Reduce Nitrate Concentrations Research Articles

External Nitrogen and Carbon Source-Mediated Response on Modulation of Root System Architecture and Nitrate Uptake in Wheat Seedlings

Nitrogen uptake efficiency is an important component trait that could be targeted for improving nitrogen use efficiency of crop plants. To understand the responses of different nitrate transport systems and the influence of root system architecture on nitrate uptake under limited nitrate conditions in wheat (Triticum aestivum L.) at the seedling stage, we studied nitrate uptake, root system architecture, and expression of different nitrate transporter genes in induced and non-induced wheat seedlings. Further, effects of inclusion of sucrose and two amino acids (glutamine and asparagine) in induction medium on these parameters were also studied. We observed that the induced wheat root system took up more nitrate as compared to non-induced root system in a dose-dependent manner. Gene expression of both high- and low-affinity nitrate transporter gene showed differential expression in the induced root tissues, as compared to non-induced tissues, depending on the concentration of nitrate present in induction medium. External nutrient media containing sucrose, glutamine, and asparagine reduce nitrate concentration in both root and shoot tissues and also influence the gene expression of these transporters. Our observations indicate that upon induction with milder external nitrate concentrations, the root architecture is modulated by changing overall lateral root size and 1st order lateral root numbers along with activation of nitrate transporters which acquire and transport nitrate in roots and shoots, respectively, depending on the carbon and nitrogen source available to seedlings.

Pre-harvest LED lighting strategies for reduced nitrate contents in leafy vegetables

Pre-harvest LED lighting strategies for reduced nitrate contents in leafy vegetables

Ebb-and-flow Subirrigation Strategies Increase Biomass and Nutrient Contents and Reduce Nitrate Levels in Lettuce

Overhead irrigation is widely used to water lettuce during commercial production in China but exerts potential water wastage and pollution. Subirrigation is thought as a water-saving, high-efficiency fertigation strategy. However, few studies have compared the nutritional value and nitrate content of lettuce grown using subirrigation with plants cultivated with overhead irrigation. Therefore, this study explored the ability of ebb-and-flow subirrigation strategies to produce high yields of a leafy lettuce (cultivar Biscia Rossa) with high nutritional value and low nitrate content. Lettuce plants were cultivated in an ebb-and-flow subirrigation system with different irrigation frequencies (every 2 or 3 days) and immersion times (5, 10 or 15 minutes); overhead irrigation was used as control. Ebb-and-flow subirrigation significantly enhanced several lettuce growth parameters, significantly increased the level of vitamin C, and significantly decreased the nitrate content of lettuce leaves compared with overhead irrigation. The optimal subirrigation strategy for lettuce production was irrigation every 3 days with 15 minutes immersion; this ebb-and-flow subirrigation protocol could potentially be used to save water and resources, improve yield and nutrient contents and reduce nitrate content in commercial greenhouse lettuce production.

Quantitative Nutrient Management Reduces Nitrate Accumulation in Hydroponic Butterhead Lettuces Grown under Artificial Lighting

To reduce nitrate concentrations in vegetables grown under artificial lighting, we determined nitrate accumulation under various conditions of nitrate availability. Butterhead lettuce plants were grown with nutrient solutions of various concentrations, which were maintained according to electrical conductivity (EC) throughout the cultivation period. Under these conditions, growth in nutrient solutions with lower EC led to slight decreases in nitrate concentrations in leaves, but also decreased fresh and dry weights of shoots, leading to the risk of a yield loss under EC control management (ECM). By contrast, when total nitrate requirement was supplied only at the start of cultivation, nitrate concentrations in leaves were decreased significantly with only slightly reduced plant growth. Hence, marketable-sized butterhead lettuces with lower nitrate concentrations can be produced by supplying total nitrate requirements in the nutrient solution at the start of cultivation.

Assessment, mapping, and management of health risk from nitrate accumulation in onion for Iranian population

Excess accumulation of nitrate in vegetable crops is normally related to the excessive use of nitrogen fertilizers applied in agricultural fields. This study was performed to evaluate the level of nitrate concentration in onion production in Isfahan province of Iran and the potential health risks associated with high level of nitrate in this crop, as an example of a case-study. The risk was estimated by using the United States Environmental Protection Agency (USEPA) method and presented as risk maps. Additionally, the impact of an improved fertilizer management practice in selected vulnerable fields for reducing nitrate concentration in onion production was evaluated. For this assessment, four different onion fields in which onion bulb nitrate concentration was higher than the safety level (70 mg kg−1 FW), provided by Welch (2003) in a survey study, were chosen. The risk maps showed that despite higher risk possibility in adults, in comparison with children, all values were lower than the acceptable level. Further, the split application of nitrogen fertilizers in all fields significantly reduced plant nitrate concentration with no reduction in yield and even observed increase in the overall economic yield production. Therefore, considering crop yields and nitrate accumulation impacts, improved nitrogen management could provide an opportunity to promote onion crop production while reducing negative health effects in high-risk regions in Isfahan province of Iran.

Effects of partial replacement of nitrate with different nitrogen forms on the yield, quality and nitrate content of Chinese kale

ABSTRACTIn this study, the yields, nutritional qualities and nitrate (NO3) content of Chinese kale were studied with two cultivars, following partial replacement of nitrate (20%) with ammonium (NH4), urea and glycine in hydroponics. The results showed that, compared with the full nitrate treatment, ammonium replacement increased the fresh weight by 18.1% and 8.0% of ‘Zaobao’ and ‘Lvbao’ cultivars respectively, whereas urea and glycine replacements decreased the biomass significantly. Adding different nitrogen (N) forms significantly improved the contents of vitamin C, soluble sugar, free amino acid, protein, soluble phenol and flavonoids in Chinese kale. Adding the three alternative N forms also reduced nitrate content significantly, in which glycine replacement was the lowest. According to the results obtained, different forms of N replacement could be used for different purposes. Glycine replacement could be the best alternative only to improve qualities, while ammonium replacement could be the best alternative to improve both the yield and qualities.

Nitrate in fruits and vegetables

Abstract The current article provides an updated review of scientific advances regarding nitrate accumulation in plant tissues and a critical examination of the genetic, agroenvironmental and postharvest factors that can modulate nitrate levels in a wide range of horticultural crops, including herbs, roots and tubers, inflorescences, buds, seeds, stems, and leafy vegetables, fungi as well as fruits. A refined classification of horticultural crops is presented according to the nitrate content of their edible product. The role of plant cultivar/morphotype and tissue age in nitrate accumulation is discussed along with the physiological role of nitrate as osmoticum in maintaining turgor and driving leaf expansion under conditions of variable photosynthetic capacity. Nitrate accumulation is examined in respect to key cultural practices, such as the timing-rate-form of N application and the use of plant biostimulants (natural substances and microbial inoculants), as well as the potential interaction with other nutrients (e.g., P, Ca, Mo and Cl). The influence of environmental conditions during plant growth (light intensity, spectral quality, photoperiod, air and root-zone temperature and atmospheric CO2 concentration), harvest stage and diurnal timing of harvest is assessed. Postharvest storage conditions (temperature, light, and duration) are discussed in respect to their effects on the putative endogenous conversion of nitrate residues to nitrites. Several approaches that may be adopted to reduce nitrate content in vegetables, fruits and herbs are analysed and warranted future research subjects are identified.

DEVELOPMENT OF AUTOTROPHIC DENITRIFICATION FOR NITRATE-CONTAMINATED INDUSTRIAL WASTEWATER

An autotrophic denitrification system was developed for treatment wastewater from steel industry. The aim was to evaluate the kinetics and capability of the system in reducing nitrate content in such industrial wastewater. The experiments were conducted in batch suspension and continuous runs. The denitrification kinetics in suspension runs obeys first order reaction with the rate constant k1 and k2 were determined to be 0.014 and 0.004 g-N/m3.d, respectively. The continuous runs used a column packed with mixture of granular sulfur and limestone. The microbes of Thiobacillus denitrificans were attached on the surface of granular sulfur in the form of biofilm. The biofilm thickness was investigated to be approximately 40 μm. The denitrification kinetics in the packed column obeys half-order reaction with the rate constant k of 0.172 g-N1/2.m1/2/(kg-S.d). The lower denitrification extent of industrial wastewater compared with the synthetic wastewater might be due to the lack of alkalinity. Keywords: Autotrophic denitrification, sulfur, packed column, thiobacillus denitrificans.

Contextualizing Wetlands Within a River Network to Assess Nitrate Removal and Inform Watershed Management

AbstractAquatic nitrate removal depends on interactions throughout an interconnected network of lakes, wetlands, and river channels. Herein, we present a network‐based model that quantifies nitrate‐nitrogen and organic carbon concentrations through a wetland‐river network and estimates nitrate export from the watershed. This model dynamically accounts for multiple competing limitations on nitrate removal, explicitly incorporates wetlands in the network, and captures hierarchical network effects and spatial interactions. We apply the model to the Le Sueur Basin, a data‐rich 2,880 km2 agricultural landscape in southern Minnesota and validate the model using synoptic field measurements during June for years 2013–2015. Using the model, we show that the overall limits to nitrate removal rate via denitrification shift between nitrate concentration, organic carbon availability, and residence time depending on discharge, characteristics of the waterbody, and location in the network. Our model results show that the spatial context of wetland restorations is an important but often overlooked factor because nonlinearities in the system, e.g., deriving from switching of resource limitation on denitrification rate, can lead to unexpected changes in downstream biogeochemistry. Our results demonstrate that reduction of watershed‐scale nitrate concentrations and downstream loads in the Le Sueur Basin can be most effectively achieved by increasing water residence time (by slowing the flow) rather than by increasing organic carbon concentrations (which may limit denitrification). This framework can be used toward assessing where and how to restore wetlands for reducing nitrate concentrations and loads from agricultural watersheds.

The Role Of Wetland Ecosystems To Reduce The Concentration Of Nitrate In Groundwater

Nitrate is a compound very soluble in water. Ichikawa city is one of the cities that have a pear farming. In this city, there was a wetland where this area was surrounded by pear farming in upland areas. There were 3 sites (S4, R2, and S14) in this area.S4 and S14 were close to pear farming, but R2 was in the middle of wetland. We used piezometers with different depth (1m, 2m, and 3m) in each site. The focus in this study is identification the role of wetland ecosystem as a green infrastructure to reduce nitrate concentration. Groundwater flow in the wetland comes from pear farming with 2 flow direction. First, groundwater comes from S4 with average nitrate concentration was 185.73 mg/L and average DO concentration 6.37 mg/L. Second, groundwater comes from S14 with average nitrate concentration was 190.29 mg/L and average DO concentration 7.00 mg/L. All this direction flow to the middle of wetland (R2) with average nitrate concentration was 3.46 mg/L and average DO concentration 1.52 mg/L.

Screening of microalgae and cyanobacteria strains for α-tocopherol content at different growth phases and the influence of nitrate reduction on α-tocopherol production

Tocopherols (vitamin E) are only synthesized by photosynthetic organisms and have wide applications in cosmetics and as dietary supplements in human nutrition and aquaculture. Tocopherols from microalgae and cyanobacteria are rarely investigated, and little is known about their contents. Therefore, 130 strains of cultured microalgae and cyanobacteria were analyzed for α-tocopherol content under various culture conditions. The growth phase had a significant effect on content of α-tocopherol. Maximal amounts were observed at the stationary growth phase. Reduction of nitrate concentration in media caused an increased production of α-tocopherol. The contents were significantly enhanced when the nitrate concentration was reduced to one fourth in culture media used. The content of α-tocopherol was found to reflect phylogenetic relationships at the level of classes, with classes of Rhodophyta and Cyanobacteria accumulating the lowest contents. Within each class, contents varied widely at the species level emphasizing the importance of extensive screening procedures for the identification of strains with high α-tocopherol contents.

Assessing the Integration of Wetlands along Small European Waterways to Address Diffuse Nitrate Pollution

Nitrate concentrations in numerous European fresh watercourses have decreased due to end-of-pipe measures towards manure and fertilization management, but fail to meet the environmental objectives. The implementation of complementary measures to attenuate diffuse nitrate pollution in densely populated regions characterised by limited available area has been barely studied. To tackle this issue, this study evaluates the feasibility of integrating Constructed Wetlands (CWs) along waterways as a promising tool to facilitate compliance with the nitrate regulations. The aim is to calculate the required area of land alongside a specific watercourse to integrate CWs to reduce nitrate concentrations consistently below the 11.3 and 5.65 mgNO3-N/L levels, according to the Nitrates Directive and the Flemish Environmental Regulations. Nitrate-nitrogen removal efficiencies achieved at case study CWs were compared and validated with reported values to estimate the needed wetland areas. In addition, the removal efficiencies and areas needed to meet the standards were calculated via the kinetic model by Kadlec and Knight. The predicted areas by both methods indicated that CWs of 1.4–3.4 ha could be implemented in certain regions, such as Flanders (Belgium), with restricted available land. To conclude, three designs for ICWs (Integrated Constructed Wetlands) are proposed and evaluated, assessing the feasibility of their implementation.

Organic whey as a source of Lactobacillus strains with selected technological and antimicrobial properties

AbstractTwenty‐five strains, isolated from raw, non‐pasteurised, organic whey samples, were identified phenotypically and genotypically. Biochemical tests were performed, and enzyme profiles, antibiotic resistance and antimicrobial properties were investigated. Sixteen strains were identified as genus Lactobacillus. Based on 16S rDNA gene sequence, the strains were identified as Lb. plantarum and Lb. fermentum. All of the strains had β‐galactosidase activity, and some of them reduced nitrate content. All strains utilised carbohydrates. The tested strains were characterised by low or average lipolytic and esterolytic activity. Moreover, the strains showed low proteolytic activity which is advantageous for their use as starter cultures for foods with low protein content. Strains Lb. fermentum S20, SM1, SM3, S2R and Lb. plantarum SM5 produced harmful N‐acetyl‐β‐glucosaminidase; moreover, the strain S20 produced also β‐glucuronidase. None of the strains produced α‐chymotrypsin. In phenotypic studies, most of the test strains were susceptible to gentamicin, ampicillin, tetracycline, chloramphenicol, penicillin and erythromycin. Strains Lb. plantarum S1 and Lb. fermentum S4, S7, S8, S10, SM1 and SM3 did not possess any transfer resistance genes. Antagonistic activity of the culture LAB strains was assessed as high or moderate in relation to the indicator strains, with the greatest zones of inhibition for E.coli and the smallest for L. monocytogenes ATCC 15313. This study reveals that the LAB strains isolated from organic whey have high potential for food application. Some strains of species Lb. fermentum (S4, S7, S8, S10) have been identified as the best candidates.

Removal of nitrate by asymmetric capacitive deionization

Contamination of groundwater with nitrates is a major concern, especially for areas relying on this as a drinking water source. In this work, a capacitive deionization (CDI) system equipped with carbon electrodes coated with different metal oxides was studied to determine its ability to reduce nitrate concentrations. Results performed in a three-electrode cell were used as a proof of concept and demonstrated that coated electrodes had higher nitrate removal than that of uncoated electrodes, likely because of a reduction in hydrophobicity and an increase in surface area provided by the metal oxides. Moreover, tests using different electrolytes (NaNO3 and Ca(NO3)2) revealed similar nitrate removal values, although different electrosorption patterns were observed for Na+ and Ca2+. Furthermore, an operational mode based on a multistep approach showed that nitrates could be removed below regulatory limits while reducing the volume of waste brine. A larger, eight-cell flow CDI reactor was also tested. The results from this reactor showed that the cell potential, as well as the ion being removed from a multicomponent solution (Ca2+, Na+, Cl−, NO3−) influence electrosorption kinetics. Different adsorption mechanisms based on ion charge/size/electrode affinity are discussed, possibly leading to a methodology for preferentially removing certain ions by CDI technology.

Effect of elevated nitrate on biodegradation of pentabromodiphenyl ether (BDE-99) and change in microbial communities during groundwater recharge with tertiary-treated municipal wastewater

The use of tertiary-treated municipal wastewater for groundwater recharge through river utilization may cause pentabromodiphenyl ether (BDE-99) pollution, which poses a potential risk to groundwater aquifers. Elevated nitrate levels may change the structure of microbial communities, thus influencing the biodegradation of BDE-99. To investigate the influence of elevated nitrate levels on the changes in microbial communities and associated biodegradation of BDE-99 appropriately, a laboratory-scale column was designed to simulate the percolation process. The results showed that the attenuation rate of BDE-99 increased with nitrate concentrations. The lower-brominated ether congeners were the primary debrominated metabolites, while high-brominated diphenyl ethers and isomers of BDE-100 also emerged, and their concentrations decreased with reduced nitrate concentrations. The microbial community composition and structure significantly changed with elevated nitrate levels and relative abundance of nitrate-reducing bacteria with diverse metabolic capabilities increased. The order of the relative abundance of the largest five classes, as well as the relative abundances of the largest five families and genera, changed with increasing nitrate concentrations. The diversity of microorganisms with universal aromatics-degrading abilities related to nitrogen transformation played an important role in mitigating the infiltration of BDE-99 to groundwater.

Bio-inducing effect on the productivity of tomato plants and rhizosphere microbiota formation

Processing seeds with bio-fertilizers reduces passage of the basic stages of organogenesis tomato plants in the seedling period accelerates the rate of formation of true leaves and flowers of the amount pledged. Using of such bio-fertilizers as Agro Buck Plus, Rost Kontsentrat (Velez-BIO, Ltd. LNG) and Ekstrasol (LLC Bisolbi-Inter) leads to an increase in dry matter content, total sugar, vitamin C, reduction of nitrate content and increase the nutritional quality of tomato fruits. Bio-fertilizers based on nitrogen-fixing bacteria Bacillus subtilis and humate potassium exhibit a stimulating effect on the number of microorganisms of the rhizosphere of agronomically important groups of tomato variety Klondayk

Cloning and elucidation of the functional role of apple MdLBD13 in anthocyanin biosynthesis and nitrate assimilation

The plant specific lateral organ boundaries domain (LBD) family of transcription factors (TFs) is involved in many aspects of plant growth and development. In this study, MdLBD13, a nitrate-induced LBD family gene from the apple (Malus × domestica), was isolated and characterized. Overexpression of MdLBD13 repressed anthocyanin biosynthesis by reducing expression of the structural genes associated with the flavonoid pathway. Overexpression ofMdLBD13 also repressed expression of the N–responsive genes that are required for nitrate uptake, transport and assimilation, resulting in reduced nitrate content and nitrate reductase activity in apple calli, as well as in Arabidopsis. Ectopic expression of MdLBD13 also promoted lateral root development in transgenic Arabidopsis. These results demonstrate that MdLBD13acts as a negative regulator in anthocyanin biosynthesis and nitrate utilization.

Effects of two slow-release nitrogen fertilizers and irrigation on yield, quality, and water-fertilizer productivity of greenhouse tomato

Technical research on efficient water and nitrogen use is crucial for sustainable agricultural development. A field experiment was conducted to investigate the combined effects of two slow-release nitrogen fertilizers (polymer-coated urea (PU) and carbon-based urea (CU)) and two different irrigation water levels (conventional irrigation, CI; 90% of conventional irrigation, RI) on tomato yield, quality, and water-fertilizer productivity. Tomato yield and irrigation water productivity improved when nitrogen fertilizer was applied. Compared with U application, CU application increased tomato fruit diameter, volume, single-fruit weight, yield, and water-fertilizer productivity, therefore increasing yield by 4600kgha−1 and net income from tomato cultivation by 6313yuanha−1. Treatment with the two slow-release nitrogen fertilizers increased soluble sugar and lycopene contents and reduced nitrate content in fruits. Compared with U treatment, PU and CU treatments decreased total nitrate nitrogen residue in the 0–100cm soil layer. Compared with CI, RI significantly reduced tomato yield and net incomes under PU treatment, whereas RI did not significantly reduce tomato yield and net income under CU treatment. RI increased fruit Vc (vitamin C) and lycopene contents. Results of the study indicated that polymer-coated slow-release fertilizers may have great potential for widespread use because they improved tomato fruit quality while reducing the environmental risks caused by soil nitrogen. In addition, carbon-based, slow-release nitrogen fertilizers promise to improve fruit quality, yield, water-fertilizer productivity, and benefits associated with tomato cultivation. These fertilizers also reduce environmental risks caused by soil nitrogen and help reduce irrigation water consumption while sustaining normal tomato growth and fruit yield, making their promotion extremely beneficial.

The Effect of Beaver Ponds on Water Quality in Rural Coastal Plain Streams

We compared water-quality effects of 13 beaver ponds on adjacent free-flowing control reaches in the Coastal Plain of rural North Carolina. We measured concentrations of nitrate, ammonium, soluble reactive phosphorus (SRP), and suspended sediment (SS) upstream and downstream of paired ponds and control reaches. Nitrate and SS concentrations decreased, ammonium concentrations increased, and SRP concentrations were unaffected downstream of the ponds and relative to the control reaches. The pond effect on nitrate concentration was a reduction of 112 ± 55 μg-N/L (19%) compared to a control-reach—influenced reduction of 28 ± 17 μg-N/L. The pond effect on ammonium concentration was an increase of 9.47 ± 10.9 μg-N/L (59%) compared to the control-reach—influenced reduction of 1.49 ± 1.37 μg-N/L. The pond effect on SS concentration was a decrease of 3.41 ± 1.68 mg/L (40%) compared to a control-reach—influenced increase of 0.56 ± 0.27 mg/L. Ponds on lower-order streams reduced nitrate concentrations by greater amounts compared to those in higher-order streams. Older ponds reduced SS concentrations by greater amounts compared to younger ponds. The findings of this study indicate that beaver ponds provide water-quality benefits to rural Coastal Plain streams by reducing concentrations of nitrate and suspended sediment.

Utilizing <i>Spirogyra grevilleana</i> as a Phytoremediatory Agent for Reduction of Limnetic Nutrients and <i>Escherichia coli</i> Concentrations

The freshwater alga Spirogyra grevilleana was used in an experimental biofiltration system to reduce levels of Escherichia coli, nitrates, and phosphates. Water collected from a 2.32 ha lake in Atlanta, Georgia, USA was pumped at a constant rate (6.17 × 10-1 m3·hr-1) through the algal filtration devices with low and high concentrations of S. grevilleana. Effluent water was tested over time for E. coli, nitrate, phosphate, dissolved oxygen, and pH levels. Both concentrations of S. grevilleana reduced E. coli by 100% and significantly reduced nitrate concentrations (30% ± 13%) and phosphate concentrations (23% ± 5%) while maintaining dissolved oxygen and pH at normal levels. Utilizing S. grevilleana in an algal filtration device could potentially provide a sustainable, flexible, and low-cost method of E. coli reduction in freshwater lakes worldwide. Initial results indicate that the use of S. grevilleana in conjunction with an algal filtration device is potentially capable of creating potable water.