Comparison of Mechanisms of N-Nitrosation and N-Nitration of Ammonia and Dimethylamine by Reactive Nitrogen Oxygen Species:A Theoretical Study

Reactive nitrogen oxygen species（RNOS） implicate damage in biological systems,especially leading to inflammation,neurodegenerative and cardiovascular diseases,and cancer by altering the functions of biomolecules through the N-nitrosation and N-nitration reactions.The mechanisms of N-nitrosation and N-nitration reactions of ammonia and dimethylamine by RNOS,i.e.,N2O3,N2O4,N2O5 and ONOOH,were investigated at the CBS-QB3 level of theory.The computational results indicate that the N-nitrosation reaction prefers a concerted mechanism,in which a H-abstraction and ON-addition occur simultaneously,whereas a stepwise mechanism（also called a free radical mechanism） is more favorable for most nitrating agents in the N-nitration reaction,where NO2 first abstracts a hydrogen atom from the nitrogen of amines and then the induced intermediate reacts with NO2 once more to form the nitration products.However,the concerted pathway is still a feasible process for some nitrating agents such as N2O5.In addition,the relationship between the structures of different RNOS and their nitrosating or nitrating abilities was also investigated.

Study on the protective effect of Tadehaginoside on the damage of endothelial cell mitochondria induced by reactive nitrogen

Objective:To investigate the protective effect of Tadehaginoside on vascular endothelial cell injury induced by reactive nitrogen.Methods:MTT colorimetry was used to detect the effect of Tadehaginoside on the survival rate of EA.hy 926 endothelial cells in the concentration range of 5~160μmol/L;1 h after pre-administration of Tadehaginoside,0.5 mM GSNO was given to damage endothelial cells.Detect the mitochondrial specific factors COX-1,ND-1 and inflammatory factor IL-1βof EA.hy 926 cells damaged by GSNO by Real time-PCR method gene intervention.At the same time,Western blot was used to detect the changes in Bax and Bcl-2 protein expression.The mitochondrial membrane potential kit(JC-1)was used to detect the change of Tadehaginoside on the mitochondrial membrane potential after GSNO induced EA.hy 926 cell injury.Results:The results of the MTT method showed that Tadehaginoside had no obvious cytotoxicity on EA.hy 926 cells in the range of 5~160μmol/L,and the optimal protective concentration of the drug was 40μmol/L.Western Blot method showed that BAX protein expression increased in a time-dependent manner after GSNO damaged EA.hy 926 cells over time,while Bcl-2 protein expression was the opposite.Real time-PCR results showed that Tadehaginoside can significantly up-regulate COX-1 gene(P<0.05),and can significantly inhibit GSNO induced ND-1(P<0.05)and IL-1βgene up-regulation(P<0.01).At the same time,the results of JC-1 showed that Tadehaginoside could significantly protect the mitochondrial membrane potential from GSNO damage.Conclusion:The GSNO damage model may induce the increase of Bax and other pro-apoptotic proteins through mitochondrial DNA damage and reduce the expression of anti-apoptotic factor Bcl-2.Tadehaginoside has a certain protective effect on endothelial cell mitochondrial damage induced by reactive nitrogen,and its mechanism is related to inhibiting the expression of ND-1 and IL-1βgenes and upregulating the expression of COX-1 genes.

MEASUREMENTS OF REACTIVE NITROGEN SPECIES IN THE EASTERN CHINA DURING THE EXPERIMENT PEM-WEST A

Measurements of NO_x(NO+NO_2),HNO_3,particulate nitrate,and total odd nitrogen NO_y were made at Lin atmosphere regional background station during the NASA GTE/PEM-WEST A in the fall of 1991.NO_x and N were measured using chemiluminescence detectors.HNO_3 and aerosol nitrate(NO_3^-)were collected by a filter syst NO_x concentration exhibits a significant diurnal variation:maximum occurring in the evening and postsunrise w peak occurring following sunrise.Unlike NO_x,NO_y does not show distinct diurnal variations.From the ratios day/night NO_x concentration and the diurnal cycles of two kinds of weather conditions,it is clear that photochemical production of NO_x varies with solar radiation.NO_x is the major component of total odd nitro NO_y and NO_2 is the major portion of NO_x as well.The regional background concentrations of NO_x,NO_y,aerosol trate(NO_3^-)and HNO_3 range from 4.77 to 7.02 ppb,9.24 to 10.95 ppb,0.33 to 2.38 ppb and 0.31 to 0.97 ppb in a day average,respectively.In the eastern China,the biomass burning is an important local emission source of nitro species.The ratios of NO/NO_2,NO_x/NO_y,HNO_3/NO_y,NO_3^-/NO_y and HNO_3/NO_x are also discussed in paper.

NIR-triggered on-site NO/ROS/RNS nanoreactor:Cascade-amplified photodynamic/photothermal therapy with local and systemic immune responses activation

Photothermal and photodynamic therapies(PTT/PDT)hold promise for localized tumor treatment,yet their full potential is hampered by limitations such as the hypoxic tumor microenvironment and inadequate systemic immune activation.Addressing these challenges,we present a novel near-infrared(NIR)-triggered RNS nanoreactor(PBNO-Ce6)to amplify the photodynamic and photothermal therapy efficacy against triple-negative breast cancer(TNBC).The designed PBNOCe6 combines sodium nitroprusside-doped Prussian Blue nanoparticles with Chlorin e6 to enable on-site RNS production through NIR-induced concurrent NO release and ROS generation.This not only enhances tumor cell eradication but also potentiates local and systemic antitumor immune responses,protecting mice from tumor rechallenge.Our in vivo evaluations revealed that treatment with PBNO-Ce6 leads to a remarkable 2.7-fold increase in cytotoxic T lymphocytes and a 62%decrease in regulatory T cells in comparison to the control PB-Ce6(Prussian Blue nanoparticles loaded with Chlorin e6),marking a substantial improvement over traditional PTT/PDT.As such,the PBNO-Ce6 nanoreactor represents a transformative approach for improving outcomes in TNBC and potentially other malignancies affected by similar barriers.

Regulatory role of peroxynitrite in advanced glycation end products mediated diabetic cardiovascular complications

The Advanced Glycation End Products(AGE)binding with its receptor can increase reactive oxygen species(ROS)generation through specific signaling mediators.The effect of superoxide(O2-)and O2-mediated ROS and reactive nitrogen species depends on their concentration and location of formation.Nitric oxide(NO)has anti-inflammatory and anticoagulant properties and a vasodilation effect,but NO can be deactivated by reacting with O_(2)^(-).This reaction between NO and O2-produces the potent oxidant ONOO−.Therefore,ONOO-'s regulatory role in AGEs in diabetic cardiovascular complications must considered as a regulator of cardiovascular complications in diabetes.

Description and Application of a Model for Simulating Regional Nitrogen Cycling and Calculating Nitrogen Flux

A regional nitrogen cycle model, named IAP-N, was designed for simulating regional nitrogen （N） cycling and calculating N fluxes flowing among cultivated soils, crops, and livestock, as well as human, atmospheric and other systems. The conceptual structure and calculation methods and procedures of this model are described in detail. All equations of the model are presented. In addition, definitions of all the involved variables and parameters are given. An application of the model in China at the national scale is presented. In this example, annual surpluses of consumed synthetic N fertilizer; emissions of nitrous oxide （N2O）, ammonia （NH3） and nitrogen oxide （NOx）; N loss from agricultural lands due to leaching and runoff; and sources and sinks of anthropogenic reactive N （Nr） were estimated for the period 1961-2004. The model estimates show that surpluses of N fertilizer started to occur in the mid 1990s and amounted to 5.7 Tg N yr^-1 in the early 2000s. N20 emissions related to agriculture were estimated as 0.69 Tg N yr^-1 in 2004, of which 58% was released directly from N added to agricultural soils. Total NH3 and NOx emissions in 2004 amounted to 4.7 and 4.9 Tg N yr^-1, respectively. About 3.9 Tg N yr^-1 of N was estimated to have flowed out of the cultivated soil layer in 2004, which accounted for 33% of applied synthetic N fertilizer. Anthropogenic Nr sources changed from 2.8 （1961） to 28.1 Tg N yr^-1 （2004）, while removal （sinks） changed from to 2.1 to 8.4 Tg N yr^-1. The ratio of anthropogenic Nr sources to sinks was only 1.4 in 1961 but 3.3 in 2004. Further development of the IAP-N model is suggested to focus upon： Ca） inter-comparison with other regional N models; （b） overcoming the limitations of the current model version, such as adaptation to other regions, high-resolution database, and so on; and （c） developing the capacity to estimate the safe threshold of anthropogenic Nr source to sink ratios.

Atmospheric deposition of inorganic nitrogen in a semi-arid grassland of Inner Mongolia, China

Due to increasing global demand for crop production and energy use, more and more reactive nitrogen（Nr） has been generated and emitted to the environment. As a result, global atmospheric nitrogen（N） deposition has tripled since the industrial revolution and the ecological environment and human health have been harmed. In this study, we measured dry and wet/bulk N deposition from July 2013 to December 2015 in a semi-arid grassland of Duolun County, Inner Mongolia, China. The samples of dry and wet/bulk N deposition were collected monthly with a DELTA（DEnuder for Long Term Atmospheric sampling） system and with Gradko passive samplers and a precipitation gauge. The measured results show that the annual mean concentrations of NH_3, NO_2, HNO_3, particulate NH_4~＋（pNH_4~＋） and particulate NO_3^-（pNO_3^-） in atmosphere were 2.33, 1.90, 0.18, 1.42 and 0.42 μg N/m3, respectively, and that the annual mean volume-weighted concentrations of NH_4~＋-N and NO_3^--N in precipitation were 2.71 and 1.99 mg N/L, respectively. The concentrations of Nr components（including NH_3, NO_2, HNO_3, p NH_4~＋, pNO_3^-, NH_4~＋-N and NO_3^--N） exhibited different seasonal variations. Specifically, NO_2 and HNO_3 exhibited higher concentrations in autumn than in summer, while the other Nr components（NH_3, pNH_4~＋, pNO_3^-, NH_4~＋-N and NO_3^--N） showed the highest values in summer. Based on measured concentrations of Nr components and their deposition velocities estimated using the GEOS-Chem global atmospheric chemical transport model, the calculated annual mean dry deposition fluxes were 3.17, 1.13, 0.63, 0.91 and 0.36 kg N/（hm^2·a） for NH_3, NO_2, HNO_3, p NH_4~＋ and pNO_3^-, respectively, and the calculated annual mean wet/bulk deposition fluxes were 5.37 and 3.15 kg N/（hm^2·a） for NH_4~＋-N and NO_3^--N, respectively. The estimated annual N deposition（including dry N deposition and wet/bulk N deposition） reached 14.7 kg N/（hm^2·a） in grassland of Duolun County, approaching to the upper limit of the N critical load（10–15 kg N/（hm^2·a））. Dry and wet/bulk deposition fluxes of all Nr components（with an exception of HNO_3） showed similar seasonal variations with the maximum deposition flux in summer and the minimum in winter. Reduced Nr components（e.g., gaseous NH_3 and p NH_4~＋ in atmosphere and NH_4~＋-N in precipitation） dominated the total N deposition at the sampling site（accounted for 64% of the total N deposition）, suggesting that the deposited atmospheric Nr mainly originated from agricultural activities. Considering the projected future increases in crop and livestock production in Inner Mongolia, the ecological and human risks to the negative effects of increased N deposition could be increased if no mitigation measures are taken.

Scavenging of reactive oxygen and nitrogen species with nanomaterials

Reactive oxygen and nitrogen species （RONS） are essential for normal physiological processes and play important roles in cell signaling, immunity, and tissue homeostasis. However, excess radical species are implicated in the development and augmented pathogenesis of various diseases. Several antioxidants may restore the chemical balance, but their use is limited by disappointing results of clinical trials. Nanoparticles are an attractive therapeutic alternative because they can change the biodistribution profile of antioxidants, and possess intrinsic ability to scavenge RONS. Herein, we review the types of RONS, how they are implicated in several diseases, and the types of nanoparticles with inherent antioxidant capability, their mechanisms of action, and their biological applications.

Modulation of microglial functions by methyl jasmonate

Neuroinflammation contributes to the neurodegenerative processes in Alzheimer＇s disease（AD）;therefore,characterization of novel drug candidates aimed at combatting inflammation in the central nervous system is one of the potential avenues for the development of effective AD treatment and prevention strategies.Non-neuronal microglial cells orchestrate neuroinflammatory reactions,and their adverse activation has been linked to AD pathogenesis.Methyl jasmonate（MJ） has anti-cancer properties and has also been shown to reduce peripheral inflammation in pre-clinical models.Recently,anti-neuroinflammatory activity of MJ was demonstrated in mice,but the exact cellular and molecular mechanisms responsible for this beneficial effect are unknown.We hypothesized that MJ can regulate select microglial functions,and used two different in vitro models of microglia to test this hypothesis.MJ inhibited the production of damaging reactive oxygen species by differentiated human HL-60 promyelocytic leukemia cells without reducing their viability.MJ also selectively upregulated phagocytic activity of murine BV-2 microglia,but had no effect on nitric oxide secretion by these cells.Since microglial phagocytosis can be beneficial for clearance of amyloid β aggregates in AD,the observed upregulation of phagocytic activity by MJ,combined with its inhibitory effect on reactive oxygen species production,supports continued studies of MJ as a candidate drug for managing adverse neuroinflammation in AD.

Injectable reactive oxygen and nitrogen species-controlling hydrogels for tissue regeneration:current status and future perspectives

The dual role of reactive oxygen and nitrogen species(RONS)in physiological and pathological processes in biological systems has been widely reported.It has been recently suggested that the regulation of RONS levels under physiological and pathological conditions is a potential therapy to promote health and treat diseases,respectively.Injectable hydrogels have been emerging as promising biomaterials for RONS-related biomedical applications owing to their excellent biocompatibility,three-dimensional and extracellular matrix-mimicking structures,tunable properties and easy functionalization.These hydrogels have been developed as advanced injectable platforms for locally generating or scavenging RONS,depending on the specific conditions of the target disease.In this review article,the design principles and mechanism by which RONS are generated/scavenged from hydrogels are outlined alongside a discussion of their in vitro and in vivo evaluations.Additionally,we highlight the advantages and recent developments of these injectable RONS-controlling hydrogels for regenerativemedicines and tissue engineering applications.

Effects of nitrogen dioxide and its acid mist on reactive oxygen species production and antioxidant enzyme activity in Arabidopsis plants

Nitrogen dioxide（NO2） is one of the most common and harmful air pollutants. To analyze the response of plants to NO2 stress, we investigated the morphological change, reactive oxygen species（ROS） production and antioxidant enzyme activity in Arabidopsis thaliana（Col-0） exposed to 1.7, 4, 8.5, and 18.8 mg/m3NO2. The results indicate that NO2 exposure affected plant growth and chlorophyll（Chl） content, and increased oxygen free radical（O2-）production rate in Arabidopsis shoots. Furthermore, NO2 elevated the levels of lipid peroxidation and protein oxidation, accompanied by the induction of antioxidant enzyme activities and change of ascorbate（As A） and glutathione（GSH） contents. Following this, we mimicked nitric acid mist under experimental conditions, and confirmed the antioxidant mechanism of the plant to the stress. Our results imply that NO2 and its acid mist caused pollution risk to plant systems. During the process, increased ROS acted as a signal to induce a defense response, and antioxidant status played an important role in plant protection against NO2/nitric acid mist-caused oxidative damage.

Reactive oxygen and nitrogen species regulate porcine embryo development during pre-implantation period:A mini-review

Significant porcine embryonic loss occurs during conceptus morphological elongation and attachment from d 10 to 20 of pregnancy,which directly decreases the reproductive efficiency of sows.A successful establishment of pregnancy mainly depends on the endometrium receptivity,embryo quality,and utero-placental microenvironment,which requires complex cross-talk between the conceptus and uterus.The understanding of the molecular mechanism regulating the uterine-conceptus communication during porcine conceptus elongation and attachment has developed in the past decades.Reactive oxygen and nitrogen species,which are intracellular reactive metabolites that regulate cell fate decisions and alter their biological functions,have recently reportedly been involved in porcine conceptus elongation and attachment.This mini-review will mainly focus on the recent researches about the role of reactive ox-ygen and nitrogen species in regulating porcine embryo development during the pre-implantation period.

Quality enhancement and microbial reduction of mung bean(Vigna radiata)sprouts by non-thermal plasma pretreatment of seeds

Mung bean(Vigna radiata)sprouts are widely consumed worldwide due to their high nutritional value.However,the low yield and microbial contamination of mung bean sprouts seriously reduces their economic value.This study investigates the effects of non-thermal plasma on the quality and microbial reduction of mung bean sprouts by pretreatment of seeds in water for different times(0,1,3 and 6 min).The quality results showed that short-time plasma treatment(1 and 3 min)promoted seed germination and seedling growth,whereas long-time plasma treatment(6 min)had inhibitory effects.Plasma also had a similar dose effects on the total flavonoid and phenolic contents of mung bean sprouts.The microbiological results showed that plasma treatment achieved a reduction of native microorganisms ranging from 0.54 to 7.09 log for fungi and 0.29 to 6.80 log for bacteria at 96 h incubation.Meanwhile,plasma treatment could also efficiently inactivate artificially inoculated Salmonella typhimurium(1.83–6.22 log)and yeast(0.53–3.19 log)on mung bean seeds.The results of seed coat permeability tests and scanning electron microscopy showed that plasma could damage the seed coat structure,consequently increasing the electrical conductivity of mung bean seeds.The physicochemical analysis of plasma-treated water showed that plasma generated various long-and short-lived active species[nitric oxide radicals(NO·),hydroxyl radicals(·OH),singlet oxygen(1O2),hydrogen peroxide(H_(2)O_(2)),nitrate(NO_(3)^(-)),and nitrite(NO_(2)^(-))]in water,thus the oxidizability,acidity and conductivity of plasma-treated water were all increased in a treatment timedependent manner.The result for mimicked chemical mixtures confirmed the synergistic effect of activity of H_(2)O_(2),NO_(3)^(-)and NO_(2)^(-)on bacterial inactivation and plant growth promotion.Taken together,these results imply that plasma pretreatment of mung bean seeds in water with moderate oxidizability and acidity is an effective method to improve the yield of mung bean sprouts and reduce microbial contamination.

Effect of low-temperature plasma on the degradation of omethoate residue and quality of apple and spinach

Dielectric barrier corona discharge was developed to generate low-temperature plasma(LTP) to treat apple and spinach samples contaminated with omethoate. Experimental results showed that,after 20 min exposure, the degradation rate of omethoate residue in apple and spinach was(94.55± 0.01)% and(95.55 ± 0.01)%, respectively. When the treatment time was shorter than 20 min,the contents of moisture, vitamin C and beta-carotene were not affected by LTP. Exploration of related mechanisms suggested that LTP might destroy unsaturated double bonds of omethoate and produce phosphate ion, eventually leading to omethoate destruction. It is concluded that appropriate dosage of LTP can effectively degrade omethoate residue in fruits and vegetables without affecting their quality.

Metal natural product complex Ru-procyanidins with quadruple enzymatic activity combat infections from drug-resistant bacteria

Bacterial infection hampers wound repair by impeding the healing process.Concurrently,inflammation at the wound site triggers the production of reactive oxygen species(ROS),causing oxidative stress and damage to proteins and cells.This can lead to chronic wounds,posing severe risks.Therefore,eliminating bacterial infection and reducing ROS levels are crucial for effective wound healing.Nanozymes,possessing enzyme-like catalytic activity,can convert endogenous substances into highly toxic substances,such as ROS,to combat bacteria and biofilms without inducing drug resistance.However,the current nanozyme model with single enzyme activity falls short of meeting the complex requirements of antimicrobial therapy.Thus,developing nanozymes with multiple enzymatic activities is essential.Herein,we engineered a novel metalloenzyme called Ru-procyanidin nanoparticles(Ru-PC NPs)with diverse enzymatic activities to aid wound healing and combat bacterial infections.Under acidic conditions,due to their glutathione(GSH)depletion and peroxidase(POD)-like activity,Ru-PC NPs combined with H2O2 exhibit excellent antibacterial effects.However,in a neutral environment,the Ru-PC NPs,with catalase(CAT)activity,decompose H2O2 to O2,alleviating hypoxia and ensuring a sufficient oxygen supply.Furthermore,Ru-PC NPs possess exceptional antioxidant capacity through their superior superoxide dismutase(SOD)enzyme activity,effectively scavenging excess ROS and reactive nitrogen species(RNS)in a neutral environment.This maintains the balance of the antioxidant system and prevents inflammation.Ru-PC NPs also promote the polarization of macrophages from M1 to M2,facilitating wound healing.More importantly,Ru-PC NPs show good biosafety with negligible toxicity.In vivo wound infection models have confirmed the efficacy of Ru-PC NPs in inhibiting bacterial infection and promoting wound healing.The focus of this work highlights the quadruple enzymatic activity of Ru-PC NPs and its potential to reduce inflammation and promote bacteria-infected wound healing.

H_2O_2-induced Leaf Cell Death and the Crosstalk of Reactive Nitric/Oxygen Species

In plants, the chloroplast is the main reactive oxygen species （ROS） producing site under high light stress. Catalase （CAT）, which decomposes hydrogen peroxide （H2O2）, is one of the controlling enzymes that maintains leaf redox homeostasis. The catalase mutants with reduced leaf catalase activity from different plant species exhibit an H2O2-induced leaf cell death phenotype. This phenotype was differently affected by light intensity or photoperiod, which may be caused by plant species, leaf redox status or growth conditions. In the rice CAT mutant nitric oxide excess 1 （noe1）, higher H2O2 levels induced the generation of nitric oxide （NO） and higher S-nitrosothiol （SNO） levels, suggesting that NO acts as an important endogenous mediator in H2O2-induced leaf cell death. As a free radical, NO could also react with other intracellular and extracellular targets and form a series of related molecules, collectively called reactive nitrogen species （RNS）. Recent studies have revealed that both RNS and ROS are important partners in plant leaf cell death. Here, we summarize the recent progress on H2O2-induced leaf cell death and the crosstalk of RNS and ROS signals in the plant hypersensitive response （HR）, leaf senescence, and other forms of leaf cell death triggered by diverse environmental conditions.

Recent advances and applications of single atom catalysts based electrochemical sensors

Single atom catalysts(SACs)have attracted considerable attention due to their unique structures and excellent catalytic performance,especially in the area of catalysis science and energy conversion and storage.In recent years,SACs have emerged as a new type of sensing material for constructing electrochemical sensors(ECSs),presenting excellent sensitivity,selectivity,and stability.Herein,we review the recent advances of SACs in electrochemical sensing and discuss the status quo of current SAC-based ECSs.Specifically,the fundamentals of SAC-based ECSs are outlined,including the involved central metal atoms and various supports of SACs in this field,the detection mechanisms,and improving strategies of SAC-based ECSs.Moreover,the important applications of SAC-based ECSs are listed and classified,covering the detection of reactive oxygen and nitrogen species,environmental pollutants,disease biomarkers,and pharmaceuticals.Last,based on abundant reported cases,the current conundrums of SAC-based ECSs are summarized,and the prediction of their future developing trends is also put forward.

Photoactivatable nanogenerators of reactive species for cancer therapy

In recent years,reactive species-based cancer therapies have attracted tremendous attention due to their simplicity,controllability,and effectiveness.Herein,we overviewed the state-of-art advance for photo-controlled generation of highly reactive radical species with nanomaterials for cancer therapy.First,we summarized the most widely explored reactive species,such as singlet oxygen,superoxide radical anion(O2●-),nitric oxide(●NO),carbon monoxide,alkyl radicals,and their corresponding secondary reactive species generated by interaction with other biological molecules.Then,we discussed the generating mechanisms of these highly reactive species stimulated by light irradiation,followed by their anticancer effect,and the synergetic principles with other therapeutic modalities.This review might unveil the advantages of reactive species-based therapeutic methodology and encourage the pre-clinical exploration of reactive species-mediated cancer treatments.

PROGRESS ON IMPROVING AGRICULTURAL NITROGEN USE EFFICIENCY: UK−CHINA VIRTUAL JOINT CENTERS ON NITROGEN AGRONOMY

Two virtual joint centers for nitrogen agronomy were established between the UK and China to facilitate collaborative research aimed at improving nitrogen use efficiency(NUE)in agricultural production systems and reducing losses of reactive N to the environment.Major focus areas were improving fertilizer NUE,use of livestock manures,soil health,and policy development and knowledge exchange.Improvements to fertilizer NUE included attention to application rate in the context of yield potential and economic considerations and the potential of improved practices including enhanced efficiency fertilizers,plastic film mulching and cropping design.Improved utilization of livestock manures requires knowledge of the available nutrient content,appropriate manure processing technologies and integrated nutrient management practices.Soil carbon,acidification and biodiversity were considered as important aspects of soil health.Both centers identified a range of potential actions that could be taken to improve N management,and the research conducted has highlighted the importance of developing a systemslevel approach to assessing improvement in the overall efficiency of N management and avoiding unintended secondary effects from individual interventions.Within this context,the management of fertilizer emissions and livestock manure at the farm and regional scales appear to be particularly important targets for mitigation.

SUSTAINABLE NITROGEN MANAGEMENT FOR VEGETABLE PRODUCTION IN CHINA

Inappropriate nitrogen fertilizer management for the intensive Chinese vegetable production has caused low N use efficiency(NUE),high reactive nitrogen(Nr)losses and serious environmental risks with limited yield increase.Innovative N management strategy is an urgent need to achieve sustainable vegetable production.This paper summarizes recent studies on Nr losses and identifies the limitations from Chinese vegetable production systems and proposes three steps for sustainable N management in Chinese vegetable production.The three N management steps include,but are not limited to,(1)knowledge-based optimization of N fertilizer rate strategy,which maintains soil N supply to meet the dynamic vegetable demand in time,space and quantity;(2)innovative products and technology,which regulates the soil N forms and promotes the vegetable root growth to reduce the Nr loss;(3)integrated knowledge and products strategy(IKPS).The knowledge-based optimization of N fertilizer rate strategy and innovative products and technology,can maintain or increase vegetable yield,significantly improve NUE,and mitigate the region-specific and crop-specific Nr losses.More importantly,IKPS,based on combination of in-season root-zone N management strategy,innovative products and technology,and best crop cultivation management,is needed to produce more vegetables with lower Nr losses.