Excess Nitrogen Research Articles (Page 1)

An incoherent feed-forward loop coordinates nitrate uptake and tillering in wheat.

Selenium nanoparticles efficiently inhibit M1 macrophage polarization by regulating selenoprotein to scavenge ROS in alleviating rheumatoid arthritis.

Long-term excessive nitrogen application decreases spring maize nitrogen use efficiency via suppressing root physiological characteristics

Abstract Background The decline in soil organic carbon accumulation caused by intensified nitrogen deposition is concerning. Although phosphorus input may alleviate the negative impacts, there is still a research gap regarding the mechanisms, particularly those involving the soil biota, that drive the stability of soil organic carbon. Methods We conducted a 2-year nitrogen (0, 30 and 90 kg N ha – 1 yr – 1 ) and phosphorus (0, 30 kg P ha – 1 yr – 1 ) addition experiment with six treatments in a 25-year-old Pinus massoniana plantation in subtropical China. Results The addition of external nutrients improved soil nutrient availability but led to a decrease in pH. Low nitrogen input promoted the particulate organic carbon (POC) and total organic carbon, whereas high nitrogen input had the opposite effect. Phosphorus addition alleviated these negative impacts to some extent. Nitrogen and phosphorus addition significantly affected the dissimilarity of soil biological communities. Nitrogen treatments generally reduced the alpha diversity index of soil bacteria, while the trend for fungi was the opposite. Arthropods showed a rise followed by a decline, with phosphorus addition weakening these effects. Soil respiration decreased with increasing nitrogen addition, and phosphorus addition didn’t alter this trend. The POC was primarily influenced by the soil environment-microorganism-respiration and environment-microorganism pathways, whereas the mineral-associated organic carbon (MAOC) was mainly influenced by the soil environment-arthropod pathway. POC (Path coefficient, pc = 0.524) and MAOC (pc = 0.237) directly determine the accumulation of organic carbon. This conceptual model explained 59.4% of the variation in total organic carbon (Goodness-of-fit, GOF = 0.594), thereby delineating the integrated mechanisms underlying SOC accumulation. Conclusions Excessive nitrogen input was unfavorable for organic carbon accumulation, while phosphorus addition partially mitigated the negative effects of nitrogen excess. Under this context, active organic carbon was significantly influenced by soil microorganisms and soil respiration, whereas stable organic carbon was primarily affected by soil arthropods. Graphical Abstract

ABSTRACT To fully exploit the potential of drinking water treatment residue (DWTR) for mitigating excessive nitrogen (N) and phosphorus (P) discharges responsible for water eutrophication, a straightforward precipitation process was used to produce Mg(OH)2-modified drinking water treatment residue (Mg-DWTR). The resulting material can simultaneously remove N and P and exhibit high adsorption capacity. The effects of solution pH, adsorbent dosage, reaction time, initial concentration and coexisting substances on the simultaneous removal of ammoniacal nitrogen (NH4 +-N) and total phosphate (TP) by Mg-DWTR were assessed. Mg-DWTR exhibited high removal capacity across a broad pH range (3–9). The adsorption process applied both pseudo-second-order and Langmuir kinetic models, with predicted maximum adsorption capacities of 43.771–50.295 mg g−1 (NH4 +-N) and 82.050–89.881 mg g−1 (TP), the adsorption process is exothermic. After five reuse cycles, Mg-DWTR retained adsorption capacities of 8.541 mg g−1 for NH4 +-N and 20.511 mg g−1 for TP. Additionally, the adsorption capacity of Mg-DWTR was markedly suppressed in the presence of K+, SO4 2−, citric acid, and humic acid. SEM-EDS, XRD, and FTIR analyses before and after adsorption revealed multiple mechanisms governing the adsorption process. Among these, the primary removal pathway for NH4 +-N and TP is due to the formation of struvite crystals. Additionally, ligand exchange, electrostatic attraction, and physical adsorption synergistically enhance the removal of nutrients. This work provides fresh insights into N and P removal in aquatic environments and the resource utilisation of DWTR, realising the concept of ‘using waste to treat waste’.

Soybean, a symbiotic nitrogen-fixing crop, experiences suppressed nodule nitrogen fixation under excessive nitrogen fertilizer. Nitric oxide (NO) is a key signaling molecule regulating development and stress, primarily via protein S-nitrosylation, although its role in soybeans is unclear. Using a unilateral nodulation system, treatments with nitrogen, an NO scavenger, and an NO donor were applied. Results showed that nitrogen application increased the NO content in the nodules and reduced the nitrogen fixation capacity. Conversely, the NO scavenger lowered the NO levels but enhanced fixation. Exogenous NO inhibited fixation by damaging the nodule structure, reducing leghemoglobin, and disrupting NO homeostasis. Quantitative proteomics with iodoTMT labeling identified 287 S-nitrosylation sites on 238 nodule proteins. Nitrogen-altered proteins were involved in nitrogenase activity, stress response, and ABC transporters. This study establishes the 'nitrogen level-NO signal-S-nitrosylation-nodule function' pathway, offering molecular insights into S-nitrosylation's role in nodule regulation.

ABSTRACT Background Soil health degradation is a major threat to European food security, biodiversity, and climate stability. While scientists have debated how to define soil health during recent decades, a quantifiable framework for monitoring, management, and policy remains lacking. Aim We introduce SHERPA (Soil Health Evaluation, Rating Protocol, and Assessment) as a framework for discussion and present a first quantitative soil health assessment across Europe. Methods All major soil degradation processes (with the exception of organic contamination) were scored, averaged, and subtracted from the intrinsic soil health resulting in quantitative final scores. Results As reported before, cropland soils throughout Europe are highly degraded. Surprisingly, soil health of grasslands is also very negatively impacted. Soil erosion, nutrient surplus, and pesticide risk are largely driving poor soil health aligning with reported high biodiversity loss in agricultural land. Forest soils are also surprisingly low in health, mainly because of nitrogen surplus, reflecting documented widespread forest decline from nutrient imbalances. Interactive maps highlight specific threats to soil health across Europe, offering valuable insights for targeted action. Conclusions SHERPA is able to quantify soil health across Europe. However, at the current state of data availability, soil health is likely to be overestimated. Monitoring data of soil structure, compaction, pesticide spread and, in forest ecosystems, disturbance of humus layer are urgently needed for final assessment of soil health.

Eutrophication of freshwater bodies is primarily caused by excessive nitrogen and phosphorus, resulting in significant environmental challenges, including harmful algal blooms and hypoxia. This review examines the potential for natural and modified zeolites to act as adsorbents and regulate nutrient concentrations in eutrophic freshwater ecosystems, excluding applications for wastewater or industrial water effluents. Natural zeolites are effective adsorbents of ammonium, whereas modified zeolites (with aluminum, iron, calcium, and many others) have been noted to have enhanced phosphate adsorption and a higher overall nutrient removal efficiency. The application of modified zeolites for controlling eutrophication in freshwater bodies has proven to have high efficiency in adsorbing nitrogen and phosphorus, resulting in reduced nutrient release from sediments and improved water quality in shallow lakes and reservoirs. This review describes the adsorption mechanisms and modification methods, with an appreciation for the multifunctional role of zeolites in nutrient immobilization and capping sediments. Finally, it presents the potential to use zeolite-based materials in eutrophic freshwater restoration through sustainable circular economy approaches. Zeolite materials present ample environmental applications for cost-effective and targeted mitigation approaches to freshwater eutrophication.

Both avian and nonavian reptiles excrete excess nitrogen in solid form─colloquially termed "urates"─as an evolutionary adaptation that aids in water conservation. Yet, there are many open questions regarding the composition, structure, and assembly of these biogenic materials. Here, analyses of urate excretions from ball python (Python regius) and 20 other reptile species reveal a clever and highly adaptable system employed to handle both nitrogenous waste and salts. Primitive species excrete urates consisting of 1-10 μm microspheres of turbostratic uric acid monohydrate (UAM) nanocrystals. The nanocrystals' high surface area and ionizable nature provides a platform to coeliminate substoichiometric concentrations of various salts through surface-ion pairing. In contrast, the granular urates produced by species from more advanced snake lineages are phase mixtures consisting of predominantly ammonium urate hydrate (AUH) and smaller amounts of other crystalline forms. Identification of microspheres as a minor but highly soluble component of these excretions suggests their likely role as reactive precursors to AUH, a hypothesis supported by in vitro experiments. Importantly, this points to a previously unrecognized physiologic function of uric acid, namely the ability to sequester ammonia by transforming it into a solid. The potential implications of this function in other species are discussed.

The eutrophication of natural water is a severe environmental risk faced by coastal marine ecosystems, and the excess nitrogen and phosphorus in aquaculture effluent are one of the main sources of environmental pollution. Effectively reducing as well as controlling the phosphorus content in aquaculture effluent is of great importance for alleviating eutrophication and the governance of coastal environments. This study focuses on addressing phosphorus pollution by developing novel bimetallic Ce-Al-MOFs adsorbents via the microwave-assisted rapid synthesis method, among which the monomer Ce3Al3-BDC3 exhibits excellent phosphate adsorption capacity (136.99 mg P g−1) and great removal efficiency over a wide pH range (2~10). Batch experiments reveal that the adsorption is followed by pseudo-second-order kinetics and the Langmuir isotherm model, indicating monolayer chemisorption. The MOFs material shows high selectivity for phosphorus even under the interference of co-existing anions, as well as excellent reusability, retaining over 65% removal efficiency after six adsorption–desorption cycles. Field tests in coastal areas and indoor aquaculture systems both achieve over 97% phosphate removal, meeting discharge standards. A series of characterization methods identify ligand exchange, electrostatic interactions and surface complexation as key adsorption mechanisms. The Ce-Al-MOFs present a promising solution for mitigating eutrophication and managing aquaculture wastewater sustainably.

Pineapple translucency is a major physiological disorder in ‘Tainong 17’ (Golden Diamond) that severely impairs fruit quality, storability, and market value, yet its physiological basis remains poorly understood. To clarify the underlying mechanisms, we conducted two seasons of field surveys across 24 plots in eleven pineapple orchards in Hainan, China, comparing translucent and healthy fruits in terms of plant growth, nutrient status, fruit quality, cell wall composition, and soil properties. Our results showed that translucency significantly reduced fruit quality, with soluble solids and ascorbic acid contents decreasing by 9.7% and 16.3%, respectively. Translucent plants exhibited markedly increased biomass, whereas fruit dry matter was reduced by 21.6%. In addition, affected plants accumulated 40–70% more nitrogen in leaves, stems, and fruits, accompanied by 23% and 14% reductions in abscisic acid concentrations in leaves and fruits, respectively. Calcium and boron allocation to fruits was impaired, with fruit Ca and B contents decreasing by 25.1% and 50.4%, respectively, despite increased levels in vegetative organs. These nutrient imbalances coincided with a 16.4% decrease in protopectin, a 5.3% decrease in cellulose, and a 15.5% increase in soluble pectin, indicating cell-wall loosening. Collectively, our findings demonstrate that excessive nitrogen input disrupts carbon–nitrogen metabolism and ABA signaling, elevates fruit N/Ca ratios, and accelerates cell-wall remodeling, thereby predisposing fruits to translucency, particularly under humid or rainy conditions.

Winter wheat covers approximately 2.21 × 108 ha globally, making it the most widely cultivated cereal crop in the world. In recent years, integrated water and fertilizer management has significantly improved winter wheat yield and nitrogen use efficiency; however, quantitative assessments of nitrogen cycling under different fertilizer forms in such high-yield systems remain limited. From 2022 to 2024, a two-year field experiment was conducted in drip-irrigated winter wheat fields in northern China. Four nitrogen fertilizer forms were applied: nitrate nitrogen fertilizer (NON), ammonium nitrogen fertilizer (NHN), amide nitrogen fertilizer (CON), and urea ammonium nitrate fertilizer (UAN), along with an unfertilized control (CK). Compared with NON, NHN, and CON, UAN reduced cumulative N2O emissions by 10.40–15.64% and NH3 volatilization by 2.04–9.33% (p < 0.05). It also increased the leaf area index and biomass accumulation at maturity, as well as grain yield (3.70–10.28%), nitrogen harvest index (4.58–12.88%), and nitrogen use efficiency (12.14–39.25%) (p < 0.05). Furthermore, UAN significantly decreased the net nitrogen surplus (24.18–45.70%) and nitrogen balance values (25.64–55.82%) (p < 0.05). Correlation analysis indicated that the reduction in nitrogen balance was primarily attributed to lower N2O emissions and improved nitrogen use efficiency (p < 0.05). In conclusion, the application of urea ammonium nitrate under integrated water–fertilizer management achieved higher yield, greater efficiency, and environmentally sustainable production in drip-irrigated winter wheat systems in northern China.

Areca (Areca catechu L.) is an important economic crop in tropical regions, but excessive nitrogen application leads to low nitrogen fertilizer utilization efficiency (approximately 30%). Vanilla (Vanilla planifolia Andrews) can be intercropped with areca to enhance land use efficiency. However, the impact of combined nitrogen reduction and Arbuscular mycorrhizal fungi (AMF) inoculation on the intercropping system of areca and vanilla remains unclear. This study examined the impact of nitrogen reduction (at levels of conventional fertilization, a 30% reduction and a 60% reduction) and the inoculation of AMF on the photosynthetic characteristics, physiological metabolism, and nitrogen utilization within an areca and vanilla intercropping system, employing a two-factor experimental design. The nitrogen reduction significantly inhibited SPAD value (chlorophyll content) (decreased by 46.21%), net photosynthesis (Pn) (decreased by 71.13%), and transpiration rate (Tr) (decreased by 44.34%) of vanilla without inoculation of AMF, but had little effect on the photosynthesis of areca. Inoculation with AMF, notably Funneliformis mosseae, alleviated the adverse effects of reduced nitrogen on vanilla. The net photosynthesis and intercellular CO2 concentration (Ci) significantly increased by 76.23% and 69.48%, respectively. Additionally, the nitrogen uptake efficiency of the areca was improved, with root vitality increasing by 39.96%. Additionally, AMF enhanced the activities of acid phosphatase (ACP) (increased by 38.86% in vanilla) and nitrate reductase (NR) (increased by 53.77% in areca), promoting soil mineral nutrient activation and nitrogen metabolism. The nitrogen reduction combined with AMF inoculation can improve the nitrogen use efficiency of the areca and vanilla intercropping system, revealing its synergistic mechanism in the tropical intercropping system.

BackgroundSecondary soil salinization adversely affects plant growth in greenhouse in China. Previous studies have suggested that the putative molybdate transporter SlMOT2 may be involved in nitrate stress tolerance in tomatoes. However, the precise regulatory mechanisms remain unclear.ResultsCalcium nitrate stress significantly induced the expression of the SlMOT2 gene. In comparison with wild-type (WT) plants, SlMOT2-overexpressing (OE) plants exhibited enhanced tolerance to nitrate stress, as evidenced by lower malondialdehyde (MDA) content, reduced hydrogen peroxide (H₂O₂) accumulation, decline in nitrate accumulation, significantly increased antioxidant enzyme activity, and a higher net photosynthetic rate under nitrate stress conditions, whereas slmot2 knockout mutant plants showed nitrate stress sensitivity. An increasing sulfur level and less nitrate content were also found in overexpression lines of SlMOT2 under calcium nitrate stress. Transcriptomic analysis revealed that nitrate stress induced the upregulation of numerous genes, with the differentially expressed genes (DEGs) in OE plants being significantly enriched in phenylpropanoid biosynthesis, abscisic acid (ABA) synthesis, amino sugar and nucleotide sugar metabolism, and amino acid metabolism in comparison with WT plants.ConclusionsThe SlMOT2 gene confers nitrate stress tolerance in tomato plants, likely through the following molecular mechanisms: (1) enhancing the biosynthesis of antioxidant compounds to improve reactive oxygen species (ROS)-scavenging capacity and maintain photosynthetic efficiency;(2) activating plant hormone signaling transduction pathways to potentiate stress responses; (3) promoting sulfate uptake to rebalance excess nitrogen in planta, thereby establishing a new nitrogen-sulfur homeostasis. These findings establish a theoretical framework for improving nitrate stress resistance during tomato cultivation.Supplementary InformationThe online version contains supplementary material available at 10.1186/s12870-025-07383-z.

Objective: To explore the efficacy and safety of instantly generated inhaled nitric oxide (iNO) for treating neonatal pulmonary arterial hypertension (PAH) complicated with severe hypoxic respiratory failure. Methods: This single-center, single-arm, prospective study included 32 neonates with PAH complicated with hypoxic respiratory failure who were hospitalized in the neonatal intensive care unit (NICU) of Beijing Children's Hospital Affiliated to Capital Medical University from March 2023 to March 2025 and received immediate iNO generation therapy. The demographic data, maternal pregnancy, mechanical ventilation parameters, arterial blood gas indexes, other hospitalization data and safety indexes of iNO treatment were collected. The time point for starting iNO treatment was set as 0 h, and the observation time points were 1, 6, 12, 24, 48 h after treatment and when iNO treatment was stopped. The positive reaction of iNO treatment was defined as the decrease of oxygenation index (OI)>10% or the increase of arterial partial pressure of oxygen (PaO2)>10% after treatment. The OI, mechanical ventilation parameters, arterial blood gas index changes and treatment positive reaction ratio were analyzed to evaluate the effectiveness of iNO treatment, and the nitrogen dioxide concentration, methemoglobin (MetHb) concentration and other indicators were analyzed to evaluate the safety of iNO treatment. Paired t test or Wilcoxon signed rank sum test was used to compare the observation indexes at different treatment times. Friedman test was used to compare the concentration of nitrogen dioxide and MetHb at multiple treatment times. Receiver operating characteristic (ROC) curve was used to analyze the best cut-off value of OI related indexes to distinguish the treatment outcome of iNO. Results: Among 32 neonates, 18 (56%) were males and 14 (44%) were females, the gestational age was 38 (35, 39) weeks, the birth weight was 3.1 (2.3, 3.4) kg, and the age of enrollment was 3 (2, 8) days. The OI and the mean airway pressure at 48 h after treatment were both lower than those at 0 h ((10.4±2.0 vs. 22.6±2.5, 13.0 (12.0, 14.0) vs. 14.0 (13.0, 16.0) cmH2O, 1 cmH2O=0.098 kPa, both P<0.05). The fraction of inspired oxygen at 24 and 48 h after treatment were both lower than those at 0 h (both P<0.05). The PaO2 at 6, 12, 24 and 48 h after treatment were all higher than those at 0 h (all P<0.05). The proportion of positive reactions to iNO treatment was 20 neonates (63%), 22 neonates (69%), 23 neonates (72%), 23 neonates (72%) and 26 neonates (8%) at 1, 6, 12, 24, 48 h after treatment, respectively. No occurrence of methemoglobinemia, excessive nitrogen dioxide concentration, or device related adverse events were observed. Out of 32 neonates, a total of 24 neonates (75%) were cured or improved and discharged according to medical advice, while 8 neonates (25%) died in the hospital. The best cut-off value of OI at 0 h and the decline range of OI at 12 h to distinguish the outcome of hospitalization were 24.8 and 22.2%, respectively. Conclusion: It was effective and safe to use instantly generated iNO to treat neonatal PAH with severe hypoxic respiratory failure.

Nitrogen fertilizers in irrigated agriculture improve cropland productivity, but contribute to groundwater contamination, air pollution, and greenhouse gas emissions. While California has implemented agricultural water quality regulations since the 1980s, targeted efforts to address nitrate contamination through nitrogen application reporting and management have been emphasized more recently under the Irrigated Lands Regulatory Program. This study uses a unique, field-level dataset from the Kings River Water Quality Coalition in California’s Central Valley to examine nitrogen management practices, including common combinations of practices (bundling), across crop types. The analysis draws on four years of data from Irrigation and Nutrient Management Plans and details nitrogen application and management strategies. The results show that in 80% of fields across crops, between 50 and 300 pounds per acre (lbs/acre) of nitrogen is applied. Crop-level nitrogen applied minus nitrogen removed (A-R) values show substantial variation, with walnuts showing a nitrogen surplus (+65.5 lbs/acre) and alfalfa a significant deficit (−424.5 lbs/acre). Many growers adopt multiple practices, with 26% of fields utilizing six practices and 24% using five. Such bundling may provide growers with more flexibility in managing nitrogen applications. Further research is needed to evaluate the effect of various nitrogen management practices on fertilizer use and water quality effects.

Abstract In this gradient study, we examined the effects of ammonia deposition on vegetation in two different heathland habitats, a dry and dune heath (Annex I code: 4030 &amp; 2140, respectively). During the summer of 2020, we conducted a vegetation survey and soil sampling along a transect at each heathland with increasing distance to a farm unit(s). At the dry heath, the transect length was ~ 1420 m; at the dune heath, the transect length was ~ 580 m. The dry heath site was mainly in the downwind or crosswind of a pig—and a cattle farm, while the dune heath site was primarily upwind of the farm. The estimated average exceedance range of the upper end of the empirical critical nitrogen load was at dune heath within ~ 400 m. At the dry heath, the upper end of the empirical critical load was estimated to be exceeded along the entire transect. We documented a significant adverse effect of high nitrogen loads on cryptogams at the dune heath and did not observe them at estimated N deposition levels above 22 kg N ha−1 year−1, confirming results from other studies that bryophytes and lichens are sensitive to excess reactive nitrogen. Moreover, we documented a significantly increased graminoid/dwarf shrub ratio on the dune heath closer to the farm, however, nitrogen deposition did seemingly not affect the graminoid/dwarf shrub ratio on the dry heath. At the dry heath, we found a decline in forbs in areas grazed by sheep and horses.

Under the condition of straw returning to the field, appropriate nitrogen fertilizer application is one of the key factors used to improve crop yield and ensure environmental safety. Therefore, an experiment with different rates of nitrogen fertilization was conducted with a randomized block design in Harbin, China. The straw was deeply plowed back into the field after harvest in the autumn. The nitrogen application rates were 0, 75, 150, 180, 225, and 300 kg·ha-1. The purpose of this study is to clarify the appropriate amount of nitrogen fertilizer under the condition of straw returning to the field and to provide technical support for high-yield and high-efficiency maize in cold regions. The results indicated that the yield of maize first increased and then stabilized as the amount of nitrogen fertilizer increased, while the economic benefits first increased and then decreased. When the nitrogen application rate exceeds 225 kg·ha-1 or is lower than 150 kg·ha-1, the economic benefits significantly decrease. When high-nitrogen fertilizer rates of 225 kg·ha-1 and 300 kg·ha-1 were applied, the residual nitrate nitrogen in the soil was increased by 2.1 times and 2.3 times, respectively, compared to before sowing. With the increase in the nitrogen application rate, the nitrogen fertilizer utilization efficiency and agronomic efficiency decreased, and the apparent nitrogen loss and nitrogen surplus significantly increased. Comprehensively considering the maize yield, benefits, and environmental risk factors the suitable nitrogen application rate was in a range of 170.2 kg·ha-1 to 178.2 kg·ha-1 in the first year and 150.0 kg·ha-1 to 171.3 kg·ha-1 in the second year. This work provides a theoretical basis and technical support for the rational application of nitrogen fertilizer and high-yield and high-efficiency spring maize under the condition of straw returning to the field.

NH3, N2O, NO and NO2 losses, emission factors and reduction mechanisms under different N managements from greenhouse vegetable soils.

Effects of microplastics and excessive nitrogen pollution on oat growth and soil nitrogen cycling.