Journal Description
Nitrogen
Nitrogen
is an international, peer-reviewed, open access journal on the whole field of nitrogen research published quarterly online by MDPI.
- Open Access—free for readers, with article processing charges (APC) paid by authors or their institutions.
- High Visibility: indexed within ESCI (Web of Science), Scopus, CAPlus / SciFinder, and other databases.
- Rapid Publication: manuscripts are peer-reviewed and a first decision is provided to authors approximately 20.9 days after submission; acceptance to publication is undertaken in 2.5 days (median values for papers published in this journal in the second half of 2024).
- Journal Rank: CiteScore - Q2 (Agricultural and Biological Sciences (miscellaneous))
- Recognition of Reviewers: APC discount vouchers, optional signed peer-review and reviewer names published annually in the journal.
Impact Factor:
2.3 (2024);
5-Year Impact Factor:
2.1 (2024)
Latest Articles
High-Power Closed-Loop Pilot System for Nitric Acid Production Using Inductively Coupled Microwave Plasma
Nitrogen 2025, 6(3), 51; https://doi.org/10.3390/nitrogen6030051 (registering DOI) - 28 Jun 2025
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This work presents the characterization of a large-scale pilot plant for nitric acid production that employs atmospheric-pressure plasma in a closed-loop configuration. The primary objective here is to evaluate the scientific and practical feasibility of using high-power Cerawave™ plasma torch technology, manufactured by
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This work presents the characterization of a large-scale pilot plant for nitric acid production that employs atmospheric-pressure plasma in a closed-loop configuration. The primary objective here is to evaluate the scientific and practical feasibility of using high-power Cerawave™ plasma torch technology, manufactured by Radom Corporation, to enhance the rate of nitric acid production of plasma-assisted nitrogen fixation systems, while achieving specific energy consumption (SEC) comparable to that of smaller-scale setups reported in the literature. We provide a comprehensive overview of the components of the pilot plant, its operational strategy, and the analytical models underlying its processes. Preliminary system optimization results are discussed alongside the outcomes from a controlled batch run. After 30.9 h of operation at 50 kW plasma power, the system produced 198.9 L of nitric acid with a concentration of 28.6% by weight, corresponding to overall SEC of approximately 5.3 MJ/mol. This SEC could be improved to 3.7 MJ/mol using absorption columns with greater than 90% absorption efficiency. Additionally, around 60% of the plasma power was recovered as usable process heat via a heat exchanger. These results demonstrate that plasma-based nitrogen fixation is scientifically and technically viable at higher production scales while maintaining competitive specific energy consumption using microwave plasma.
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Open AccessArticle
Insights into Pyrite-Based Autotrophic Denitrification: Impacts of the Initial Addition of Organic Co-Substrates at a Low Concentration
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Baokun Xu, Lihong Zhang, Niannian Yuan, Yujiang Xiong and Haolong Fu
Nitrogen 2025, 6(3), 50; https://doi.org/10.3390/nitrogen6030050 (registering DOI) - 28 Jun 2025
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Pyrite-based autotrophic denitrification is an effective method for nitrate removal. However, pyrite does not exist alone and is inevitably accompanied by the presence of organic matter in nature, and thus the influence of organic co-substrates on pyrite-based denitrification should be taken into consideration.
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Pyrite-based autotrophic denitrification is an effective method for nitrate removal. However, pyrite does not exist alone and is inevitably accompanied by the presence of organic matter in nature, and thus the influence of organic co-substrates on pyrite-based denitrification should be taken into consideration. Even in a circumstance where no addition of an exogenous organic carbon source is implemented, the introduction of pyrite into groundwater and sediment is capable of stimulating both autotrophic and heterotrophic denitrifying bacteria. In this study, the impact of the initial addition of organic co-substrates on the performance and dynamics of bacterial communities in pyrite-based denitrification processes was evaluated under low-concentration conditions. The findings suggest that the initial addition of organic co-substrates at low concentrations (6–48 mg L−1) could enhance the efficiency of pyrite-based autotrophic denitrification. In contrast, the competitive effects of organic co-substrates became positive with increasing additions of initial organic co-substrates. When an organic co-substrate was added at an initial concentration of 96 mg L−1, the competition between heterotrophic denitrification and pyrite-based autotrophic denitrification was found to be more pronounced than their promotion role as the majority of nitrate was consumed by heterotrophic denitrification. Thiobacillus was the most dominant bacterium in the denitrification system, where pyrite served as the sole electron donor. At the same time, the addition of organic co-substrate under low initial concentration, led to a different microorganism composition.
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Open AccessArticle
Partial Substitution of Synthetic Nitrogen with Organic Nitrogen Enhances Soil Fertility, Photosynthesis, and Root Growth of Grapevine Seedlings
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Feng Han, Binxian Jiang, Wenyu Wang, Shuang Wu, Jinggui Wu, Yan Ma and Xiaochi Ma
Nitrogen 2025, 6(3), 49; https://doi.org/10.3390/nitrogen6030049 - 25 Jun 2025
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The overuse of synthetic nitrogen fertilizer in vineyards degrades soil quality and poses environmental risks. Partial substitution of synthetic nitrogen with organic alternatives may enhance grapevine performance and soil sustainability, depending on the substitution rate. This study evaluated the effects of replacing synthetic
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The overuse of synthetic nitrogen fertilizer in vineyards degrades soil quality and poses environmental risks. Partial substitution of synthetic nitrogen with organic alternatives may enhance grapevine performance and soil sustainability, depending on the substitution rate. This study evaluated the effects of replacing synthetic nitrogen with composted spent mushroom substrate at five different rates (0%, 25%, 50%, 75%, and 100%, denoted as NOS, OS-25, OS-50, OS-75, and OS-100, respectively) and a control with no nitrogen fertilization applied (CK), on soil fertility, root growth, and photosynthetic performance in grapevine seedlings. Compared to CK, nitrogen fertilization and organic substitution significantly increased soil electrical conductivity, organic matter, and macronutrient contents, but had no significant effect on soil pH. Organic substitution markedly improved leaf photosynthetic capacity in the summer, with the highest rates observed under OS-25, exceeding CK and NOS by 32.98–63.19% and 13.93–27.38%, respectively. Root growth was also significantly enhanced by organic substitution, with OS-25 exhibiting the best performance. Fine roots in the 0.0–0.5 mm diameter class were dominant, accounting for 56.88–63.06% of total root length and 96.22–97.31% of total root tip count. Increasing substitution rates beyond 25% yielded no further improvements in photosynthesis or root growth. Mantel test analysis indicated strong positive correlations between soil fertility parameters (e.g., alkali-hydrolyzable nitrogen, available phosphorous and potassium) and both photosynthetic efficiency and root growth. These findings suggest that an appropriate substitution rate (i.e., 25%) of organic nitrogen using spent mushroom substrate effectively improves soil fertility, simultaneously optimizing photosynthetic capacity and root growth of grapevine seedlings.
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Open AccessArticle
Fertilizer Use Efficiency and Profitability of Maize Varieties with Different Maturity Classes in Semi-Arid Ghana
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Dilys Sefakor MacCarthy, Bright Salah Freduah, Yvonne Ohui Kugblenu Darrah, Samuel Godfried Adiku, Daniel Etsey Dodor, Joseph Kugbe and Alpha Yaya Kamara
Nitrogen 2025, 6(3), 48; https://doi.org/10.3390/nitrogen6030048 - 24 Jun 2025
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Optimizing the efficiency of fertilizer use is critical for sustainable maize production and food security, particularly in smallholder systems. Sub-optimal application rates pose a significant risk of soil nutrient depletion and low productivity. Split plot experiments were conducted across four locations in Ghana’s
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Optimizing the efficiency of fertilizer use is critical for sustainable maize production and food security, particularly in smallholder systems. Sub-optimal application rates pose a significant risk of soil nutrient depletion and low productivity. Split plot experiments were conducted across four locations in Ghana’s Guinea Savannah using seven maize varieties from three different maturity classes. The study assessed the response to nitrogen fertilizer applications (0, 60, 90, and 120 kg N ha−1) regarding yield, Agronomic Efficiency (AEN), Water Use Efficiency (WUE), and economic feasibility. Grain yields across locations and varieties demonstrated a strong linear response to nitrogen fertilization. The 90 kg N ha−1 application generally produced the highest AEN for all sites and varieties. Gross Revenue (GR) and WUE increased with higher N rates, with Value-to-Cost Ratios (VCR) consistently exceeding 2. Applying 90 kg N ha−1 resulted in statistically similar Gross Revenues (GRs) to the 120 kg N ha−1 fertilization. Different maturity classes significantly impacted fertilizer efficiency in semi-arid Ghana, with intermediate varieties outperforming extra-early ones. Though a 90 kg N ha−1 rate was generally identified as the economically optimal rate of N fertilization for the locations, targeted fertilizer recommendations based on maize maturity groups and location are strongly advised.
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Open AccessArticle
Productive Performance of Brachiaria brizantha cv. Paiaguás in Response to Different Inoculation Techniques of Azospirillum brasilense Associated with Nitrogen Fertilization in the Brazilian Amazon
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Gianna Maria Oscar Bezerra, Cleyton de Souza Batista, Daryel Henrique Abreu de Queluz, Gabriela de Jesus Coelho, Daiane de Cinque Mariano, Pedro Henrique Oliveira Simões, Perlon Maia dos Santos, Ismael de Jesus Matos Viégas, Ricardo Shigueru Okumura and Raylon Pereira Maciel
Nitrogen 2025, 6(2), 47; https://doi.org/10.3390/nitrogen6020047 - 17 Jun 2025
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With the increase in prices of correctives and fertilizers, the investigation of the interactions between plants and plant growth-promoting bacteria shows an economically viable and sustainable alternative, and the use of Azospirillum brasilense has shown an increase in efficiency of nitrogen use and
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With the increase in prices of correctives and fertilizers, the investigation of the interactions between plants and plant growth-promoting bacteria shows an economically viable and sustainable alternative, and the use of Azospirillum brasilense has shown an increase in efficiency of nitrogen use and increased pasture yield. This study, conducted in the Brazilian Amazon, aimed to evaluate the effect of different inoculation techniques of Azospirillum brasilense associated with the dose of nitrogen topdressing on the productive performance of Brachiaria brizantha cv. Paiaguás is a grass species commonly cultivated in this region. The experiment was conducted in the Experimental Forage Sector of the Federal Rural University of the Amazon, Parauapebas city, Brazil. The experimental design was a randomized block design in a 3 × 3 factorial arrangement, with three inoculation methods (control, seed, and foliar) and three nitrogen fertilization doses (0, 75, and 150 kg ha−1 of N), with four replicates. An effect was observed in interaction between inoculation and nitrogen fertilization (p ≤ 0.05) for the variables total forage green mass, total forage dry mass, dry mass of leaf blade, dry stem mass, and number of tillers m−2. The dose of 150 kg ha−1 of N promoted a positive effect of N on the total forage dry mass and LAI (leaf area index). Inoculation with Azospirillum brasilense, especially foliar application, efficiently increased Brachiaria brizantha cv. Paiaguás yield, potentially reducing the use of nitrogen fertilizers, promotes greater sustainability in pasture management.
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The Effect of Zeolitic Fertilizer on Nitrogen Retention in Soil and Its Availability to Plants
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Ayaz Ahmad, Shahzada Sohail Ijaz, Fengliang Zhao, Hafeez Ullah Rafa and Ghulam Farid
Nitrogen 2025, 6(2), 46; https://doi.org/10.3390/nitrogen6020046 - 13 Jun 2025
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Global crop yield is stagnant due to quick release of N from fertilizers and its lower availability at critical growth stages of crops. Urea impregnation of aluminosilicate minerals, especially zeolites, holds NH4+ and delays its release for later crop stages. limited
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Global crop yield is stagnant due to quick release of N from fertilizers and its lower availability at critical growth stages of crops. Urea impregnation of aluminosilicate minerals, especially zeolites, holds NH4+ and delays its release for later crop stages. limited information is available in the literature about the effect of zeolite-based urea fertilizer on soil nitrogen dynamics. Zeolitic urea formulation was prepared and tested in a field experiment under a wheat–rice cropping system. Sources of N were urea and zeolitic urea formulation. N was reduced up to 50% in the treatments from zeolitic urea. Soil parameters (NH4-N, NO3-N, available N and total N) and plant parameters were recorded by following the standard procedures. Zeolitic urea retained the highest contents of NH4-N and NO3-N at critical growth stages (booting and maturity) of wheat crop. Zeolitic urea retained the highest NO3 in 0–30 cm soil depth, while these were highest at 60–90 cm depth with urea. Grain yield of wheat crops with N100%U were similar to that of with N75%ZU, where 25% less N was applied and nitrogen use efficiency was improved to 25.82% by zeolitic urea. Zeolite-based N fertilizer retains N in soil for an extended period of time and maintains crop yield even with less applied N as compared with urea.
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Three Years After Soybean-Cover-Crop Rotation in Conventional and No-Till Practices: What Are the Consequences on Soil Nitrous Oxide Emissions?
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Nokwanda O. Dlamini, Lindsay Banda, Laura M. Cardenas, Aranzazu Louro-Lopez and Jerry C. Dlamini
Nitrogen 2025, 6(2), 45; https://doi.org/10.3390/nitrogen6020045 - 11 Jun 2025
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Nitrous oxide is a potent greenhouse gas due to its long atmospheric lifespan (121 years) that results in a high global warming potential (GWP). Research has shown that no-tillage may be implemented as a mitigation strategy to reduce N2O emissions. The
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Nitrous oxide is a potent greenhouse gas due to its long atmospheric lifespan (121 years) that results in a high global warming potential (GWP). Research has shown that no-tillage may be implemented as a mitigation strategy to reduce N2O emissions. The objective of the was to evaluate how conventional tillage (CT) and no-tillage (NT) can potential influence N2O emissions in soybean rotation in a semi-arid region of the central Free State of South Africa. The effect of conventional and no-till tillage practices on N2O emissions under soybean rotation was evaluated in the 3rd year of a 5-year rotation system, in a semi-arid region of the Free State of South Africa, from December 2022 to December 2023. The experimental area was divided into three blocks and there were two plots in each block: in total there were six plots. The treatments were planted in a soybean rotation system under no-tillage and conventional tillage. The monthly averages of N2O emissions were significantly different from each other during the soybean growing season; the highest emissions were recorded in August/September 2023 from both the NT and CT treatments after harvest. During this time, there were crop residues in the soil that increased soil carbon. There was a positive correlation between N2O emissions and soil carbon content (p = 0.21) and between N2O emissions and soil organic matter (p = 0.43). Emissions were significantly higher in CT (LSD = 0.3) than in NT. The lowest N2O emissions were recorded in December 2023 (LSD = 0.05) and were significantly reduced in the no-till plots compared to those of the conventional tillage plots. Furthermore, the lowest cumulative N2O emissions of 0.26 ± 0.22 kg N2O-N ha−1 were recorded during NT in the winter season and were significantly different from CT (LSD = 0.19). The results from our study indicate that the no-till practices in soybean rotation can decrease N2O emissions.
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Open AccessArticle
Optimising Legume Integration, Nitrogen Fertilisation, and Irrigation in Semi-Arid Forage Systems
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Luís Silva, Sofia Barbosa, Fernando Cebola Lidón, Benvindo Maçãs, Salvatore Faugno, Maura Sannino, João Serrano, Paola D’Antonio, Costanza Fiorentino, Francesco Cellini, Paulo Ferreira and Luís Alcino Conceição
Nitrogen 2025, 6(2), 44; https://doi.org/10.3390/nitrogen6020044 - 10 Jun 2025
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Monoculture systems depend on high nitrogen (N) fertilisation. Incorporating legumes into forage crops offers a sustainable alternative with agronomic and economic benefits. This study assesses the impact of legumes in fodder systems, evaluating yield, N use efficiency (NUE), and profitability while identifying the
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Monoculture systems depend on high nitrogen (N) fertilisation. Incorporating legumes into forage crops offers a sustainable alternative with agronomic and economic benefits. This study assesses the impact of legumes in fodder systems, evaluating yield, N use efficiency (NUE), and profitability while identifying the best cropping strategy under semi-arid conditions. The experiment, conducted at Herdade da Comenda, Elvas, Portugal, used a split–split-plot randomised block design to analyse N doses, forage species, and irrigation. Economic metrics, including costs, net revenue, return on investment, and risk analysis, were also assessed. Moderate N doses (120 kg ha−1) resulted in significantly higher NUE (15.67 kg kg−1 N) than higher doses (200 kg ha−1), which yield only 1.40 kg kg−1 N (p < 0.05), particularly in mixed fodder crops. Irrigation improved N absorption, crop nutrition, and yield, leading to higher profitability despite increased initial costs. Agronomically, irrigation and N doses influenced yield and nutrient uptake, while no significant differences were observed between different forage crops in terms of yield or NUE. Economically, the irrigated mixed crop showed the highest return on investment (ROI = 247.37 EUR ha−1), whereas ryegrass presented lower financial risk (BE = 2213.24 kg ha−1) due to lower establishment costs. Yield was the strongest predictor of net profit (R2 = 0.89). Looking ahead, optimising N management, irrigation strategies, and mixed grass–legume crops will be crucial to maximising economic returns while minimising environmental impacts.
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Open AccessArticle
Effects of Corn Silage and Alfalfa Hay on Production and Nitrogen Excretion in Lactating Dairy Cows
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Daniel Scoresby, Izabelle A. M. A. Teixeira and Mireille Chahine
Nitrogen 2025, 6(2), 43; https://doi.org/10.3390/nitrogen6020043 - 10 Jun 2025
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A meta-regression was conducted on studies published from 2018 to 2023 to explore the effects of nutrient intakes from alfalfa (ALF) and corn silage (CS) on milk yield (MY), energy-corrected milk yield (ECM), N efficiency (NEFF), milk urea nitrogen (MUN), and
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A meta-regression was conducted on studies published from 2018 to 2023 to explore the effects of nutrient intakes from alfalfa (ALF) and corn silage (CS) on milk yield (MY), energy-corrected milk yield (ECM), N efficiency (NEFF), milk urea nitrogen (MUN), and manure nitrogen excretion (NMANURE) in Holstein lactating cows. The analysis included 193 studies with 698 individual treatment means. Multiple models were developed for each response variable using a backward stepwise approach and cross-evaluated against the database. Nutrient intake from both CS and ALF influenced MY and ECM, with ALF generally having a positive effect. The NEFF was also affected by nutrient intakes from both forages. Generally, greater protein intake reduced NEFF, whereas greater MY was associated with improved NEFF. An increase in the rumen-degradable protein intake (RDPI), especially from ALF, increased MUN. However, no significant effect of protein intake from CS on MUN was observed. Additionally, an increase in crude protein intake and RDPI, regardless of source (CS or ALF), led to an increase in g/d of NMANURE. Our results indicate that nutrient intakes from ALF and CS have different effects on production, excretion, and nitrogen efficiency, supporting their use in targeted nutrient and waste management strategies.
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Effects of Nitrogen Fertilizer Application on Growth, Vegetation Indices, and Ammonia Volatilization in Korean Radish (Raphanus sativus L.)
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TaeSeon Eom, TaeWan Kim and SungYung Yoo
Nitrogen 2025, 6(2), 42; https://doi.org/10.3390/nitrogen6020042 - 9 Jun 2025
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Nitrogen use efficiency (NUE) in plants is reduced when treated with excess nitrogen fertilizer. Our study aimed to investigate the impact of varied concentrations of urea on the growth responses, vegetation indices, and ammonia volatilization in radishes. The experiment was conducted across four
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Nitrogen use efficiency (NUE) in plants is reduced when treated with excess nitrogen fertilizer. Our study aimed to investigate the impact of varied concentrations of urea on the growth responses, vegetation indices, and ammonia volatilization in radishes. The experiment was conducted across four concentrations of urea (nitrogen source): 0 N (0 kg urea ha−1), 0.5 N (117 kg urea ha−1), 1 N (234 kg urea ha−1), and 2 N (468 kg urea ha−1). Compost was applied as a basal fertilizer in all treatments. Aboveground and belowground biomass were evaluated to measure growth response. The dynamic chamber method was used to collect ammonia volatilized from the cultivation area, and the vegetation index analysis was conducted to assess the effects of nitrogen fertilizer treatment. Our study results suggest there are no significant differences in the yield of radishes between the recommended nitrogen fertilization level (1 N) and half the recommended level in the Republic of Korea (0.5 N). Ammonia volatilization was significantly the lowest in the 0.5 N nitrogen fertilizer treatment among all treatments. Except for a few specific indices, there were no significant differences observed in most analyzed vegetation indices. Based on the specific environmental and soil conditions examined in this study, our results indicate that nitrogen input in radish cultivation in the Republic of Korea could be reduced without significant yield penalties, offering potential benefits in terms of reduced production costs and environmental impact. Nevertheless, to establish optimized fertilizer recommendations, further studies across diverse environmental conditions and cultivation practices, including planting timing, are essential.
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(This article belongs to the Special Issue Monitoring Nitrogen in Soils and Plants: Recent Methods, Soil Properties and Plant Characteristics)
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Nitrate–Conductivity Correlations in Aqueous Environments: From Standard Solutions to Natural Water Bodies
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Al Mamun
Nitrogen 2025, 6(2), 41; https://doi.org/10.3390/nitrogen6020041 - 31 May 2025
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The relationship between nitrate concentration and electrical conductivity (EC) in aqueous environments is crucial for water quality assessment, especially in regions with limited laboratory access and monitoring resources. This study investigates nitrate–EC correlations across standard solutions and various natural water sources, identifying where
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The relationship between nitrate concentration and electrical conductivity (EC) in aqueous environments is crucial for water quality assessment, especially in regions with limited laboratory access and monitoring resources. This study investigates nitrate–EC correlations across standard solutions and various natural water sources, identifying where EC may serve as a reliable proxy for nitrate. In the standard and controlled laboratory solution reference samples, a strong linear correlation in controlled environments (R2 ≈ 0.99) between the nitrate concentration and EC was observed, providing a reliable baseline for calibration and suggesting that EC-based estimation is feasible under ideal conditions. In shallow wells, particularly in agricultural zones, a moderate-to-strong correlation was also observed, likely due to surface contamination from fertilizers. Natural water bodies exhibit more complex relationships owing to environmental factors and their ionic composition. In contrast, deep groundwater, often subjected to geological filtration and treatment processes, displayed inconsistent relationships, underscoring the complexity of using EC as a nitrate proxy in such systems. These findings suggest that EC can support preliminary screening for nitrate in specific water types, particularly in agricultural and rural settings, while emphasizing the need for site-specific calibration and caution against overgeneralization. The study offers a foundational framework for employing EC as a low-cost, rapid monitoring tool in resource-constrained environments.
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Open AccessArticle
Optimizing Rice Yield and Heat Stress Resilience Through Nitrogen Top Dressing Before Panicle Emergence
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Shafiqullah Aryan, Gulbuddin Gulab, Safiullah Habibi, Tayebullah Zahid, Zabihullah Safi, Nasratullah Habibi, Abdul Basir Mahmoodzada, Mohammad Wasif Amin, Ijaz Ahmad Samsor and Kenji Erie
Nitrogen 2025, 6(2), 40; https://doi.org/10.3390/nitrogen6020040 - 29 May 2025
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The increased frequency of extreme heat stress events due to climate change is adversely impacting rice yield. Nitrogen (N) is an essential element in the synthesis of chlorophyll in rice, contributing substantially to the achievement of spikelet fertility and addressing the high yields.
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The increased frequency of extreme heat stress events due to climate change is adversely impacting rice yield. Nitrogen (N) is an essential element in the synthesis of chlorophyll in rice, contributing substantially to the achievement of spikelet fertility and addressing the high yields. Two experiments were conducted in Japan and Afghanistan in 2020 and 2022, respectively, utilizing IR64 and Nipponbare (NPB) varieties to elucidate the efficacy of N top-dressing on spikelet fertility and yield of rice under heat stress conditions. In experiment I, the treatments involved were based on N application before panicle emergence in pots, including (1) control (fertilized at the tillering stage), (2) control + N topdressing, (3) heat stress (fertilized at the tillering stage), and (4) heat stress + N topdressing. Experiment II consisted of (1) control (basal dressing at the tillering stage) and (2) control + N topdressing, which was conducted under field conditions. Results showed that N application significantly (p < 0.05) increased SPAD values and spikelet fertility rates in both experiments. A positive correlation (range; r = 0.83–0.98) was observed between enhanced SPAD values and spikelet fertility rates in IR64 and NPB rice varieties under both ambient and heat stress conditions. Moreover, there were notable increases in photosynthetic rate (7.4% to 52.6%) and leaf transpiration. N top dressing significantly (p < 0.05) increased the panicle length, panicle weight, number of secondary branches/panicle, filled grain/panicle, total spikelets/panicle, and yield/plant. However, there was no significant difference in the number of primary branches per panicle and 1000-grain weight. In addition, the number of unfilled grains/panicle decreased from 5.5 to 49.7% with N top dressing in both experiments. Applying N as a top dressing improved the spikelet fertility percentage and other yield components, resulting in a high yield/plant.
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Multivariate Analyses of Soil Properties and CO2 Emissions Under Long-Term Fertilization and Crop Rotation in Luvic Chernozem
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Gergana Kuncheva, Galin Gynchev, Jonita Perfanova, Milena Kercheva, Lev Tribis and Hristo Valchovski
Nitrogen 2025, 6(2), 39; https://doi.org/10.3390/nitrogen6020039 - 22 May 2025
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The key objectives of contemporary agriculture are restoring biodiversity, preserving ecosystem health, reducing the effects of climate change, and producing safe and healthy foods. Maintaining high soil fertility while reducing greenhouse gas emissions requires a precise assessment of how fertilization and crop rotation
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The key objectives of contemporary agriculture are restoring biodiversity, preserving ecosystem health, reducing the effects of climate change, and producing safe and healthy foods. Maintaining high soil fertility while reducing greenhouse gas emissions requires a precise assessment of how fertilization and crop rotation affect carbon and nutrient cycles in agroecosystems. Fertilization affects soil conditions, which alters the environment for soil microbial development and influences the number and composition of soil microbial communities, leading to changes in nutrient and carbon cycling. There is a lack of long-term experimental data on the impact of fertilizer treatments on soil CO2 emissions, soil microbial communities, and their interactions. The novelty of this study is that it identified the fertilization effects on soil carbon sequestration, soil properties, and microbial communities in the context of a long-term fertilizer experiment in Luvic Chernozem. The fertilization treatments that were continuously pplied for 64 years under a four-crop (wheat, barley, corn, and bean) rotation were nitrogen (N), phosphorus (P), potassium (K), NP, NK, PK, NPK, and control. The chemical and microbiological soil properties and soil CO2 emissions were monitored. The highest organic carbon content was observed under the NPK (1.42%) and NP (1.43%) treatments. N fertilizer application most significantly affected soil properties, including pH, electrical conductivity, and soil organic carbon content, altering the environment for soil microbial development and influencing the number and composition of soil microbial communities. On average, the field-measured soil C-CO2 emissions were the most intensive under NP (2.76 kg ha−1 h−1), NPK (2.83 kg ha−1 h−1), and PK (2.51 kg ha−1 day−1) treatments.
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Open AccessArticle
Analysis of GmERF5 Response to the Rhizobial Type III Effector NopAA Underlying the Nodule in Soybeans
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Lianheng Xia, Yunshan Song, Tong Yu, Ying Pei, Hongwei Jiang, Qingshan Chen and Dawei Xin
Nitrogen 2025, 6(2), 38; https://doi.org/10.3390/nitrogen6020038 - 21 May 2025
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Soybean, an important leguminous crop valued for its high protein and oil content, obtains most of its nitrogen through symbiotic fixation processes. The symbiosis between soybeans and rhizobium can provide sufficient nitrogen for soybean growth. However, the signaling pathways underlying the establishment of
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Soybean, an important leguminous crop valued for its high protein and oil content, obtains most of its nitrogen through symbiotic fixation processes. The symbiosis between soybeans and rhizobium can provide sufficient nitrogen for soybean growth. However, the signaling pathways underlying the establishment of the symbiosis are not so clear, especially the rhizobial type III effector-induced host response. In this study, we found that the single mutant HH103 nopAA::kan significantly affected the nodule number in soybeans. To further demonstrate the NopAA-triggered response in soybeans. Initial quantitative real-time PCR (qRT-PCR) tests showed that NopAA affects the expression of the soybean gene GmERF5, which was significantly upregulated upon inoculation with HH103 nopAA::kan, acting as a positive regulator of nodulation. The direct interaction between NopAA and GmERF5 was confirmed through yeast-two hybrid analysis. Furthermore, overexpression of GmERF5 in hairy roots indicated that GmERF5 may underlie the nodule phenotype of soybeans in response to NopAA. These findings provide new insights into the mechanisms by which soybean genes respond to rhizobial type III effectors to regulate symbiosis.
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(This article belongs to the Special Issue Microbial Interactions with Plants: Advancing Nitrogen Fixation, Uptake, and Utilization)
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Sustainable Treatment of Landfill Leachate Using Sugar Lime Sludge for Irrigation and Nitrogen Recovery
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Tilila Baganna, Assmaa Choukri and Khalid Fares
Nitrogen 2025, 6(2), 37; https://doi.org/10.3390/nitrogen6020037 - 20 May 2025
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Water scarcity is a global crisis and of particular concern in arid regions like Morocco. One creative solution is mining unusual water sources, such as landfill leachate. The presence of nitrogen in the sediment was studied as part of the use of sugar
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Water scarcity is a global crisis and of particular concern in arid regions like Morocco. One creative solution is mining unusual water sources, such as landfill leachate. The presence of nitrogen in the sediment was studied as part of the use of sugar lime sludge in treating landfill leachate for irrigation purposes. A volume of 40 L of landfill leachate was treated with three different concentrations of sugar lime sludge (25%, 35%, and 50%). After homogenization and agitation of the mixture for 24 to 36 h, it was permitted to settle through the concrete decantate and supernatant. Nitrogen was efficiently decanted into the sediment during the composting process with green waste, enhancing the quality of the finished compost. The supernatants underwent physicochemical and microbiological analyses to ascertain their suitability for irrigation. The findings showed that the number of fecal streptococci was decreased by 99.13% at a 25% concentration of sugar lime sludge. The percentage of organic matter in the sediment rose from 10% to 40%, suggesting that the leachate had partially depolluted. The pH and electrical conductivity of the supernatants were within irrigation guidelines. The safety of diluted supernatants for plant germination was verified by phytotoxicity experiments conducted on maize seeds. The compost made from the decantate and green waste showed acceptable physical and chemical properties. Statistical analysis was conducted using JAMOVI software version 2.6.26. One-way ANOVA was used to assess the significance of treatment effects on microbiological and physicochemical parameters. The results confirmed statistically significant differences (p < 0.05) between the sludge concentrations, supporting the effectiveness of the treatment process. This study demonstrates how sugar lime sludge can be used to turn landfill leachate into a sustainable and safe irrigation water source, resolving environmental issues and promoting creative water management techniques.
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Open AccessArticle
Optimizing Nitrogen Management for Sustainable Wheat Production in Semi-Arid Subtropical Environments: Impact on Growth, Physio-Biochemical, and Yield Attributes
by
Barira Shoukat Hafiza, Wajid Ishaque, Muhammad Akhtar, Muhammad Yousaf Shani, M. Azmat, William L. Bauerle, Mehdi Rahimi and Muhammad Yasin Ashraf
Nitrogen 2025, 6(2), 36; https://doi.org/10.3390/nitrogen6020036 - 16 May 2025
Cited by 1
Abstract
Nitrogen fertilization plays a critical role in promoting plant growth, improving physiological and biochemical traits, and enhancing wheat productivity. This study aimed to evaluate the effects of seven nitrogen (N) doses—0, 45, 90, 135, 180, 225, and 270 kg N ha−1—on
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Nitrogen fertilization plays a critical role in promoting plant growth, improving physiological and biochemical traits, and enhancing wheat productivity. This study aimed to evaluate the effects of seven nitrogen (N) doses—0, 45, 90, 135, 180, 225, and 270 kg N ha−1—on wheat performance under semi-arid subtropical conditions over three consecutive growing seasons (2015–2018). A randomized complete block design (RCBD) was used to assess a comprehensive set of agronomic, physiological, biochemical, and nutritional parameters. Key factors examined included grain yield, above-ground biomass, nitrogen harvest index, total nitrogen content in grains and straw, and physiological traits such as photosynthetic rate, stomatal conductance, transpiration rate, and the accumulation of soluble proteins, sugars, and amino acids. The study also incorporated multivariate statistical techniques, such as multi-trait genotype–ideotype distance index (MGIDI), principal component analysis (PCA), and descriptive statistics to identify the most effective nitrogen dose. Results indicated that 180 kg N ha−1 (T4) was the most effective treatment for improving wheat growth, physiological efficiency, and grain yield, with 135 kg N ha−1 (T3) also showing favorable outcomes. In contrast, higher doses (225 and 270 kg N ha−1) led to diminished performance, suggesting a threshold beyond which nitrogen becomes counterproductive. These findings support 180 kg N ha−1 as the optimal dose for maximizing yield and biochemical quality while contributing to more sustainable and profitable wheat production.
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(This article belongs to the Special Issue Nitrogen: Advances in Plant Stress Research)
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Open AccessArticle
Variation in Leaf C, N, and P Stoichiometric Characteristics of Populus euphratica Communities in a Desert Riparian Ecosystem of Northwest China
by
Xiaolong Zhang, Xianmeng Liu, Lijiang Shi, Yinbo Zhang, Jingwei Wang, Feng Gao, Hao Qin, Min Shi, Yongji Wang and Yuanrun Zheng
Nitrogen 2025, 6(2), 35; https://doi.org/10.3390/nitrogen6020035 - 16 May 2025
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Despite extensive research on how climate and environmental factors influence leaf stoichiometry at national and global scales, experimental evidence on their effects at the community level remains limited, particularly in extremely arid regions. Herein, we investigated the leaf stoichiometry including carbon (C), nitrogen
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Despite extensive research on how climate and environmental factors influence leaf stoichiometry at national and global scales, experimental evidence on their effects at the community level remains limited, particularly in extremely arid regions. Herein, we investigated the leaf stoichiometry including carbon (C), nitrogen (N), and phosphorus (P) along a fine-scale riparian gradient (50–1250 m from the riverbank) in an extremely arid Populus euphratica forest in northwest China. Our results show that the community-averaged leaf total carbon (TC), total nitrogen (TN), and total phosphorus (TP) contents were 442.58 mg/g, 21.69 mg/g, and 1.18 mg/g, respectively. The community-averaged C:N, C:P, and N:P ratios were 20.74, 379.97, and 18.43, respectively. Compared to findings from other studies, the P. euphratica community exhibited lower leaf TC and TP contents but higher TN content and N:P ratios. A high N:P ratio (mean = 18.43, N:P > 16) suggests that the P. euphratica community is more susceptible to phosphorus limitation. Along the riparian gradient, community-averaged leaf TC, C:N, and C:P increased significantly, reaching their maximum (479.49 mg/g, 27.12, and 478.06, respectively) at 1250 m from the riverbank. Conversely, leaf TN and TP contents, as well as N:P, decreased significantly with increasing distance from the river, reaching their minimum values (17.49 mg/g, 0.99 mg/g, and 17.17, respectively) at 1100–1250 m. Soil available phosphorus, soil water content, soil bulk density, and soil electrical conductivity significantly influenced the leaf stoichiometry of the P. euphratica community, collectively explaining 61.78% of the total variation. Among these factors, soil water content had the most pronounced effect, surpassing soil available phosphorus, bulk density, and electrical conductivity in shaping leaf stoichiometric characteristics. Our findings indicate that at fine spatial scales, the distribution of leaf nutrients and stoichiometry seem to be predominantly influenced by local-scale factors such as soil water content, soil nutrient levels, and salt stress; P. euphratica forests would be experiencing more negative impacts in leaf nutrients and stoichiometry due to increased droughts or salt stress.
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Open AccessReview
Integrating Agronomic and Molecular Advancements to Enhance Nitrogen Use Efficiency (NUE) and Promote Sustainable Rice Production
by
Uttam Bahadur Kunwar, Nazer Manzoor, Jiancheng Wen and Naba Raj Pandit
Nitrogen 2025, 6(2), 34; https://doi.org/10.3390/nitrogen6020034 - 14 May 2025
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Rice is a major crop for half of the world’s population, and nitrogen (N) fertilizers play a crucial role in its production. However, imbalanced N fertilizer uses and traditional fertilization practices have led to low nitrogen use efficiency (NUE), increased N footprints, and
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Rice is a major crop for half of the world’s population, and nitrogen (N) fertilizers play a crucial role in its production. However, imbalanced N fertilizer uses and traditional fertilization practices have led to low nitrogen use efficiency (NUE), increased N footprints, and reduced rice yields and farmers’ income. There are limited studies where the integration of both agronomic and molecular advancements to enhance NUE is discussed, particularly in developing countries. This review highlights novel agronomic and molecular strategies to enhance NUE, rice yields, and profitability, while minimizing environmental impact. The agronomic strategies include the 4R Nutrient Stewardship framework, enhanced efficiency nitrogen fertilizers (EENFs), nano-fertilizers, biochar-based fertilizers, biological N fixation, and sensor-based fertilizer management in major rice-growing countries. The molecular mechanisms focus on N uptake, assimilation, and utilization, highlighting the role of hormones, key genes, transcription factors (TFs), and regulatory pathways. Moreover, we examine promising rice genotypes and cultivars with improved NUE and grain yield. Additionally, this paper offers deep insights into recent advancements in molecular genetics, such as multi-omics approaches (transcriptomics, metabolomics, and metagenomics), the Genome-Wide Association Study (GWAS), Quantitative Traits Loci mapping (QTLs), Single Nucleotide Polymorphisms (SNPs) analysis, and Clustered Regularly Interspaced Short Palindromic Repeats (CRISPR-Cas9)-mediated genome editing, which serve as valuable tools for developing rice cultivars with enhanced NUE and grain yield.
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Open AccessArticle
Impact of Nitrogen Fertilization on Rosemary: Assessment of Physiological Traits, Vegetation Indices, and Environmental Resource Use Efficiency
by
Christos A. Dordas
Nitrogen 2025, 6(2), 33; https://doi.org/10.3390/nitrogen6020033 - 2 May 2025
Abstract
Rosemary (Salvia rosmarinus L.) is a versatile and resilient plant with significant culinary, medicinal, and ecological value. This study evaluates the impact of four nitrogen (N) fertilization levels (0, 50, 100, and 150 kg N ha⁻¹) on the morphological, physiological, and agronomic
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Rosemary (Salvia rosmarinus L.) is a versatile and resilient plant with significant culinary, medicinal, and ecological value. This study evaluates the impact of four nitrogen (N) fertilization levels (0, 50, 100, and 150 kg N ha⁻¹) on the morphological, physiological, and agronomic traits, as well as vegetative indices, of rosemary over two growing seasons (2022 and 2023). The results indicate that plant height and leaf area index (LAI) increased with N application. Additionally, physiological characteristics such as chlorophyll content, photosynthetic efficiency, and assimilation rates (A) increased by an average of 32%, 17%, and 55%, respectively, compared to the control. Biomass production also improved with N fertilization, with yields rising by 32% in 2022 and 58% in 2023. Furthermore, both essential oil concentration and essential oil yield were enhanced by N application. Radiation use efficiency (RUE), water use efficiency (WUE), agronomic efficiency (AE), and partial factor productivity (PFP) also increased, indicating more efficient utilization of environmental resources. Moreover, higher N rates consistently enhanced vegetation indices, reflecting improved plant health, greenness, biomass, photosynthetic activity, and energy utilization. Therefore, this study highlights that the optimal N range appears to balance biomass yield and essential oil yield while maximizing the efficiency of environmental resource use.
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(This article belongs to the Special Issue Monitoring Nitrogen in Soils and Plants: Recent Methods, Soil Properties and Plant Characteristics)
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Linking Satellite and Ground Observations of NO2 in Spanish Cities: Influence of Meteorology and O3
by
Carlos Morillas, Sergio Álvarez, José C. M. Pires, Adrián Jesús García and Sara Martínez
Nitrogen 2025, 6(2), 32; https://doi.org/10.3390/nitrogen6020032 - 2 May 2025
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In Spain, several major cities face high rates of avoidable deaths due to NO2 exposure. Understanding NO2 atmospheric dynamics is essential to support public health efforts and policymaking. Recent satellite products have proven useful in characterizing urban atmospheric composition in various
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In Spain, several major cities face high rates of avoidable deaths due to NO2 exposure. Understanding NO2 atmospheric dynamics is essential to support public health efforts and policymaking. Recent satellite products have proven useful in characterizing urban atmospheric composition in various regions. This study compares NO2 concentration data from in situ air quality monitoring networks and the Sentinel-5P TROPOMI satellite in Spain’s three largest cities (Madrid, Barcelona, and Valencia), alongside O3 levels —due to its close photochemical relationship with NOx—wind speed and direction, temperature, relative humidity, and solar radiation. Data from 2022 were analyzed using Pearson correlation coefficients and Principal Component Analysis (PCA) to identify key relationships and patterns. Results showed a consistent negative correlation between NO2 and O3, wind speed, temperature, and solar radiation. Differences between in situ and satellite data were more pronounced in coastal cities, influenced by wind patterns and urban morphology (Madrid: r = 0.86, v = 1.34 m/s; Valencia: r = 0.68, v = 2.97 m/s; Barcelona: r = 0.65, v = 8.04 m/s). These insights enhance the understanding of NO2 behavior in urban environments and support the use of remote sensing to estimate surface-level pollution in areas lacking ground-based monitoring infrastructure. This is the first study in Spain to jointly evaluate NO2 from satellite and in situ data across multiple cities, linking pollutant concentrations with meteorological and chemical drivers to improve surface-level estimation strategies and support air quality assessment in under-monitored areas.
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