Dissertationen zum Thema „Effect of nitrogen on“
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1
Farr, C. R. „Nitrogen Stabilizer Effect on Nitrate Nitrogen Management in Soils“. College of Agriculture, University of Arizona (Tucson, AZ), 1987. http://hdl.handle.net/10150/204454.
2
Zhou, Maoqian 1961. „Nitrogen fixation by alfalfa as affected by salt stress and nitrogen levels“. Thesis, The University of Arizona, 1989. http://hdl.handle.net/10150/277231.
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The growth and Nitrogen fixation by one low salt tolerant alfalfa (Medicago sativa L.) and two germination salt tolerant selections inoculated with were investigated at two salt levels (0, -0.6 Mpa) and two N rates (1, 5ppm) using a system which automatically recirculates a nutrient solution. The high level of salinity (-0.6 Mpa osmotic potential of culture solution) resulted in substantial reduction in the N fixation percentage and total fixed N. The effect of salinity was more pronounced for later cuttings than for the earlier cutting. The N fixation percentages were substantially decreased by increasing N level and the reduction was enhanced by time. The N treatment levels did not exhibit a significant effect on total fixed N. Cultivars did not differ in either growth or N fixation. However, the interaction of N and salinity significantly decreased the percentage and amount of N fixation.
3
Haig, Paul Andrew. „Effect of dietary nitrogen solubility on nitrogen losses from lactating dairy cows“. Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp01/MQ43169.pdf.
4
Bhogal, Anne. „Effect of long-term nitrogen applications on nitrogen cycling under continuous wheat“. Thesis, University of Nottingham, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.294731.
5
Saunders, Eleanor Margaret. „The effect of mineral nitrogen on ectomycorrhizas with special reference to nitrogen deposition“. Thesis, University of Sheffield, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.299547.
6
Cepeda, Jose de los Angeles 1955. „Nitrogen fixation by alfalfa as affected by osmotic potentials and measured by nitrogen-15 techniques“. Thesis, The University of Arizona, 1987. http://hdl.handle.net/10150/276591.
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One low salt tolerant alfalfa (Medicago sativa L.) cultivar and two germination salt tolerant alfalfa selections were compared for growth and N fixation at four salinity levels (0, -0.3, -0.6 and -1.2 Mpa). In the first experiment a Hoagland's solution at 5 ppm-N was used; in the second experiment the solution had a 1 ppm-N concentration and supplemental light was used. No significant differences were found among the cultivars. This provides additional support that germination salt tolerance is not necessarily related to salt tolerance for growth. Nitrogen fixed to the first harvest was 61, 48, 49, and 27% of the total shoot N for plants in the control, -0.3, -0.6, and -1.2 Mpa solutions, respectively. At the second harvest, N fixation percentages were 94, 89, 80, and 57% for the corresponding salinity levels which showed significant reduction in N fixation at -0.3 Mpa. The evaluation of N fixation was by 15N techniques.
7
Ippersiel, Denis. „The effect of foliar nitrogen fertilization on nitrogen distribution, yield and protein quality of forage corn /“. Thesis, McGill University, 1986. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=63798.
8
Papadopoulos, Anastasios K. „Nitrogen and moisture distributions under subirrigated soybeans“. Thesis, McGill University, 1994. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=55520.
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A field lysimeter experiment was conducted on a sandy loam soil during the 1990 and 1991 growing seasons. The experiment tested the effects of different watertables on soybean yields, and on moisture distribution and nitrogen concentration of the soil profile. The watertable depths were 40, 60, 80, and 100 centimeters (cm).Yields were measured in terms of number of beans per plant, number of pods per plant, number of beans per pod, and seed protein content at harvest.
Soil samples collected at depths of 30 and 70 cm from the soil surface were analyzed for moisture content and NO$ sb3 sp-$-N and NH$ sb4 sp+$-N concentrations.
The experimental results showed that controlled watertable management increased the yield and decreased soil NO$ sb3 sp-$-N levels. The best results from the watertables tested were found to be at 60 and 80 cm. This is suggested as the range of watertable depths that should be maintained for optimum soybean production.
9
Denton, Bethany L. „Effect of Orange Peels on Nitrogen Efficiency in Ruminants“. The Ohio State University, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=osu1471877758.
10
Choudhury, D. „The effect of honeydew on leaf-litter decomposition, soil non-symbiotic nitrogen fixation and nitrogen mineralization“. Thesis, University of Oxford, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.376903.
11
Van, Wijk Kim. „The effect of organic carbon and nitrogen additions on inorganic nitrogen uptake by phytoplankton and bacteria“. Master's thesis, University of Cape Town, 1991. http://hdl.handle.net/11427/18342.
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Bibliography: pages 76-89.This study examines the effects of enrichment with organic carbon and nitrogen on inorganic nitrogen partitioning between phyto- and bacterio- plankton. Strongly preferential uptake of ammonium over nitrate was observed by both the phytoplanktonic and bacterial fractions, with RPINH4 values typically between 1 and 5. The bacterial fraction ( <0.8μm) was found to be responsible for as much as 48-75% of community uptake of ammonium; while the netplanktonic fraction was observed to take up approximately 50% of intact community uptake of nitrate. The addition of amino acids appeared to mediate bacterial competition for ammonium, indicating their preference for DON as a nitrogen source and allowing increased ammonium uptake by the nanoplanktonic fraction. The effect of glucose enrichment was complicated by the presence of protozoans, which appeared to be indirectly responsible for decreased ammonium uptake due to depletion of this substrate in the presence of added glucose. The nanoplankton appeared to be responsible for the least nitrogen uptake with respect to biomass, indicating that they may have been subject to competition pressure from both the bacterial and netplanktonic fractions.
12
Jackson, Brian A. „Nitrogen mineralization of incorporated bahiagrass sod and its effect on nitrogen uptake and yield of maize“. [Gainesville, Fla.] : University of Florida, 2003. http://purl.fcla.edu/fcla/etd/UFE0001441.
13
Green, Emma Rachel. „The effect of nitrogen deposition on Lowland heath ecosystem“. Thesis, Imperial College London, 2006. http://hdl.handle.net/10044/1/11421.
14
Foroutan-Pour, Kayhan. „Aspects of barley post-anthesis nitrogen physiology“. Thesis, McGill University, 1994. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=22730.
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The protein concentration of cereal grains is low and the production of cereal crops with increased grain protein concentrations is desirable. This work investigates the physiological aspects of protein accumulation potential in barley grain. A recently developed perfusion system was used in four experiments conducted in 1993 and 1994. In the field experiment, plants were allowed to take up urea at 15 or 30 mM N, or ethephon at 15 $ mu$ M. Abscisic acid and 2,4-D decreased total seed weight spike$ sp{-1}$. Gibberellic acid and 2,4-D increased seed protein concentration and content, while ABA decreased both of these. Kinetin and abscisic acid treatments resulted in the highest and lowest levels, respectively for flag leaf photosynthesis, stomatal conductance, transpiration and intercellular CO$ sb2$ concentration. Both protein content spike$ sp{-1}$ and seed protein concentration were elevated in plants fertilized with 10.7 mM N via the soil and plants perfused with 30 mM N via the peduncle. Plants receiving treatments of 10.7 mM N from the soil and mixture of 30 mM N and GA$ sb3$ or 2,4-D through the peduncle had increased protein content seed$ sp{-1}$, and the highest seed weight spike$ sp{-1}$, respectively. Peduncle perfusion with 30 mM N increased spike protein concentration and content and grain protein concentration without affecting seed weight spike$ sp{-1}$. Grain protein concentration was increased by peduncle perfusion with ethephon. The perfusion technique worked well under field conditions. (Abstract shortened by UMI.)
15
TOKOROYAMA, Takayuki, und Noritsugu UMEHARA. „Effect of nitrogen atoms included in CNx coatings on friction sliding against Si3N4 ball in nitrogen gas“. IEEE, 2007. http://hdl.handle.net/2237/9456.
16
Ottman, Michael J., Duarte E. Diaz, Michael D. Sheedy und Richard W. Ward. „Nitrogen Fertilizer Rate Effect on Forage Sorghum Yield, Quality, and Tissue Nitrogen Concentrations at Maricopa, AZ, 2015“. College of Agriculture, University of Arizona (Tucson, AZ), 2017. http://hdl.handle.net/10150/625439.
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13 pp.A nitrogen fertilizer study was conducted in order to determine the effect of N rates on forage sorghum yield and quality and to develop tissue testing guidelines for fertilizer application to forage sorghum. The study was conducted at the University of Arizona Maricopa Agricultural center on sandy clay loam soil irrigated using the flood method. Forage sorghum was fertilized with six N rates varying from 0 to 250 lb N/acre in 50 lb N/acre increments. The whole plant, lower stem, and most recently expanded leaf were sampled five times during the growing season and analyzed for N content in order to establish tissue N guidelines for fertilizer application. The plant part that was most sensitive to N fertilizer application and plant N status was lower stem. Leaf and plant N levels were not affected by fertilizer application. The stem nitrate and stem N tests were able to identify N deficient plants very early in the season, long before plant growth was affected by the N deficiency, unlike leaf and plant N. Forage yield at final harvest fitted to a quadratic function was maximized at the 250 lb N/acre N rate. However, the yield increase with any amount of fertilizer did not pay for the cost of the fertilizer and the most economical N rate for yield was no N fertilizer applied at all. In terms of milk per acre, the maximum was achieved at 150 lb N/acre, and the economic optimum in terms of milk was slightly less than this amount of fertilizer.
17
Morton, Lincoln William. „The role of dietary phenolic compounds in the detoxification of reactive nitrogen species“. University of Western Australia. Dept. of Medicine, 2003. http://theses.library.uwa.edu.au/adt-WU2003.0026.
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[Truncated abstract. Please see the pdf format for the complete text.] Interest in the role of peroxynitrite in the pathogenesis of atherosclerosis has increased due to many in vitro studies which have demonstrated its potent oxidising and nitrating capability and immunohistochemical staining studies which demonstrate nitration of tyrosine in vivo. It is frequently suggested that the production of nitric oxide and superoxide at sites of inflammation implicates peroxynitrite as the major damaging reactive nitrogen species in vivo. Evidence for a role for peroxynitrite is often demonstrated by measurement of 3-nitrotyrosine yet even this cannot distinguish peroxynitrite from other nitrating species. Clearly, however, if peroxynitrite is important in atherogenesis, then identification of mechanisms for its detoxification could provide a means of preventing such effects. Therefore, this Thesis has sought to determine whether phenolic compounds of dietary origin can be preferentially nitrated by reactive nitrogen species thereby protecting endogenous structures, such as low density lipoproteins, from atherogenic modifications. This Thesis focuses upon phenolic acids as they have received relatively less attention than other classes of phenolic compounds, such as flavonoids, yet they are quite abundant in socially important beverages such as red wine. In order to complete the required analyses, the development of methods to detect phenolic acids and their nitration products together with 3-nitrotyrosine, dityrosine and 5-nitro-γ-tocopherol was necessary. The initial in vitro experiments described herein sought to determine the products of reaction of peroxynitrite with phenolic acids of the 4-hydroxy and 3,4-dihydroxy type and then to examine whether these products could account for a protective effect upon tyrosine, lipids and endogenous anti-oxidants, if any was observed, when isolated LDL was treated with SIN-1, which releases peroxynitrite through the simultaneous generation of nitric oxide and superoxide. A concurrent minor focus was to examine the relationship between structure and activity of these phenolic acids under various regimes of oxidative insult. These experiments indicate that, at least in this in vitro model, oxidation is a dominant mechanism over nitration. Peroxynitrite was shown to nitrate coumaric acid in moderate yields but exclusive oxidation of caffeic acid appeared to occur. Although a potential role for γ-tocopherol as an anti-nitration agent was inferred, all types of chemical treatment of LDL in the presence of phenolic acids yielded oxidation as the primary end point. In fact, nitration of tyrosine was not detected and nitration of coumaric acid was at the limit of detection. Since nitration of tyrosine is generally regarded as important in many disease states, a more physiological nitrating mechanism involving artificially stimulated neutrophils was used. This system demonstrated that although physiologically relevant reactive nitrogen species can result in nitration of phenolic compounds, in a complex system including biological structures (LDL) and phenolic compounds, oxidation but not nitration of all species appears to occur. As a consequence of the results above, an examination of carotid plaque was undertaken to determine to what extent nitration occurred relative to oxidation in atherosclerotic tissue. These studies applied methods developed herein to detect 3-nitrotyrosine and dityrosine in complex biological matrices as markers of nitration and oxidation respectively. The data obtained demonstrated that nitration was a minor modification of protein (0.01%) compared to oxidation (0.3%) even in a highly diseased tissue such as carotid artery plaque. A secondary study examining plasma revealed that dityrosine, which has been implicated in irreversible albumin aggregation in chronic renal failure and more recently in heart disease, is elevated in chronic renal failure subjects compared to well matched controls. A separate examination of plasma from healthy subjects revealed that in both the fasting and post prandial state 3-nitrotyrosine could not be detected and, in fact, interfering species could be problematic in the GC-MS analysis of 3-nitrotyrosine. The lack of nitration of any substrate observed in vitro using reactive nitrogen species generated in the aqueous phase, the relative lack of nitration of tyrosine in plaque proteins and the lipophilicity of nitric oxide, the precursor of all reactive nitrogen species, suggested that nitration could be more closely associated with lipid structures. The known ability of γ-tocopherol to form 5-nitro-γ-tocopherol was used to probe this concept. The 5-nitro-γ-tocopherol content of lipid extracts obtained from carotid artery plaques was very high (30%). This indicated that nitration is predominantly a lipid phase phenomenon and that nitrating species are present in much greater abundance than oxidising species in vivo.
18
Ariapour, Azita. „Effect of nitrogen on Fe-Mn-based shape memory alloys“. Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape11/PQDD_0002/NQ41396.pdf.
19
Khamees, H. S. „Effect of some ecological factors on nitrogen fixation by cyanobacteria“. Thesis, Swansea University, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.637784.
20
Reece, William Hugh Hathorn. „The effect of reactive nitrogen intermediates on Leishmania mexicana mexicana“. Thesis, University of Glasgow, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.363164.
21
Diallo, Sory. „Effect of genotypes and nitrogen on grain quality of sorghum“. Thesis, Kansas State University, 2012. http://hdl.handle.net/2097/14628.
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Master of ScienceDepartment of Agronomy
P.V. Vara Prasad
Sorghum (Sorghum bicolor L. Moench) is cultivated as an important food grain in the semi-arid regions of Africa. Processed grain sorghum is traditionally consumed as porridge, couscous, traditional tô or beer. The quality of such foods is highly dependent upon grain characteristics. Sorghum grain quality traits mainly include kernel hardness, kernel weight, kernel size, protein content and kernel color. Grain quality traits are often influenced by environment, genotypes, fertilizer management and their interaction. The objective of this study was to determine the impact of different levels of nitrogen application (0, 45, and 90 kg ha[superscript]-1) on grain quality of selected sorghum genotypes. The field experiment was conducted at three locations in 2010 (Manhattan, Ottawa, and Hays) and at two locations in 2011 (Manhattan and Ottawa). The experiment was laid in split plot randomized complete bloc design and replicated four times. The main plots were assigned to three N regimes: control (0 kg N ha[superscript]-1), half recommended rate (45 kg N ha[superscript]-1) and recommended rate (90 kg N ha[superscript]-1). The subplots were assigned to twelve genotypes (six hybrids and six inbred lines). Plot size was 6.1 m x 3.0 m with a row spacing of 0.75 m. After harvest, grain quality traits (hardness, weight, diameter and protein content) were evaluated using standard procedures and the data subjected to statistical design using SAS. There were significant effects of genotype for most grain quality traits across both locations in Manhattan. Inbred lines SC35 and SC599 had maximum hardness at all locations while hybrid 95207, had the lowest hardness for all locations. Also, Inbred lines SC35 and Tx340 had maximum protein content at all the locations. While hybrids 95207, 26056, 23012 had the lowest protein content. Genotypes Tx430, SC35, had higher hardness and with higher protein content were classified as high quality. We conclude that application of N (45 or 90 kg ha[superscript]-1) significantly improved grain protein, but not other quality traits. There are opportunities to improve grain protein through fertilizer management and plant breeding.
22
Gentili, Matilde. „Effect of nitrogen nutrition on yeast ecology and alcoholic fermentation“. Master's thesis, ISA-UL, 2016. http://hdl.handle.net/10400.5/12216.
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Mestrado Vinifera Euromaster - Instituto Superior de Agronomia - ULWine is an alcoholic beverage obtained from the fermentation of grape juice. Alcoholic fermentation is the main process to obtain the final product but of course other reactions take place during the transformation of grape juice into wine. Yeasts are one of the fundamental microorganisms to realize the alcoholic fermentation, that leads sugars to be transformed in ethanol and to development of other compounds. Yeasts as known are living organisms so they need nutrients for their reproduction and often the lack of some important nutrients can lead to a stuck or slug in their metabolic activity. One of the most important nutrient for yeasts growth is Nitrogen, main component of aminoacids and proteins, that constitute the basic structures of the microorganism.In winemaking, both in the cellar and in the vineyards, the addition of nitrogen under different circumstances is a common practice. Nitrogen seems to influence not only fermentation rate and yeast growth but many of the fermentation product such as ethanol, acetic acid, glycerol, and of course residual sugars and the production of some off flavours,such as hydrogen sulphide. Although each yeast, species and strains,showed different behaviour both in the fermentation rates, growth and production of different metabolites. Not only the quantity and kind of Nitrogen source but also the timing of the addition seem to influence all these aspects in slightly different way between different strain. The nitrogen compounds especially apparently ammino acids showed also a particular relationship with the production of esters of higher alcohols and other compounds but the pattern of ester production is still uncertain. In this study there will be considered the main aspects of nitrogen nutrition, how it affects the yeasts ecology and the different conditions on which it is used and also different strains and species requirements
23
Horner, Emily Renee. „THE EFFECT OF NITROGEN APPLICATION TIMING ON PLANT AVAILABLE PHOSPHORUS“. The Ohio State University, 2008. http://rave.ohiolink.edu/etdc/view?acc_num=osu1211932436.
24
Payne, Kathryn Marie. „ENHANCED EFFICIENCY NITROGEN FORMULATION EFFECT ON GRASS-LEGUME PASTURE PRODUCTIVITY“. UKnowledge, 2019. https://uknowledge.uky.edu/pss_etds/113.
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The use of nitrogen (N) fertilizer is generally restricted on mixed species forage systems due to its stimulatory effect on grasses which increases competition with legume species. Reduced legume growth from this competition can compromise forage nutritive value and prospective yields. The controlled-release nature of several enhanced efficiency fertilizer N products holds the potential to improve legume persistence in mixed species pastures while providing supplemental N required by the grass component. The studies contained in this dissertation evaluated the effect of different enhanced efficiency N formulations (ATU, ESN, methylene urea, SuperU, and a 75% ESN: 25% urea blend) and untreated urea on yield, nutritive value, and legume persistence in a ‘Wrangler’ bermudagrass and ‘Durana’ white clover mixture (2014-2016 growing seasons), ‘KY-31’tall fescue and ‘Kenland’ red clover mixture (2015-2016 growing seasons), and ‘KY-31’ stockpiled tall fescue (2015-2017). The three studies were conducted at the University of Kentucky Spindletop Research Farm in Lexington, KY in a randomized complete block design. In the bermudagrass-white clover study, all enhanced efficiency N sources maintained white clover populations similar to the unfertilized grass/clover control, but only ESN caused greater clover composition than standard urea. Total forage yields increased linearly with N rate in all years, but dry weather conditions in the second and third years resulted in lower total yield. Forage nutritive value followed general trends throughout each growing season, but ESN’s ability to maintain clover resulted in higher nutritive value. In the tall fescue-red clover, total forage yields curvilinearly increased with N rate in 2015 but did not vary in 2016. ESN and ESN+urea blend treatments retained clover composition similar to that of the unfertilized control. Stockpiled forage yield increased with higher N rates. Enhanced efficiency N fertilizers with the ability to control N release can enhance forage yield while maintaining clover in mixed species swards.
25
Al-Rawahy, Salim Ali. „Nitrogen uptake, growth rate and yield of tomatoes under saline conditions“. Diss., The University of Arizona, 1989. http://hdl.handle.net/10150/184894.
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Results of two studies are reported here, a greenhouse study and a field study. In the greenhouse study, dry matter yield and nitrogen (total and 15N) uptake of leaves, stems and roots of tomato plants (Lycopersicum esculentum Mill., cv. Columbia) subjected to saline stress by NaCl were studied. The integrated effects of responses of these tissues to salinity on the whole plant basis and levels of Na⁺, Cl⁻ and K⁺ accumulation in these tissues were also studied. The treatments consisted of low (control, 0.3 bar), medium (4.3 bars), and high (8.3 bars) salinity. The saline treatments were prepared by adding NaCl to nutrient solution in sand culture. The plants were 80 days old at the start of the treatments and each was in a pot containing 1.8 kg of quartz sand. The ¹⁵N was provided to plants by adding K¹⁵NO₃ to the pots and the 15N treatment continued with the saline treatments up to 30 days. The plants were harvested at each 5-day interval during the treatment period. Dry matter production and nitrogen (total and ¹⁵N) uptake were significantly lower for saline treatments as compared with the control. Differences in dry matter production and ¹⁵N uptake on whole plant basis appeared in the latter part of the treatment period between the two saline treatments. For most of the parameters studied, the leaves were found to be affected most by salinity, the roots were intermediate in their response and the stems were the least affected by salinity. The effect of salinity on the studied parameters were attributed to osmotic effects and specific ion effects of Na⁺ and/or Cl⁻. A field study with two cultivars--Columbia and Pearson was conducted at the Safford Agricultural Center. Three N treatments were used: 0 kg N/ha, 84 kg N/ha and 168 kg N/ha and two treatments consisting of two water sources--river water with an EC of 1.15 dS/m and more saline well water of EC of 2.21 dS/m. Columbia had a significantly higher yield of tomatoes than Pearson for both water types. The N treatments had no effect on tomato yield apparently due to high residual N remaining in the field from the previous crop. Commercially acceptable fresh market yields were approached with both varieties and waters in spite of moderate salinity and sodium under heavy textural soil conditions, high temperatures and the presence of certain diseases in the area.
26
Nilsson, Hultén Leo. „Nitrogen Without Oxygen : The effect of ferroalloys added after vacuum treatment on cleanliness of nitrogen-alloyed tool steel“. Thesis, KTH, Materialvetenskap, 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-298093.
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Nitrogen-alloyed tool steel is made at Uddeholms AB by adding high-nitrogen ferroalloy after vacuum degassing where introduced impurities are hard to remove. In this thesis two types of high-nitrogen ferrochromium are compared, a solid version and a powder cored wire. They are examined in crossection and 16 samples from four charges are examined with Pulse Distribution Analysis as well as systematic microscopy of polished cross sections. The PDA results missed smaller spinel inclusions shown in previous research to be detrimental. The wire form shows promise but more charges need to be evaluated before a conclusion is drawn.Kvävelegerat verktygsstål tillverkas hos Uddeholms AB genom tillsats av kväverika ferrolegeringar efter vakumavgasning, och orenheter som introduceras i detta steg är svåra att avskilja. I den har uppsatsen jämförs två typer av kväverikt ferrokrom varav en i form av stycken och en i form av tråd med pulverkärna. De undersöks i tvärsnitt och totalt 16 prov från fyra charger undersöks med PDA (pulsfördelningsanalys) och systematisk mikroskopering i tvärsnitt. Resultaten från PDA missade mindre inneslutningar av spinell vilka tidigare har visat sig problematiska. Trådformen verkar lovande men fler charger behöver undersökas för att kunna dra en definitiv slutsats.
27
Tshuma, Takula. „The effect of blood urea nitrogen on reproductive performance of beef heifers on different levels of nitrogen supplementation“. Diss., University of Pretoria, 2013. http://hdl.handle.net/2263/36790.
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Ruminants have a unique ability to acquire protein from non-protein nitrogen (NPN)
sources, and to recycle nitrogen back into the rumen, instead of excreting all of it via the
urine, faeces and milk. However, a high concentration of blood urea nitrogen (BUN) has a negative influence on conception. Additionally, a high dietary nitrogen intake poses a
challenge to the environment in the form of ammonia emissions, eutrophication and bad
odours. This calls for strategies to reduce the environmental impact of livestock production.
Variation exists in the ability of cattle to recirculate nitrogen between as well as within
cattle breeds. The purpose of this study was to investigate the effects of BUN concentration on reproductive performance in beef heifers under different management systems in South Africa. Serum samples from 369 Bonsmara heifers were taken in November and December 2010 to determine the BUN concentrations prior to the onset of the breeding season.
Heifers were from five herds with different levels of protein supplementation during the
weeks before the commencement of the breeding season. Body mass, age, body condition score (BCS) and reproductive tract score (RTS) were recorded at the same time as BUN concentration. Trans-rectal ultrasound and/or-palpation was performed four to eight weeks after the three-month breeding season to detect and estimate the stage of pregnancy. Days to pregnancy (DTP) was defined as the number of days from the start of the breeding season until a heifer was successfully mated. Logistic regression and Cox proportional hazards survival analysis were performed to estimate the effect of BUN concentration on subsequent pregnancy and DTP respectively, while stratifying by herd and adjusting for potential confounders. The correlations between BUN concentration, BCS and RTS were estimated using Spearman’s rho. Pearson correlations were used for the normally distributed variables of age and body mass. BUN concentration was not a significant predictor of pregnancy status but was a significant (P = 0.007) and independent predictor of DTP in heavily and some moderately supplemented herds. As BUN concentration increased,
DTP also increased [hazard ratio (HR) = 0.827; 95% CI: 0.721 – 0.949; P = 0.007], while the chance of becoming pregnant decreased, although this was not statistically significant [odds ratio (OR) = 0.882; 95% CI: 0.772 – 1.007; P = 0.063]. Bonsmara heifers with higher BUN concentration, which suggests a better ability to recirculate nitrogen, might be at a disadvantage when the production system includes high levels of RDP supplementation because of this negative impact on reproductive performance. It is proposed that production systems be adapted to avoid selection against animals with an improved ability to recirculate nitrogen.Dissertation (MMedVet)--University of Pretoria, 2013.
gm2014
Production Animal Studies
Unrestricted
28
Thaung, Tint Lwin. „Effect of nitrogen fertiliser additions on nitrogen fluxes and plantation productivity in young eucalyptus cloeziana (F. Muell) plantations /“. [St. Lucia, Qld.], 2002. http://www.library.uq.edu.au/pdfserve.php?image=thesisabs/absthe16847.pdf.
29
Pandeya, Hemant Raj. „Carbon and nitrogen flux dynamics in highly weathered tropical mango soils: Effect of leaf litter and nitrogen fertiliser“. Thesis, Queensland University of Technology, 2022. https://eprints.qut.edu.au/232828/1/Hemant%20Raj_Pandeya_Thesis.pdf.
Annotation:
This thesis is a comparative study of carbon and nitrogen flux dynamics following sole and combined application of mango leaf litter mulch and inorganic fertiliser in highly weathered tropical mango orchard soils. In doing so, the thesis investigated litter decomposition dynamics and litter carbon mass balance and provided baseline datasets of seasonal and annual reactive nitrogen losses (through hydrological and gaseous pathways) under the tropical environmental conditions of Northern Territory Australia.
30
Mooleki, Siyambango Patrick. „Synchronization of nitrogen availability and plant nitrogen demand, nitrogen and non-nitrogen effects of lentil to subsequent wheat crops“. Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2000. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape2/PQDD_0029/NQ63902.pdf.
31
Antunes, Cristiane Leite [UNESP]. „Fertirrigação nitrogenada por gotejamento e época de aplicação foliar de ácido giberélico 'GA IND.3' em alface americana (Lactuca sativa L.)“. Universidade Estadual Paulista (UNESP), 2001. http://hdl.handle.net/11449/93828.
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antunes_cl_me_botfca.pdf: 3224894 bytes, checksum: ebe83c98cf65dede1137b2f26b044f56 (MD5)Com o objetivo de avaliar os efeitos do nitrogênio aplicado ao solo, via fertirrigação por gotejamento, e a aplicação foliar do ácido giberélico (GA3), na nutrição e nos componentes de produção da alface tipo americana, cv. 'Lucy Brown', em cultivo protegido, foi efetuado o presente trabalho. O delineamento experimental utilizado foi o de blocos casualizados em esquema de parcelas subdivididas: quatro doses de nitrogênio (60, 120, 180 e 240 kg de N.ha-1), na parcela, e quatro épocas de aplicação de GA3 (0, 40, 55 e 70 DAS - dias após a semeadura), na subparcela. O ácido giberélico foi aplicado com pulverizador costal de CO2, numa concentração única de 20 mg do ingrediente ativo.L-1 de solução, nas subparcelas nas épocas determinadas. Foram realizadas quatro coletas para avaliação dos parâmetros vegetativos e análise de nutrientes, com intervalos de 15 dias, iniciando-se aos 51 DAS (23 DAT- dias após o transplantio) até 96 DAS (64 DAT). Os trabalhos foram conduzidos na área experimental da Fazenda São Manuel, no município de São Manuel - SP. Não foi observada interação entre a aplicação de nitrogênio e o ácido giberélico nos parâmetros vegetativos avaliados, bem como no teor e acúmulo dos macronutrientes. Contudo, houve influência dos fatores de variação de forma independente nos parâmetros ao longo do ciclo. O nitrogênio é extremamente importante no crescimento e acúmulo de matéria fresca na planta de alface tipo americana e pode ser usado em doses maiores quando há disponibilidade de cálcio e potássio. Tendo sido os melhores resultados alcançados com a dose de 180 kg de N. ha-1. O uso do ácido giberélico (GA3), aos 70 DAS (dias após a semeadura) proporcionou os melhores resultados nos parâmetros relativos ao crescimento. Enquanto a época de aplicação aos 40 DAS, promoveu o desenvolvimento intenso do caule, levando a efeitos... .
With the goal of estimating the nitrogen effects applied on the soil, through fertigation by dripping, and the foliar application of gibberellic acid (GA3), in the nourishment and in the components of Crisphead Lettuce production, cv. 'Lucy Brown', in protected cultivation, this paper was done. The used experimental drawing was made of casual blocks in subdivided portions: four doses de nitrogen (60, 120 180 and 240 kg de N.ha-1), in the portion, and four application times of GA3 (0, 40, 55 e 70 DAS - days after sowing) in the subportion. The gibberellic acid was applied with a costal pulverize machine of CO2, in a unique dose of 20 mg.L-1 of the active ingredient, in the subportions in the specific times. Four collects were done for the evaluation of the vegetative parameters and nutrient analysis, with a 15-days recess, beninning on 51 DAS (23DAT) to 96 DAS (64 DAT). The works were managed in the experimental area of São Manuel Farm, in São Manuel County - SP. It wasn't observed interaction between nitrogen application and the gibberellic acid in the evaluated vegetative characteristics, as well as in the tenor and accumulation of macro-nutrients. However, there was na influence of changing factors in na independent way in the parameters along the cycle. The nitrogen is extremely important in the growth and accumulation of fresh material in the Crisphead lettuce vegetable and it can be used in bigger doses when there is availability of calcium and potassium. These have been the best results got with the dose 180 kg of N.ha-1. The usage of gibberellic acid (GA3), on 70 DAS (days after the sowing) provided the best results in the characteristics related to the growth. As long as the application time on 40 DAS, provided the intense satlk growth, conducing to the depreciatory effects, as the plants arranged in layers, a bigger number of external leaves, and a samller accumulation of fresh... (Complete abstract, click electronic address below).
32
Yu, Shaobing. „Winter wheat nitrogen management in south coastal British Columbia“. Thesis, University of British Columbia, 1990. http://hdl.handle.net/2429/29888.
Annotation:
Nitrogen is essential to obtain high yields of winter wheat in south coastal British Columbia, which includes Vancouver Island and the lower Fraser Valley. An accurate recommendation for N application is required to keep input costs down for most economical returns and to limit environmental problems related to leaching of excess N. The questions are how much, when and which form of N should be applied to winter wheat. The general objective of this study is to improve our understanding of winter wheat growth and N uptake. This study monitors the soil N supply and characterizes the plant development, dry matter accumulation, and N uptake of winter wheat in South Coastal B.C.. Also, it compares the effectiveness of conventional and intensive crop N management and urea and ammonium nitrate sources of fertilizer N under intensive crop management.
A series of field experiments was conducted in 1986-87 and 1987-88 with winter wheat to evaluate conventional and intensive N management in the area. Additionally, a N source
study was carried out in the latter year to compare ammonium nitrate and urea.
Soil N supply for winter wheat ranged from 52 to 151 kg N/ha through the two years of field experiments at five sites. Available N in the 0-50 cm soil depth varied from 10 to 100 kg N/ha through the growing season in the different treatments. An accurate estimate of N behavior involves N accumulation in the crop. During the early spring until harvest, the crop dry matter yield and N uptake patterns were plotted. The grain yields ranged from 4 to 9 t/ha for the conventional management (75 kg N/ha), and from 4 to 11 t/ha for the intensive crop management (I.CM. 225 kg N/ha) system. Between the conventional and I.CM., there was no significant difference in grain yield but there was in quality, specifically grain protein. Grain protein ranged from 8.2 to 9.7% for the conventional and from 10 to 13.7% for the I.CM. treatment. Also, there was no difference in grain yield or quality between ammonium nitrate and urea fertilized plots at final harvest. However, in the early stage at GS31, crop took up more N from ammonium nitrate (97 kg N/ha) than from urea (75 kg N/ha) and soil mineral N levels with urea were higher than with ammonium nitrate.Land and Food Systems, Faculty of
Graduate
33
Heidari, Sharif Abad Hossein. „Variation in the sensitivity of nodulation and nitrogen fixation to nitrate in annual "Medicago" species“. Title page, table of contents and abstract only, 1994. http://web4.library.adelaide.edu.au/theses/09PH/09phh465.pdf.
Annotation:
Bibliography: leaves 153-179. Annual species of Medicago, or medics, are important pasture legumes in the neutral to alkaline soils of southern Australia but their nodulation and nitrogen fixation processes are retarded by soil nitrate. This study ascertains whether an observed tolerance to nitrate among medic species can be substantiated, and attempts to understand the underlying factors responsible.
34
Caglia, Stefania. „Nitrogen Removal in the Pilot Plant ITEST (Increased Technology in Sewage Treatment)“. Thesis, KTH, Mark- och vattenteknik (flyttat 20130630), 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-171846.
Annotation:
Regions with a cold winter, as in the Baltic countries, have a problem to meet the nitrogen requirement in the Urban Wastewater Treatment Directive 98/15/EC. Especially in the winter season, the temperature of the influent wastewater could arrive also below 10°C and this delays the biological processes that takes place in the wastewater treatment. With the decrease of the temperature, the efficiency of nitrogen removal in the system decreases and leads to a high nitrogen loading in the effluent. The ITEST (Increased Technology and Efficiency in Sewage Treatment) project situated in Hammarby Sjöstadsverk in Stockholm has as its main aim to enhance nitrogen removal, thereby increasing the temperature in the incoming wastewater. The pilot plant ITEST is comprised of two treatment lines, one works with natural temperature influent and the other works at the temperature of 20 °C. In order to warm the incoming water a heating system, using waste heat, is used, leading to save energy. The two test lines were compared analyzing different parameters from January to May 2013. Total nitrogen, nitrate-nitrogen and ammonium-nitrogen concentrations were measured in the incoming water and in the effluent from the two treatment lines. Hence, the efficiency of the nitrogen removal was compared between the reference and the temperature line. In the period where the system was well functioning, the results show a nitrogen efficiency with a maximum of 92 % of removal of total nitrogen for the temperature line compared to only 65 % for the reference line. In the period where the system did not have any troubles the total nitrogen is under 10 mg/l, which is the limit of total nitrogen discharges specified in the Directive. Instead, for the sludge volume and the suspended solids any particular difference can be noticed from the two lines of treatment. In conclusion, in the temperature line can be noticed a great efficiency in nitrogen removal compared to the reference line.
35
Thanapornpoonpong, Sa-nguansak. „Effect of nitrogen fertilizer on nitrogen assimilation and seed quality of amaranth (Amaranthus spp.) and quinoa (Chenopodium quinoa Willd)“. Doctoral thesis, [S.l.] : [s.n.], 2004. http://hdl.handle.net/11858/00-1735-0000-0006-AB4D-1.
36
Hanson, Carter Curtis. „Temporal effect on nitrogen removal in a subsurface flow constructed wetland“. Virtual Press, 1996. http://liblink.bsu.edu/uhtbin/catkey/1027117.
Annotation:
A subsurface flow constructed wetland planted with the common reed (Phragmites australis) and softstem bulrush (Scirpus validus) was built in East Central Indiana. The objective of this study was to determine if temperature had an effect on nitrogen (N) removal from the wetland. The research was conducted from the first week of October 3, 1995 to the first week in December 5, 1995 why the wetland froze. Water samples were taken from 5 samplings sites in the system. Each sample was analyzed for organic-N, ammonia, nitrate, and total-N. In the system statistically significant amounts of organic-N, nitrate, and total-N were removed. Ammonia lever reductions, however, were not significant. Organic-N had a mean removal of 37% (8 mg/1) 'Nitrate had a mean removal of 96% (2.3 mg/1). Total-N removal over the sampling period averaged 30% (12 mg/1). The N results were regressed against air and wastewater temperatures. Wastewater temperature was more important because it had a direct impact can the plants and microbes in the system. Warmer temperatures sustained a higher metabolism for the biota in the system. Air temperature had an indirect impact on efficiency of N removal from the wastewater flowing through the wetland. The primary impact .: f the air temperature was on water temperature which then affected the metabolism of or a nc ns in the wetland cell. Greater removal efficiencies were seen during high temperature periods and lower removal efficiencies were noted when the temperatures were low.Department of Natural Resources and Environmental Management
37
Ayub, Najma. „The effect of VAM inoculation on interplant ¹⁵N transfer“. Thesis, University of Aberdeen, 1991. http://digitool.abdn.ac.uk/R?func=search-advanced-go&find_code1=WSN&request1=AAIU546184.
Annotation:
This thesis reports a study carried out to investigate the involvement of VA mycorrhizas in interplant 15N transfer in a model pasture system and in a model agroforestry system. Two pot experiments were designed to investigate the effect of VAM inoculation on 15N transfer from clover to rye grass in sterile (in the first experiment the sterilisation was by autoclaving and in the second, by gamma-irradiation) and fresh soil. A third pot experiment was designed to investigate the effect of VAM inoculation on 15N transfer from grass and clover to wild cherry seedlings in fresh soil. For these pot experiments donor plant seedlings were labelled with 15N by growing in Hoaglands solution containing K 15NO3 (5 atom % 15N). To study 15 N transfer and its possible mechanisms, plants and soil samples were analysed for 15N, total N (14N + 15N) and P concentrations. Rates of soil nitrogen mineralisation and nitrification, as well as 15N enrichment of available N were also determined to investigate N transfer through soil. There was transfer of 15N from donor to receiver in the simulated pasture system as well as in simulated agroforestry system. The transfer of 15N was increased by VAM inoculation. The transfer of 15N was small in relation to plant nutrition and was not associated with an increase in total N in the receiver plants although P concentrations were generally increased. There was no increase in the soil N fluxes of mineralisation and nitrification associated with enhanced 15N transfer from donor to receiver in the VAM inoculated system. In addition, there was often no increase in the 15N concentration in the soil available N pool of VAM inoculated systems. There was no evidence, therefore, of increased transfer of 15N through the soil in VAM inoculated systems with enhanced 15N interplant transfer, suggesting the likely involvement of VAM fungal hyphae. There was no marked effect on plant growth due to VAM inoculation. The growth of cherry, however, was reduced when grown with grass and this may have been due to N competition between the root systems. The growth of cherry seedlings was reduced to a lesser extent when grown with clover compared to when grown with grass. The findings of this study suggest that VA mycorrhizal hyphae play a part in interplant transfer of nitrogen. Although the study did not demonstrate high rates of 15N transfer in VAM inoculated system, circumstances are discussed where VAM interplant transfer of nutrients may become significant at the single plant, community and ecosystem level. The benefits to man of VAM mediated N transfer may be best realised in land use systems such as pastures having legumes and non-legumes, in mixed cropping of legumes and non-legumes and in an agroforestry system with a legume component, particularly when the soil is deficient in nutrients such as nitrogen and phosphorus.
38
Sivapathasundram, Sudhersha. „The effect of nitrogen starvation on PS2 in the cyanobacterium synechococcus“. Thesis, Liverpool John Moores University, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.275823.
39
Young, Sarah Louise. „Effect of nitrogen fertiliser on bacterial community dynamics in arable soils“. Thesis, University of Essex, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.423712.
40
Clark, Lee J., und Bryant R. Gardner. „Effect of Nitrogen Fertilizer Application on Cotton Yields, Safford Agricultural Center“. College of Agriculture, University of Arizona (Tucson, AZ), 1986. http://hdl.handle.net/10150/219792.
Annotation:
The 1985 and 1986 Cotton Reports have the same publication and P-Series numbers.A soil depleted of nitrogen by cropping with Sudan grass and removing all the residues was planted to Upland (DP 90) and Pima (S-6) cotton. Nitrogen was added in the form of urea at three different stages of plant growth, applying a total of 0, 50 or 100 pounds of nitrogen. The yield of lint from DP 90 was increased where nitrogen was added; however, there were no differences in yield with the timing nor total amount of nitrogen added. In the case of S-6, fertilizer nitrogen did not increase yield.
41
Doerge, Thomas A., T. C. Tucker und T. W. McCreary. „Effect of Nitrification Inhibitors on Nitrogen Utilization Efficiency in Sweet Corn“. College of Agriculture, University of Arizona (Tucson, AZ), 1991. http://hdl.handle.net/10150/221451.
Annotation:
A field experiment using subsurface drip irrigation was conducted at the Maricopa Agricultural Center on a Casa Grande sandy loam soil to evaluate the effect of varying nitrogen (N) sources on the growth and yield of 'Sweetie' 82' sweet corn when applied with, and without four nitrification inhibitors (Nl). The NI treatments included nitrapyrin (N-Serve*), dicyandiamide (DCD), ammonium thiosulfate, and N-Hib Calcium™. Nitrogen was supplied as urea -ammonium nitrate (UAN -32). In addition, an all nitrate source plus a control which received no added N were used. Al! N treated plots received a total of 111 lbs. N acre in split applications at the V3, V6 and the V12 stages. All solutions were applied through buried, perforated PVC tubing to simulate application through the buried drip irrigation system. The inclusion of the nitrification inhibitors with UAN-32 had no significant effect on marketable ear yield, total N uptake or nitrogen use efficiency.
42
Yarber, Elizabeth Lee. „Assessing the Effect of Nitrogen Sources, Rates and Time of applications on Yield and Quality of Stockpiled Fescue and Tall Fescue Pastures“. Thesis, Virginia Tech, 2008. http://hdl.handle.net/10919/33692.
Annotation:
In Virginia, tall fescue [(Schedonorus phoenix (Scop.) Holub,) formally known as Festuca arundinacea L.] can be found on more than 4 million ac of hay and pastureland. Two separate experiments were conducted at three different geographical locations over two growing seasons. The objective of Experiment 1 was to evaluate the influence of N sources and rates on yield and nutritive value of stockpiled tall fescue. Experiment 2 examined the effect of split spring and fall N applications at various rates on yield and nutritive value of tall fescue pastures. The first experiment was conducted at three locations (Blacksburg, Blackstone, and Steeles Tavern, VA) while the second experiment was conducted only at the Blacksburg and Steeles Tavern locations. In Experiment 1, the N sources included ammonium nitrate, ammonium sulfate, urea, urea + Agrotain®, Environmentally Smart N® (ESN), Nutrisphere (NSN), Nitamin® (Blackstone only), pelleted biosolids (Blackstone only), and broiler litter (Steeles Tavern only) applied at 0, 28, 56, 84, and 112 kg plant available N (PAN) ha-1. Plots were harvested in mid-December (Blacksburg and Steeles Tavern) and late January (Blackstone). The yield of the stockpiled tall fescue in 2006 ranged from 1,300 to 2,900, 1,700 to 3,000, and 2,600 to 3,300 kg DM ha-1 for the Blacksburg, Steeles Tavern and Blackstone locations, respectively. In 2007, however, the yield response to N rate and sources was significantly less than that of 2006 due to low rainfall. At the Blacksburg location, ammonium sulfate and ESN resulted in higher CP concentrations, ranging from 11-14% and 12-20% for 2006 and 2007 growing seasons, respectively. Similar variation (12-20%) was observed for the Steeles Tavern location in 2006. In general, the ADF and NDF content decreased as N rate increased from 0-112 kg ha1. Although the source and rate that resulted in high yield and nutritive value varied across location and years, N rates and sources improved the quality and yield of stockpiled fescue. Experiment 2 utilized urea which was applied in the fall at the rates of 0, 45, 90 or 135 kg N ha-1. followed by spring application of 0, 45, 90 or 135 kg N ha-1. A total of 16 treatment combinations per replication were used. Yields ranged from 1,900 to 3,600 kg DM ha-1 and 700 to 2,500 kg DM ha-1 in 2007 and 2008, respectively. At the Steeles Tavern location, yields ranged from 3,100 to 5,700 kg DM ha-1 and 2,500 to 5,100 kg DM ha-1, in 2007 and 2008, respectively. In both years CP increased with increasing N fertilization. On a dry matter basis, CP values ranged from 14 to 23% for both years. Treatments did not affect on NDF and ADF values. Split fall/spring N applications did not maximize yield of cool-season grass pastures in these experiments.Master of Science
43
Darwiche, Amal Omar 1964. „Effect of cytokinin, gibberellin, and nitrogen applications on the growth of eldarica pine seedlings“. Thesis, The University of Arizona, 1989. http://hdl.handle.net/10150/276979.
Annotation:
A greenhouse experiment was conducted over a ninety day period to test the effect of different nitrogen fertilizer regimes and several application rates of compounds with gibberellin and cytokinin activity (GA4/7 and BA, respectively) on the growth and development of Pinus brutia var. eldarica. Nitrogen produced no significant effects and this was attributed to its abundance in the potting medium, to begin with. All levels of growth regulators used showed a highly significant effect on vegetative development. A reduction in root collar diameter, shoot elongation, needle nitrogen content and oven-dry weight, was observed, especially when the medium and high hormonal rates were used. Phytotoxicity increased with the increase in concentration of both chemicals. Ba induced a proliferation of adventitious buds along the stem of saplings, but this was accompanied with rapid new top growth and branching at the top only when BA was applied in conjunction with GA4/7.
44
Campbell, Richard John. „Effect of nitrogen fertilization on the physiological damage and subsequent recovery of mite-infested apple leaves /“. This resource online, 1988. http://scholar.lib.vt.edu/theses/available/etd-04122010-083649/.
45
Beltran, Casellas Gemma. „Effect of low temperature fermentation and nitrogen content on wine yeast metabolism“. Doctoral thesis, Universitat Rovira i Virgili, 2005. http://hdl.handle.net/10803/8651.
Annotation:
Les fermentacions a baixes temperatures (13ºC o inferiors) són interessants en l'elaboració de vins blancs i rosats, ja que augmenten la retenció i la producció dels aromes, i per tant la qualitat del producte final. Però aquestes baixes temperatures també tenen certs desavantatges, com una disminució en la velocitat de consum de sucres, obtenint fermentacions més llargues i amb risc de parades.Per intentar millorar el procés fermentatiu i la qualitat del producte final es van fixar els següents objectius:
- L'estudi del metabolisme del llevat a baixes temperatures de fermentació (13ºC), i la seva influència en aspectes com la cinètica fermentativa, el creixement dels llevats; el metabolisme lipídic; la producció dels aromes, i la expressió gènica global del llevat.
- El coneixement del metabolisme nitrogenat del llevat en la fermentació alcohòlica, així com en les addicions de nitrogen realitzades a diferents moments de la fermentació.
Els resultats obtinguts mostren que les baixes temperatures, a part d'augmentar la durada de fermentació, augmenten la viabilitat dels llevats al llarg del procés, provoquen canvis en la composició lipídica, augmentant la fluïdesa de la membrana, i milloren la composició aromàtica del vi, incrementant la producció d'aromes beneficiosos i disminuint-ne la de compostos perjudicials pel la qualitat vi final.
Amb l'objectiu d'identificar els mecanismes moleculars que causen aquests canvis metabòlics a baixes temperatures, vam utilitzar la tècnica de "chips de DNA" o "microarrays" per comparar l'expressió global dels gens del llevat fermentant a 13ºC i fermentant a 25ºC. En general, aquest anàlisis de l'expressió global del llevat dut a terme per primer cop en condicions industrials rebel·la importants canvis en la expressió d'alguns gens tant al llarg de la fermentació com entre les dos temperatures. La fermentació a 13ºC presenta l'avantatge d'induir una ràpida resposta al estrès que podria aportar més resistència al llevat al llarg de la fermentació, i per això augmentar-ne la seva viabilitat.
En l'estudi del metabolisme nitrogenat del llevat al llarg de la fermentació, vam observar que en la fermentació alcohòlica les cèl·lules evolucionen d'una situació de repressió per nitrogen al començament de la fermentació, quan hi ha compostos nitrogenats en el medi, a una situació de de-repressió quan el nitrogen ha estat consumit pel llevat. Aquestes situacions de repressió/de-repressió determinen el perfil de consum de l'amoni i dels aminoàcids, els quals determinen a la vegada la producció d'alguns compostos aromàtics. La repressió dels gens de les permeases GAP1 i MEP2, la baixa activitat arginasa o la inhibició en la captació de l'arginina, poden ser considerats bons marcadors de Repressió Catabòlica per Nitrogen (NCR).
L'addició de nitrogen és una pràctica habitual en bodega per evitar problemes fermentatius. Els nostres estudis demostren que el moment de dur a terme aquesta addició condiciona no només la cinètica fermentativa i el creixement del llevat, sinó també el perfil de consum d'amoni i aminoàcids, i la producció de compostos secundaris.
L'assimilació de nitrogen per part dels llevats també depèn de la temperatura de fermentació, la qual determina tant la qualitat com la quantitat dels requeriments nitrogenats dels llevats. A baixa temperatura de fermentació, l'amoni i la glutamina són menys consumits, mentre que els aminoàcids regulats per NCR ho són més.
Aquesta tesi és una aproximació global al comportament del llevat a baixes temperatures i al metabolisme nitrogenat, i ens obra moltes possibilitats d'estudi, punts on s'hauria d'aprofundir per un millor coneixement i millora d'aquestes fermentacions.
Wines produced at low temperatures (10-15ºC) are known to develop certain characteristics of taste and aroma, not only related to primary aroma retention. However, low temperature fermentations have also some disadvantages that comprise an increase of the duration of the process and a higher risk of stuck and sluggish fermentation.
In order to improve the fermentation performance and the quality of wine, we established the following objectives:
- The study of wine yeast metabolism at low temperature fermentation (13ºC), and its influence in aspects as the fermentation kinetic, the yeast growth, the yeast lipid metabolism, the production of aromatic compounds, and the global yeast gene expression.
- The study of nitrogen metabolism of yeast in alcoholic fermentation, as well as the study of nitrogen supplementations at different points of the fermentation.
Our results showed that low temperatures increased the length of fermentation, the yeast viability along the process, but also modified the lipid composition of yeast cells, increasing the membrane fluidity, and improved the aromatic composition of the wine, increasing the flavour-active compounds and decreasing the unpleasant ones such as acetic acid and fusel alcohols.
To identify the molecular mechanism that causes these changes in aroma profiles and to verify that 13°C-fermentation does not hinder other cellular properties, we compared the expression programs during wine fermentation at 13ºC and 25°C (using Microarrays technology), and tentatively correlated the differential genes expression with changes in intracellular lipid content, and in the production of flavour-active metabolites
This genome-wide analysis carried out for the first time with a commercial yeast strain under true industrial conditions revealed many major differential genes expression both during the course of the wine fermentation and between two fermentation temperatures. With respect to industrial output, wine fermentation conducted at 13°C presents the advantage to induce an early cold stress response that apparently does not penalize the wine fermentation process, further than the longest fermentation length.
In the study of the nitrogen metabolism of yeast along the fermentation we observed that in wine fermentations the cells evolve from a nitrogen-repressed situation at the beginning of the process to a nitrogen-derepressed situation as the nitrogen is consumed. These nitrogen-repressed/derepressed conditions determined the different patterns of ammonium and amino acid consumption. Arginine and alanine were hardly used under the repressed conditions, while the uptake of branched-chain and aromatic amino acids increased. The repression of GAP1 and MEP2 genes in the cells, low arginase activity or inhibition of arginine uptake could be considered as a good Nitrogen Catabolite Repression markers.
Winemakers systematically supplement grape musts with diammonium phosphate to prevent nitrogen-related fermentation problems. The timing of the nitrogen additions influenced the biomass yield, the fermentation performance, the patterns of ammonium and amino acid consumption, and the production of secondary metabolites. These nitrogen additions induced a nitrogen-repressed situation in the cells, and this situation determined which nitrogen sources were selected.
Nitrogen assimilation also depends on fermentation temperature. Fermentation temperature is an important factor determining utilization of nitrogen sources during fermentation of grape juice, and influences the quantity and the quality of nitrogen requirement. Ammonium and glutamine, the preferred source for biomass production, are less consumed at low temperature. Likewise amino acids that are only taken up under derepressed conditions (arginine, alanine, asparagine, etc.) are more consumed at low temperature.
The information provided by this thesis represents a starting point for deciphering the regulatory circuits during wine fermentation, overall at low temperature, and should help us to understand the properties of wine yeasts. Our results open up a lot of interesting perspectives that will further our knowledge of wine yeast metabolism during wine fermentations.
46
Lotfollahi, Mohammad. „The effect of subsoil mineral nitrogen on grain protein concentration of wheat“. Title page, table of contents and summary only, 1996. http://web4.library.adelaide.edu.au/theses/09PH/09phl882.pdf.
Annotation:
Copy of author's previously published work inserted. Bibliography: leaves 147-189. This project examines the uptake of mineral N from the subsoil after anthesis and its effect on grain protein concentration (GPC) of wheat. The overall objective is to examine the importance of subsoil mineral N and to investigate the ability of wheat to take up N from the subsoil late in the season under different conditions of N supply and soil water availability. Greenhouse experiments investigate the importance of subsoil mineral N availability on GPC of wheat and the factors that contribute to the effective utilisation of N. The recovery of N from subsoil, the effect of split N application on GPC and short term N uptake by the wheat at different rooting densities are also studied.
47
Roy, Vincent. „Effect of exhaust gas recirculation on fuel consumption and nitrogen oxides emissions“. Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2001. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp05/MQ63554.pdf.
48
Strange, Malinda Range. „The effect of pathology on the stable isotopes of carbon & nitrogen“. Diss., Online access via UMI:, 2006.
49
Venkataraman, Prakash. „Effect of nitrogen filling on tire rolling resistance and vehicle fuel economy“. Connect to this title online, 2007. http://etd.lib.clemson.edu/documents/1202498590/.
50
Smith, Jennifer M. „The effect of nitrogen on competitive interactions in a weed-crop community“. Thesis, University of East Anglia, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.357959.