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This study evaluated the effect of feeding silage to pigs on nitrogen (N) utilization and ammonia (NH3) volatilization. In total, 128 Yorkshire × Hampshire (30–110 kg) pigs were fed commercial feed (Control) or commercial feed mixed with dried, milled silage in pelleted form (Pellet-S), fresh, chopped silage (Silage-Ch) or intensively treated silage (Silage-Pr). Silage replaced 20% of the crude protein (g/kg). Diet affected daily N excretion, which was higher for pigs fed Silage-Ch and Silage-Pr than for pigs in the Pellet-S and Control treatments. Ammonium nitrogen (NH4-N) content in the manure and NH3 volatilization from fresh manure were higher for Control pigs than for pigs in the other treatments. Overall, these results show that pre-treatment of silage influences N utilization and excretion. Furthermore, the results indicate that feeding silage to pigs can reduce NH3 volatilization from fresh manure. [ABSTRACT FROM AUTHOR]

The preferable N source for tropical grasses and its effects on the nutritional status are still matters of priority investigation. This study aimed to explore the effects of N sources and N deprivation on growth and uptake of elements in a newly-released ruzigrass cultivar, BRS Integra. Plants were grown under controlled conditions in vermiculite and were supplied with nutrient solution containing either NH4+, NH4++NO3-, NO3- or no N added in solution making. Plant biomass, chlorophyll content, transpiration, N status, and levels of selected elements were evaluated. NH4+ improved biomass production and aboveground N contents. Other elements exhibited high (N, K and Na), medium (Mn), low (Ca, Cd, Cr, Cu, Mg, Ni and Zn) or non-detected (Al and Fe) translocation. Cd was included in the study because of its hazardous concentrations in agricultural soils in Brazil and its influence on N uptake and translocation in the genus Urochloa. All N sources increased the uptake of whole plant Cu and K and Al, and root Fe and Mg. Other favorable relations prevailed in the roots, specifically of NO3- on Ca and Ni, NH4+ and NH4++NO3- on Cr, and NH4+ on Cd. Removal of N supply caused increases on Mn and Na aboveground and Zn in roots. Overall, the more evident N source-induced uptakes were, in order of decrease, of NO3- on Ca, NH4++NO3- on Ni, and NH4+ on Cr, Cu and Mn. It is concluded that NH4+ is more efficient for fertilizing ruzigrass by improving growth and N uptake compared to NH4++NO3- or NO3-. In addition, the diverse effects of varying N sources on the uptake of 12 elements indicate such interactions should be taken into account to further improve fertilizer formulations. [ABSTRACT FROM AUTHOR]

We evaluated the effects of isoforms of ammonium transporters (AMT) and amino acid transporters (AAT) on three rice varieties cultivated with different levels of ammonium (NH4+) and its biochemical responses. The rice varieties used were IAC-47 (improved), Manteiga and Piauí (landraces), cultivated under 0.2 mM NH4+ (low N, LN), 1 mM NH4+ (sufficient N, SN) or resupply with 1 mM of NH4+ after three days without nitrogen (N). When cultivated with LN, the Piauí variety presented a higher expression of AAT (Lysine-Histidine Transporter 4 (OsLHT4) and GABA Transporters (OsGAT1)) in roots, while Manteiga and IAC-47 presented higher expression of the Amino Acid Permease 1 (OsAAP1) and Ammonium Transporter 1.1 (OsAMT1.1), respectively. Additionally, Piauí had the higher expression of glutamine synthetase (OsGS1.1 and OsGS1.3) in shoots cultivated with LN or resupply. The Piauí variety displayed higher glutamine synthetase activity and amino acid content under resupply. Manteiga and Piauí presented a lower reduction in fresh weight of leaves and sheaths under LN compared to IAC-47. The results suggest that the improved variety IAC-47 is more efficient when cultivated with SN, while, under LN or resupply, the landrace varieties were superior. Overall, the molecular responses were different among the varieties, which may affected their nitrogen metabolism. [ABSTRACT FROM AUTHOR]

Nitric oxide (NO) is involved not only in the regulation of plant growth, development, and stress responses but also in the regulation of plant-microbe interactions. Here, we demonstrate that Piriformospora indica can induce tobacco nitrate reductase to produce a NO signal in roots which enhances nitrogen uptake capacity by inducing the expression of ammonium and nitrate transporter genes and the development of lateral root and root hair, thereby promoting tobacco growth. In addition, the NO signal induced by P. indica is significantly different from that induced by the pathogen Phytophthora nicotianae. Inoculation with P. indica did not produce H2O2 and maintained high expression of Phytoglobin 1 in roots, resulting in a significantly lower NO level than in the roots inoculated with P. nicotianae. These findings suggest that an appropriate NO level is the likely basis of plant-P. indica symbiosis, which promotes the growth of host plants. [ABSTRACT FROM AUTHOR]

In this study, two experiments were conducted to evaluate the plant response of Brachiaria brizantha cv. MG5 to nitrogen forms and different pH of nutrient solution. For this, nutrient solutions containing ammonium and ammonium nitrate were fixed at pH 4, 6 or 8, and nutrient solution containing nitrate was fixed at pH 6. The pH adjustment was done by different compounds including MES, calcium hydroxide, calcium carbonate and sulfuric acid. In another experiment the seedlings were grown in nutrient solution with different N forms, but without pH adjustment. The results showed that plants in ammonium or ammonium nitrate at pH = 4 had better growth and performance, followed by pH = 6, compared to plants grown at pH = 8 (buffered with calcium carbonate). Calcium carbonate (bicarbonate) especially in higher amounts in nutrient solution (pH = 8) significantly reduced plant growth particularly root growth as the toxic effects were visible on the roots. The adverse effect of carbonate at high pH was more than those at low pH. High concentration of carbonate in presence of ammonium also was toxic for plants probably due to additional toxic effect of ammonia. However, plants were able to grow normally with different N forms under hydroponics culture, independent of pH effect. When pH was not controlled under different N-forms, there was no significant difference between root and shoot biomass production or leaf SPAD value and protein concentration. So, the presence of carbonate but not pH, was determined as an inhibiting factor for growth of Palisadegrass plants. [ABSTRACT FROM AUTHOR]

The response of pepper (Capsicum annuum L.) to Ammonium-N was studied in a multispan greenhouse under soilless culture using coir fiber as substrate. Ammonium-N application rates were 0, 2, 4, 6 and 8 mM with a total-N concentration of 13 mM. The total content of the rest of all macronutrients in the nutrient solution was maintained from the beginning of the experiment until the end. The highest water uptake was recorded at 2 mM ammonium concentration in the nutrient solution. Compared to nitrate, ammonium nitrogen caused a decrease in nitrate absorption, but led to an increase when applying 8 mM ammonium. Despite a progressive increase in ammonium content in the nutrient solution, potassium absorption was constant below the ammonium concentration of 8 mM. Under a high N-NH4 content (from 6 to 8 mM) in the nutrient solution, high toxicity was found, deriving in the appearance of deformed or noncommercial fruits. There was a significant benefit by the use of ammonium as a component in the nutrient solution. The optimum yield ammonium concentrations were found in the range from 2 to 4 mM. Nevertheless, concentrations higher than 6 mM led into a decrease in commercial production, with the production of increasing deformed fruit, out of size and/or blossom-end rot. [ABSTRACT FROM AUTHOR]

Ammonium (NH4+) is a major nitrogen source for tea plant growth. Although NH4+-induced growth of tea plants were reported, it was still unclear to elucidate the mechanism of proteins in tea plants in responding to NH4+ resupply. In the present study, the proteomic profiles of tea leaves under N deficiency/resupply were investigated by using LC-MS/MS and PRM technique. Compared with N deficiency, there were 247 and 328 proteins significantly expressed after 3 h and 3d of N resupplied, respectively. And compared with 3 h of N resupplied, there were 186 proteins significantly expressed after 3d of N resupplied. According to bioinformatics analysis, the results showed that different expressed proteins participated in various biological processes, such as PsbO, Pbs27, PsaN, and PsaF were involved in photosynthesis, ADH1, AOC3, URE, GDH1-2, and argD were involved in amino acid metabolism, CHI and ANR were involved in flavonoid biosynthesis, GSTF9, APX, and GSS were involved in glutathione metabolism, and PdxT and PdxS were involved in vitamin B6 metabolism. Through PPI analysis, the results showed that the interactions between different expressed proteins mainly occurred in the photosynthetic pathway. Ammonium supply has a profound impact on photosynthesis, amino acid metabolism, flavonoid biosynthesis, glutathione metabolism, and vitamin B6 metabolism. [ABSTRACT FROM AUTHOR]

Rice (Oryza sativa L.) is one of the most produced cereals in the world. Among the essential nutrients required by this crop, nitrogen (N) is of paramount importance to achieve optimum yields. In paddy fields, ammonium (NH4+) represents the main source of N. This work aimed to evaluate the root morphology, ammonium uptake kinetics and N accumulation in two upland rice varieties, Piauí and Manteiga from Maranhão – Brazil. The varieties were cultivated in hydroponic conditions and submitted to three different doses of ammonium: 1 – constant treatment with 0.2 mM NH4+, 2 – constant treatment with 1 mM NH4+ and 3 – constant treatment with 1 mM NH4+, followed by N starvation during 72 h and resupply with 1 mM NH4+. The varieties present contrasting behaviors when submitted to different doses of NH4+. Piauí showed higher biomass and root length under the treatment with 0.2 mM NH4+. The favorable kinetics parameters observed contributed to a higher N accumulation by Piauí in low dose of NH4+. Under 1 mM NH4+, a higher root biomass and favorable kinetics parameters was recorded by Manteiga. This variety presented a better performance with higher doses of N. Under the treatment of N resupply, Piauí variety showed to be more adapted, due to the greater root plasticity observed. For one hand, the results suggest that Piauí variety presents greater growth in environments with low dose or seasonal flux of NH4+. On the other hand, Manteiga variety presents better growth when submitted to higher levels of NH4+. [ABSTRACT FROM AUTHOR]

Macroalgal growth in temperate coastal ecosystems is primarily regulated by light and inorganic nitrogen availability. The effect of light (photon irradiance) on NO3- and NH4+ uptake, and NO3- - assimilation, were studied in the red macroalga, Hemineura frondosa, which does not operate a carbon concentrating mechanism (non-CCM). Non-CCM macroalgae grow in low and high light environments but become increasingly dominant with depth, suggesting a mechanism for 'preserving energy' under low light levels. H. frondosa was acclimated to limiting (30 µmol photons m-2 s-1) and saturating (150 µmol photons m-2 s-1) irradiances for 8 days. Then, NO3- and NH4+ uptake rates were measured under limiting and saturating irradiances at six concentrations ranging from 2--64 µM. NO3- uptake did not follow saturating uptake kinetics at both irradiances suggesting multiple uptake mechanisms. NH4+ uptake saturated at concentrations <32 µM under limiting but not under saturating irradiance. Saturating irradiance resulted in greater maximum uptake rates of both NO3- and NH4+. There was no evidence that irradiance regulated NO3- reduction by nitrate reductase. Also illustrated is the importance of measuring nitrate reductase activity on fresh material, as freezing in liquid nitrogen and storage at -80°C for 7 days caused a 65% decline in activity. Photosynthetic pigments, soluble tissue nitrogen and % total tissue nitrogen were all higher in limiting irradiance. In this first study of the nitrogen physiology of a non-CCM seaweed, we show that light regulates NO3- and NH4+ uptake but not NO3- assimilation. [ABSTRACT FROM AUTHOR]

This study examined the effect- of starvation on the chemical composition (total protein, crude fat, dry matter, ash) and the excretion of nitrogen (N) and phosphorus (P) of the Antarctic fish Notothenia coriiceps and Notothenia rossii. Starvation resulted in a decrease in lipid content in both species. In Notothenia coriiceps the body fat content decreased from 2.3% to 1.88% and in Notothenia rossii from 0.82% to 0.6%. Excretion rates of N and P were highest on the first day of starvation, then gradually decreased. Average excretion rates (in µmol N or P h−1 100 g−1) of ammonium nitrogen, organic nitrogen, reactive phosphorus, and organic phosphorus respectively were higher for N. coriiceps (8.71, 2.93, 1.09, 0.46) than N. rossii (6.28, 4.94, 0.54, 0.13). During starvation, the proportion of TON in the total excreted nitrogen was on average 43.5% for N. rossi and 24.1% for N. coriiceps, and remained at a relatively stable level. The study confirmed the natural adaptation of the studied fish to the long-term lack of food, and that the excreted loads of N and P may be a source of biogens for autotrophs and serve as a chemical signal in trophochemoreception. The inter-species differences in the excretion of N and P could be due to the differences in fish size, gonad stage of maturity, and nutritional preferences. [ABSTRACT FROM AUTHOR]

Anaerobic ammonium oxidation (anammox), a promising technology for bio-nitrogen removal, has been a research hotspot in the field of leachate treatment. However, the inhibitory effect of organic matter and high-strength nitrogen on anammox bacteria and the limitation of the theoretical total nitrogen removal efficiency of anammox (<90%) are obstacles to its wider application. The mechanisms of the inhibitory effects of organic matter, ammonium, and nitrite on anammox bacteria, and the corresponding control strategies are summaries. The anammox-based processes developed for advanced nitrogen removal (ANR) in recent years, including anammox-based heterotrophic denitrification, anammox-based partial denitrification, and anammox-based constructed wetlands are systematically discussed. An integrated anaerobic system of simultaneous denitrification and methanogenesis (anaerobic membrane bioreactor) + anammox-based processes was proposed for the ANR and optimal energy recovery from leachate. This process showed a 16% increase in biogas yield, a 64% decrease in aeration energy consumption, and the decrease in the external carbon source is expected to be 100% compared to conventional leachate treatment processes such as anoxic/oxic-membrane bioreactors. Finally, a few research perspectives on leachate treatment using anammox-based processes are reviewed. The conclusions drawn from the studies presented herein provide guidance for further research and engineering applications in the field of leachate treatment. AnMBR pretreatment is proposed for energy recovery and elimination of inhibition of anammox bacteria by organics. Anammox-based heterotrophic denitrification, partial denitrification, and anammox-based constructed wetlands are discussed for ANR. SDM is proposed for ANR from leachate via anammox effluent recirculation. An SDM(AnMBR)+anammox based process is proposed for energy saving and recovery. [ABSTRACT FROM AUTHOR]

This study aimed at quantifying nitrogen (N) and potassium (K) released from winery solid waste (WSW) composts during laboratory incubation to address deficiency in two texturally distinct soils. Composts had 4, 10, 20, 30, 40% (w/w) of filter materials (FMs) mixed with grape marc and pruning canes. The composts were mixed with the soils at equivalent rate of 200 kg N ha−1 and incubated for 42 days. Quantitatively higher (p < 0.05) ammonium N content was recorded in sandy than sandy loam soil during the incubation duration while exchangeable K was increased in K-deficient sandy soil. Cumulative total mineralized N (TMN) measured during the incubation duration ranged from 59 mg kg−1 to 672 mg kg−1 depending on compost type and soil texture while a 10-fold increase in compost FMs content resulted in 144% and 139% increases in cumulative mineralized K in sandy and sandy loam textured soil, respectively. Percent N mineralized from the composts relative to the amount applied during the incubation duration was less than 54% reflecting the composts and soils inherent characteristics. The high ammonium N and K mineralized suggests that farmers must be cautious in utilizing these composts for field crops production due to the potential environmental risks. [ABSTRACT FROM AUTHOR]

Nitrogen is an essential element for living organisms because it is a crucial constituent of biomolecules. Inadequate supply of usable nitrogen reduces plant growth and crop yield. The primary nitrogen sources for plants are nitrate and ammonium in soils, and plants have multiple layers of sensing and adaptive mechanisms that respond to the availability of these nutrients. The adaptive responses are called ‘nitrogen responses,’ which include morphological and physiological responses enabling plants to efficiently take up nitrogen and adapt to spatiotemporal fluctuations in nitrogen abundance in the field. In this review, we summarize the strategies that plants use to respond to changes in the nitrogen nutrient status in the soil and discuss different effects produced by nitrate and ammonium, emphasizing the important role of nitrate for plant growth. Recent studies revealed the molecular mechanism mediating the primary response to nitrate provision and the molecular mechanisms that coordinate the nitrogen response with responses to another macronutrient, phosphorus. We thus discuss these molecular mechanisms as well. [ABSTRACT FROM PUBLISHER]

Nitrogen is an essential element for plant growth. Development of the root system architecture is highly correlated with nitrogen availability from the environment. Recent studies show that auxin response modules are involved in nitrate-dependent lateral root growth. However, the role of auxin in nitrogen metabolism remains to be elucidated. Few researchers have addressed the effect of auxin signaling modules on the use of ammonium for nutrition. The purpose of this study was to describe and examine the relation between auxin signaling modules and ammonium for nutrition. The growth of T-DNA insertion lines for auxin signaling modules was compared with that of a wild type under different nitrogen regimes. Nitrogen use efficiency consists of two components: metabolism and uptake. The nitrogen usage index was calculated following elemental analysis to evaluate nitrogen metabolism. Isotope-labeled ammonium uptake was measured under nitrogen-deficient and -sufficient conditions. Transcriptional levels and accumulation of enzymes necessary for primary ammonium assimilation, glutamine synthetase and glutamate synthase were evaluated. One of the T-DNA insertion lines for the auxin signaling module, IAA17, showed severe growth reduction in hydroponic solution containing ammonium as a major nitrogen source. The accumulation of cytosolic glutamine synthetase was reduced in the roots of iaa17. The expression of cytosolic glutamine synthetase 1;2 in iaa17 did not respond to ammonium supply. Here we show that the auxin signaling module has an effect on ammonium use by regulating the transcriptional level of cytosolic glutamine synthetase 1;2 in the root, the gene essential for ammonium assimilation. [ABSTRACT FROM PUBLISHER]

This study was done to evaluate the growth responses of tomato plants (Lycopersicon esculentumMill.) to foliar application of ammonium sulfate in different concentrations of 0, 50, 100, or 200 mM once per week, as well as 50 mM in every other day under greenhouse and hydroponic culture system. The results showed that foliar application of ammonium restricted the plant height, yield, and vitamin C content of fruits, but it increased the chlorophyll content in treated plants. The highest and the lowest yield were obtained from zero (control) and 200 mM treated plants, respectively. Fruit hardness was not affected by treatments, while blossom end rot disorder was increased by higher concentrations of ammonium sulfate. In general, the result indicated that tomato plant is rather sensitive to foliar application of ammonium sulfate particularly to higher concentrations and application numbers. [ABSTRACT FROM PUBLISHER]

The brucellae are α-Proteobacteriacausing brucellosis, an important zoonosis. Although multiplying in endoplasmic reticulum-derived vacuoles, they cause no cell death, suggesting subtle but efficient use of host resources. Brucellae are amino-acid prototrophs able to grow with ammonium or use glutamate as the sole carbon–nitrogen sourcein vitro. They contain more than twice amino acid/peptide/polyamine uptake genes than the amino-acid auxotrophLegionella pneumophila, which multiplies in a similar vacuole, suggesting a different nutritional strategy. During these two last decades, many mutants of key actors in nitrogen metabolism (transporters, enzymes, regulators, etc.) have been described to be essential for full virulence of brucellae. Here, we review the genomic and experimental data onBrucellanitrogen metabolism and its connection with virulence. An analysis of various aspects of this metabolism (transport, assimilation, biosynthesis, catabolism, respiration and regulation) has highlighted differences and similarities in nitrogen metabolism with other α-Proteobacteria. Together, these data suggest that, during their intracellular life cycle, the brucellae use various nitrogen sources for biosynthesis, catabolism and respiration following a strategy that requires prototrophy and a tight regulation of nitrogen use. [ABSTRACT FROM AUTHOR]

Co-composting of chicken slurry and rice straw with clinoptilolite zeolite and urea as additives was conducted to determine the characteristics of a compost and their effects on controlling ammonium (NH4+) and nitrate (NO3−) losses from urea. Quality of the compost was assessed based on temperature, moisture content, ash, pH, electrical conductivity, carbon/nitrogen (C/N) ratio, NH4+, NO3−, macronutrients, heavy metals, humic acid, microbial population, germination index, and phytotoxicity test. Moisture content and C/N ratio of the compost were 43.83% and 15, respectively. Total N, humic acid, ash, NH4+, NO3−, phosphorus (P), calcium (Ca), magnesium (Mg), potassium (K), and sodium (Na) increased after co-composting rice straw and chicken slurry. Copper, iron (Fe), manganese (Mn), zinc (Zn), and microbial biomass of the compost were low. The germination rate of Zea mays on distilled water and Spinacia oleracea growth on peat-based growing medium (PBGM) and compost were not significantly different. Urea amended with compost reduced N loss by retaining NH4+and NO3−in the soil. [ABSTRACT FROM AUTHOR]

In this study, the removal of medium–low concentration ammonium–nitrogen () from waters and wastewaters on D113 resin was investigated with respect to pH, initialconcentration, temperature and contact time. The equilibrium ofon D113 resin reached in 20–30 min. The process ofremoval by D113 resin fitted Langmuir isotherm well. The pseudo second-order kinetic and intra-particle diffusion models were used to investigate the kinetic data ofon D113 resin. The desorption solution can be returned to production after pretreatment. The mechanism of removal ofby D113 resin was coexistence of adsorption and cation exchange. When the dosage of D113 resin was 5 g L−1, pH 6, contact 30 min at room temperature, initialconcentration being 116 mg L−1in rare earth metallurgical wastewater was reduced to 13 mg L−1after adsorption treatment. [ABSTRACT FROM PUBLISHER]

Water contamination by ammonium ions presents huge risks to the ecosystems. This work evaluated the potential of biochar as an alternative adsorbent to remove ammonium from aqueous solutions. Nine types of biochars were converted from three types of agricultural residuals at three pyrolysis temperatures. Batch sorption experiment showed that all the biochars effectively removed ammonium ions from water. The biochars produced at low pyrolysis temperatures, however, showed higher sorption of ammonium. The low-temperature biochars showed relatively fast sorption kinetics of ammonium, which reached equilibrium around 10 h. Sorption isotherms showed that the low-temperature biochars had high sorption capacities to the ammonium, and the Langmuir maximum capacities were all higher than 200 mg/g. Batch sorption experiments also showed the sorption of ammonium onto the biochar was affected by pH and temperature, but not by ionic strength. The biochar showed good sorption ability to ammonium in aqueous solutions under all of the tested conditions. Findings from this work indicated that biochar could be used as an alternative adsorbent for the treatment of ammonium in water. [ABSTRACT FROM AUTHOR]

A global dataset was compiled to examine relations between the total nitrogen to total phosphorus ratio (TN:TP) and microcystin concentration in lakes and reservoirs. Microcystin concentration decreased as TN:TP ratios increased, suggesting that manipulation of the TN:TP ratio may reduce microcystin concentrations. This relationship was experimentally tested by adding ammonium nitrate to increase the TN:TP ratio in large-scale (70 m3),in situmesocosms located in a eutrophic reservoir that routinely experiences toxic blooms of cyanobacteria. At a TN:TP ratio >75:1, chlorophytes dominated the phytoplankton community in the mesocosms, while cyanobacterial biovolume was significantly reduced and microcystin was not detected. In contrast, the unmanipulated reservoir was dominated by cyanobacteria, and microcystin was detected. Secchi depths were 1.1 to 1.8 times greater in the mesocosms relative to the reservoir. Cladoceran zooplankton had a larger body size (0.14 mm on average) in the mesocosms compared to conspecifics in the reservoir, which was likely related to the higher quality food. Combined, these empirical and experimental data indicate that although nutrient addition is counterintuitive to current cyanobacteria management practices, increasing the TN:TP ratio by adding nitrogen may be a potential short-term management strategy to reduce cyanobacteria and cyanotoxins when other alternatives (e.g., phosphorus reduction) are not possible. Additional experimental studies with careful controls are needed to define best management practices and identify any potential unintended consequences before nitrogen addition is implemented as a lake and reservoir management practice. [ABSTRACT FROM AUTHOR]

Mathematical models have been developed to describe nitrogen uptake and duckweed growth experimentally to study the kinetics of ammonium uptake under various concentrations. The kinetics of duckweed ammonium uptake was investigated using the modified depletion method after plants were grown for two weeks at different ammonium concentrations (0.5–14 mg/L) in the culture medium. The maximum uptake rate and Michaelis–Menten constant for ammonium were estimated as 0.082 mg/(g fresh weight·h) and 1.877 mg/L, respectively. Duckweed growth was assessed when supplied at different total nitrogen (TN) concentrations (1–5 mg/L) in the culture medium. The results showed that the intrinsic growth rate was from 0.22 to 0.26 d−1, and TN concentrations had no significant influence on the duckweed growth rate. [ABSTRACT FROM AUTHOR]

Strawberries (Fragaria × ananassa Duch. cv. Nyoho) grown in peat-based substrate often suffer interveinal chlorosis in their immature leaves 10–20 d after planting. Based on our previous results and observations from growing practice, we hypothesized that the cause of this phenomenon could be due to drastic changes in plant nitrogen (N) nutrition in strawberries just after planting into peat bags. To determine optimal sampling time, diurnal variations in foliar ammonium (NH4)-N concentration were evaluated under greenhouse conditions. Results showed a broadly similar pattern of diurnal variation, with the rates increasing to a maximum at midday and decreasing steadily during the second-half of the light period. However, foliar NH4-N concentration was higher under sunny than under cloudy or shaded light conditions. In the second part of this study, changes in foliar NH4-N and in nitrate (NO3)-N in petioles in relation to the occurrence of interveinal chlorosis were investigated. When the plants were supplied with 30 (control) or 50% ‘Ohtsuka A’ nutrient solution for two weeks after planting, foliar NH4-N concentrations increased earlier than petiole NO3-N concentrations, and reached their peak 8 and 10 days after planting in 50% (1.90 μmol g−1FW) and 30% (1.78 μmol g−1FW) treatment respectively. Interveinal chlorosis was observed in immature leaves in 50% treatment about 10 days after planting while there was no chlorotic symptom in control treatment. The absence of interveinal chlorosis in immature leaves in control plants, led to the conclusion that a high leaf NH4-N concentration and related accumulation of NH4-N play an important role in triggering interveinal chlorosis. [ABSTRACT FROM PUBLISHER]

Experiments were performed to remove nitrogen as ammonium in biotrickling filters (BTFs) treating synthetic swine manure. Two BTFs packed with polypropylene spheres and ceramic beads were used. BTFs were continuously fed, and leachate obtained was recirculated at different flow rates in the range from 0 to 1.5 L min−1. When increasing the recirculation flow rate, the carbon dioxide (CO2) production rate increased from 16.5 to 25.6 g CO2 m−3 h−1and nitrogen elimination decreased from 99% to 86% for the polypropylene spheres, whereas for the ceramic beads the CO2production rate decreased from 20.3 to 15.0 g CO2 m−3 h−1and nitrogen removal from 99% to 90%. The increase of recirculation flow rates also promoted the production of nitrite () in the leachate. For both packing types, when increasing nitrogen loads from 60 to 240 g N m−3 day−1without recirculation of leachate, the BTFs achieved nitrogen removals of more than 99%. For the same nitrogen loads, nitrogen removal increased from 90% to 99% for the BTF packed with ceramic beads at a recirculation flow rate of 0.6 L min−1. Operating the BTFs with continuous purge was optimal for biomass production with a maximum level of 71.3 g m−3 day−1. [ABSTRACT FROM PUBLISHER]

The application of batch systems to the direct treatment of dairy wastewater was investigated. Batch experiments were conducted to study the organics removal and simultaneous nitrification and denitrification (SND) process. The experiment was conducted by varying four independent parameters (mixed liquor suspended solids, chemical oxygen demand [COD]/N ratio, aeration time and cycling time), using a central composite design under response surface methodology. The process responses of five dependent parameters (COD, Total kjehldahl nitrogen (TKN), NO3-, effluent NO3- and effluent total nitrogen) were studied, and in each case, the percentage removal in batch runs was determined with each process displayed in contour plots. Finally, after optimizing the process conditions, the best treatment of dairy wastewater under optimized conditions was established and the responses were shown. This study shows that microbial granules cultivated under the alternating aerobic/anaerobic conditions in batch systems could efficiently remove organic carbon and convert all the ammonium to nitrogen gas. [ABSTRACT FROM AUTHOR]

This study developed a capsule bioreactor made from polyvinyl alcohol (PVA) to entrap anaerobic ammonium oxidation (ANAMMOX) bacteria for the removal of nitrogen from synthetic wastewater. Experimental results demonstrate that the ANAMMOX bacteria were entrapped inside the capsule and not washed out from the bioreactor. This method also avoids damaging the ANAMMOX bacteria during immobilization. The proposed bioreactor also has a shorter start-up period. The diffusion rate of ammonium and nitrite from the bulk solution through the capsule determined the rate of the ANAMMOX reaction. The optimal ratio of was approximately 1 for the bioreactor. In addition, the capsule protected the ANAMMOX bacteria from nitrite inhibition. The bioreactor achieved a high stable nitrogen removal rate (5.8 Kg-N m−3 day−1) at high nitrite levels (up to 600 mg-N L−1 in the influent). Therefore, the proposed capsule bioreactor has considerable potential for actual nitrogen removal applications. [ABSTRACT FROM PUBLISHER]

Hydroponics is a common culture method for production of herbs. It is necessary to determine optimal ranges of elements in nutrient solutions. Four nutrient solutions, with different total nitrogen concentrations and ammonium-to-nitrate ratios were used to determine effects on yield and quality of basil (Ocimum basilicum L.) and cress (Lepidium sativum L.). Increasing ammonium benefited cress but not basil. Increasing nitrate positively affected basil. Cress and basil do not appear to need high levels of nutrients for production using hydroponics. [ABSTRACT FROM PUBLISHER]

It is hypothesised that NH -N is more mobile in soils than often thought. However, because litter layers and live vegetation can modify N species transformation in soils, intact microcosms were employed to investigate NH -N, NO -N and total dissolved inorganic N (DIN) leaching in soils from across an unfertilised and N-impacted grassland in York, UK. Simulated rain of diverse compositions was applied to five intact core microcosms, and leachate samples were collected at regular intervals. Leaching with simple simulated rain, consisting of appropriately dilute NaCl solution, showed that broadly comparable NH -N and NO -N leaching would occur from freely draining profiles. Profiles of heavy textured soils result in marginal DIN losses, primarily as NH -N because of denitrification, but possibly substantial losses as NH -N via overland flow during heavy precipitation. Further sequential leaching experiments on freely draining profiles with rain containing supplementary NH -N showed enhanced NH -N and NO -N leaching in two of three pairs of microcosms. However, one profile showed consistently lower NH -N leaching associated with the development of a consistently higher nitrification rate. The marked difference between profiles was thought to be due to the presence of a more distinct surface litter layer in one profile, compared with observable litter incorporation into subsoils for other profiles. Effects on mineral N species mobilities of drying and rewetting were also assessed. This confirmed that a delay of several days is required to re-establish the microbial population and its activities. Final phases, in which NO -N and then NH4NO3 were added via the rain, confirmed the mobility of N pollutant inputs through the freely draining soils. [ABSTRACT FROM PUBLISHER]

Zeolite minerals may improve nitrogen availability to plants in soil and reduce losses to the environment. A study was conducted to determine the influence of clinoptilolite (CL) on nitrogen (N) mineralization from solid dairy manure (224 kg N ha−1) in a sandy soil. Clinoptilolite was added to soil at six rates (0 to 44.8 Mg CL ha−1), each sampled during 11 sampling dates over a year. Over time, nitrate (NO3)-N increased, ammonium (NH4)-N decreased, but total inorganic N increased. Clinoptilolite did not influence the nitrification rates of initial manure NH4-N or mineralization of organic N (ON) over time. It is possible that adsorption of manure-derived potassium (K) outcompeted the NH4-N for CL exchange sites. The ON concentration was constant up to 84 days and then decreased by approximately 18% over the remaining time of the study across all treatments. Clinoptilolite use in this sandy soil did not alter mineralization of N from dairy manure. [ABSTRACT FROM AUTHOR]

Eutrophication has altered food webs across aquatic systems, but effects of nutrient stoichiometry (varying nutrient ratios) on ecosystem structure and function have received less attention. A prevailing assumption has been that nutrients are not ecologically relevant unless concentrations are limiting to phytoplankton. However, changes in nutrient stoichiometry fundamentally affect food quality at all levels of the food web. Here, 30-year records of nitrogen and phosphorus concentrations and ratios, phytoplankton, zooplankton, macroinvertebrates, and fish in the San Francisco Estuary (Bay Delta) were examined to collectively interpret ecosystem changes within the framework of ecological stoichiometry. Changes in nutrient concentrations and nutrient ratios over time fundamentally affect biogeochemical nutrient dynamics that can lead to conditions conducive to invasions of rooted macrophytes and bivalve molluscs, and the harmful cyanobacterium Microcystis. Several other aquatic ecosystems considered here have exhibited similar changes in food webs linked to stoichiometric changes. Nutrient stoichiometry is thus suggested to be a significant driver of food webs in the Bay Delta by altering food quality and biogeochemical dynamics. Since nitrogen-to-phosphorus ratios have increased over time, an overall implication is that remediation of fish populations in the San Francisco Estuary will require significant nitrogen reductions to restore the historic ecological stoichiometric balance and the food web. [ABSTRACT FROM AUTHOR]

Net nitrogen transformation was investigated under different climate conditions by soil transplantation and in situ incubation of forest surface soils using the resin-core method. Selected conditions were considered to reflect those of the natural climate gradient in the Japanese archipelago. Study sites were established in natural forests in northern Hokkaido (Uryu), northern Kanto (Kusaki), central Kinki (Kamigamo), and southern Kyushu (Takakuma), representing the northernmost to the southernmost island regions of Japan. Field experiments comparing soils incubated at 'native' and 'transplanted' sites were conducted from June 2008 to May 2009. Net production, accumulation, and leaching of soil ammonium (NH) and nitrate (NO) were measured at each of the sites during the growing season (June-October), the dormant season (November-May), and throughout the year. Net nitrate production was highest in Kusaki soil, especially during the growing season, whereas net ammonium production was highest in Uryu soil, the coldest site, especially during the dormant season. Net nitrate production increased significantly in soils transplanted to a warmer climate during the growing season. However, net ammonium production increased in soils transplanted to colder climates during the dormant season. These findings indicate that, with the exception of the infertile soil samples from Kamigamo, the range of natural climates in Japan has a significant effect on nitrogen availability in surface soil. In addition, the original characteristics of the nitrogen cycle of the surface soil from each native site were retained, even when marked changes in soil temperature (approximately 8°C) occurred after transplantation. [ABSTRACT FROM AUTHOR]

The major objective of this research was to investigate the efficiency of zeolite in the removal of NH4-N from swine wastewater and desorption of the sorbed NH4-N from the zeolite saturated with N. Sorption experiments were conducted on the sorbents, zeolites I, II and III. Zeolites II and III which are natural and unmodified, showed better sorption (4400-4500 mg kg-1 with 500 mg L-1 feed concentration) compared to Zeolite I (3053 ± 127 mg kg-1 with 500 mg L-1 feed concentration), which is a surfactant modified zeolite. Freundlich and Langmuir isotherms were plotted from the sorption experimental data. Column studies indicated that, columns with flow rates of 2 and 3 mL min-1, reached the breakthrough point within about 100 h. The possibility of regeneration of the column material was investigated by flushing the column with 0.1 N HCl. The results from this experiment showed that even after desorption with DI water for more than 250 h, considerable amount of N was still available in the column that was available for desorption by 0.1 N HCl. This confirms that zeolite could be a good substrate for slow N release in soil. The application of Zeolite II for the NH4-N removal from swine wastewater supports this observation. [ABSTRACT FROM AUTHOR]

The effect of different levels and forms of nitrogen (N) fertilizer on cadmium (Cd) concentrations in potato (Solanum tuberosum L.) tubers, a large component of the northern European diet, was investigated with the aim of decreasing the Cd content. A high and a low Cd-accumulating cultivar were used in two field trials and a pot experiment. The N fertilizers tested were balanced N- phosphorus (P)- potassium (K) 11-5-18 + micronutrients, alkaline calcium nitrate and acidic ammonium sulfate at levels of 60, 160, and 240 kg N ha-1 at planting or (for the higher N doses) split between two or three occasions. The Cd concentration in tubers of both cultivars decreased when increasing the N fertilizer from 60 to 160 or 240 kg N ha-1, indicating that Cd uptake and translocation are not positively correlated to the growth rate of the potato plant. A strong positive linear correlation was found between the Cd concentration in leaves at 77 days after planting and the Cd concentration in tubers at harvest, irrespective of N treatment, although the Cd concentration was three-fold higher in the leaves. The genetic variation in leaf and tuber Cd accumulation was consistent, regardless of the form of N fertilizer used. Ammonium sulfate decreased soil pH and increased tuber Cd concentration in both cultivars compared with NPK fertilizer, possibly due to increased amounts of plant-available Cd arising from the pH decrease after ammonium sulfate application. The tuber Cd concentration in the low Cd-accumulating cultivar increased when fertilized with calcium nitrate, an effect attributed to Cd availability being influenced by the increased Ca2+ concentration. [ABSTRACT FROM AUTHOR]

Removal of total nitrogen from anaerobically digested sludge reject water by a fully autotrophic process in either one- or two-reactor systems was compared. Autotrophic nitrogen removal is currently most often applied in the one-reactor system primarily in the DEMON configuration. The two-reactor systems had a similar nitrogen removal rate to the one-reactor systems. It was evident that the limiting step was partial nitrification. Increase in partial nitrification can be difficult in a one-reactor system, where the overall conditions, such as the oxygen concentration or substrate concentrations, would progress to full nitrification. The partial nitrification of the two-reactor system may be improved by adjusting key parameters: the un-ionized form of the substrates, the oxygen concentration or the solids residence time. The impact of two process configurations on the operational stability and process performance was presented based on two cases - DEMON and the SHARON-ANAMMOX process. [ABSTRACT FROM AUTHOR]

The objective of the experiment was to identify the most favorable nitrogen (N) source ratio of ammonium (NH4+) and nitrate (NO3-) for aeroponically-grown Douglas-fir when pH was maintained at pH 4.0. Seedlings were grown in controlled environments with solutions containing 0:100, 20:80, 40:60, 60:40, 80:20 or 100:0 NH4+:NO3- ratios. Nutrient additions in the aeroponic culture units were controlled by solution conductivity set points. Seedling growth and nutrient allocation was observed for 45 days. Different NH4+:NO3- ratios resulted in significant differences in the rate of N addition, growth, morphology, and nutrient allocation. Seedlings grown in solutions containing 60 or 80% NO3- were characterized by a combination of high growth and photosynthetic rates, high and stable internal plant N concentrations, and sufficient levels of other essential nutrients. High proportions of NH4+ in solution resulted in low rates of N addition, stunted lateral root growth, and may have been toxic. [ABSTRACT FROM AUTHOR]

The present work evaluates whether ammonium and nitrate ions become linked with diluted olive oil mill wastewaters (OOMW). From a laboratory experiment it was concluded that the ammonium ion linked with OOMW in the presence of carbonates or hydroxides and OOMW could block up to a third of the present ammonium-N ion. On the other hand, OOMW are capable of joining with the nitrate ion, in a sulphuric diluted medium at room temperature, retaining up to 80% of nitrate-N. These complexes could be useful for recycling OOMW as new OOMW-N fertilizers. In soils treated with OOMW-N fertilizers, the nitrate-N emissions were reduced by 90% for two months. So, inorganic-N fertilizers mixed with OOMW could produce new organic fertilizers with a higher efficiency index for N. [ABSTRACT FROM AUTHOR]

Crop residues are an important component of N cycling in the agro-ecosystem. In this study, a loam soil was amended with cabbage residues and the N mineralization from soil organic matter and residues, as well as N uptake by Italian rye grass, were investigated. Four mineral fertilizer-residue combination treatments and two application times were tested in micro-plots. For uncropped micro-plots, application of residue resulted in higher soil mineral N content (43 mg N kg-1, 63 days post application) versus 30.5 mg N kg-1 for an unamended soil. Both bulked dry matter production and N uptake by the rye grass decreased in the order full mineral fertilizer > half mineral fertilizer + half residue > full residue applied 3 weeks before sowing > full residue applied at sowing, but the differences were more pronounced in the N uptake. Shoot N recovery from the applied residue (27.5-31.4%) was much smaller than that from the full fertilizer (70.2%), but was still considerable. Apparent net N mineralization from soil organic matter was significantly depressed in the treatments where mineral fertilizer was added. Cropping also reduced apparent net N mineralization, but this effect was reduced when residues were applied 3 weeks before sowing. Results showed that crop residues play an important role in crop production, in terms of obtaining comparable dry matter production to that of full mineral fertilizer application. Moreover, nitrogen supplied as residue is less liable for loss due to leaching during the growing season. The efficiency of crop uptake to residue-derived nitrogen could be increased by earlier application time. [ABSTRACT FROM AUTHOR]

An experiment was carried out to study the changes in nutrient contents during preparation of enriched organomineral fertilizers using rice straw, low-grade rock phosphate (RP), waste mica, and phosphate-solubilizing microorganism (Aspergillus awamori). Composting reduced the total carbon (C) but increased total nitrogen (N) content with the progress of composting. This was reflected in the decrease of the C/N ratio. Significant increases in total phosphorus (P) and potassium (K) were also observed where both RP and waste mica was added along with Aspergillus awamori. Ammonium N (NH4 +-N) decreased while nitrate N (NO3 --N) increased at the end of composting. Olsen P content increased up to 90 days, thereafter decreased up to day 150, whereas ammonium acetate K (NH4OAc-K) increased gradually with the progress of composting. The study thus revealed that crop residue could be converted into a value-added product through composting technology using low-grade rock phosphate and waste mica along with phosphate-solubilizing microorganisms. [ABSTRACT FROM AUTHOR]

Adequate availability of nitrogen (N) to satisfy potato crop N requirement is critical for production of optimal tuber yields with high processing qualities, which will contribute to maximum net returns. The agroclimatic conditions in the Columbia Basin region in the Pacific Northwest (PNW) supports high potato tuber yields with high processing qualities. Best management of N fertilization is important to increase N uptake efficiency and to minimize N losses. Monitoring soil and petiole N provides a basis to evaluate available N in the soil and N status in the plants. This study was conducted on a Quincy fine sand (mixed, mesic Xeric Torripsamments; >95% sand) using 'Ranger Russet' potato cultivar. Potato followed by 2 years of sweet corn rotation was adapted in this study. Treatments included the following preplant (PP) + in-season (IS) N rates in kg ha-1: (i) 56 + 280, (ii) 112 + 224, or (iii) 112 + 336 in 2004 or 112 + 112 in 2005. The IS N was applied in five equally divided doses at 2-week intervals, 3 weeks after seedling emergence. An additional treatment was included with treatment (ii) N rates, except that IS N was delivered in 10 weekly applications. Total tuber yield ranged from 54 to 64 and 78 to 90 Mg ha-1, respectively, in 2004 and 2005. In 2004, during the first 65 days after emergence (DAE), petiole nitrate (NO3) concentration was lower in the treatment (i) than that in the other treatments. This difference was not evident in 2005. The petiole NO3 concentrations were lower in 2005 than that in 2004, particularly during latter part of the growing period. Soil available N [nitrate NO3-N + ammonium (NH4) N in the top 30 cm] concentrations were also greater in 2004 than those in 2005. Soil N appeared to increase toward the end of the growing season in 2004, which has negative effects on tuber yield and quality. Across all treatments, total tuber yield and that of >340-g grade tubers were greater in 2005 than that in 2004. [ABSTRACT FROM AUTHOR]

Black walnut (Juglans nigra L.) half-sib 1+0 seedlings were exponentially fertilized with ammonium (NH4+) as ammonium sulfate [(NH4)2SO4], nitrate (NO3-) as sodium nitrate (NaNO3), or a mixed nitrogen (N) source as ammonium nitrate (NH4NO3) at the rate of 0, 800, or 1600 mg N plant-1 and grown for three months. One month following the final fertilization, N concentration, growth, and photosynthetic characteristics were assessed. Compared with unfertilized seedlings, N addition increased plant component N content, chlorophyll content, and photosynthetic gas exchange. Net photosynthesis ranged from 2.45 to 4.84 μmol m-2 s-1 for lower leaves but varied from 5.95 to 9.06 μmol m-2 s-1 for upper leaves. Plants responded more favorably to NH4NO3 than sole NH4+ or NO3- fertilizers. These results suggest that N fertilization can be used to promote net photosynthesis as well as increase N storage in black walnut seedlings. The NH4NO3 appears to be the preferred N source to promote black walnut growth and physiology. [ABSTRACT FROM AUTHOR]

Soluble amino acids in roots and primary amino acids, which were involved in primary ammonium assimilation, in the metabolites of 14C-glucose fed to roots for 3 h in the dark were analyzed in the roots of non-nodulated soybean and pea plants grown in ammonium, nitrate or nitrogen-free media for 1 day. Compared with the effect of nitrate, ammonium supply strongly affected the content and synthesis of the amino acids in the roots. In both soybean and pea roots, the supply of ammonium increased considerably the concentrations of the primary amino acids, and asparagine was the most predominant amide, followed by glutamine. In nitrate-supplied soybean roots, the concentrations of asparagine, aspartate and alanine increased, but the concentration of glutamine was low. In the roots of pea plants grown in nitrate media, asparagine was the predominant amino acid, although the composition of the primary amino acids was little affected by nitrate supply. The proportion of amino acids synthesized from 14C-glucose increased and asparagine rather than glutamine was predominantly synthesized in ammonium-supplied soybean and pea roots, whereas in nitrate-supplied roots asparagine was more actively synthesized than glutamine, although asparagine was not predominant. The ratio of C4 (asparagine + aspartate) to C5 (glutamine + glutamate) amino acids was twofold higher in ammonium-supplied and nitrate-supplied soybean roots than in roots receiving no nitrogen. In contrast, in pea roots, the C4/C5 ratio was twofold higher only in ammonium nutrition. The results obtained suggest that the roots of leguminous plants might possess an indigenous ability to provide a carbon skeleton for preferential synthesis of asparagine rather than glutamine with a high intensity of ammonium supply. [ABSTRACT FROM AUTHOR]

It had previously been shown that ammonium selective natural zeolite clinoptilolite may be used successfully as an ion exchanger for ammonium removal and nitrogen control from domestic wastewater. The process had been reported to be acceptable either by itself alone or as an upgrade. In this work, the possibility of using clinoptilolite for ammonium removal from fertilizer production wastewater was investigated. The fertilizer plant under consideration was rather a non-typical one with a lower ammonium strength than what is normally expected, and a variable effluent concentration. Batch experiments were performed to assess the capacity of clinoptilolite towards ammonium removal from an industrial wastewater at two different pHs. Flow experiments for the characterization of system behavior under continuous feeding conditions at different contact times were conducted for breakthrough analysis. Both real and simulated fertilizer wastewater samples were investigated and the results have shown that the real one may successfully be represented by the simulated one. Experimental results have shown that surface capacities exceeding 14 mg ammonium g-1 clinoptilolite could be attained, complete removal of ammonium may be achieved with empty bed contact times of 10 min or higher and ion exchange with clinoptilolite could be used successfully to comply with the effluent standards given for the fertilizer plant. [ABSTRACT FROM AUTHOR]

Continuous flow analysis (CFA) with photometric detection is widely used to quantify [image omitted]. However, low-molecular-weight amines interfere with CFA measurements. Therefore, we compared CFA and ion-selective electrode (ISE) measurements using an ISE25NH4 electrode from Radiometer Analytical for determining [image omitted] in wastewater streams in a plant where protein separation media are manufactured. Approximately 50% of the trimethylammonium chloride in one of the samples was recorded by CFA as ammonium nitrogen. Furthermore, CFA spikings using 6 mg N/L [image omitted] additions to the wastewater showed less accuracy compared with equivalent ISE spikings. Direct ISE measurements of [image omitted] levels in wastewater across the concentration range 0.1-1400 mg N/L typically showed >90% accuracy, with <1% RSD repeatability (both within- and between-day). Furthermore, due to the excellent selectivity of the electrode for [image omitted] over Na+ (logKNH4 - N, NaPot) = -3.11, the presence of potentially interfering Na+ ions in selected wastewaters did not affect the readings. ISE measurements obtained by multiple standard addition methodology showed similar levels of accuracy and repeatability, except that the accuracy of the determinations was affected by the non-linear electrode responses to samples with low [image omitted] concentrations (<1 mg N/L). Direct ISE and CFA measurements on two types of wastewater streams revealed significant differences (p < 0.05). The ISE results showed on average 18 and 112% higher [image omitted] concentrations compared with CFA results. The known occasional ammonium increase in one of the streams was not detected by the CFA method. [ABSTRACT FROM AUTHOR]

Aerobic incubation methods have been widely used to assess soil nitrogen (N) mineralization, but standardized protocols are lacking. A single silt loam soil (Catlin silt loam; fine-silty, mixed, superactive, mesic, Oxyaquic Arguidoll) was subjected to aerobic incubation at six USDA-ARS locations using a standardized protocol. Incubations were conducted at multiple temperatures, which were combined based on degree days (DD). Soil water was maintained at 60% water-filled pore space (WFPS; constant) or allowed to fluctuate between 60 and 30% WFPS (cycle). Soil subsamples were removed periodically and extracted in 2 M potassium chloride (KCl); nitrate (NO3) and ammonium (NH4) concentrations in extracts were determined colorimetrically. For each location, the rate of soil organic-matter N (SOMN) mineralization was estimated by regressing soil inorganic N (Ni) concentration on DD, using a linear (zero-order) model. When all data were included, the mineralization rate from four datasets was not statistically different, with a rate equivalent to 0.5 mg N kg-1 soil day-1. Soil incubated at two locations exhibited significantly higher SOMN mineralization rates. To assess whether this may have been due to pre-incubation conditions, time-zero data were excluded and regression analysis was conducted again. Using this data subset, SOMN mineralization from five (of six) datasets was not significantly different. Fluctuating soil water reduced N-mineralization rate at two (of four) locations by an average of 50%; fluctuating soil water content also substantially increased variability. This composite dataset demonstrates that standardization of aerobic incubation methodology is possible. [ABSTRACT FROM AUTHOR]

Solar drying has been used extensively to dewater biosolids for ease of transportation and to a lesser degree to reduce pathogens prior to land application. The nitrogen in biosolids makes them a relatively inexpensive but valuable source of fertilizer. In this study, nitrogen loss from tilled and untilled biosolids was investigated during the solar drying process. Samples of aerobically and anaerobically digested biosolids during three solar drying experiments were analyzed for their nitrate (NO3-) and ammonium (NH4+) ions concentrations. Nitrogen losses varied depending on the solar drying season and tillage. Although not directly measured, the majority of nitrogen loss occurred through ammonia volatilization; organic nitrogen content (organic N) remained relatively stable for each sample, nitrate concentrations for the majority of samples remained below detectable levels and the decline of ammonium-nitrogen (NH4+-N) generally followed the trend of moisture loss in the biosolids. [ABSTRACT FROM AUTHOR]

Two cultivars of pea: 'PS210713' ('PS'), sensitive to iron deficiency, and 'Marveille de Kelvedon' ('MK'), tolerant, were cultivated in controlled climatic conditions during one month, on a nutrient solution containing either nitrate (NO3-, 4 mM) or ammonium (NH4+, 4 mM) and in the presence of bicarbonate (10 mM). The effects of these nitrogen forms on the growth and the mineral nutrition, and especially iron nutrition are analyzed. The reduction of growth by bicarbonate was approximately 30% in case of NO3- nutrition in the two cultivars, whereas in ammoniacal treatment the reduction is only 6% and 18% respectively in 'PS' and 'MK' cultivars. In presence of bicarbonate, the plant growth is not stimulated by NO3-relatively to its growth on ammoniacal medium, as often noticed when plants are cultivated on medium without bicarbonate: In presence of this compound, the biomass production of plant pea, was not influenced by the nitrogen forms. The nitric source led to a ferric chlorosis in the sensitive cultivar plants whereas any chlorosis was noted when ammoniacal source was applied. On the other hand, nitric nitrogen form decreased the nitrogen feeding of plants and increased the potassium one, while the effect of the ammoniacal nitrogen form on these nutrients was quite the inverse. In addition, the later increased the allocation of iron towards shoots. Besides, with this nitrogen source there was not accumulation of nitrate in the plant tissues. In nitric feeding case, the nitrate is mainly accumulated in the roots of the two cultivars. It is noticeable that the sensitive cultivar ('PS') accumulates three times more nitrate than the tolerant one ('MK'). On the level of the whole plant, the iron and phosphorus nutrition seems unaltered by the nitrogen form. [ABSTRACT FROM AUTHOR]

Aquatic plants can be used for treating eutrophicated water in a simple and cost-effective manner, but many such plant systems remain to be characterized. The effects of growing Eichhornia crassipes on removal of nitrogen (N) from the eutrophicated water were investigated in a large-scale enclosure system installed in hyper-eutrophicated water in Hua-jia-chi pond, Hangzhou city, China. Total N concentration in the enclosures decreased from 2.1 to 0.50 mg L- 1 after growing Eichhornia crassipes for 44 d. Ammonium concentration decreased at least 2-fold after plant growth. Nitrite concentration decreased to below detection limit after growing Eichhornia crassipes for only 14 d and was maintained at that level afterwards. Chlorophyll a concentration (an indicator of water eutrophication) decreased to 10 μ g L- 1 after 44 d. The water transparency increased significantly, reaching the depth of 1.8 m (i.e., to the bottom of the pond) after 44 d. Eichhornia crassipes removed 21.7 kg nitrogen from 6,000 t of hyper-eutrophicated water in the enclosures, thus quickly and effectively improving the water quality. Growing Eichhornia crassipes is the first step toward re-establishing natural ecosystem functions in eutrophicated water bodies. [ABSTRACT FROM AUTHOR]

The short-term fate and retention of ammonium (NH4)-15nitrogen (N) applied to two types of forest soils in east Tennessee was investigated. Four ridgetop forests, predominantly oak (Quercus spp.), were studied. Five applications of NH4-15N tracer were made to the forest floor at 2- to 4-week intervals over a 14-week period in 2004. Nitrogen-15 recovery in the forest floor, fine roots (<2 mm), and the mineral soil (0-20 cm) was calculated at 6, 21, and 42 weeks after the last application. Most of the 15N was retained in the forest floor and the mineral soil, with only small amounts (≤2%) found in roots from both soil layers. Recovery of NH4-15N was greater in Inceptisols, which had a wider carbon (C)-to-N ratio than Ultisols. For both soil types, higher NH4-15N recoveries and long retention times (half-lives>100 weeks) indicated the forest floor is an effective filter for atmospheric N inputs. [ABSTRACT FROM AUTHOR]

A routine soil test that accurately predicts soil nitrogen (N) mineralization has long eluded researchers. Soil incubations, which are not practical for routine soil testing, are the only methods that have proven successful. Although several quick analytical methods have been proposed, no one method has correlated consistently enough to be implemented into a soil-testing program. The objective of this study was to compare proposed quick analytical procedures with the amount of ammonium (NH4)-N mineralized after a 14-d anaerobic incubation. The analytical methods of interest were applying a mild acid oxidation to the soil using acidified permanganate; analyzing a 1 M potassium chloride (KCl) soil extract in the ultraviolet (UV) spectrophotometric range before and after nitrate (NO3) removal with Devarda's alloy; and quantifying soil amino sugar-N content using the Illinois soil N test (ISNT) diffusion method. Fifty agricultural soils with different physical and chemical properties were utilized in this study. All methods displayed significant relationships with the anaerobic incubation procedure; however, some methods displayed higher, more acceptable, coefficients of determination. The ISNT and UV spectrophotometry measurement at 210 nm after NO3 removal failed to accurately estimate N mineralization (R2=0.45 and 0.31, respectively). The acid oxidation procedure and UV measurement at 260 nm of soil extracts before NO3 removal produced better results with coefficients of determination of 0.58 and 0.56, respectively. We suspect the ability of some methods to predict N mineralization was hindered because of the wide variety of geographic locations from which the soils were collected. Additional analyses were conducted on a subset of 16 silt-loam soils from Arkansas. The coefficient of determinations increased for each method: acid oxidation procedure increased to 0.83, the ISNT increased to 0.71, and the UV method (at 260 nm before NO3 removal) increased to 0.63. If anaerobic incubation is a true indication of N mineralization in the field, the aforementioned methods display promise to correlate with N uptake by field-grown plant studies when adapted to a specific geographic location and/or soil series. [ABSTRACT FROM AUTHOR]

On the basis of the principle of reaction continuous-flow quadrupole mass spectrometry, an automated sample preparation unit for inorganic nitrogen (SPIN) species was developed and coupled to a quadrupole Mass Spectrometer (MAS). The SPINMAS technique was designed for an automated, sensitive, and rapid determination of 15N abundance and concentration of a wide variety of N-species involved in nitrogen cycling (e.g. [image omitted] , [image omitted] , NH2OH etc.). In this paper, the SPINMAS technique is evaluated with regard to the determination of 15N abundance and concentration of the most fundamental inorganic nitrogen compounds in ecosystems such as [image omitted] , [image omitted] , and [image omitted] . The presented paper describes the newly developed system in detail and demonstrates the general applicability of the system. For a precise determination of 15N abundance and concentration, a minimum total N-amount of 10 μg [image omitted] - N, 0.03 μg [image omitted] - N, or 0.3 μ g [image omitted] - N has to be supplied. Currently, the SPINMAS technique represents the most rapid and only fully automated all-round method for a simultaneous determination of 15N abundance and total N-amount of [image omitted] , [image omitted] , or [image omitted] in aqueous samples. [ABSTRACT FROM AUTHOR]

Three DNA fragments belonging to genes involved in nitrogen uptake and assimilation, including a nitrate transporter gene (IgNr12), an ammonium transporter gene (IgAmt), and a glutamine synthetase gene (IggInIl), were obtained from the marine haptophyte, Isochrysis galbana. Based on alignments of the deduced amino acid sequences, the IgNRT2 fragment shared 47% identity with the Cylindrotheca fusiformis (Bacillariophyceae) nitrate transporter, the IgAMT fragment shared 48% identity with the C. fusiformis ammonium transporter, and the IgGSII fragment shared 61% identity with Skeletonema costatum (Bacillariophyceae) glutamine synthetase. Southern hybridization indicated that both IgNrt2 and IgAmt may have more than one copy in the genome of I. galbana, but only a single copy was detected for IggInII. The transcript abundances of these three genes under various nitrogen-supply conditions were monitored simultaneously by quantitative real-time polymerase chain reaction (PCR). In the presence of ammonium, both IgNrt2 and IgAmt were severely repressed with mean mRNA concentrations of 0.67 and 3.45 μmol (mol 18S rRNA)-1. IgNrt2 and IgAmt mRNA transcripts increased 41-fold and 8.3-fold, respectively, in the presence of nitrate, and increased 160-fold and 15-fold, respectively, in the nitrogen-depleted condition. The mRNA level of IggInII was low in cells grown in the presence of ammonium [3.98 μmol (mol 18S rRNA)-1], but mild increases in the range of 2- to 4-fold were observed in cells grown in both nitrate-containing and nitrogen-depleted cultures. Our results demonstrated that the expression patterns of IgNrt2. IgAmt, and Igglnll shared a common trend with their homologous genes in diatoms and green algae under various nitrogen-supply conditions. This group of genes could be used as indicators in natural environments to estimate the degree of nitrogen deficiency and chemical forms of nitrogenous nutrients in use on a species-specific basis. [ABSTRACT FROM AUTHOR]