forms to influence root growth. For example, ammonium can promote the density of secondary and tertiary lateral roots, leading to the formation of a highly branched root system. This increases the root absorption area and enhances plant nutrient uptake capacity. Also, nitrate stimulates the secretion of plant growth hormones, promoting the growth and differentiation of plant tissues, including root elongation and development. Additionally, nitrate can increase the number of fine roots (capillary roots) and improve their development, further expanding the plant nutrient absorption area and enhancing uptake efficiency. Secondly, it is by regulating the spatial distribution of nutrients in soil, which influences root system development. Certain inhibitors, such as DMPP, can inhibit nitrification in the soil, thereby altering the distribution of nitrate. Since nitrate is more mobile than ammonium, the inhibition of nitrification changes the distribution pattern of nitrate in the soil, ultimately affecting the efficiency of nutrient absorption and use by plants. Lastly, it is by regulating nutrient concentration, which also influences root growth. Stabilized fertilizers can delay nitrogen release, effectively preventing the rapid release of nutrients that could lead to excessively high nutrient concentrations, which may inhibit root growth and development. When nitrogen concentrations are low, the main and lateral roots of the plant tend to elongate, and root hairs become denser and longer. This is an adaptive mechanism that helps roots acquire nutrients moving by diffusion. In a pot experiment with maize conducted in Gansu Province, the addition of nitrification inhibitors was found to enhance the supply of ammonium, promoting root growth and development in ammonium-preferring crops. This was evidenced by increases in root length, root surface area and root volume (Fig.4 and Tab.14)
[44].
3.6 Improving element availability
In addition to improving nitrogen use efficiency, the application of stabilized fertilizers also has a positive impact on the availability of other elements. Firstly, the application of stabilized fertilizers alters the availability of other elements by influencing soil pH. Taking phosphorus as an example, the application of nitrification inhibitors increases the supply of ammonium and promotes its uptake by plants. This, in turn stimulates the release of H+ by plants, lowering the pH of the rhizosphere soil. This acidic environment facilitates the release of phosphorus in the soil and enhances its uptake by plants. Concurrently, it decreases the conversion of ammonium to nitrate, thereby alleviating nutrient competition between phosphorus and nitrate and promoting the absorption and use of phosphorus. For trace elements, when ammonium is the dominant form of nitrogen in the soil, the uptake of ammonium by plants leads to the release of H+, causing rhizosphere acidification. This may increase the availability of iron, manganese and copper. Additionally, in alkaline soils, the inhibition of nitrification may slightly lower the pH, enhancing the solubility of iron, manganese and zinc.
Secondly, stabilized fertilizers affect the mobility of trace elements in the soil by altering the rate of nitrogen transformation. There is a close relationship between the forms of nitrogen in the soil and the mobility of trace elements. For example, when ammonium is the dominant form of nitrogen in the soil, rhizosphere acidification promotes the reduction of Fe3+ to Fe2+ (which has higher water solubility), thereby increasing the availability of iron. Additionally, certain rhizosphere-promoting bacteria (e.g., Pseudomonas) exhibit enhanced activity in ammonium-enriched environments, secreting organic acids or siderophores (e.g., ferrioxamines), which facilitate the solubilization of iron and zinc. The use of stabilized fertilizers can delay the nitrification process, thereby reducing the negative impact of nitrate on trace elements. This helps maintain the stable presence of trace elements in the soil and promotes their uptake by plants.
Finally, stabilized fertilizers not only influence nitrogen dynamics in the soil, they can also affect soil microbial communities. Certain trace elements (e.g., copper and zinc) are critical for the metabolism and functionality of soil microorganisms, and these microbial activities, in turn, influence the availability of trace elements
[46]. Studies have shown that the use of inhibitor fertilizers can alter the structure of soil microbial communities, thereby affecting the transformation and availability of trace elements
[47]. For example, soil microorganisms contribute to the release of trace elements through processes such as organic matter decomposition and mineralization of nutrients. The application of stabilized fertilizers may enhance microbial activity, thereby improving the availability of trace elements.
3.7 Reducing soil acidification and salinization
Soil acidification can degrade soil structure, impair crop root growth and increase the solubility of heavy metal elements (e.g., aluminum and manganese) in the soil. Stabilized fertilizers mitigate the risk of soil acidification by regulating nutrient release, thereby reducing their acidifying effects. Given the characteristics of acidic soils in southern China, particularly the higher risk of soil acidification and severe nitrogen loss, DMPP is a more suitable choice. It effectively slows the conversion of nitrogen fertilizers and reduces acidification caused by nitrification. However, NBPT is more effective in reducing ammonia volatilization losses from urea, especially when urea is used under high-temperature and high-humidity conditions. However, in terms of controlling acidification in acidic soils, NBPT is less effective compared to DMPP. In calcareous soils in northern China, acidification is not a significant concern and receives less attention. However, these soils are prone to nitrogen loss through ammonia volatilization. NBPT is suitable for reducing ammonia volatilization during urea application, making it effective in improving nitrogen use efficiency in such contexts.
In addition, the slow-release properties of stabilized fertilizers can effectively reduce salt accumulation caused by fertilizer application, particularly in arid regions and irrigated agriculture, where this issue is especially problematic. By controlling the release rate of fertilizers in a rational manner, stabilized fertilizers can mitigate the formation of saline-alkali soils and maintain soil health. Research has shown that when urea is applied in combination with nitrification inhibitors, it can reduce the losses of calcium and magnesium ions through leaching, prevent salt accumulation in the soil and lower the risk of soil salinization (Tab.15)
[48].
4 Precision application technologies for stabilized fertilizer
4.1 Application domains of stabilized fertilizers
Until recently, the application for nitrification inhibitors and urease inhibitors was inadequately defined. However, with ongoing research, gradually several highly promising application contexts have been identified. For example, the use of nitrification inhibitors in low-temperature regions and high-pH soils has been demonstrated to be particularly suitable (Tab.16). In low-temperature areas, these inhibitors not only maintain their activity but also enhance the supply of ammonium nitrogen, thereby promoting root development. In high-pH regions, controlling the nitrification rate to increase ammonium nitrogen supply has also shown significant advantages. Contrary to previous beliefs, high-pH soils do not predominantly cause the degradation and deactivation of DMPP. Additionally, while it was once thought that DMPP should be avoided in areas with heavy rainfall, current experimental results indicate that in such regions or irrigation zones, DMPP can effectively leverage the advantage of decreased ammonium loss, thereby improving nutrient supply.
The efficacy of urease inhibitors remains relatively stable, consistently reducing ammonia volatilization losses in most scenarios. Their potential for emission reduction is particularly pronounced in regions or soils with substantial ammonia volatilization losses. Also, they reliably enhance crop yield and production efficiency. However, it is important to note that in low-temperature conditions (e.g., regions with an average annual temperature below 10 °C), the yield-increasing effects may not be significant. It is recommended to apply urease inhibitors in high-pH soils and in areas with high temperatures and surface-applied nitrogen fertilizers.
4.2 Technological innovations in stabilized fertilizer application
In the current relevant standards of China, only the upper limit of the inhibitor addition amount is set, but no lower limit is specified. This has led to the common phenomenon of the inhibitor addition being insufficient, thereby affecting its potential effect. The standards in Europe and America stipulate that the addition range of inhibitors is 0.8%–1.6% for DMPP and 0.09%–0.2% for NBPT. However, this standard may not be fully applicable to the actual situation in China (Tab.17).
The research team of China Agricultural University conducted in-depth studies on five representative soils across China and found that there is a correlation between the usage amount of urease inhibitors (e.g., NBPT) and the application amount of urea fertilizer (Fig.5). According to different studies and field trials, the common rate of urease inhibitor used should be in the range of 0.09%–1.0% of the total amide nitrogen content in the applied fertilizer. For example, 0.05–0.5 kg of NBPT is usually added per 100 kg of urea. This rate range can effectively delay the decomposition of urea and decrease ammonia volatilization. The rate can be appropriately adjusted according to the application environment. For example, in warm and humid environments, due to the faster hydrolysis rate of urea, a higher rate of inhibitor may be needed whereas e in cold or dry areas, the urea hydrolysis process itself is slower, and the rate of inhibitor can be appropriately reduced.
4.2.1 Rate of the nitrification inhibitor
The rate of nitrification inhibitors is usually closely related to the type of nitrogen fertilizer and the application method. The common concentration of nitrification inhibitors is in the range 0.05%–1.2% of the total amount of amide nitrogen and ammonium nitrogen in the applied fertilizer. Generally, the standard concentration of nitrification inhibitor DMPP is 0.5–1.0 kg·t−1 of fertilizer. When adding DMPP to urea or ammonium nitrogen fertilizers, the concentration is usually between 0.5 and 2 kg·ha−1, and the specific concentrations can be appropriately adjusted according to the application type of the fertilizer and the actual needs of the crops (Fig.6). The application rate for nitrate-containing fertilizers (e.g., ammonium nitrate) may need to be adjusted appropriately according to the soil conditions and the needs of the crops. When DMPP is applied in a liquid form (e.g., through drip irrigation systems), the recommended concentration range is 0.5 to 2 kg·ha−1.
4.2.2 Adjustment and optimization of inhibitor concentration
The optimal concentration and application methods of urease inhibitors vary depending on environmental conditions. They need to be adjusted according to factors such as soil pH value, temperature, urease activity, fertilizer application methods and plant type. For example, in red soil double-cropping paddies, the addition of NBPT should be 1.0% for urea to achieve the goals of economic efficiency, increased yield and decreased fertilizer usage. When 0.5% NBPT is added, the total nitrogen content, nitrogen uptake, and nitrogen fertilizer use efficiency of rape are all relatively high, and no significant reduction in quality indicators such as VC content and soluble sugar content have been observed.
The effect of applying nitrification inhibitors is influenced by various factors, including their type, rate and physicochemical properties, as well as soil and environmental conditions, and field management. The effect of applying nitrification inhibitors varies greatly in different types of soil. For example, the effects of DCD and nitrapyrin on nitrification in loamy soil and paddy soil have significant rate response. Specifically, when the concentration of DCD and nitrapyrin reaches 5%–10% of the elemental nitrogen and 0.5%–1.0%, respectively, their effects are the most significant (Fig.7). Numerous studies have confirmed that adding 1% of the nitrogen content as DMPP is the optimal choice. Therefore, when selecting the best inhibitor type, it is necessary to comprehensively consider the local climate and ecological environment, adopt a local approach, and also fully consider the environmental benefits brought by different rates.
4.2.3 Soil type
Different types of soil have differences in their adsorption capacity of fertilizers and the rate of nutrient release. In light soil (e.g., sandy soil), nutrients are lost more quickly, so the rate of inhibitors can be appropriately increased, whereas in heavy soil (e.g., clay soil), nutrient release is slower, and the application rate of inhibitors can be appropriately reduced.
4.2.4 Climatic conditions
Climatic conditions significantly influence the release of fertilizers and nutrient loss. In hot and humid climates, urea and nitrate fertilizers decompose and transform more quickly, and the rate of inhibitors may need to be increased whereas in arid or cold regions, the decomposition speed of fertilizers is slower and the application rate of inhibitors can be reduced.
4.2.5 Crop requirements
Different crops have different requirements for nitrogen and their absorption rates. Therefore, the application rate of inhibitors should also be adjusted according to the growth requirements of the crops. For crops with a long growth period (e.g., maize and rice), the supply of nitrogen needs to last longer, and controlled-release fertilizers and inhibitors can be used to ensure that the crops can obtain balanced nutrient supply throughout their growth period.
4.2.6 Fertilizer application methods
Different fertilizer application methods (e.g., banding, broadcasting and fertigation) also have different requirements for inhibitors. Local fertilizer application methods such as banding and fertigation have more precise control over fertilizers, and the rate of inhibitors can be appropriately reduced whereas broadcast methods may lead to uneven distribution of fertilizers, the application rate of inhibitors needs to be adjusted according to the total amount of fertilizers.
4.3 Synergistic integration of inhibitors and fertilizers
When the application rate of nitrogen fertilizer is usually high enough that nitrogen element is no longer limiting for crop yield, the effect of applying inhibitors is often poor. For example, when DMPP and NBPT inhibitors are applied to maize in Northwest China, significant yield-increasing effects are observed under low-nitrogen conditions, but the yield-increasing effect is not obvious under high-nitrogen conditions. Therefore, the main problem is currently not if inhibitors can enhance yield, but rather will it is necessary to determine if the application rate of nitrogen fertilizer should be reduced to be consistent with crop demand when inhibitors are also used.
During the application of inhibitors, it is necessary to ensure that they are applied concurrently with fertilizers so that the inhibitors can effectively combine with the fertilizers and exert their effects, and prolong the fertilizer efficacy. In areas with large rainfall, applying inhibitors after rainfall may cause the inhibitors to be washed away by rain, resulting in their spatial separation from the fertilizers and thus failing to fully exert their effects. To ensure effectiveness, the application rate of inhibitors can be appropriately increased. Especially in the application of water-fertilizer integration, the inhibitors and fertilizers need to be fully mixed to ensure that they are spatially consistent.
5 The vast potential of inhibitors in China’s green agricultural transition
In the face of global environmental challenges, green, low-carbon and sustainable development have become core issues. How to jointly promote the green transformation of fertilizers, enhance their use efficiency and effectively reduce environmental pollution has become an urgent task for sustainable agricultural development. Through scientific nitrogen fertilizer management and vigorously developing stabilized fertilizers, China has achieved initial results in promoting the green transformation of fertilizers. In the future, China will continue to firmly promote the green transformation of fertilizers, demonstrating national commitment to and responsibility in environmental governance.
5.1 Advancing nitrogen fertilizer upgrades with stabilized fertilizers to enhance efficiency and sustainability
To adapt to the requirements of agricultural green development, China’s nitrogen fertilizer products are undergoing a comprehensive upgrade. The nitrogen fertilizer industry is undergoing supply-side reform from scale expansion to quality and efficiency improvement (Fig.8)
[49]. During this process, in combination with fertilizer application methods and regional characteristics, stabilized fertilizers will have the following development trends.
The output of ammonium chloride and ammonium sulfate in China is equivalent to about 5 Mt of N, accounting for about 20% of the total nitrogen fertilizer output. As they are industrial byproducts, they have low energy consumption and low emissions, and have a relatively low nitrification rate. When combined with urea to produce urea-ammonium nitrogen fertilizers (urea-ammonium sulfate and urea-ammonium chloride), they are particularly suitable for high pH soils and rice. However, there is still a problem of high ammonia emissions. By adding inhibitors, comprehensive effects such as emission reduction and delayed release can be achieved
[45,
50].
In China, about 50% of the cultivated land is irrigated. While developing liquid nitrogen fertilizers (e.g., urea nitrate solution applied in northern and north-western China) in 20% of the irrigation systems, inhibitors are added simultaneously to delay nitrogen release and control nitrogen in the root zone
[51]. During the topdressing of wheat and rice, a certain proportion of the area still requires the method of spreading urea (accounting for about 20% of the total nitrogen fertilizer application in China). Whether using ground-level or aerial (drones) spreading of urea, there is a risk of NH
3 volatilization. Adding urease inhibitors can effectively control losses and improve fertilizer efficiency
[52,
53]. The economic crop system consumes 40% of the nitrogen fertilizer, mainly through compound fertilizers and water-soluble fertilizers. Considering the large-scale flood irrigation methods and the need for lower root density of economic crops, adding inhibitors can achieve better benefits.
5.2 Extending nitrogen regulation to aquaculture, grassland management and manure treatment
Aquaculture, grassland management and manure treatment are important components of agricultural ecosystems and are significant fields for achieving sustainable agricultural development at present. Their coordinated development is crucial for promoting the widespread application of stabilized fertilizers and the continuous improvement of the agricultural ecological environment (Tab.18).
In aquaculture, the application of stabilized fertilizers is a key measure for regulating the content of nitrite in water bodies, improving the oxygen supply level of water bodies, enhancing the ecological quality of water bodies, and promoting the healthy development of aquaculture. For example, developing green stabilized fertilizers designed for aquaculture characteristics, through scientific proportioning, optimizing the nitrogen, phosphorus, potassium and other nutrient elements in water bodies, promoting the healthy growth of aquatic organisms, regulating the content of nitrite in water bodies, and improving the oxygen supply level of water bodies. In the future, biotechnology and microbial preparations can be introduced to further increase fertilizer use efficiency and reduce nutrient loss.
In pastures, especially in artificially managed pastures, animal manure and urine produce a large amount of ammonia volatilization
[54]. By adding urease inhibitors and/or nitrification inhibitors, these fertilizers can slow the rate at which urea decomposes into ammonia, reducing the loss of ammonia volatilization, while concurrently inhibiting the conversion of ammonium to nitrate, reducing the loss of nitrogen through leaching. Thus, the fertilizer use efficiency can be improved, and the productivity of pastures can be enhanced. The nitrogen in livestock manure is an important component of the nitrogen cycle in pastures. By reducing the loss of nitrogen in manure, stabilized fertilizers help maintain soil fertility in pastures, promote the growth of forage grass, and thereby increase the overall productivity and sustainability of pastures
[55,
56].
Animal manure treatment is one of the important directions for the green transformation of fertilizers in the future
[57]. During the processes of manure generation, collection, storage and treatment, there is a large amount of ammonia volatilization. Adding inhibitor products can effectively inhibit the emission of ammonia gas, N
2O and other odorous gases, thereby decreasing nitrogen loss and producing green organic fertilizers rich in nitrogen. After adding stabilized fertilizers or inhibitor products to the manure and returning it to the field, it can achieve a dual effect of simultaneously realizing soil improvement and environmental emission reduction. Through the recycling and complementary effect of resources, more efficient and sustainable agricultural development can be achieved.
5.3 Leveraging stabilized fertilizers to adapt to and mitigate climate change impacts
Global climate change poses significant challenges to agricultural production. Stabilized fertilizers can meet the demand for precise nutrient regulation brought about by climate change.
It is important to enhance the stability of crop yields and lower greenhouse gas emissions. Stabilized fertilizers can maintain the stability of crop yields under the influence of climate change. Long-term field trials have shown that the use of stabilized fertilizers can reduce the fluctuations in crop yields between different years and improve the stability of crop yields. This is crucial for ensuring food security and agricultural productivity. Also, stabilized fertilizers can lower the emissions of volatilized ammonia and N
2O from the soil, lower the nitrification and denitrification processes in the soil, and increase the use efficiency of nitrogen fertilizers. Through precise design, scientific management and technical services, stabilized fertilizers can increase the nitrogen fertilizer use efficiency to 60%, lower N
2O emissions by more than 60% and decrease nitrogen usage by 20%–50%
[43].
Intelligent sensing of soil environment and precise release of nutrients need to be adopted. Environmental conditions, such as temperature and moisture, affect crop growth and nutrient absorption. Stabilized fertilizers combined with temperature-sensitive or water-sensitive materials can autonomously regulate the release of nutrients and water according to environmental changes, meet the nutrient requirements of crops and regulate the release of nutrients based on soil pH and root exudates to ensure precise delivery
[58].
It is also important to develop new types of stabilized fertilizers with the corresponding functions to achieve the synergy of resistance, low-carbon and high-efficiency. Develop resistant fertilizers to enhance the adaptability of crops to extreme climates (e.g., cold and drought tolerance). By adding substances such as biological stimulants, improve the growth and yield of crops in harsh environments and reduce the impact of climate change on agriculture
[59].
In the future, the green transformation of fertilizers will comprehensively cover nitrogen fertilizer innovation, manure treatment, aquaculture and grassland management, actively respond to climate change, relying on scientific and technological innovation, policy support and international cooperation, China will continue to lead this transformation process and make important contributions to the sustainable development of global agriculture.
5.4 Developing and implementing plans designed for local conditions
Scientific and technological innovation should serve agricultural reality and enhance farmer trust and willingness to use new types of fertilizers. This will strengthen technical promotion at the front line and encourage fertilizer enterprises to go deep into the production front line to demonstrate the efficiency-enhancing effects of stabilized fertilizers and optimize application methods. Through demonstration fields and data feedback, farmer awareness can be enhanced and scientifically-based management promoted. It is important to explore precise fertilizer application systems based on soil monitoring and remote sensing data to help achieve the goal of green and efficient agricultural production. In 2024, with the support of the Provincial Agricultural Soil Conservation and Protection Station and the Agricultural Technology Extension Center, Wuwei Jincang Bioscience Co., Ltd. conducted experimental demonstrations on crops including maize, potatoes and wheat. This was done through on-site surveys, based on local soil and climate conditions and crop requirements, select inhibitor types and ultimately determine the optimal nitrogen, phosphorus and potassium ratios, and the best application methods for fertilizers. For example, in the wheat demonstration, by optimizing the formula, the final choice was the additive fertilizer formula of Enhancing No. III (Added DMPP and NBPT), and the wheat agronomic traits were excellent, with an increase in yield of 25%. Currently, the total experimental area is over 2.7 kha, and crop yields have generally increased by 8%–10%, with significant growth in the net income of farmers, contributing to increasing farmers awareness of stabilized fertilizers and improving market acceptance.
5.5 Strengthening legal compliance and governance in fertilizer management
Promoting the development of stabilized fertilizer industry requires a sound institutional mechanism. However, there are currently a range of problems including the absence of relevant laws and regulations, weak market supervision, low fertilizer use efficiency and insufficient technical proficiency of agricultural practitioners in the management of stabilized fertilizers.
The novel fertilizer industry in China started relatively late and lacks core technologies and innovation capabilities, resulting in weak product competitiveness. There are also no specific laws and regulations to for fertilizer production and operation, leading to ineffective fertilizer market supervision and overlapping responsibilities among various departments without effective coordination. Concurrently, the standards for stabilized fertilizers are not yet sufficiently refined, there is no unified assessment standards for products and the market products are not adequately monitored
[60]. According to the
Fertilizer Registration Management Measures, fertilizer enhancers need to be registered with the Ministry of Agriculture and Rural Affairs. As of July 2023, only two enterprises, Zhejiang Sunfit Advanced Materials Co. Ltd. and Shanxi Sunger Bioscience Co., Ltd., have completed the registration of inhibitor products. The professional ability of agricultural technicians is insufficient, and the lack of financial support for agricultural development further restricts the scientific management of stabilized fertilizers and the sustainable development of agriculture. To solve these problems, efforts should be made from multiple aspects including technological innovation, improvement of laws and regulations, strengthening market supervision, improving fertilizer use efficiency and enhancing the quality of agricultural practitioners. This will promote the scientific management of stabilized fertilizers and the green development of agriculture. China should accelerate the construction and improvement of a modern agricultural institutional system with clear orientation, scientific decision-making, strong execution and effective incentives, and continuously enhance governance efficiency in green agricultural development, providing a solid guarantee for the promotion and high-quality development of stabilized fertilizers and the industry
[19].
6 Innovation and upgrading directions for stabilized fertilizer
6.1 Application of synthetic biology in stabilized fertilizer development
With the rapid development of synthetic biology, the potential of this field in enhancing agricultural productivity, improving crops, reducing production costs and achieving sustainable development is increasingly prominent. Particularly, by adopting microbial or metabolic engineering approaches to reduce the use of agricultural fertilizers, it should significantly overcome the current agricultural constraints and bring about breakthrough growth in agricultural production capacity and nutrition, thus realizing the, so called, second green revolution in agriculture
[61]. For example, through genetic engineering to optimize fertilizer carriers (e.g., biological and microbial carriers), the release efficiency and stability of fertilizers can be enhanced, and the risks of fertilizer loss and pollution can be mitigated
[62].
6.2 Research and development of high-efficiency and environmentally safe inhibitors
It is important to develop novel inhibitors that are safer, more effective and harmless to soil and crops. These inhibitors should have obvious inhibitory effects on nitrogen transformation process, possess low environmental toxicity, low bio-toxicity and degradability
[63]. During the deployment of the new products, problems such as optimization of production process, stability of products, validation of effectiveness and market promotion will need to be solved. These new products will also need to meet the actual needs of farmers, such as convenience of use, reasonable cost (reducing research and development costs, lowering the final product price through large-scale production and thereby generating strong market competitiveness) and acceptable plant-growth effects.
6.3 Integrating inhibitors with novel biological agents for enhanced efficiency
Biological agents, especially biological nitrogen fixation technology, rely on the interactions of soil, soil microorganisms, microbial metabolites, plants and plant metabolites, which can efficiently convert atmospheric nitrogen into nitrogen sources that plants can absorb and utilize
[64]. Integrating nitrification inhibitors with nitrogen fixation technology can, to a certain extent, overcome a reliance on standard mineral nitrogen fertilizers and construct a new nitrogen cycle model of increasing income and reducing expenditure. At the front end, biological nitrogen fixation provides a sustainable nitrogen supply channel. At the back end, nitrification inhibitors are used to enhance nitrogen use efficiency, forming a closed-loop system from nitrogen source supply to nitrogen regulation. This system will exhibit considerable agricultural sustainable production vitality. The key to this technology integration lies in breaking through the compatibility problem between inhibitors and biological technology carriers and formulating technical integration plans based on different soil types and crop nitrogen demand patterns.
6.4 Enhancing compatibility technologies for inhibitors and fertilizers
The future development trend of inhibitor and fertilizer compatibility technology will focus on greening and environmental friendliness to meet the global demands for reducing environmental pollution and improving fertilizer use efficiency
[17]. Technological innovation will drive the development of novel and efficient inhibitors, and enhance the performance of existing types, while promoting the upgrading of fertilizer products, such as value-added fertilizers and microbial fertilizers
[60]. The research and development of specialized fertilizers will target specific crops and regions to enhance the specificity and effectiveness of fertilizers. The addition of technology of inhibitors and functional substances in combination will further develop to maximize fertilizer effects and enhance the stress resistance of crops. The improvement of production processes will increase the persistence and stability of stabilized fertilizer products, and concurrently, cost control and market competitiveness improvement will be key factors.
6.5 Priority areas and target crops for stabilized fertilizer promotion
In the future, the key promotion areas for stabilized fertilizer will be concentrated in regions with high agricultural production intensity, low fertilizer use efficiency and severe soil nutrient loss, particularly in northern and north-eastern China and the middle and lower reaches of the Yangtze River, but also in other major grain-producing areas. These regions have long applied large amounts of nitrogen fertilizers, resulting in nitrogen fertilizer loss and environmental pollution. Therefore, stabilized fertilizers can effectively improve nitrogen fertilizer use efficiency and decrease environmental pollution. Additionally, in arid and semiarid areas, and ecologically fragile regions, such as the north-western region, stabilized fertilizers can decrease water and fertilizer loss, save water resources and mitigate soil salinization problems
[65]. Crops, including cereal crops (e.g., wheat, maize and rice), economic crops (e.g., fruit trees and vegetables) and high-yield crops in facility agriculture (e.g., capsicum and tomato), as well as improved grasslands, all have high demand for nitrogen fertilizers and are susceptible to nitrogen fertilizer waste and environmental pollution. Stabilized fertilizers can ensure that crops receive sufficient nutrients during critical growth periods by improving fertilizer use efficiency, delaying nitrogen transformation processes, and reducing environmental pollution
[43].
6.6 Carbon emission certification and trading for novel stabilized fertilizer products
The carbon emission certification and trading of stabilized fertilizer products will become a key link in promoting the green development of agriculture. With the intensification of global climate change, stabilized fertilizers have significant potential for decreasing nitrogen fertilizer loss in the agricultural sector and lowering greenhouse gas emissions
[66]. Establishing a scientific carbon emission efficiency assessment and certification system is necessary to provide authoritative carbon emission certification for stabilized fertilizers and lay the foundation for entering the carbon emission market. On this basis, agriculture, enterprises and farmers can obtain economic returns through the carbon emission trading market and promote the adoption of more green and low-carbon technologies. Also, government policy support, incentives from the carbon trading market and the promotion of green product certification will further promote the popularization and application of stabilized fertilizers. Concurrently, with the unification of carbon emission standards among countries, the carbon emission certification of stabilized fertilizers is expected to enter the international carbon market, promoting green agricultural development on a global scale. Through these measures, stabilized fertilizers will not only enhance fertilizer use efficiency and decrease environmental pollution, but also deliver economic returns to agricultural enterprises and promote global sustainable agricultural development.
7 Conclusions
Amid the global agricultural resource scarcity and escalating environmental challenges, stabilized fertilizers are poised to make a crucial contribution to achieving sustainable agricultural development. These fertilizers enhance nutrient use efficiency and decrease environmental pollution. At present, scientific and technological innovations are driving the green transformation of agriculture. The application of stabilized fertilizers not only ensures food security but also fosters ecological balance.
In the future, through the use of stable fertilizers, it is expected that an increase in the nitrogen fertilizer use efficiency in China from 40% to 60%, and the use of nitrogen fertilizer from 23 to 21 Mt. DMPP demand is expected to range from 5 to 122 kt and NBPT demand from 1.3 to 7.2 kt. Nationwide, it is estimated that 2 Mt of nitrogen fertilizer can be saved, the increase effect is conservatively estimated to reach 5%–8%, and the income per ha can be increased by 600–960 yuan. The national application area of stable fertilizer inhibitors is expected to be about 13–20 Mha, and the total increase is expected to be about 8–19.2 billion yuan.
We urge research institutions, agricultural enterprises, government agencies and farmers to collaborate in advancing the research and adoption of stabilized fertilizer technology, jointly safeguarding the land, achieving sustainable agricultural development and contributing to a green future.
The Author(s) 2025. Published by Higher Education Press. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0)
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