Nitrogen

The substrate-induced respiration-inhibition (SIRIN) method has been used to estimate fungi-derived N₂O emissions, but its contribution to soil N₂O emissions remains unclear. There is a need to quantify the fungal fraction of N₂O production more precisely. Here, using isotopocule analysis, we assessed the relative contribution of fungi to soil N₂O production potential under denitrifying conditions, where key limiting factors of denitrification (soil moisture, soil NO₃⁻, and electron donor) were removed. The result showed that the ratio of fungi-derived N₂O emissions (R_F) was 0.83~4.28% in paddy soils, 13.80~23.21% in vineyard soils, and 15.34~65.94% in vegetable field soils, respectively. This indicated that the bacteria were the dominator of soil N₂O production potential in most cases, but fungal pathways could be significant in vegetable field soils. The experiment with bactericide addition showed that inhibitors could affect non-target microorganisms in the SIRIN method. Our further analyses suggest that it is worth to explore the effect of soil organic carbon and microbial synergies on fungi-derived N₂O emissions. Full article

Management of livestock manure is a major concern due to its environmental impacts; consequently, laboratory-based incubations aim to quantify the C and N mineralization of organic matter (OM) to assess its potential to supply OM to soils. However, they can be limited by methodological constraints, notably the drying process of organic products. While litterbag experiments allow in situ decomposition of OM to be monitored, they often focus only on mass loss on a dry matter basis, which may overestimate biodegradation rates. To address these limitations, we designed an experiment that combined the measurement of material fluxes with the characterization of OM using transmission electron microscopy. Raw and dried farmyard cattle manure were incorporated into the soil and incubated in litterbags (200 µm mesh) for 301 days. The results demonstrated that drying significantly altered the biochemical composition of the cattle manure and influenced its microbial dynamics at the beginning of the incubation. However, this alteration did not influence the C mineralization rate at the end of incubation. Biodegradation alone could not explain C losses from litterbags after day 112 of incubation, which supports the assertion that physical and biological processes transferred large amounts of matter from the litterbags to the soil. These results highlight the importance of conditioning samples before laboratory incubations. Full article

Crops and arbuscular mycorrhizal (AM) fungi can enhance nitrogen (N) transformation and utilization efficiency in the soil, and this effect is regulated by soil N application rates. However, it remains unclear whether the N utilization efficiency of cotton can be improved through the symbiosis of cotton with AM fungi under reduced N application rates. Therefore, we conducted ¹⁵N labeling experiments using a compartmentalized culture system with Gossypium hirsutum L. as the experimental plant. We established three N treatments (0.15 g·kg⁻¹, 0.10 g·kg⁻¹ and 0 g·kg⁻¹) to investigate the effects of different fertilization rates on N utilization, soil N priming effects, and differences in N accumulation in various parts of cotton plants within the soil–AM fungi–cotton system. The results indicate that under reduced N application, symbiosis between cotton and AM fungi increased the N fertilizer utilization efficiency and the soil N priming effect. Specifically, reducing the fertilization dosage from 0.15 g·kg⁻¹ to 0.10 g·kg⁻¹ increased the N fertilizer utilization efficiency and soil N priming effect by 8.87% and 11.67%, respectively, and decreased the N loss rate by 7.02%. The symbiosis between cotton and AM fungi after N reduction significantly increased N accumulation in the roots and leaves. Moreover, the N fertilizer content accounted for 5.89% of the total N content in roots. Overall, when N application was reduced, symbiosis with AM fungi effectively promoted the rhizosphere N priming effect, which reconciled the conflict in N nutrient allocation within cotton and thus enabled the efficient utilization of soil N. Full article

This study aimed to determine the optimal nitrogen (N) fertilization rate per regrowth cycle for Megathyrsus maximus cv. BRS Tamani by evaluating its effects on forage production, nutrient uptake, bromatological composition, and in vitro degradation kinetics. A randomized complete block design with five N doses (0, 40, 80, 120, and 160 kg N ha⁻¹) and seven replications was conducted over two rainy seasons. From December 2019 to April 2020, canopy height and light interception were measured weekly. When canopy height reached 95% of light interception the grass was harvest and productive and morphological structure were measured. Nitrogen fertilization increased forage mass and yield up to the dose of 40 kg N ha⁻¹, resulting in 1959 and 9798 kg DM ha⁻¹, respectively, while nitrogen use efficiency declined at higher doses. Weed mass was decreased at 0 kg ha⁻¹, and chlorophyll index increased with the N dose. Nitrogen and potassium were the most extracted nutrients, with nitrogen uptake being highest at 80 kg ha⁻¹. Fertilization elevated the levels of crude protein, NDIP, cell content, and cell wall-bound protein, while ash content decreased. In vitro fermentation showed a reduced gas volume at higher N doses and improved degradation and digestibility up to 40 kg ha⁻¹. Nitrogen fertilization enhanced the forage yield and quality of BRS Tamani, with 40 kg ha⁻¹ maximizing efficiency and digestibility. Full article

Grassland biomass yield reflects a complex interaction of management intensity and environmental factors, yet quantifying the relative role of practices such as mowing and fertilization remains challenging. In this study, we introduce a multi-class machine learning framework to predict above-ground biomass on 150 permanent grassland plots across eight years (2009–2016) in Germany’s Biodiversity Exploratories and to evaluate the influence of key management variables. Following rigorous data cleaning, imputation of missing nitrogen values, feature standardization, and encoding of categorical practices, we trained CatBoost classifiers optimized via Bayesian hyperparameter search and mitigated class imbalance with ADASYN oversampling. We assessed model performance under binary, three-class, four-class, and five-class quantile-based categorizations, achieving test accuracies of 0.76, 0.57, 0.42, and 0.38, respectively. Across all schemes, mowing frequency and mineral nitrogen input emerged as the dominant predictors, while secondary variables such as drainage and conditioner use contributed as well. These results demonstrate that broad biomass categories can be forecast reliably from standardized management records, whereas finer distinctions necessitate additional environmental information or automated sensing to capture nonlinear effects and reduce reporting bias. This work shows both the potential and the limits of machine learning for informing sustainable grassland management and explainability thereof. Frequent mowing and higher mineral nitrogen inputs explained most of the predictable variation, enabling a 76% accurate separation of low and high biomass categories. Predictive accuracy fell below 60% for finer class resolutions, indicating that management records alone are insufficient for detailed yield forecasts without complementary environmental data. Full article

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. Full article

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. Full article

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. Full article

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 (AE_N), 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 AE_N 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. Full article

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. Full article

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 N_100%U were similar to that of with N_75%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. Full article

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. Full article

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. Full article

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 (N_EFF), milk urea nitrogen (MUN), and manure nitrogen excretion (N_MANURE) 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 N_EFF was also affected by nutrient intakes from both forages. Generally, greater protein intake reduced N_EFF, whereas greater MY was associated with improved N_EFF. 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 N_MANURE. 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. Full article

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. Full article

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. Full article

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. Full article

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. Full article