Nitrogen

Accurate assessment of nitrous oxide (N₂O) emissions from agricultural soils is essential for developing effective mitigation strategies. However, Pakistan’s current baseline estimates show inconsistencies. The updated Nationally Determined Contributions for 2018 report total greenhouse gas emissions from managed soils at 74.98 Mt CO₂e, while the first Biennial Update Report (BUR 1) estimates N₂O-specific emissions at 70.7 Mt CO₂e, rising under a business-as-usual scenario to 282.8 Mt CO₂e by 2030, an increase of nearly 300%. This study revisits these baselines using verified national datasets from Pakistan’s BUR 1 and the National Inventory Report 2021. The 2018 baseline was recalculated using the IPCC Tier 1 methodology, with fertilizer offtake and cropped-area data from national annual reports. Applying the updated IPCC AR6 global warming potential for N₂O (273) revised the BUR 1 2018 estimate to 62.26 Mt CO₂e, closely aligning with the NIR 2021 estimate of 62.4 Mt CO₂e. The study further disaggregates emissions by crop and source. Synthetic fertilizers were the largest direct source of N₂O emissions (14.72 Mt CO₂e), with wheat accounting for 50% (7.36 Mt CO₂e), mainly due to its extensive cropped area. Indirect emissions represented 35% of the revised baseline. Supported by uncertainty and sensitivity analyses, this refined baseline and its crop- and source-specific allocation provide a more reliable and transparent foundation for targeted mitigation in Pakistan’s most emission-intensive cropping systems. The findings also highlight the need for crop-specific fertilizer-use surveys to strengthen Tier 1 reporting where country-specific Tier 2 emission factors are unavailable. Full article

This study aimed to evaluate the comprehensive effects of foliar fertilization on maize-related traits and to identify nutrient-related factors associated with yield variation. A single-site field experiment was conducted during the 2024 growing season using maize cultivar ‘Zhengdan 958’. Two fertilization treatments, conventional fertilization (CF) and conventional fertilization combined with foliar fertilization (OF), were applied, with each treatment consisting of three replicate plots. Thirty variables related to yield, yield components, plant nutrient status, and grain nutrient accumulation were measured and included in subsequent exploratory analyses. Analysis of variance (ANOVA) combined with exploratory multivariate statistical analyses was employed to evaluate treatment effects, examine statistical associations among measured variables, and develop the exploratory yield regression models. Compared with CF, OF significantly increased several yield component traits, including kernels per row, ear length, and grain weight per ear, with increases ranging from 9.8% to 20.5%. OF increased grain nitrogen and carbon accumulation by 17.8% and 26.8%, respectively, and increased maize yield, gross revenue and net profit by 20.3–20.5%. Exploratory multivariate statistical analyses indicated that foliar fertilization under conventional fertilization conditions significantly improved several maize yield-related traits. Grain nutrient accumulation, yield components, and yield and economic performance were all important variables that distinguished fertilization treatments and exhibited progressively increasing relative contributions. Further analyses indicated a hierarchical pattern of statistical associations among yield components, grain nutrient accumulation, and maize yield. Grain nitrogen, phosphorus, and carbon accumulation were nutrient-related variables showing statistical associations with maize yield, and their associations with yield were mainly mediated through key yield components. Among the evaluated nutrient variables, GNA showed a strong mathematically coupled statistical association with GY within the evaluated dataset. These findings provide new insights into the statistical relationships between nutrient accumulation and maize yield under foliar fertilization and may contribute to the optimization of nutrient management strategies in maize production. Full article

Wheat dust, an underutilized agro-industrial by-product, is rich in nutrients and may serve as a sustainable soil amendment. This study evaluated its effects on wheat (Triticum durum L.) growth, nitrogen metabolism, and drought tolerance. Two greenhouse experiments were conducted. First, a dose–response trial (0, 2, 5, 10, 20% w/w) assessed biomass, chlorophyll content (SPAD), and expression of nitrogen-related genes (NR, NRT1, NRT2, GS2). Second, a factorial experiment (0, 10, 20% × well-watered or 50% water capacity) examined growth, yield components, oxidative stress markers (MDA), antioxidant enzymes, soil enzymatic activities, and multivariate responses. Wheat dust elicited concentration-dependent, context-specific effects. Under well-watered conditions, 10% was optimal, increasing shoot biomass (+39%) and chlorophyll (+10–15%), accompanied by upregulation of NR, NRT1, and NRT2, indicating enhanced nitrogen acquisition. Under drought, 20% produced the strongest effects: biomass increased by +313%, seed number per spike by +3900%, and seed weight per spike by +1650% relative to the stressed control. Lipid peroxidation declined by 83%, while chlorophyll increased by +215%, reflecting strong protection of membrane integrity and photosynthetic capacity. Soil biological activity was markedly stimulated at 20% under drought, with FDA hydrolysis (+1320%) and protease activity (+8250%) indicating enhanced microbial functioning and nitrogen cycling. Principal component analysis confirmed a systemic shift from stress-dominated profiles in controls to growth- and metabolism-oriented profiles at 20%, with convergence of stressed and non-stressed plants. Thus, wheat dust improves productivity at moderate doses and confers pronounced drought resilience at higher rates, supporting its valorization within climate-resilient, circular agricultural systems. Full article

Crop rotation and fertilization are two of the most important agrotechnical measures that influence the chemical properties of the soil and its capacity to support stable agricultural production, especially in areas affected by erosion and climate change. The aim of this study was to evaluate the influence of crop rotation and fertilization on the main soil properties (pH, total nitrogen, available phosphorus and potassium, humus content) in moderately eroded cambic chernozems of the Bârlad Plateau, as well as the effect of experimental factors on wheat yield. The research was carried out in the period 2021–2025 in a stationary experiment located on a slope with a slope of 12–13% at “Mircea Moțoc” Soil Erosion Research and Development Station (M.M.S.E.R.D.S.) Perieni. Two wheat cropping systems were analyzed, namely, monoculture and five-year rotation, in combination with five fertilization variants (N₀P₀, N₃₂P₃₂, N₉₆P₉₆, N₁₂₈P₁₂₈ kg ha⁻¹ and 50 t ha⁻¹ manure). The determinations targeted pH, total nitrogen, mobile phosphorus, mobile potassium, humus content in the 0–20 cm and 20–40 cm soil layers and yield. The results highlight the depletion in available nitrogen, phosphorus, and potassium reserves, alteration of soil reaction in monoculture, and significant improvement in N (from 0.1% to 0.19%), P (from 95.5 to 485.5 mg ha⁻¹) and K (from 188.4 to 227.5 mg ha⁻¹) soil content at the time of final sample collection in the five-year rotation. The application of manure as well as the inclusion of legumes and perennial crops in the rotation contributed to the accumulation of organic matter, to the improvement in soil reaction and to the optimization of nutrient cycling. The highest yields, significant at p ≤ 0.001, were obtained with the application of N₉₆P₉₆ 2858 kg ha⁻¹ in monoculture and 3689 kg ha⁻¹ in the five-year rotation. The study confirms that long rotations associated with organic fertilization represent an effective strategy for the conservation of agricultural soil fertility in areas vulnerable to erosion and drought. Full article

Variation in maize performance under different nitrogen fertilization regimes depends on genotype response, environmental conditions, and their interaction. This study evaluated three commercial maize hybrids contrasting maturity groups (G1–P9537, G2–P9911 and G3–P0412, representing early, medium, and late FAO maturity groups, respectively) across two growing seasons and five nitrogen treatments (0, 50, 100, 150, and 200 kg N ha⁻¹) using the Additive main effects and multiplicative interaction (AMMI) model. Analysis of variance revealed significant genotype and environment effects on grain yield, whereas genotype by environment interaction (GEI) was not significant. However, decomposition of the GEI using the AMMI model indicated that the first interaction principal component (IPCA1) was statistically significant and accounted for 90.6% of the GEI sum of squares, indicating that the interaction component was predominantly described by a single multiplicative axis. Genotype G3 achieved the highest mean grain yield and low IPCA1 score, demonstrating relatively stable performance across the evaluated nitrogen environments in this study. In contrast, G2 exhibited narrower adaptation and was more closely associated with control and low-nitrogen environments, while G1 had the lowest mean yield but exhibited a low interaction IPCA score. These findings provide useful information for hybrid evaluation under various nitrogen environments and may contribute to improved nitrogen management and hybrid selection under conditions similar to those investigated in this study. Full article

Partial replacement of chemical fertilizers, particularly nitrogen fertilizers, with biological fertilizers is considered an effective strategy for reducing the negative environmental impacts associated with excessive fertilizer use. This study aimed to optimize N use through the application of bacterial-based biofertilizer, specifically plant growth-promoting rhizobacteria (PGPR), in different maize cultivars under semi-arid conditions. A randomized complete block design (RCBD) arranged in a split-plot arrangement was used, with the three hybrids (Shahkar, Bumbus and DK 7024) assigned to the main plots and different N treatments allocated to sub-plots. The field experiment was conducted during two consecutive spring seasons (Feb to June 2024 and 2025). The N treatments were defined as follows: control, 100% recommended N (200 kg/ha), 100% N with Pseudomonas stutzeri, 100% N with Bacillus subtilis, 100% N with Enterobacter sp., 50% N with Pseudomonas stutzeri, 50% N with Bacillus subtilis, 50% N with Enterobacter sp., 100% Pseudomonas stutzeri, 100% Bacillus subtilis, and 100% Enterobacter sp. The N treatments included synthetic fertilizer alone at the 100% recommended N rate and a combination of 100%, 50% and 0% of recommended levels with three N-fixing bacterial strains. Among the hybrids, DK 7024 exhibited the highest 1000-grain weight (349 g and 362.5 g), grain yield (6756 and 6971 kg ha⁻¹) and total dry matter (17,500 and 18,368 kg ha⁻¹) in 2024 and 2025, respectively. Among N levels, maximum 1000-grain weight, grain yield and total dry matter were noticed in 100% N with Enterobacter sp.: 402 g, 8446 kg ha⁻¹ and 21,656 kg ha⁻¹ in 2024 and 421 g, 8684 kg ha⁻¹ and 22,237 kg ha⁻¹ in 2025. Nitrogen application increased grain yield and total dry matter production; however, the treatment combined with 100% recommended synthetic N fertilizer with biofertilizer (Enterobacter sp.) showed superior performance compared with 100% N applied through only the synthetic fertilizer. The interaction between maize hybrids and N levels was statistically non-significant, suggesting that 100% N plus biofertilizers could be an effective strategy for achieving higher yields across different maize cultivars. Additionally, the beneficial effects of PGPR may contribute to sustainable agricultural practices. Further research is recommended to evaluate strategies involving reduced-N inputs combined with biological fertilizer, including the application of 100% N with biofertilizer. The present study suggests that N application in combination with biofertilizers has the potential to improve crop growth while promoting sustainable crop production. Full article

Nitrogen (N) is one of the most important nutrients influencing wheat growth, plant nutrition, and grain production. Appropriate timing of nitrogen application is essential to synchronize nutrient availability with crop demand. This study evaluated seven nitrogen management treatments, including a control (N0) and six split nitrogen application schedules (N1–N6), in durum wheat under Mediterranean conditions using an integrated approach combining ground-based hyperspectral sensing and unmanned aerial vehicle (UAV)-based multispectral imagery. Plant nutrient concentrations (N, P, K, Ca, and Mg), spectral reflectance, vegetation indices, plant height, and grain yield were evaluated at different phenological stages. Split nitrogen application significantly affected plant nutrient concentrations, spectral reflectance, vegetation indices, plant height, and grain yield. Plant nutrient concentrations generally declined with crop development, whereas spectral reflectance increased across the visible and near-infrared regions of the spectrum. Vegetation indices derived from both hyperspectral and UAV multispectral data successfully differentiated phenological stages and nitrogen treatments. UAV-derived plant height showed strong agreement with field measurements, confirming the reliability of photogrammetric measurements for monitoring crop development. Among the nitrogen treatments, the N3 split application schedule produced the most favorable overall crop response, with higher plant nitrogen concentration, stronger spectral responses, and the highest grain yield. In addition, UAV-derived NDVI measured at the booting stage showed the strongest relationship with grain yield (r = 0.717, p < 0.01). These findings demonstrate that integrating ground-based hyperspectral sensing with UAV multispectral imagery provides complementary information for evaluating crop development and plant nutritional responses under different split nitrogen application schedules. Full article

Symbiotic nitrogen fixation (SNF) in forage legumes is a key biological process that provides nitrogen inputs and enhances soil fertility in agroecosystems. Enhancing SNF efficiency helps reduce dependence on synthetic nitrogen fertilizers and improve nitrogen use efficiency. Humic substances (HS) have been reported to stimulate root development and nutrient acquisition in different crop species. However, their effect on root nodulation and SNF in forage legumes remains poorly understood. This study investigated the effects of a humic acid-based soil amendment (liquid Humalite) on root growth, nodulation, SNF, and plant nitrogen acquisition in red clover. Red clover seedlings were grown in a modified Leonard jar system placed under controlled environmental conditions and treated with 0.1, 0.2, 0.4, and 0.8% (v/v) liquid Humalite. Plant biomass, root morphological traits, nodulation parameters, SNF, and shoot nitrogen accumulation were assessed after 6 weeks. SNF was quantified using the ¹⁵N-isotope dilution method. Application of liquid Humalite significantly affected plant growth and SNF responses in red clover. The 0.2% liquid Humalite treatment significantly increased root and total plant biomass by 35% compared to the untreated control. Total root length, surface area, and volume increased by 20–25% at 0.2% liquid Humalite. Nodule number, nodule dry weight, shoot nitrogen concentration, and shoot C:N ratio did not differ among treatments. However, the percent nitrogen derived from the atmosphere (%Ndfa) was significantly higher under the 0.2% liquid Humalite treatment (47%) as compared to the untreated control (28%). Under the 0.2% liquid Humalite, total fixed and accumulated shoot nitrogen increased by 134% and 37%, respectively, compared to the control. Overall, these findings indicate that humic substances may enhance SNF and nitrogen accumulation in red clover, highlighting their potential as a management strategy to improve forage productivity. Full article

Feeds rich in protein are the dominant nitrogen input in intensive aquaculture, yet only part of dietary nitrogen is retained as animal biomass; the remainder enters water and sediment through uneaten feed, feces, dissolved wastes, mucus, sloughed tissue, and branchial ammonia excretion. This review aims to integrate nutritional, physiological, microbial, and disease-related evidence into an evidence-graded framework that positions ammonia nitrogen as a reactive node linking feed, host, water, sediment, and pathogen risk. To assemble this evidence, we conducted a structured narrative search of Web of Science and PubMed for records in English or Chinese published from 2006 to July 2026, with no restriction on publication type, and classified evidence as direct, indirect, or conceptual. The strongest evidence shows that dietary protein supply, amino acid balance, digestibility, and feeding regime regulate nitrogen retention and ammonia output, while microbial ammonification, nitrification, denitrification, dissimilatory nitrate reduction to ammonium, anammox, and assimilation determine whether reactive nitrogen is regenerated, retained, or removed. Experimental studies further show that ammonia impairs oxidative balance, mucosal barriers, immunity, and disease resistance. In contrast, evidence that pathogen infection quantitatively alters nitrogen retention, ammonia excretion, organic nitrogen release, and sedimentary ammonium regeneration remains limited and largely indirect. Accordingly, ammonia nitrogen is framed as a measurable reactive node rather than a unique source or a universally validated causal loop. Practical management should combine precision nutrition with water, biofloc, sediment, and disease surveillance, while future factorial studies and isotope tracer studies should quantify the complete nitrogen budget under pathogen challenge. Full article

This study aimed to investigate the effects of different nitrogen (N) fertilizer rates and sowing dates on grain yield, protein content, grain N uptake, and nitrogen recovery efficiency (NRE) in spring and facultative wheat (Triticum aestivum L.) cultivated in northwestern and central Romania from 2018 to 2020. The experiment was designed as a split–split plot study with two spring sowing dates (SDs): an optimal date (1–15 March) and a delayed date (postponed by two weeks). All treatments received a basal autumn fertilizer supplying 36 kg N ha⁻¹ and 92 kg P ha⁻¹. In spring, three N treatments were evaluated: no additional N (N₃₆), 72 kg N ha⁻¹ (N₁₀₈), and 105 kg N ha⁻¹ (N₁₄₁), with the supplementary N top-dressed at the booting stage. The results showed that delayed sowing significantly altered grain N uptake dynamics and reduced NRE, even under standard fertilization regimes. Specifically, delayed sowing reduced grain yield by 7.52% to 28.39% compared to optimal sowing, while adverse climatic interactions in delayed setups reduced the mean NRE to as low as 16.43%. These findings indicate that conventional N application strategies may be suboptimal under variable sowing conditions and highlight the importance of adaptive N management to improve both agronomic performance and environmental sustainability. Full article

Efficient nitrogen (N) management is essential for sustaining crop productivity while minimizing environmental impacts associated with nitrogen losses. However, the high spatial and temporal variability of soil nitrogen dynamics and crop nitrogen status makes field-scale monitoring challenging, while conventional soil and plant sampling methods are labor-intensive, destructive, and provide limited spatial coverage. Recent advances in remote sensing technologies and machine learning (ML) offer promising alternatives for high-throughput, non-destructive monitoring of crop nitrogen status and related nitrogen dynamics in agroecosystems. This review synthesizes current progress in the use of proximal and remote sensing platforms, including unmanned aerial vehicles (UAVs), satellites, and ground-based sensors for assessing crop nitrogen status and inferring soil nitrogen availability. We examine spectral, thermal, and structural indicators, together with emerging sensor-fusion and time-series approaches. We also evaluate ML algorithms, including emerging foundation model approaches, for estimating crop nitrogen status and inferring soil nitrogen indicators, highlighting their performance, limitations, and transferability across environments. Particular emphasis is placed on field-scale applications in heterogeneous and water-limited systems, where nitrogen-water interactions critically influence crop responses. Finally, we discuss current challenges, including data scarcity, model generalization, and operational constraints, and outline future directions toward integrated, real-time decision support systems for precision nitrogen management. Overall, this review provides a comprehensive framework for leveraging remote sensing and data-driven approaches to improve nitrogen monitoring and enhance nitrogen use efficiency in diverse cropping systems. Full article

Rice production in coastal tidal floodplains is severely constrained by periodic tidal submergence, making modern semi-dwarf varieties unsuitable. While local landrace cultivars are widely grown for their adaptability, their adaptation mechanisms and response to nitrogen management under tidal ecosystems remain poorly understood. This two-year on-farm study (aman seasons, 2021 and 2022) evaluated landrace rice cultivars against a modern check (BR23) under different nitrogen-management practices: urea super-granule deep placement and prilled urea application. Landraces adapted better to tidal submergence than BR23, exhibiting greater plant height, culm strength, biomass, and nutrient accumulation. Cultivar effects explained most of the variation in grain yield (38–40%), followed by nitrogen management (18–21%). Deep placement of urea super-granule significantly enhanced growth, yield, and nutrient uptake compared to prilled urea. Shorna showed the highest grain nitrogen uptake (48.23 kg ha⁻¹), agronomic efficiency (20.81 kg grain kg⁻¹ nitrogen), and partial factor productivity (71.91 kg grain kg⁻¹ nitrogen). Bhushiara achieved the highest grain harvest index (0.54) and nutrient harvest indices, indicating efficient nutrient partitioning to grains. During grain-filling, nitrogen and phosphorus efficiently remobilized to the grains, while potassium remained mostly in the straw. Ultimately, pairing resilient landraces like Shorna, Bhushiara, Dudmona, and Lalmota with optimized nitrogen management, specifically urea super-granule application, substantially improves productivity, nutrient efficiency, and climate resilience. This study provides some of the first comprehensive evidence on how genotype-specific adaptation and deep-placed nitrogen interact to support sustainable rice production in Bangladesh’s coastal floodplains. Full article

Acidic soil stress can limit sunflower productivity by reducing nutrient availability, impairing root development, and affecting early plant establishment, while foliar nutrient application and seed pretreatment may provide additional support under recommended nitrogen fertilization. This study evaluated the potential of selected nutrient-based products to mitigate acidic environment stress in sunflower through a field experiment and a complementary laboratory germination test. The field experiment was conducted in 2025 at Ivankovo, Croatia, on acidic soil (pH KCl 4.47), under a recommended nitrogen fertilization dose of 85 kg N/ha for sunflower production. Foliar treatments included Barrier, Bioplex, Borealg, and Bor-feed, while the control was left without additional foliar treatment. Seed yield, yield components, seed oil and protein content, and oil and protein yield were determined. In parallel, sunflower seeds were pretreated with the same products and germinated under controlled conditions in aqueous solutions with pH values ranging from 3.5 to 8.5. Germination, seedling morphology, fresh biomass, total phenolic content, antioxidant activity, and free proline content were analysed. Under field conditions, foliar treatments significantly affected plant height, head diameter, seed mass per head, seed oil and protein content, and seed yield. Barrier produced the highest seed yield (5.3 t/ha), oil yield (2.8 t/ha), and protein yield (0.8 t/ha), whereas Bor-feed had the highest seed oil content (54.36%) but the lowest seed yield (2.5 t/ha). In the laboratory experiment, average total germination was 92%, with maximum values of 96–97% depending on treatment and pH. Barrier most strongly promoted root, shoot, and total seedling length, while Borealg increased root, shoot, and total fresh mass. Biochemical responses depended on seed pretreatment and pH, with the highest antioxidant activity recorded in Bioplex at pH 7.5 and higher proline accumulation generally observed in untreated seedlings. The highest antioxidant activity was recorded in Bioplex seed pretreatment at pH 7.5 (5.34 mM Fe(II)/g FW), while the highest free proline content was observed in the control at pH 5.5 (7.87 mM/g FW) and pH 3.5 (7.79 mM/g FW), indicating a stronger stress response in untreated seedlings. The present study indicates that selected foliar products and seed pretreatments may support sunflower productivity and early growth under acidic stress conditions, with Barrier showing the most consistent positive response. Full article

Nitrogen is integral to all living systems, but its diverse forms are interconverted dynamically through reductions and oxidations that constitute the nitrogen cycle. Ecosystems gain combined nitrogen by bacterial and archaeal reduction in atmospheric N₂, while combined nitrogen is lost to the atmosphere as nitrogenous gases through denitrification. We sought to characterize the diversity and activity of free-living nitrogen-fixing bacteria or diazotrophs in natural prairie grasslands and the activity of the other steps of the nitrogen cycle through metatranscriptomics. DNA and mRNA were obtained from prairie sites that did not contain any leguminous plants to avoid symbiotic nitrogen fixation. Both 16S rRNA gene and nifH amplicon pools were sequenced to characterize the diversity of diazotrophs, and the expression levels of N-cycle genes were quantified by RNAseq. Nitrogen fixation without and with added carbohydrates was quantified by measuring the incorporation of ¹⁵N₂. The soil samples contained a diversity of diazotrophs, as reflected both by 16S rRNA gene and nifH gene sequences. Carbohydrate amendment of soil samples led to substantial ¹⁵N₂ incorporation, showing that members of the resident microbiota were able to fix nitrogen. However, we did not detect ¹⁵N₂ incorporation in unamended soil samples, pointing to a lack of in situ fixation. The very low levels of nitrogenase gene transcripts supported this finding. In contrast, transcripts for nitrification and denitrification genes were expressed, pointing to a gap in the nitrogen cycle. The prevalence of diazotrophs with undetectable nitrogen fixing activity suggested the absence of available carbohydrates to provide the energy needed. The apparent imbalance in the nitrogen cycle would not be sustainable, so other possible mechanisms of acquiring combined nitrogen should be explored. Full article

Forage sorghum is widely used in the southern Great Plains because of its drought tolerance, high biomass productivity, and suitability for multi-cut hay systems; however, information on nitrogen (N) management for forage production and quality in the region remains limited. This study evaluated the effects of N rate and application timing on forage sorghum biomass production and quality at two Oklahoma locations during 2021 and 2023. Biomass production increased with N fertilization at both locations, but response functions differed between sites, with a quadratic response at one location and a linear response at the other. Split N applications primarily altered seasonal biomass distribution by increasing second-harvest regrowth contribution, although total seasonal biomass increased only at the highest split N rate treatment. Forage quality was affected more strongly by harvest timing than by N rate or application timing, with second-harvest forage exhibiting lower fiber concentrations and greater total digestible nutrients. Nitrate concentrations in the forage increased with N rate but remained well below livestock toxicity thresholds. Overall, these results indicate that forage sorghum N management in multi-cut systems should balance sufficient early season N supply to maximize initial biomass production with continued N availability to sustain regrowth productivity and improve seasonal forage distribution. Full article

Despite the pivotal importance of soil microbial communities in regulating the terrestrial carbon (C) cycle and ecosystem functioning, their vertical patterns and their responses to long-term nitrogen (N) deposition, in terms of microbial biomass and relative abundance, still remain unclear, particularly for fungi versus (vs.) bacteria and Gram-positive (GP) vs. -negative (GN) bacteria, where they traditionally have contrasting biological characteristics. In this study, we investigated the responses of GP and GN bacteria, total bacteria (TB), and fungi (TF) and their relationships with four nutrient ratios to 10 years of N addition with three N addition rates (control, N2, and N10 representing 0, 2, and 10 g m⁻²yr⁻¹, respectively) across a 100 cm soil profile (0-10-20-30-40-70-100 cm) in a semiarid grassland, both in terms of absolute biomass and relative abundance represented by the amount and percentage of phospholipid fatty acids (PLFAs) (e.g., GP bacterial PLFAs: total PLFAS) of specific microbial groups, respectively. Our results showed that N addition has significant negative effects on the biomass of these four microbial groups across the whole soil profile, while N addition significantly decreased the relative abundance of GN bacteria and increased those of TF and GP bacteria. Additionally, N addition significantly decreased the biomass of TF and GP bacteria in 0–10 cm soil, and of TB and GN bacteria in 0–10, 40–70, and 70–100 cm soils, with the significant increase or decrease mainly occurring at the N10 rate. Our results also showed that the biomass of these four microbial groups decreased with soil depth regardless of N addition, but that of TB and GN bacteria decreased faster than that of TF and GP bacteria did, and further caused the relative abundance of TF and GP bacteria to increase with soil depth. Significant Pearson correlations among the biomass and relative abundance of these microbial taxa with soil pH, total phosphorus, NH₄⁺-N, and NO₃⁻-N were mainly found in 0–10 cm soil. C:N and NH₄⁺-N: NO₃⁻-N ratios increased with increasing soil depth, while C: phosphorus (P) and N:P ratios decreased. N addition significantly increased C:P and NH₄⁺-N: NO₃⁻-N ratios and decreased N:P ratios, especially under the N10 rate. Among these four nutrient ratios, N:P significantly explained the highest variations in F:B (76%) and GP:GN (38%) across the whole soil profile. Together, these results underline the different responses of soil microbial relative abundance and biomass along the soil profile under long-term N addition. They also suggest a relationship between soil microbial diversity and biomass relationships, and how this links to nutrient ratios in the subsoil needs to be investigated in future. Full article

Balanced fertilization is essential for improving the growth and productivity of Sapindus mukorossi plantations. In this study, a three-year “3414” fertilization experiment was conducted in a six-year-old plantation of the new S. mukorossi cultivar ‘Yuanhua’ to evaluate the effects of nitrogen, phosphorus, and potassium fertilization on vegetative growth, fruit yield, yield stability, and gross output value. Fertilizer levels were set at 0, 300, 600, and 900 kg N ha⁻¹, 0, 250, 500, and 750 kg P₂O₅ ha⁻¹, and 0, 200, 400, and 600 kg K₂O ha⁻¹. NPK fertilization promoted tree height, ground diameter, crown width, and fruit yield compared with the unfertilized control. Among the 14 fertilization treatments, N₁P₁K₂ produced the greatest mean annual increment in tree height, N₁P₂K₁ produced the greatest ground-diameter increment, and N₂P₂K₁ produced the greatest crown-width increment. Fruit yield was highest under N₂P₂K₂ in 2021 and 2022 and under N₂P₂K₁ in 2023. The highest three-year mean yield was obtained under N₂P₂K₂, reaching 1278.93 kg ha⁻¹, and the highest yield stability index was observed under N₂P₂K₂ and N₂P₁K₂. Gross output value showed a pattern consistent with fruit yield, with N₂P₂K₂ producing the highest values in 2021 and 2022 and N₂P₂K₁ producing the highest value in 2023. Among the tested fertilization combinations, N₂P₂K₂, corresponding to 600 kg N ha⁻¹, 500 kg P₂O₅ ha⁻¹, and 400 kg K₂O ha⁻¹, showed the best overall performance for six-year-old S. mukorossi ‘Yuanhua’ plantations under the conditions of this study. These findings indicate that balanced NPK fertilization can improve vegetative growth, fruit yield, yield stability, and gross output value in S. mukorossi ‘Yuanhua’ plantations. Full article

Adequate fertilization is essential for optimizing soybean productivity and seed quality, while supplementary fertilization plays a key role in correcting nutrient deficiencies and supporting plant performance under varying environmental conditions. This study evaluated the effects of the foliar application of macro- and micronutrients enriched with free amino acids and Ascophyllum nodosum extract applied at two phenological stages—six fully developed trifoliate leaves (V6) and beginning flowering (R1)—on soybean grain yield, protein content and oil content. Experiments were conducted over two growing seasons at ARDS Turda, Romania, using a randomized complete block design with three replications to compare three fertilization treatments: basic mineral fertilization (control), mineral fertilization supplemented with foliar application at the V6 vegetative stage, and mineral fertilization supplemented with foliar application at the R1 reproductive stage. Basic fertilization was performed before sowing using granulated nitroclacium at a rate of 100 kg ha⁻¹. Foliar fertilization included Naturamin WSP applied at a rate of 0.5 kg ha⁻¹ and Pleniflor and Naturfruit at a rate of 2 L ha⁻¹. Foliar fertilization at the V6 stage significantly improved grain yield in most cultivars, with increases ranging from 1% to 18%, particularly in the 000 and 00 maturity groups (MGs). Across the maturity groups, the highest average yields were recorded in MG 0 cultivars (up to 2845 kg ha⁻¹). In contrast, foliar application at the R1 stage was more effective in increasing seed protein content, with improvements of up to 11% in early maturity cultivars. Oil content showed only minor and inconsistent responses, with maximum increases of 4% depending on genotype. Linear Discriminant Analysis (LDA) revealed that environmental conditions and genotype explained most of the observed variation (Axis 1 = 89.91%, Axis 2 = 7.79%), indicating that cultivar response to foliar fertilization was strongly influenced by genotype × environment interactions. The effectiveness of foliar fertilization depends on application timing, cultivar maturity group and environmental conditions. Full article

Global food demand is projected to rise by approximately 56 percent between 2010 and 2050, intensifying reliance on synthetic nitrogen fertilizer during a time when only about half of all applied nitrogen is recovered by crops, with the remainder split between genuine environmental loss and retention within soil and biomass pools. The fraction that is genuinely lost drives substantial economic costs and contributes disproportionately to global nitrous oxide emissions, a greenhouse gas with a warming potential far exceeding that of carbon dioxide. This review synthesizes recent literature across three interdependent domains including nitrogen use efficiency strategies spanning agronomic, genetic, and microbial approaches, decarbonization pathways for ammonia synthesis ranging from conventional to green production routes, and gas sensing technologies for monitoring ammonia and nitrous oxide emissions in agricultural settings. Rather than treating these domains separately, this review proposes that their effects on overall emissions are complementary and potentially compounding rather than strictly additive. Efficiency improvements reduce the total fertilizer volume subject to production emissions, while cleaner production cannot offset nitrogen loss in the field. The exact extent of any combined benefit depends on the relative proportion of field emissions and production emissions within each farming system. Another important finding is the pronounced asymmetry in monitoring readiness. Ammonia sensing has reached field-deployable maturity for detection and concentration monitoring. In contrast, nitrous oxide sensing remains constrained by unresolved challenges in sensitivity and long-term stability despite the gas’s significant contribution to climate change. This asymmetry limits the verification of mitigation outcomes at farm and regional scales. The review further identifies that intervention effectiveness depends on farm structure in the studied context, that global nitrogen policy remains weighted toward incentivizing use rather than reducing pollution, and that the evidence base surveyed here is geographically uneven. Together, these findings indicate that reconciling rising food production with greenhouse gas reduction targets requires integrated frameworks linking field nitrogen budgets, production emissions, and monitoring capability, alongside policy instruments designed around their interdependence. Full article