Enhanced Efficiency Fertilizers Research Articles

Nitrogen: from discovery, plant assimilation, sustainable usage to current enhanced efficiency fertilizers technologies – A review

ABSTRACT From 1913 onwards, the global situation changed from a scenario of nitrogen (N) scarcity to an abundance of ammonia (NH 3 ) produced synthetically via the Haber-Bosch process. Several N compounds have been synthesized since then, with urea becoming the main source of N, accounting for 55 % of current N consumption. However, N efficiency in agroecosystems is low and, normally, N recovery in cultivated plants is less than 50 %. This occurs because a large amount of reactive N is lost to the environment, inducing various forms of pollution, threatening human and environmental health, in addition to causing a negative economic impact on the farmer. The main processes responsible for low N efficiency are NH 3 volatilization, leaching, and N denitrification. Considering global NH 3 volatilization losses of 14 %, it can be assumed that up to 8.6 million Mg of urea are lost every year in the form of NH 3 . For each ton of NH 3 produced, 1.9 to 3.8 Mg of CO 2 is emitted into the atmosphere. Therefore, increasing N use efficiency (NUE) without compromising yield is a necessity and a challenge for crop improvement programs and current management systems, in addition to reducing greenhouse gas emissions. In this context, enhanced efficiency fertilizers (EEFs), which contain technologies that minimize the potential for nutrient losses compared to conventional sources, are an alternative to increasing the efficiency of nitrogen fertilization. Currently, EEFs are classified into three categories: stabilized, slow-release, and controlled-release. This study aims to understand the technologies used to produce EEFs and the factors that govern their availability to plants. This review covers the following topics: the discovery of N, N dynamics in the soil-atmosphere system, N assimilation in plants, strategies to increase NUE in agrosystems, NH 3 synthesis, NH 3 volatilization losses, N fertilizer technologies, the importance of characterization of EEFs, conventional nitrate or ammonium-based fertilizers to reduce gaseous losses of NH 3 and future prospects for the use of N fertilizers in agriculture.

Global impact of enhanced-efficiency fertilizers on vegetable productivity and reactive nitrogen losses

Vegetables are the most consumed non-staple food globally, and their production is crucial for dietary diversity and public health. Use of enhanced-efficiency fertilizers (EEFs) in vegetable production could improve vegetable yield and quality while reducing reactive nitrogen (Nr) losses. However, different management and environmental factors has significantly distinctive impacts on the effectiveness of EEFs. In this study, a worldwide meta-analysis based on the data collected from 144 studies was performed to assess the impacts of EEF (nitrification inhibitor [NI] and polymer-coated urea [PCU]) application on vegetable yield, nitrogen (N) uptake, nitrogen use efficiency (NUE), vegetable quality and Nr losses (nitrous oxide [N2O] emissions, ammonia [NH3] volatilization, and nitrate [NO3−] leaching). The effects of the applied EEFs on vegetable yields and N2O emissions were assessed with different management practices (cultivation system, vegetable type and N application rate) and environmental conditions (climatic conditions and soil properties). Compared to conventional fertilizers, EEFs significantly improved vegetable yield (7.5–8.1 %) and quality (vitamin C increased by 10.7–13.6 %, soluble sugar increased by 9.3–10.9 %, and nitrate content reduced by 17.2–25.1 %). Meanwhile, the application of EEFs demonstrated a great potential for Nr loss reduction (N2O emissions reduced by 40.5 %, NO3− leaching reduced by 45.8 %) without compromising vegetable yield. The NI was most effective in reducing N2O emissions (40.5 %), but it significantly increased NH3 volatilization (32.4 %). While PCU not only significantly reduced N2O emissions (24.4 %) and NO3− leaching (28.7 %), but also significantly reduced NH3 volatilization (74.5 %). And N application rate, soil pH, and soil organic carbon (SOC) were the main factors affecting the yield and environmental effects of EEFs. Moreover, the yield-enhancing effect of NI and PCU were better at low soil N availability and SOC, respectively. Thus, it is important to adopt the appropriate EEF application strategy targeting specific environmental conditions and implement it at the optimal N application rate.

Leveraging digital agriculture for on-farm testing of technologies

The Precision Nitrogen Project (PNP) worked with more than 80 corn and winter wheat producers to inexpensively design and implement randomized, replicated field strip trials on whole commercial farm fields, and to provide site-specific testing of current nitrogen (N) technologies. This article proposes a conceptual framework and detailed procedure to select the N technology to be tested; design and implement field trials; generate, process, and manage field trial data; and automatically analyze, report, and share benefits from precision N technology. The selection of the N technology was farmer-driven to ensure a good fit and to increase the likelihood of future technology adoption. The technology selection method was called the “N tiered approach”, which consisted of selecting a technology that progressively increases the level of complexity without exceeding the farmer’s learning process or farm logistic constraints. The N tools were classified into (1) crop model-based, (2) remote sensing-based, (3) enhanced efficiency fertilizers, and (4) biologicals. Field strip trials comparing producers’ traditional management and the selected N technology were combined with site-specific N rate blocks placed in contrasting areas of the fields. Yield data from the N rate blocks was utilized to derive the site-specific optimal N rate. The benefits of current N technologies were quantified by comparing their yield, profit, and N use efficiency (NUE) to growers’ traditional management and to the estimated site-specific optimal N rate. Communication of the trial results back to the growers was crucial to ensure the promotion and adoption of these N technologies farm wide. The framework and overall benefits from N technologies was presented and discussed. The proposed framework allowed researchers, agronomists, and farmers to carry out on-farm precision N experimentation using novel technologies to quantify benefits of digital ag technology and promote adoption.

Evaluating novel biodegradable polymer matrix fertilizers for nitrogen-efficient agriculture.

Enhanced efficiency fertilizers (EEFs) can reduce nitrogen (N) losses in temperate agriculture but are less effective in the tropics. We aimed to design a new EEF and evaluate their performance in simple-to-complex tests with tropical soils and crops. We melt-extruded urea at different loadings into biodegradable polymer matrix composites using biodegradable polyhydroxyalkanoate (PHA) or polybutylene adipate-co-terephthalate (PBAT) polymers with urea distributed throughout the pellet. These contrast with commercially coated EEF that have a polymer-coated urea core. We hypothesized that matrix fertilizers would have an intermediate N release rate compared to fast release from urea or slow release from coated EEF. Nitrogen release rates in water and sand-soil columns confirmed that the matrix fertilizer formulations had a more progressive N release than a coated EEF. A more complex picture emerged from testing sorghum [Sorghum bicolor (L.) Moench] grown to maturity in large soil pots, as the different formulations resulted in minor differences in plant N accumulation and grain production. This confirms the need to consider soil interactions, microbial processes, crop physiology, and phenology for evaluating fertilizer performance. Promisingly, crop δ15N signatures emerged as an integrated measure of efficacy, tracking likely N conversions and losses. The three complementary evaluations combine the advantages of standardized high-throughput screening and more resource-intensive and realistic testing in a plant-soil system. We conclude that melt-blended biodegradable polymer matrix fertilizers show promise as EEF because they can be designed toward more abiotically or more microbially driven N release by selecting biopolymer type and N loading rate.

Novel core-shell microcapsules incorporating macro/micronutrients in PVA/starch matrix

Enhanced efficiency fertilizers (EEFs) have been widely used due to their ability to meet crop nutritional needs and reduce the main problem of leaching. In this work, we compared the effects of spray-dryer microspheres and microcapsules on nutrient encapsulation and identified the spheres and core-shell structures by fluorescence microscopy using Rhodamine B (RB) as the fluorescent material. The microsphere matrix was based on starch, and the microcapsules consisted of starch as the core and poly (vinyl alcohol) as the shell. The fluorescent images confirmed that the RB was incorporated into the starch, as the overlap of fluorescence and brightfield images covered the entire area for microspheres and only the core for microcapsules. Microspheres exhibited an irregular and non-spherical morphology, whereas microcapsules presented a spherical shape with a smooth and homogeneous surface featuring small aggregated particles. The microparticle structures remained unchanged even after incorporating KNO3, Fe, Cu, and Mn. Thermal analysis indicated lower initial mass loss temperatures for the microcapsules, suggesting polymer interactions during drying and formation. FTIR further supported this, which revealed structural changes and partial oxidation during drying, contributing to reduced thermodegradation. Notably, micronutrient-based microcapsules demonstrated a significantly lower burst release than macro/micronutrient-based microcapsules and micronutrient-based microspheres. Fe and Cu were released most rapidly from microspheres in the first hour, reaching 84.2% and 79.4%, respectively. In contrast, macro/micronutrient-based microcapsules released 66.1% and 67.7%, while micronutrient-based microcapsules released 53.1% and 61.5%. As for Mn, macro/micronutrient-based microcapsules exhibited the highest initial release at 72.4%, followed by micronutrient-based microcapsules at 62.2%, with microspheres releasing at 55.8%. Additionally, the Peppas-Sahlin model provided the best fit, indicating diffusional and polymer relaxation contributions. The morphology, release, and kinetics behaviors confirmed that the core-shell prolonged the nutrient release by reducing the initial burst release, thanks to the diffusion barrier provided by the PVA layer.

Effects of straw mulching, liming, and soil texture on ammonia volatilisation: a study of conventional and enhanced efficiency fertilisers

Context In no-tillage agriculture, maintenance of soil cover combined with liming without incorporation increases nitrogen (N) loss via ammonia (NH3) volatilisation, decreasing the efficiency of nitrogen fertilisers. Aims To quantify N losses by NH3 volatilisation from conventional and enhanced efficiency fertilisers applied to a clayey and a sandy loam soil subjected or not to lime (CaCO3) application and straw mulching. Methods Two laboratory experiments were carried out; one using a clayey soil, and the other using a sandy loam soil. Both experiments followed a 4 × 2 × 2 factorial design with four N sources (urea, urea-NBPT, urea-formaldehyde, and ammonium sulfate), absence and presence of liming, and absence and presence of Brachiaria ruziziensis straw mulching. NH3 volatilisation was measured using closed flasks containing filter paper soaked with sulfuric acid and quantified by titration with sodium hydroxide. Key results NH3 volatilisation was up to 62% of the N applied. Losses due to NH3 volatilisation from both soil types decreased in the following order of treatment: liming + straw mulching > straw mulching only > liming only. Urea-formaldehyde and ammonium sulfate were the most efficient in reducing NH3 emissions. However, when ammonium sulfate was applied to a clayey soil after liming, it resulted in higher NH3 emissions than conventional urea. Conclusions Urea-formaldehyde showed better performance in reducing NH3 losses due to greater stability in the presence of straw or liming. Implications Soils with straw and limestone can lead to large NH3 volatilisation losses if urea conventional is broadcast.

Modifying soluble NPK release with hydrophobized nanocellulose-based hydrogels for sustainable enhanced efficiency fertilizers

Introduction of a hydrophobic shell to a regenerated cellulose-based bead through gas-phase esterification results in slowing of plant nutrient release by an order of magnitude.

Integrating Enhanced‐Efficiency Fertilizers in 4R Nutrient Management

AbstractThe 4R nutrient stewardship framework has brought us closer to improving our nutrient use efficiency. However, given the inherent “leakiness” of the N cycle, it is challenging to increase N use efficiency to optimum levels. Newer fertilizer technologies, like enhanced‐efficiency fertilizers (EEFs), are tools that can help achieve this goal. To determine if EEFs should be incorporated into nutrient management programs, growers and crop advisers should consider the various types of EEFs available, their functions within the soil, and the timing of application relative to the crop’s nutrient uptake demand. Earn 1 CEU in Nutrient Management by reading this article and taking the quiz at https://web.sciencesocieties.org/Learning‐Center/Courses.

Enhanced-efficiency fertilizers on the growth of coffee plants under weed (Bidens Pilosa) competition stress

The interference of weeds in coffee cultivation is one of the factors contributing to losses and impairments in crop growth and productivity. Consequently, it becomes necessary to employ strategies aimed at mitigating this stress and facilitating optimal crop development through enhanced nutritional practices. This study aimed to assess the impact of various sources and modes of release of enhanced-efficiency phosphate fertilizers on the initial growth of Coffea arabica L. plants in competition with the weed Bidens pilosa in a greenhouse. The experiment was conducted at the Federal University of Vales do Jequitinhonha and Mucuri – Diamantina MG, Brazil, employing a block design in a 4 x 6 factorial arrangement with four replications. The factors corresponded to four levels of B. pilosa infestation and six phosphorus sources (Super Single, Conventional, MAP, Granulated Organomineral, Pelleted Organomineral, MAP Coated with Polymer, and a control treatment without fertilization). The findings suggest that under the experimental conditions of this research, the escalating density of weed competition from B. pilosa negatively impacts the initial growth of coffee plants. However, this effect is dependent on the source of phosphate fertilization. Fertilizers with slow-release phosphate sources are recommended for coffee plantations, as they contribute to reduced weed growth in comparison to coffee plants.

Mitigate N2O emissions while maintaining sugarcane yield using enhanced efficiency fertilisers and reduced nitrogen rates

Mitigate N2O emissions while maintaining sugarcane yield using enhanced efficiency fertilisers and reduced nitrogen rates

Improving Nitrogen Use Efficiency for Corn (Zea mays L.) Production

Nitrogen (N) fertilizer is one of the main expenses for crops in high-input agricultural systems. Insufficient use of N is not only responsible for higher cost of crop production, but also for environmental pollution. Corn is one of the most important crop in the world. Application of N is a primary method used to maintain soil nutrients and increase corn yield. economic and environmental challenges are driving increased interest in improving NUE. Opportunities abound for improving NUE through implementation of fundamental BMPs, including selection of genetics with high NUE, development of enhanced-efficiency fertilizer products (CRF and NI), precision nutrient application at optimum rate, timing and placement, and carefully water management.

Integrating enhanced efficiency fertilizers and nitrogen rates to improve Canada Western Red Spring wheat

Granular urea fertilizer applied at planting is prone to nitrogen (N) losses in certain environments. Enhanced efficiency fertilizers (EEFs) are developed to mitigate losses and optimize plant uptake. To determine the benefits of EEFs in grain yield and quality enhancement in Canada Western Red Spring (CWRS) wheat, an experiment was conducted from 2019 to 2022 at eight sites in Alberta and Saskatchewan, Canada. The effects of five N sources [urea; urea + urease inhibitor, N-( n-butyl)thiophosphoric triamide (NBPT); urea + nitrification inhibitor, nitrapyrin; urea + dual-inhibitor, NBPT + dicyandiamide; and polymer-coated urea, ESN® (Environmentally Smart Nitrogen®)] and four N rates (60, 120, 180, and 240 kg N ha−1) on CWRS wheat production were examined. Results indicated that N source affected grain yield in Dark Brown Chernozem soils but not in Black Chernozem or Dark Grey Luvisol soils. In Dark Brown Chernozem soils, a dual inhibitor increased grain yield by 3.1% and 3.9% relative to urea and polymer-coated urea, respectively, while all other EEFs attained similar results. The use of a dual inhibitor EEF led to greater net returns compared to urea and polymer-coated urea in the Dark Brown Chernozem soils. Grain protein concentration increased linearly with increasing N rate from 60 to 240 kg N ha−1. Generally, a rate of 120 kg N ha−1 was optimal for CWRS wheat grown in Canadian prairie conditions when coupled with EEFs, particularly a dual inhibitor, and grain yield and protein were often responsive.

Enhanced efficiency urea fertilizers and timing effects on N2O emissions from spring wheat production in Manitoba

AbstractOpportunities exist to reduce nitrous oxide (N2O) emissions from nitrogen (N) fertilizers using enhanced efficiency fertilizers (EEFs) and managing application timing. This study examined (1) application timing (fall/spring) and (2) fertilizer N source on N2O emissions, yield, and N uptake of Canadian hard red spring wheat (Triticum aestivum L.) in Southern Manitoba. Fertilizer N sources included granular urea and four EEF products: (1) polymer‐coated urea (environmentally smart nitrogen [ESN]); (2) urea plus nitrification inhibitor (eNtrench); (3) urea plus urease inhibitor (Limus); and (4) urea plus nitrification and urease inhibitor (SuperU). Nitrification‐inhibited products most consistently reduced N2O emissions while maintaining productivity. Compared to urea alone, urea + eNtrench was most effective in reducing cumulative N2O emissions by 47%–64% at four of six site‐years. SuperU reduced N2O emissions by 37%–57% at three of six site‐years. ESN and urea + Limus did not affect emissions in most years. Wheat yield, protein, and N uptake were unaffected by N source in five of six site‐years. Compared to spring, fall application gave greater N2O emissions by 33%–67% at three of six site‐years due to spring‐thaw emissions. Fall was inferior to spring application in wetter site years with lower yield, protein, and N uptake. Overall, nitrification‐inhibited products—either alone or with a urease inhibitor—are a promising tool to reduce N2O emissions while maintaining wheat productivity in Manitoba. However, given that there were few consistent increases in yield or protein, the additional cost of the inhibitors will be a barrier to adoption.

Drug discovery-based approach identifies new nitrification inhibitors

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

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

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

Novel Curve Fitting Analysis of NDVI Data to Describe Turf Fertilizer Response

Evaluating the effectiveness of fertilizers on crops without traditional yield is difficult, as clipping collection is time-consuming and not indicative of the desired response to the fertilizer. Remote sensing techniques, like the normalized difference vegetation index (NDVI), have emerged as an effective tool to combat these issues. Canopy reflectance, measured by NDVI, is commonly used to differentiate turfgrass response to nitrogen (N) fertilization treatments; however, advancements in data processing are needed for greater differentiation between treatments and better testing of the effects of fertilizer responses. Presented here is an advancement in the processing of NDVI data by applying a compound exponential (pulse peak) function to changes in NDVI over time, relative to a control. This method’s effectiveness in differentiating between fertilizers was evaluated by applying polymer-coated urea (PCU), an enhanced efficiency fertilizer (EEF), and urea on turfgrass to show the usefulness of the novel curve fitting in highlighting differences in fertilizer response. The field study was carried out on an established Kentucky bluegrass (Poa pratensis L.) blend on a sandy loam soil rootzone maintained with a typical home lawn maintenance regime. Ratios of PCU to urea ranging from 100% urea to 100% PCU with increments of 20% of PCU were used to observe a continuum of response between the two fertilizer types. The N rate for all blends was 73 kg ha−1, with unfertilized plots used as a control to set baseline measurements for the curve fitting. Turfgrass response to N fertilization treatments was assessed through visual turfgrass quality ratings, dry matter yield, and canopy reflectance, where higher urea content resulted in the shortest time to maximum ∆NDVI (24 days), while 100% EEF reached maximum ∆NDVI at 56 days. The novel curve fitting analysis of the NDVI data allowed for differentiation between treatments, provided a measure of fertilizer effects, and differentiated between urea and enhanced efficiency fertilizers.

Alternative fertilization approaches in enhancing crop productivity and nutrient use efficiency: A review

The greatest challenge of our time is to meet the global food demand by producing enough food without harming the environment. Over application and misuse of synthetic fertilizer is a major challenge that results in lower fertilizer use efficiency (FUE), stagnated crop yield, and environmental pollution. In this review study, three alternative fertilization options (AFOs), such as the use of organic fertilizer enhanced-efficiency fertilizer (EEFs), and secondary, and micronutrient fertilizers were evaluated. The adoption of appropriate fertilization practices was believed to improve crop yield and FUE over the conventional fertilization approach. As of late, the use of organic fertilizers has received more attention as a better alternative to counter the challenges posed by the inappropriate use of chemical fertilizers. The formulation of slow or controlled-release fertilizers contributes to preventing nutrient losses by slowing down nutrient release patterns in the soil and allowing better synchrony between crop nutrients requirement and nutrient supply. The use of secondary macronutrients and micronutrient also has considerable importance to improve nutrient uptake, grain yield, and quality. In summary, the review result showed that the adoption of AFOs can enhance crop yield and nutrient use efficiency.

Withdrawal: Enhanced efficiency fertilizers decrease nitrate movement while maintaining yield in sugarcane production system

Withdrawal: Enhanced efficiency fertilizers decrease nitrate movement while maintaining yield in sugarcane production system

Impact of contrasting fertilizer technologies on N dynamics from subsurface bands of “pure” or blended fertilizer applications

Abstract. Enhanced efficiency fertilizer (EEF) technologies that employ product coatings to delay nitrogen (N) release or are chemically stabilized to inhibit key steps of N transformations in soil offer potential for improving N use efficiency (NUE) in agricultural systems. However, the dynamics of N release and transformation from single technologies may result in a spatial or temporal mismatch of N supply and demand during a growing season. This may be overcome by use of blends of different technologies, provided the reduction in the concentration of stabilizing products does not reduce effectiveness. Laboratory incubations quantified the N dynamics around bands of controlled-release fertilizer (CRF) and nitrification-inhibited (NI) urea and varying blends of these technologies and referenced this against conventional urea and biodegradable, plant-oil-coated urea (POCU) applied at the same rates in two contrasting soils over 60 d. Blends of NI urea (3,4-dimethylpyrazole phosphate, DMPP urea) and a CRF (polymer-coated urea, PCU) typically resulted in N concentrations and distribution that were intermediate to those of the constituent products in unblended applications. Changes in the proportions of each product were mirrored by urea nitrogen (urea-N) concentrations around the bands in both soils, while the proportions of DMPP urea in each blend were only related to the extent of nitrification inhibition in the Vertisol. A proportion of the POCU granules burst during the early stages of incubation, resulting in initially higher mineral N concentrations compared to PCU. However, both CRFs delayed N release and formation of nitrate nitrogen (NO3-N) relative to granular urea, and mineral N distribution was similar within each soil. Soil type had a significant impact on banded N dynamics. Where there was little effect of N-fertilizer treatment on NO3-N production in the Ferralsol, the higher impedance to solute transport in the Vertisol contributed to a significant inhibitory effect of NI urea on nitrification in both pure and blended DMPP urea treatments. Using NO3-N production as a benchmark for the risk of environmental loss, the efficacy of fertilizer treatments in this soil was of DMPP urea / PCU blends (higher ratio of PCU may offer small but insignificant benefit) > DMPP urea = PCU > urea. These findings highlight the importance of soil properties in determining the N dynamics from different banded EEF products. Insights into the efficacy of biodegradable alternatives to polymer coatings and the efficacy of blended EEF products can improve the reliability of N supply while reducing environmental impacts, therefore offering greater opportunities to sustainably improve fertilizer NUE in cropping systems.

Innovative nitrogen management strategy reduced N2O emission while maintaining high pepper yield in subtropical condition

High N fertilizer inputs in subtropical vegetable systems under the warm and humid climatic conditions increase the risk of nitrous oxide (N2O) emissions. However, there is limited information available on integrated N management strategies to reduce N2O emissions from intensive open-field vegetable systems in subtropical region. Two plot-based field experiments were conducted in subtropical southwest China to examine the effects of different N management strategies on N2O emissions from a typical open-field pepper (Capsicum annuum L.) production system. Experiment 1 included five N rates (0, 175, 250, 325, and 400 kg ha−1) with conventional urea. Experiment 2 included a 0 N control and four N sources (conventional urea, organic fertilizer, nitrification inhibitor-based enhanced efficiency fertilizer ENTEC26, and controlled release urea) applied under an optimized N rate (250 kg N ha−1). The results of Experiment 1 showed that cumulative N2O emission and emission factor were 4.05 kg N ha−1 season−1 and 0.96%, respectively, under the conventional management (N400). N2O emissions increased exponentially with increasing N rates. Compared to the N400 treatment, application of conventional urea at the optimal rate (250 kg N ha−1) significantly reduced cumulative N2O emissions by 54% while maintaining similar pepper yield. The results from Experiment 2 indicated that the use of enhanced efficiency fertilizers at the optimal rate further reduced N2O emission by 30%− 50% compared to conventional urea, while increasing pepper yield by 6.7%− 9.0%. This resulted in a 36%− 53% reduction of yield-scaled N2O emission intensity. In particular, the use of nitrification inhibitor was 28% more effective than controlled release urea for N2O mitigation. These results suggest that the application of enhanced efficiency fertilizers at an optimum N rate could produce more vegetables while reducing N2O emission, thereby promoting sustainable vegetable production in the subtropic regions.