Levels Of NO3 Research Articles

Point-of-use sensors and machine learning enable low-cost determination of soil nitrogen.

Overfertilization with nitrogen fertilizers has damaged the environment and health of soil, but standard laboratory testing of soil to determine the levels of nitrogen (mainly NH4+ and NO3-) is not performed regularly. Here we demonstrate that point-of-use measurements of NH4+, combined with soil conductivity, pH, easily accessible weather and timing data, allow instantaneous prediction of levels of NO3- in soil (R2 = 0.70) using a machine learning model. A long short-term memory recurrent neural network model can also be used to predict levels of NH4+ and NO3- up to 12 days into the future from a single measurement at day one, with [Formula: see text] and [Formula: see text], for unseen weather conditions. Our machine-learning-based approach eliminates the need for dedicated instruments to determine the levels of NO3- in soil. Nitrogenous soil nutrients can be determined and predicted with enough accuracy to forecast the impact of climate on fertilization planning and to tune timing for crop requirements, reducing overfertilization while improving crop yields.

The Effect of Curcuma longa on Inflammatory Mediators and Immunological, Oxidant, and Antioxidant Biomarkers in Asthmatic Rats.

The effects of Curcuma longa (C. longa) on total and differential WBC, inflammatory and immunologic mediators, and oxidant and antioxidant biomarkers in bronchoalveolar lavage fluid (BALF) of rats model of asthma were assessed. Animals were divided to 5 groups including control (C), asthma (sensitized to ovalbumin), and asthmatic groups treated with 0.75, 1.50, and 3.00 mg/ml C. longa (CL) and 1.25 μg/ml dexamethasone (D) (8 rats in each group). Total and differential WBC count, concentrations of phospholipase A2 (PLA2), total protein (TP), interferon-gamma (IFN-γ), interleukin-4 (IL-4), immunoglobulin E (IgE), NO2, NO3, malondialdehyde (MDA), superoxide dismutase (SOD), catalase (CAT), and thiol in BALF were assessed. Total and most differential WBC counts and BALF levels of PLA2, TP, IgE, IL-4, and oxidants in asthma group were higher but antioxidants and IFN-γ levels as well as IFN-γ/IL-4 ratio were lower than control group (p < 0.001 for all cases). Total WBC and levels of PLA2, IgE, NO2, and NO3 were significantly reduced following treatment with C. longa, compared to asthma group (p < 0.001 for all cases). In groups treated with dexamethasone and two higher concentrations of C. longa, neutrophil and eosinophil counts as well as TP, IL-4, and MDA levels were significantly decreased but IFN-γ, IFN-γ/IL-4 ratio, and antioxidants were increased (except IFN-γ/IL-4 ratio), compared to asthma group (p < 0.05 to p < 0.001). Compared to dexamethasone, C. longa exerted more pronounced effects on lung inflammation, oxidative stress, and immune system in asthmatic rats.

Comparative health risk assessment of nitrate in drinking groundwater resources of urban and rural regions (Isfahan, Iran), using GIS.

Infantile methemoglobinemia, thyroid disorders, and probably some carcinogenic effects are health concerns associated with dietary nitrate. Isfahan province has a dry and semi-arid desert climate such that the main source of various applications in this province is groundwater resources. This study evaluated spatial analysis of the groundwater NO3- concentrations and its possible health risk to residents. Method 8171 Hach was used for nitrate measurement of 1319 groundwater samples from March 2018 to February 2019. Non-carcinogenic risk due to NO3- exposure through consumption of drinking water was assessed, and the associated zoning maps were presented using geographic information system (GIS). Nitrate concentrations in the rural and urban areas were within 0.4-137mg/L NO3- and 2.9-209mg/L NO3-, respectively. Also, 226 (25%) and 104 (24%) of samples in the rural and urban areas, respectively, were detected above the Iran and WHO guideline NO3- values of 50mg/L. The highest levels of NO3-, which were found in the western and central groundwater resources, occurred in the agricultural and residential areas. The NO3- concentrations were higher in urban than rural areas in the many studied counties. Also, nitrate was higher in wet seasons than in dry ones. Infants' non-carcinogenic risks were higher than the other groups. Infants (HQ > 1) were the most vulnerable group compared with the other groups in some counties. Thus, there are potential risks of methemoglobinemia, especially for infants. It is critical to adopt specific strategies to reduce the nitrate concentration in the studied groundwater.

Biological control of Listeria monocytogenes in soil model systems by Enterococcus mundtii strains expressing mundticin KS production

The agricultural practices applied in pre-harvest greatly influence the presence and the levels of microorganisms in fresh produce. Among these, Listeria monocytogenes represents one of the most lethal foodborne pathogens associated with vegetables. The main hypothesis of this work is that bacteriocin producer Enterococcus mundtii strains can be effective against L. monocytogenes in soil. To this purpose, bacteriocin production by E. mundtii WFE3, WFE20 and WFE31, three strains showing a strong bacteriocin activity in terms of inhibitory power and inhibition spectra, was evaluated in sterile extracts from agricultural soil and peat moss, in organic nutrient solution (ONS) and mineral nutrient solution (MNS). ONS supernatants from E. mundtii WFE3 showed the highest inhibition of the strain L. monocytogenes ATCC 19114. Thus, this strain [104 colony forming units (CFU) g−1 dw] was co-inoculated with E. mundtii WFE3 (106 CFU g−1 dw) in the sterile extracts and solutions. A general increase of E. mundtii cell densities and the contemporary decrease of the levels of L. monocytogenes were observed, particularly in ONS. This solution was used to amend autoclaved soil to test in vivo the competition among bacteriocin producer and sensitive strain. L. monocytogenes decreased of almost 1.5 log CFU when E. mundtii was added to soil. The test was also carried out with basil plants showing that the anti-Listeria effect of E. mundtii is exerted during the very first days from inoculation. After 2 days, the levels of NO3−-N in soil increased for all trials, while the concentrations of ammonium and α-amino N decreased. The lowest concentrations of NH4+-N were found in presence of L. monocytogenes. At harvest, the plants were analysed for the presence of E. mundtii and L. monocytogenes, but none of the two bacterial species deliberately added to soil was transferred to plants. Although a biocontrol based on bacteriocin application in soil has to be properly set, this study provides useful insight for the future development of chemical-free agricultural strategies.

Assessment of surface water quality of Onuiyieke river in Imo State, Nigeria

This research aimed to assess the surface water of Onuiyieke River to ascertain its quality status. Measurements were made on samples collected from seven locations with 500ml sample bottles according to standard methods. Samples for heavy metals were collected in 250ml bottle and fixed with concentrated HN03. Descriptive analysis, variation plots, ANOVA, Duncan Multiple Range tests, Principal Components Analysis (PCA), Pearson Correlation (r) and Water Quality Index (WQI) were used to analyze data. Mean values of the parameters obtained were: Total Suspended Solids (TSS) 198.19 ± 80.93mg/L; Electrical Conductivity (EC) 331.81 ± 59.78µ; Turbidity 18.84 ± 2.22 NTU; Nitrate ions 14.77 ± 0.92mg/L; Dissolved Oxygen (DO) 6.58 ± O.22mg/L and Biological Oxygen Demand (BOD) 1.77 ± 0.10mg/L. Mean values of the Trace Metals obtained were: Iron (Fe) 1.93 ± 0.23mg/L; Magnesium (Mg)0.22 ± 0.02mg/L and Calcium (Ca) 15.15 ± 1.87mg/L while the mean value of Faecal Coliform was 1.91 ± O.10MPN/100. pH, EC, TSS, BOD, turbidity, N03-, Ammonia, Fe and Faecal coliforms exceeded the NESREA and WHO maximum permissible limits. There were significant spatial differences in levels of TDS, EC, NO3, NH3, DO and Faecal coliforms (Sig F=0.000 to 0.039) and significant temporal differences in levels of PO43- (Sig F= 0.078 to 1000) between the control and other locations at p&lt;0.05. Four Principal Components (PCs) formed the extraction solution with a cumulative percentage variability of about 77.67%. The Water Quality Index revealed that the rating for the water quality across the sampling locations was between excellent and unsuitable. Appropriate monitoring procedures for the sustainable development of the river should also be put in place.

MtNPF6.5 mediates chloride uptake and nitrate preference in Medicago roots.

The preference for nitrate over chloride through regulation of transporters is a fundamental feature of plant ion homeostasis. We show that Medicago truncatula MtNPF6.5, an ortholog of Arabidopsis thaliana AtNPF6.3/NRT1.1, can mediate nitrate and chloride uptake in Xenopus oocytes but is chloride selective and that its close homologue, MtNPF6.7, can transport nitrate and chloride but is nitrate selective. The MtNPF6.5 mutant showed greatly reduced chloride content relative to wild type, and MtNPF6.5 expression was repressed by high chloride, indicating a primary role for MtNPF6.5 in root chloride uptake. MtNPF6.5 and MtNPF6.7 were repressed and induced by nitrate, respectively, and these responses required the transcription factor MtNLP1. Moreover, loss of MtNLP1 prevented the rapid switch from chloride to nitrate as the main anion in nitrate-starved plants after nitrate provision, providing insight into the underlying mechanism for nitrate preference. Sequence analysis revealed three sub-types of AtNPF6.3 orthologs based on their predicted substrate-binding residues: A (chloride selective), B (nitrate selective), and C (legume specific). The absence of B-type AtNPF6.3 homologues in early diverged plant lineages suggests that they evolved from a chloride-selective MtNPF6.5-like protein.

Removal of saccharin by UV/persulfate process: Degradation kinetics, mechanism and DBPs formation

As a widely used artificial sweetener, saccharin (SAC) has received extensive attention due to its widespread detection in aquatic environment and potential risk to human health. In this study, the SAC removal by UV-activated persulfate (PS) was comprehensively examined. The results demonstrated that SAC could be eliminated effectively through UV/PS oxidation and its removal behavior can be well described by pseudo-first-order kinetic model. The introduction of different scavengers manifested that sulfate radicals (SO4−∙) were identified to be the major reactive radicals under acidic and neutral conditions, while hydroxyl radicals (HO∙) were determined to be the dominant species under alkaline environments. The reaction rates of SAC with SO4−∙ and HO∙ were calculated to be 1.48 × 108 and 1.56 × 109 M−1 s−1, respectively. The degradation rate constant was positively related to PS dosage (0.21–2.52 mM). The degradation decelerated with the increase of pH from 4.0 to 8.0 and slightly accelerated at pH 9.0. The introduction of Cl− posed a positive impact, while the presence of HCO3−, Br− and humic acid overall retarded SAC removal. Low concentrations of NO3− promoted the degradation, whereas the high levels of NO3− exerted a negative effect. The SAC degradation by UV/PS was mainly initiated through the hydroxylation of the benzene ring, cleavage of C-N bonds, decarboxylation and denitrogenation. The SAC removal in real water matrices by UV/PS treatment was still relatively efficient. Of note, the increased yield of trichloromethane, dichloroacetic acid, trichloroacetic acid and dichloroacetonitrile was found due to chlorination after UV/PS pretreatment.

Grafting improves nitrogen-use efficiency by regulating the nitrogen uptake and metabolism under low-nitrate conditions in cucumber

Excessive application of nitrogen (N) fertilizer can inhibit plant growth, reduce the N-use efficiency (NUE), increase fertilizer waste, and leads to secondary salinization. Grafting provides a feasible method for improving N uptake and utilization of plants under abiotic stress, but the mechanism by which grafting regulates N uptake, assimilation, and metabolism under low-nitrate conditions is poorly known. To explore the mechanism of rootstock grafting promoting plant growth and N absorption and utilization, in this study, a commercial cucumber cultivar (‘Jinchun No. 4’, a relatively N-inefficient cultivar) was self-grafted and grafted onto two pumpkin rootstocks (‘Figleaf Gourd’, a relatively N-medium efficiency pumpkin cultivar, and ‘Ribenjingtiantaimu’, a relatively N-efficient pumpkin cultivar, respectively). The grafted plants were exposed to two levels of NO3−-N (7 and 4 mM) under substrate culture conditions. Root morphological traits; NH4+, NO3−, and total N contents; N-based enzymatic activities; and N metabolite contents of self-grafted plants (J/J) were all markedly inhibited by low-nitrate treatment, leading to lower N accumulation (NA), N-uptake efficiency (NUpE), N-utilizition efficiency (NUtE) and NUE than rootstock-grafted plants (J/F and J/R). In contrast, the inhibition caused by the low-nitrate treatment was effectively alleviated in J/R-grafted plants, as J/R-grafted plants had the largest root systems and the strongest potential for N absorption and metabolism. Variation in these parameters was determined by the rootstock genotype and contributed greatly to improvements in NUpE, NUtE and NUE. Overall, our findings demonstrate that grafting with N-efficient rootstock can permit plants to make better use of their roots and enhance N absorption and N metabolism potential, thereby promoting the growth and NUE of cucumber seedlings. Furthermore, our findings infer that grafting with N-efficient rootstock may permit high levels of productivity to be maintained under low N supplies during cucumber production.

The Roles of Dominance of the Nitric Oxide Fractions Nitrate and Nitrite in the Epilepsy-Prone EL Mouse Brain.

Oxidative stress is thought to be closely related to epileptogenesis. We have previously reported that nitric oxide (NO) levels are higher in epilepsy-prone EL mice between the ages of 3 and 8 weeks than in control mice. However, NO is divided into two fractions, nitrite (NO2) and nitrate (NO3), which appear to play different roles in epileptogenesis. NO2 and NO3 levels were measured, in EL mice and the control mice, in the parietal cortex, which is thought to be the primary epileptogenetic center in EL mice, and measured in the hippocampus, which is thought to be the secondary center. NO3 levels in the hippocampus and parietal cortex of the immature EL mice (3 to 8 weeks of age) were significantly higher than those in the control mice; NO2 levels were significantly higher in the EL mice throughout the study period. The NO3 levels were significantly higher than the NO2 levels in the immature EL mice, but after the onset of ictogenesis at 10 weeks of age, the relative levels of the two fractions reversed. The reversal of the NO fraction distribution at the onset of seizures that we observed may be related to the developmental process of seizure susceptibility in the neural network of EL mice.

Isotope and isotopomer ratios of dissolved N2O as indicators of nitrogen apportionment and transformation in shallow groundwater in Dongguan, southern China

Nitrogen source identification is critical to effectively govern nitrogen contamination, as excessive nitrogen content in groundwater has become a crucial global environmental problem. The traditional stable isotope approach (δ15N-NO3–, δ18O-NO3–, δ15N-NH4+) has been widely used to identify nitrogen sources by comparing the isotopic signals between groundwater samples and the possible nitrogen source. However, nitrogen source apportionment based only on that method would be inaccurate because isotopic signals overlap between the nitrogen sources and nitrogen that has undergone biochemical reactions. To solve the shortcomings of the traditional stable isotope approach, the isotope ratios of N2O, the SP-δ18O model and the traditional stable isotope approach were combined to depict the nitrogen transformation processes and reconstruct the “initial” isotopic compositions of nitrogen sources. A total of 58 groundwater samples were collected in the Dongguan Basin and were analysed during June-July 2018. NO3–-N was the dominant species of dissolved inorganic nitrogen in most of the groundwater samples. In the groundwater flow direction, NO3– contents decreased, while the δ15N-NO3– and δ18O-NO3– values increased. The positive relationship between δ15N-NO3– and δ18O-NO3– and the calculation results of the SP-δ18O model indicated that both denitrification and nitrification processes occurred in the groundwater, and denitrification acted as the dominant nitrogen transformation process. The initial isotope ratio of nitrogen obtained from the combined use of the calculation results of the SP-δ18O model and δ15N-NO3– (or δ15N-NH4+) value suggested that manure and septic wastes were the primary sources of NO3– and NH4+ in the groundwater. The redox-sensitive components and the calculation results of the SP-δ18O model depicted the reductive level of NO3– in the groundwater flow direction: NO3– reduction did not occur in the upstream area, NO3– reduction was strong in the intermediate transition zone, and NO3– contents were completely consumed and CH4 occurred in the downstream region. This study demonstrated that the combination of the traditional stable isotope approach and the isotope ratios of N2O are useful tools for revealing the source and transformation of nitrogen in groundwater. The method used in this study provides new insight for nitrogen source identification.

Study of Biofilter Planted with Basil for Removal of Ammonia in Aquaponic Water

Abstract This experimental investigation of a laboratory scale aquaponic system included testing of a biofilter with basil plant as the biofilter part on aquaculture water quality. Irridescent shark was selected as aquaculture species. The biofilter consist of natural biomaterials such as coconut husk, coco peat, and coarse aggregates. The experiment was carried out for three short water recirculation durations of 2, 3, and 4 h/day. The influent and effluent ammonia NH3, total ammonia nitrogen (TAN), nitrites NO2 and nitrates NO3 levels were measured and analysed. The results showed that the biofilter effectively removed NH3 (65 - 71 %), TAN (34 - 58 %), and NO2 (60 - 67 %) from the aquaculture water. The dissolved oxygen (DO) levels were maintained between 3 - 7.0 mg/l during all the recirculation durations. The significance of water recirculation period was assessed by calculating the differences between the means of water quality parameters with a statistical test named one-way analysis of variance (ANNOVA) with significant level P taken as 5 %, i.e., P ≤ 0.5. The effluent mean NH3 levels 0.030 mg/l, 0.033 mg/l, and 0.022 mg/l exhibited significant difference at 4 h/d periods while effluent TAN levels 0.81, 0.77, and 0.77 showed no difference with varying periods.

Bio-assessment of wastewater effluent conditions with algal pollution index and multivariate approach

Water scarcity and water pollution are important issues in the world. Therefore, reusing treated wastewater for irrigation can be a crucial approach in arid and semi-arid regions. There are still some concerns about the sustainability of wastewater irrigated agriculture. Thereby, the present study is aimed to evaluate responses of algal species to stressors in the central wastewater treatment plant using the modified algae pollution index and multivariate approaches to assess healthy sustainability of wastewater effluent quality and to give the suggestion for reusing such kind of waters, especially for irrigation. Samplings of water and algae were carried out twice a month between October 2019 and August 2020. Canonical correspondence analysis (CCA) explained 94.1% of the relationships between environmental factors and species. Water and air temperatures, precipitation, chemical oxygen demand (COD), electrical conductivity (EC), pH, and NO3 played important roles in the temporal occurrence/succession of algae composition in the wastewater treatment plant. Ordination of commonly encountered algae species relatively near the center of the CCA indicates their wide range of tolerance levels to the changes in environmental conditions in the system. Of the species, Navicula aitchelbee, Nitzschia fonticola, and Euglena oxyuris preferred high EC levels; Brachysira exilis, Chlorella vulgaris, G. parvulum, and C. ovata associated with high COD levels, and Navicula tripunctata, Nitzschia umbonata and C. vulgaris related to high NO3 levels (>75% of the percentile). The modified pollution index developed in the present study indicated that the wastewater treatment plant had mainly high organic pollution (>3.00) in the summer and fall seasons, when it had moderate organic pollution (>2.50) in the winter and spring seasons. Results of the study suggest that crucial algae-stressors relationships can be used as an assessment tool to ensure sustainable water supply for the irrigation purpose in arid and semi-arid regions.

Anthropogenic nitrate in groundwater and its health risks in the view of background concentration in a semi arid area of Rajasthan, India

An increased nitrate (NO3−) concentration in groundwater has been a rising issue on a global scale in recent years. Different consumption mechanisms clearly illustrate the adverse effects on human health. The goal of this present study is to assess the natural and anthropogenic NO3− concentrations in groundwater in a semi arid area of Rajasthan and its related risks to human health in the different groups of ages such as children, males, and females. We have found that most of the samples (n = 90) were influenced by anthropogenic activities. The background level of NO3− had been estimated as 7.2 mg/L using a probabilistic approach. About 93% of nitrate samples exceeded the background limit, while 28% of the samples were beyond the permissible limit of 45 mg/L as per the BIS limits. The results show that the oral exposure of nitrate was very high as compare to dermal contact. With regard to the non-carcinogenic health risk, the total Hazard Index (HITotal) values of groundwater nitrate were an average of 0.895 for males, 1.058 for females, and 1.214 for children. The nitrate health risk assessment shows that about 38%, 46%, and 49% of the samples constitute the non-carcinogenic health risk to males, females, and children, respectively. Children were found to be more prone to health risks due to the potential exposure to groundwater nitrate.

Revising petiole nitrate sufficiency/deficiency guidelines for irrigated cotton in the Desert Southwest

AbstractPetiole nitrate‐nitrogen (NO3–N) sampling and testing remains a popular in‐season nitrogen (N) management practice in the western United States for cotton (Gossypium hirsutum L.). However, the present guidelines used by Arizona are greater than 35 yr old and are in need of updating. The objectives of this study were to relate in‐season petiole NO3 levels with lint yields and N deficiencies and to revise the former critical deficiency level guidelines by growth stage. Petioles were sampled between first square and peak bloom in nine site‐years of cotton N management field trials in Maricopa and Safford, AZ, from 2014 to 2018. Irrigation type in Maricopa was overhead sprinkler irrigation (OSI) (2014–2015) and subsurface drip irrigation (SDI) (2016–2018). In Safford (2014–2017), surface irrigation (SI) was used. Petiole NO3 in SDI was dramatically lower than with SI or OSI, mostly in the deficient range. Lower lint yields in zero‐N treatments compared with pre‐plant soil NO3 test–based reference treatments occurred in eight site‐years (Safford 2016 crop lost to late hailstorm) and were considered N deficient. Critical petiole NO3–N levels from 1984 were revised downward 1 g N kg−1 because several N‐fertilized treatment means of petiole NO3 were in that range and did not exhibit an N rate–related yield depression. Sampling cotton plants for petiole NO3 analysis should start within 1 wk of first bloom. Petiole NO3 dynamics and critical levels in SDI cotton required further study.

Higher Biochar Rate Can Be Efficient in Reducing Nitrogen Mineralization and Nitrification in the Excessive Compost-Fertilized Soils

The effects of a high biochar rate on soil carbon mineralization, when co-applied with excessive compost, have been reported in previous studies, but there is a dearth of studies focusing on soil nitrogen. In order to ascertain the positive or snegative effects of a higher biochar rate on excessive compost, compost (5 wt. %) and three slow pyrolysis (&gt;700 °C) biochars (formosan ash (Fraxinus formosana Hayata), ash biochar; makino bamboo (Phyllostachys makino Hayata), bamboo biochar; and lead tree (Leucaena leucocephala (Lam.) de. Wit), lead tree biochar) were applied (0, 2 and 5 wt. %) to three soils (one Oxisols and two Inceptisols). Destructive sampling occurred at 1, 3, 7, 28, 56, 84, 140, 196, 294, and 400 days to monitor for changes in soil chemistry. The overall results showed that, compared to the other rates, the 5% biochar application rate significantly reduced the concentrations of inorganic N (NO3−-N + NH4+-N) in the following, decreasing order: lead tree biochar &gt; bamboo biochar &gt; ash biochar. The soil response in terms of ammonium and nitrate followed a similar declining trend in the three soils throughout the incubation periods, with this effect increasing in tandem with the biochar application rate. Over time, the soil NO3−-N increased, probably due to the excessive compost N mineralization; however, the levels of soil NO3−-N in the sample undergoing the 5% biochar application rate remained the lowest, to a significant degree. The soils’ original properties determined the degree of ammonium and nitrate reduction after biochar addition. To reduce soil NO3−-N pollution and increase the efficiency of compost fertilizer use, a high rate of biochar application (especially with that pyrolyzed at high temperatures (&gt;700 °C)) to excessively compost-fertilized soils is highly recommended.

The enrichment of diet with beneficial bacteria (single- or multi- strain) in biofloc system enhanced the water quality, growth performance, immune responses, and disease resistance of Nile tilapia (Oreochromis niloticus)

The present study examined the influences of dietary single strain (SSP; Lactobacillus plantarum) or multi-strain (MSP; Bacillus subtilis, L. plantarum, L. rhamnosus, L. acidophilus, L. delbrueckii) potential probiotics on Nile tilapia (Oreochromis niloticus) in biofloc (BF) and stagnant-renewal (SR) culture systems. Fish (8.63 ± 3.35 g) were allotted in six groups: T1, SR control; T2, SR + SSP; T3, SR + MSP; T4, BF + MSP; T5, BF + SSP; T6, BF control. After 112 days, water dissolved oxygen (O2), pH, electrical conductivity (EC), total dissolved solids (TDS), total suspended solids (TSS), total ammonia nitrogen (TAN), un-ionized ammonia (NH3), and nitrite (NO2) levels were significantly increased while nitrate (NO3) concentrations were decreased under BF condition. Also, bacterial supplements showed significant effects on EC, TAN, NH3, NO2, and NO3 levels. The BF availability remarkably enhanced the activities of digestive enzymes and fish fed SSP-containing diet presented significantly superior weight gain and average daily growth over other diets. A significant effect on amylase activity was detected by probiotic and culture system interactions. Meanwhile, serum total protein, albumin, globulin, total immunoglobulin, superoxide dismutase (SOD), myeloperoxidase (MPO), and respiratory burst activity (RBA) were significantly higher and malondialdehyde and endotoxin were lower for fish stocked in BF system. Additionally, MSP-containing diet significantly promoted serum protease, SOD, catalase (CAT), alkaline phosphatase (AP), MPO, and RBA activities compared to other tested diets. Interestingly, serum alternative complement (ACH50) and lysozyme activities were merely affected by the main effect of probiotics. However, probiotics and culture system found to have individual or combined effects on the intestinal antioxidant enzymes, AP, and pro-inflammatory cytokines (tumor necrosis factor alpha and interleukin-1 beta). Further, tilapia challenged with Aeromonas hydrophila showed reduced mortality in BF groups fed probiotics. The results suggested that the effect of probiotics greatly differed upon the culture condition and the application of multiple strains probiotics had higher efficiency toward immunity than single strain probiotic.

Potential effect of nitrate applied during flood period on N2O emissions during subsequent drainage in a paddy soil

Application of nitrate (NO3−) in flooded soil promotes denitrification activity and N2O emissions, accompanied by NO3− depletion. However, whether the stimulating effect of NO3− on flooded soil still affects the response of nitrifiers and denitrifiers to subsequent water drainage remains unclear, as does the N2O emission dynamics. We conducted a microcosm experiment using intact paddy soil columns with three levels of NO3− treatment under flooded conditions: the application of NO3− solutions with 0, 60 and 200 kg KNO3-N per hectare (N0, N60, and N200, respectively). The N2O emission rate was measured using a closed chamber method, and the community composition and abundance of nitrifiers and denitrifiers were determined using the terminal restriction fragment length polymorphism (T-RFLP) and real-time quantitative polymerase chain reaction (qPCR) methods, respectively. The results showed that all the added NO3− was exhausted during the flood period and below 0.50 mg kg−1 at the end of flooded incubation. Arch-amoA and narG gene abundance were significantly elevated by NO3− application before drainage. Then water drainage promoted the narG gene numbers of N60- and N200-treated soils increase by 109 copies g−1 more than N0 treatment, and the community compositions of narG- and nirK-containing denitrifiers differed significantly among the three NO3− treatments. In addition, draining resulted in clear shifts in the community structures of Arch-amoA- and Bac-amoA-containing nitrifiers in the N60-treated soils, and also resulted in higher increase of Arch-amoA gene abundance in the N60- and N200-treated soils than in N0 treatment. These results indicate that NO3− application on flooded soil enhance the response of Arch-amoA and narG gene abundance to subsequent water drainage. However, the differences in the denitrifier community had few correlations with N2O emissions during draining (p > 0.05), while the Arch-amoA gene abundance in the N0- and N60-treated soils increased about 6.45 and 3.70 times respectively after drainage (p < 0.05) and strongly correlated with higher N2O emissions (r > 0.92, p < 0.01). Considering the NH4+-N consumption and the NO3−-N production, we could speculate that the changes in the ammonia-oxidizing archaea community after drainage are only important regulators of N2O emission rates in this paddy soil columns.

Hyperspectral imaging techniques for rapid detection of nutrient content of hydroponically grown lettuce cultivars

The analyses of online quality measurements of four lettuce cultivars (Rex, Tacitus, Black Seeded Simpson, Flandria) using hyperspectral image processing techniques have been studied. Seedlings were planted in Rockwool cubes and fed for 3 weeks using hydroponic nutrient solution containing 0, 50, 100, 150, 200, 250, and 300 ppm nitrogen. The hyperspectral images of the freshly cut lettuce leaves were captured using hyperspectral camera in the wavelength range of 400–1,000 nm. The algorithm to measure nutrient levels of leaf tissues including nitrate (NO3–), calcium (Ca2+), potassium (K+), soluble solid content (SSC), pH, and total chlorophyll concentration (SPAD reading) for lettuce was developed. To locate the optimum wave band combination values, simple linear regression models with two spectral data values, namely reflectance and its first derivative, and two spectral indices, namely ratio spectral index (RSI) and normalized difference spectral index (NDSI), were found. The optimal wave bands were within 506–601 nm and 634–701 nm. The nutrient levels of NO3–, Ca2+, K+, SSC, pH, and SPAD in the leaf samples were estimated using partial least squares regression (PLSR) and principal component analysis (PCA) techniques of the four optimal wave bands. Both PLSR and PCA models produced well correlated outcome in comparison with the laboratory measured freshly cut lettuce leaves in predicting nutrient contents with R2 = 0.784–0.987.

Effect and mechanism of silver nanoparticles on nitrogen transformation in water-sediment system of a hypereutrophic lake

Industrialization and urbanization are expected to increase the release of silver nanoparticles (AgNPs) into aquatic ecosystems. However, it remains to be determined how AgNPs influence nitrogen transformation and the underlying mechanism in natural water bodies. Here, the impact of AgNPs on nitrogen cycling in water-sediment system of a hypereutrophic lake was studied and the mechanism of nitrogen transformation was investigated in terms of the nitrogen functional enzymes and genes. Following 7 days of water-sediment microcosm experiments, the levels of total nitroten (TN) and organic nitrogen (OrgN) were significantly increased by 50 mg/L Ag+ treatment when compared with the non-Ag control (P < 0.05). In contrast, the levels of TN and Org-N were both slightly decreased by AgNPs treatments (0.5 and 50 mg/L). Additionally, the levels of NO3−-N were evidently reduced with the presence of AgNPs (P < 0.05). Further, our data proved that enzymes and those enzyme encoding genes involved in the nitrogen transformation may directly responsible for the alterations of nitrogen transformation. Overall, our work suggested that the short-term exposure to AgNPs might cause hormetic effects on nitrogen-transforming microorganisms in hypereutrophic lakes, and have a potential to result in non-negligible changes in the nitrogen cycling of hypereutrophic lakes.

Response of olive tree to ammonium nitrate fertilization under saline conditions

Water scarcity and salinity are major concerns for the new intensive olive groves in arid and semi-arid areas in Tunisia. Furthermore, an inadequately applied fertilization program should aggravate the problem of salinity. The main aim of the present study is to assess the effects of salinity and ammonium nitrate (AN) on the behavior of olive plants (Olea europaea L.var. Arbequina). The experiment was performed with four NaCl levels (0.5, 50, 100, and 150 mM) combined with three levels of NH4 NO3 (0, 50, 100 g) by adding the nutrient solution of ½ Hoagland. Salinity had a statically significant negative effect on the considered responses, although the severity of the effect varies among treatments. High concentrations of salt (100, 150 mM) decreased vegetative growth, the production of fresh and dry biomass, leaf area, chlorophyll concentration, and increased leaf succulence. Similarly, salinity induced an accumulation of toxic ions and loss of electrolytes in the leaves. The use of ammonium nitrate is noticed to be ineffective in improving various growth and physiological parameters of olive plants grown under saline conditions, and it depressed all studied parameters mainly at the highest dose. This depression could be attributed to an increase in leaf sodium concentration after ammonium nitrate application, in spite of the increase of leaf nitrogen concentration. A better management of nitrogen fertilization in saline conditions should be considered mainly in relation to the right source.