Dissertations / Theses on the topic 'Water Victoria Nitrogen content'

Laboratory soil columns, 0.3 m diameter $ times$ 0.7 m long, and two computer simulation models, LEACHM-N and NTRM, were used to investigate nitrate-nitrogen ($ rm NO sb{3 sp{-}}$-N) leaching in a sandy loam soil. The following treatments were studied: no-till (NT), reduced tillage (RT), and conventional tillage (CT) practices, with residue (R) and without residue (NR). Nitrogen fertilizer was applied at a rate of 180 kg/ha in granular form (experiment I), and in solution form a year later (experiment II). In both experiments, water was applied 5 times over 3 to 4 weeks duration, with each application lasting for 30 minutes. Each column received an average of 24 mm water in experiment I and 32 mm in experiment II. Soil moisture contents were measured and water for $ rm NO sb{3 sp{-}}$-N concentration determination sampled at 0.1, 0.2, 0.4, and 0.6 m depths, following each water application.
In each experiment I, higher nitrate-nitrogen concentrations ($ lbrack rm NO sb{3 sp{-}}$-N)), occurred at the 0.1 and 0.2 m soil layers in RT and CT treatments initially, but less leached to lower layers, while more $ rm NO sb{3 sp{-}}$-N leached to lower depths (below 0.4 m) in the NT treatment. In experiment II, more $ rm NO sb{3 sp{-}}$-N leached below 0.4 m in RT and CT than in NT treatments. Conventional tillage exhibited the lowest drainage rates. Tillage and residue effects were significant only at early stages (4 hours or before) at some depths of experiment I ($P<0.05$). Maximum $ lbrack rm NO sb{3 sp{-}}$-N) occurred at 0.4 m depth in all treatments.
LEACHM-N estimated more $ rm NO sb{3 sp{-}}$-N leaching below 0.4 m in RT and CT treatments than in NT treatment. The model performed poorly only immediately after fertilizer application, showing up to 50% deviation from observed data. Although LEACHM-N overpredicted $ lbrack rm NO sb{3 sp{-}}$-N) in the 0.2 m soil layers in all treatments, estimations remained within standard deviations of observed data. NTRM performed well below 0.4 m depths, but often underpredicted $ rm NO sb{3 sp{-}}$-N leaching at shallower depths.
From both the laboratory experiments and mathematical simulations it was concluded that when fertilizer is applied in granular form, no till practice is undesirable because deeper $ rm NO sb{3 sp{-}}$-N leaching (below 0.4 m) occurs. Reduced tillage may be the preferred choice in such a situation. When fertilizer is applied in solution, reduced and conventional tillage practices are undesirable because deeper $ rm NO sb{3 sp{-}}$-N leaching occurred. No till practice may be a better choice in such a case.

Thesis (PhD)--University of Stellenbosch, 2005.
ENGLISH ABSTRACT: Several genera of cyanobacteria produce a range of toxins. The increased rate of eutrophication of surface fresh waters due to anthropogenic inputs has resulted in more frequent and severe cyanobacterial bloom events. Such bloom events make impoundments unsuitable for recreational use and increase the cost of production of potable water due to the necessity for removal of toxins released from cells during the purification process. Microcystis aeruginosa is the major freshwater bloom-forming toxic cyanobacterium. Concentrations of the hepatotoxin, microcystin, are highly variable in blooms. Published literature on environmental conditions leading to increased microcystin production was often contradictory and in many cases did not consider all relevant parameters. However, environmental nitrogen and phosphorus, temperature and light, and growth rate were implicated in regulation of toxin content. The purpose of this work was therefore to investigate environmental factors (specifically nitrogen and phosphorus) and cellular activities (specifically carbon fixation and nitrogen uptake rates and growth rate) involved in the modulation of microcystin production in M. aeruginosa in order to clarify the role of these parameters, and in an attempt to identify regulatory mechanisms for microcystin production. Environmental nitrogen, phosphorus and growth rate were shown to co-modulate microcystin production in M. aeruginosa. Adequate phosphorus is required for photosynthetic carbon fixation. Phosphorus uptake by M. aeruginosa is strongly correlated with carbon fixation rate. Although microcystin content increased with increasing nitrogen:phosphorus ratios in culture medium, under phosphorus limitation microcystin content was lower irrespective of nitrogen concentrations. This observation and the requirements for fixed carbon for nitrogen assimilation therefore prompted investigation of the effects of cellular carbon fixation and nitrogen uptake in the modulation of microcystin production. Microcystin production was found to be enhanced when nitrogen uptake rate relative to carbon fixation rate was higher than that required for balanced growth. The cellular nitrogen:carbon ratio above which microcystin concentrations increased substantially, corresponded to the Redfield ratio for balanced growth. Investigation of potential regulatory mechanisms involving the cyanobacterial nitrogen regulator, NtcA, yielded putative NtcA binding sites indicative of repression in the microcystin synthetase gene cluster. In culture, the polypeptide synthetase module gene, mcyA, and ntcA were inversely expressed as a function of carbon-fixation:nitrogen-uptake potential. However, no increase or decrease in microcystin production could be linked to either glutamine, glutamate or a-ketoglutarate, metabolites that are involved in regulation of ntcA. The role of NtcA in regulation of microcystin production could therefore not be confirmed. In conclusion, these data suggest that microcystin production is metabolically regulated by cellular C:N balance and specific growth rate. The primary importance of nitrogen and carbon was demonstrated by a simple model where only nitrogen uptake, carbon fixation and growth rate were used to predict microcystin levels. The model also explains results previously described in literature. Similarly, an artificial neural network model was used to show that the carbon fixation dependence on phosphorus allows accurate prediction of microcystin levels based on growth rate and environmental nitrogen and phosphorus.
AFRIKAANSE OPSOMMING: Verskeie genera van sianobakterieë produseer 'n verskeidenheid van toksiene. Die toename in die tempo van eutrofikasie van varswater oppervlaktes as gevolg van antropogeniese insette veroorsaak al hoe meer en al hoe erger sianobakteriële infestasies. Dit veroorsaak probleme vir ontspanninggebruik van hierdie waters en verhoog die koste van produksie van drinkbare water as gevolg van die noodsaak om die toksiene wat deur die selle gedurende die suiweringsproses vrygelaat word te verwyder. Microcystis aeruginosa is die belangrikste varswater bloeisel-vormende toksiese sianobakterium. Die konsentrasie van die hepatotoksien mikrosistien is hoogs varieerbaar in sulke bloeisels. Gepubliseerde literatuur oor die omgewingskondisies wat lei na verhoogde mikrosistienproduksie is dikwels weersprekend en neem in vele gevalle nie al die relevante parameters in ag nie. Desnieteenstaande word omgewingstikstof, fosfor, temperatuur en lig, asook groeisnelheid, geïmpliseer in die regulering van toksieninhoud. Die doel van hierdie navorsing was dus om omgewingsfaktore (spesifiek stikstof en fosfor) en sellulêre aktiwiteite (spesifiek koolstoffiskering en die snelheid van stikstofopname en van groei) betrokke by die modulering van mikrosistienproduksie in M. aeruginosa te ondersoek in 'n poging om die rol van hierdie parameters te verstaan en om regulatoriese meganismes vir mikrosistienproduksie te identifiseer. In hierdie studie is aangetoon dat omgewingstikstof en fosfor sowel as groeisnelheid mikrosistienproduksie in M. aeruginosa ko-moduleer. Genoegsame fosfor word benodig vir fotosintetiese koolstoffiksering. Fosforopname deur M. aeruginosa korreleer sterk met die snelheid van koolstoffiksering. Alhoewel mikrosistieninhoud toegeneem het met 'n toename in die stikstof:fosfor verhouding in die kultuurmedium, was die mikrosistieninhoud onder kondisies van fosforlimitering laer ongeag die stikstofkonsentrasie. Hierdie waarneming, tesame met die noodsaak van gefikseerde koolstof vir stikstofassimilering, het gelei na 'n studie van die effekte van sellulêre koolstoffiksering and stikstofopname op die modulering van mikrosistienproduksie. Dit is gevind dat mikrosistienproduksie verhoog was wanneer die snelheid van stikstofopname relatief tot die snelheid van koolstoffiksering hoër was as die waarde wat benodig word vir gebalanseerde groei. Die sellulêre stikstof:koolstof verhouding waarbo mikrosistienkonsentrasies beduidend verhoog is stem ooreen met die Redfield verhouding vir gebalanseerde groei. 'n Ondersoek na potensiële reguleringsmeganismes waarby die sianobakteriële stikstofreguleerder NtcA betrokke is het gelei na die ontdekking van moontlike NtcA bindingseteis; dit kan dui op die repressie van die mikrosistiensintetase geengroepering. Onder kultuurkondisies is gevind dat die geen vir die polipeptiedsintetase module, mcyA, en ntcA omgekeerd uitgedruk word as 'n funksie van koolstofopname:stikstofopname potensiale. Geen toename of afname in mikrosistienproduksie kon egter gekoppel word aan óf glutamien, óf glutamaat, óf a-ketoglutaraat nie, metaboliete wat betrokke is by die regulering van ntcA. Die rol van NtcA in die regulering van mikrosistienproduksie kon dus nie bevestig word nie. Die gevolgtrekking is dus gemaak dat mikrosistienproduksie metabolies gereguleer word deur die C:N balans en die spesifieke groeisnelheid. Die primêre belang van stikstof en koolstof is gedemonstreer deur 'n eenvoudige model waarin slegs stikstofopname, koolstoffiksering en groeisnelheid gebruik word om mikrosistienvlakke te voorspel. Die model verklaar ook resultate wat tevore in die literatuur beskryf is. Soortgelyk is 'n artifisiële neurale netwerkmodel gebruik om te toon dat die afhanklikheid van koolstoffiksering van fosfor akkurate voorspelling van mikrosistienvlakke gebaseer of groeisnelheid en omgewingstikstof en fosfor moontlik maak.

Blue Lake, Jefferson County, Oregon, has high summer surface phosphorus concentrations (ca. 30 ug/l) yet is oligotrophic (summer Secchi depth is 11 to 16 meters). Nutrient enrichment experiments done with 1000 1 polyethylene enclosures indicate nitrate limitation of phytoplankton growth. Basin morphology may be an important factor in nutrient cycling in this lake. The lake has a maximum depth of 95.7 meters with an average depth of 42.7 meters. The lake basin has steep sides with only 4% of the lake bottom less than 3.3 meters deep. of recent volcanic origin. In contrast, Suttle Lake, which is immediately downstream from Blue Lake, is moderately eutrophic (Secchi depth 1.7 meters) and supports much larger populations of phytoplankton, including nitrogen fixing cyanophytes. Suttle Lake is shallower and more subject to wind mixing.

A subsurface flow constructed wetland was built at the Wastewater Treatment Plant in Muncie, Indiana, in May, 1995. In May, 1996, this wetland was divided into two equal cells and planted with Scirpus validus vahl (softstem bulrush). Samples were collected from July 30, 1996, through October 22, 1996. This study had two objectives. The first was to determine if harvesting the aboveground biomass of the Scirpus would affect the wetland's ability to remove nitrogen from the wastewater. The second objective of this study was to determine if harvesting the bulrush twice during a growing season would substantially increase the annual biomass production. Water was collected from four locations in each cell and analyzed for organic nitrogen, ammonical nitrogen, nitrate, and total nitrogen. The concentration of each nitrogen parameter was significantly reduced between the inlet and well 1 in each cell of the wetland. There were no significant reductions in nitrogen concentration in subsequent sampling locations. There were also no significant differences between the two wetland cells.
Department of Natural Resources and Environmental Management

Concern about NO$ sb3 sp-$-N leaching and groundwater pollution from monoculture corn (Zea mays L.) has prompted investigation of alternative production systems which reduce N leaching. Both intercrop systems and water table controls alone have been shown to increase nitrogen (N) uptake and reduce soil NO$ sb3 sp-$-N accumulation in cropping systems. There is a need to maintain crop productivity while reducing the potential for soil NO$ sb3 sp-$-N leaching into groundwater. However, there has been no information available regarding agronomic and physiological aspects of N and water management for monocrop corn and corn competing with annual Italian ryegrass (Lolium multiflorum Lam) in an intercrop system. A study was conducted in southwestern Quebec during 1993 and 1994. Nitrogen and dry matter components in the plant-soil system were determined. Intercropped corn grain yield did not differ from monocropped corn under high N fertility. At harvest, the corn-annual ryegrass intercrop system increased total aboveground N uptake by 77.2 and 50.7 kg ha$ sp{-1}$ when compared with the corn monocrop system in 1993 and 1994, respectively. The intercrop system reduced the amount of NO$ sb3 sp-$-N in the top 1 m of soil by 47% (92.3 kg N ha$ sp{-1}$) at harvest in 1993. Water table controls had little effect on corn yield, N use efficiency and soil NO$ sb3 sp-$-N accumulation over the two years of this study. Both plant establishment and weather conditions affected the ability of annual ryegrass to aid in the uptake of soil NO$ sb3 sp-$-N. The reproductive development of water stressed plants after silking was limited more by overall plant changes due to water stress than assimilate supply. The delivery of C (sucrose) and N ($ sp{15}$N urea) into corn plants via stem-injection showed that externally supplied C changed both the source strength (photosynthetic inhibition) and sink strength (decreased total grain production), while distribution of $ sp{15}$N was affected by p

Sustainable vegetable production is one of the most active areas of vegetable research and of concern to all producers. Everyone, both producers and consumers, are concerned with sustainability. Brussels sprouts and sweet basil are high value commodities, but increasing global concerns about water availability, insect-pest problems, and costly fertilizer inputs severely impact the growth and production of these crops. Low tunnels covered with spun-bonded fabric can improve production of vegetables and herbs in Virginia and the U.S. This study investigated the performance of Brussels sprouts and basil grown under low tunnels (LTs), and their relationship with water use efficiency, nitrogen use efficiency, and the level of protection against insect injury. Low tunnels increased yield, number of sprouts, and water use efficiency of Brussels sprout production. In addition, LTs decreased irrigation requirements, irrigation events, leaf feeding injury, and insect populations in comparison to open field. Similarly, LTs increased summer production of sweet basil as measured by fresh weight and biomass. In addition, plant N uptake was greater under the LTs; however, the increase in nitrogen use efficiency was inconsistent.
Master of Science in Life Sciences
Brussels sprouts and sweet basil are economically important cash crops on the East Coast. Brussels sprouts is a Cole crop and an important source of dietary fiber, vitamins (A, C & K), calcium, iron, manganese and antioxidants. Similarly, sweet basil is a member of the mint family and important high-value herb in the U.S. and the world. It is mainly grown for culinary purposes as a dried and fresh spice in the U.S. However, demand for these commodities is increasing. Low tunnels (LTs) covered with spunbonded fabric can be a practical management tool to increase yield. Results from this study indicate that LTs increase yield of Brussels sprouts and basil, water use efficiency and total nitrogen uptake, while reducing insect pest infestation. Therefore, LTs can be a useful tool to improve sustainability of Brussels sprouts and basil production.

Thesis (Ph. D.)--Earth and Atmospheric Sciences, Georgia Institute of Technology, 2007.
Martial Taillefert, Committee Member ; Jay Brandes, Committee Member ; Markus Huettel, Committee Member ; Philip Froelich, Committee Member ; Ellery Ingall, Committee Member ; Richard A. Jahnke, Committee Chair.

Canals surrounding the Everglades carry enriched and polluted water high in minerals and nutrients. These enriched waters impact adjacent marsh habitats, altering flora and fauna species and abundance. Multiple studies have found gradients in nutrient levels as a function of distance from canals and emphasize the sensitivity of some organisms to these changes in water chemistry. Florida apple snails, Pomacea paludosa Say, are just one of many Everglades species sensitive to changes in water chemistry. They serve as an important staple in the diets of many Everglades predators including turtles, crayfish, limpkins and most importantly the endangered snail kite, Rostrahamus sociabilis which feeds almost exclusively on the apple snail. To examine potential effects of water chemistry on apple snail breeding patterns, we observed snail egg size, egg number per clutch, and carbon and nitrogen contents along water chemistry gradients and among snail breeding months at the Arthur R. Marshall Loxahatchee National Wildlife Refuge. Egg number per clutch and egg diameters were greatest in the most impacted zones and lowest in the pristine, interior zone. Carbon contents of eggs were highest in the interior and east side of the Refuge and lowest in the west side. Nitrogen contents of eggs were highest in the interior and west side of the Refuge, and lowest in the east side. Significant, albeit weak, positive trends were found between N content and egg diameter, C content and egg diameter, and between egg number per clutch and egg diameter, but only among specific zones and months. Results from this study suggest that snails in areas of the Refuge that are influenced by canal-water may produce greater numbers of apple snail offspring with greater egg diameters than those in less impacted areas. However, we do not know if this translates into higher hatchling success and survival.

Thesis (Ph. D.)--Joint Program in Oceanography/Applied Ocean Science and Engineering (Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences; and the Woods Hole Oceanographic Institution), 2010.
Cataloged from PDF version of thesis.
Includes bibliographical references.
Excess nitrogen input is deleterious to coastal waters, resulting in deterioration of the water quality, increases in harmful algal blooms and disease in commercial fish stocks. A significant portion of this nitrogen enters coastal waters through groundwater systems. Here we use isotopic and molecular biological methods to identify the populations of nitrifiers and denitrifiers, where they occur, and what levels of activity are present through the upper four meters of a coastal groundwater system. This work shows two different populations of putative ammonia-oxidizing archaea (AOA) based on the ammonia mono-oxygenase gene (amoA), one shallow population most closely related to open ocean water column-like sequences and a deeper population that is more closely related to estuarine-like AOA. Interestingly, while the surface population has a potential nitrification rates (456 pmol g-1 sediment day-) similar to marine sediments, the deeper population does not show detectable evidence of nitrification. Between these two archaeal populations resides an active population of ammonia-oxidizing bacteria with similar nitrification rates as the surface AOA population. The upper meter of the aquifer is also an active area of denitrification as evidenced by the coincident drop in nitrate concentration and increase in both 15N (up to + 20. 1%o) and 5180 (up to + 11. 7%o), characteristic of groundwater affected by denitrification. 16S rRNA gene surveys of the organisms present in the upper meter also are similar to soil/sediment type environments including many potential denitrifiers. However, nitrite reductase, nirS and nirK, genes were also recovered from the sediments with nirK dominating in the surface sediments. This contrasts with the deep salt wedge, where the microbial community 16S rRNA genes appear more closely related to marine or reducing sediment/wastewater type organisms, and nirS genes become the dominant denitrification gene.
by Daniel Richard Rogers.
Ph.D.

The purpose of this study was to evaluate the level of nitrate contamination in the water in Cherry Valley. It examines the theory that human effluent is the source of the nitrate and evaluates the role of politics in the nitrate issue.

碩士
明道大學
材料暨系統工程研究所
95
Switchgrass (Panicum virgatum L.) is a C4 perennial grass grown naturally in most of the central and eastern United States. A stand of switchgrass can grow vigorously over 10 years, resist drought, and survive with low fertilizer inputs. Thus, the U.S. Department of Energy has identified switchgrass as the most promising species for development into herbaceous biomass fuel crop. Switchgrass is also cultivated for the purpose of soil reclamation and habitat development of grassland birds. Switchgrass is as a multi-purpose crop with ecological function, soil conservation and bioenergy production. However, studies on switchgrass cultivation in Taiwan are very limited. In order to assess the feasibility of establishment of this multi-purpose crop in Taiwan, it is required to do detailed researches on cultivation management of switchgrass. In this study, two ecotypes of switchgrass, Alamo (A) and Blackwell (B), were selected for pot experiments. Seedling were grown in pots containing Yuliao soil and were maintained in a greenhouse for 6 months. Nitrogen (N) was applied at the rate of 0, 25, 50, 125 kg ha-1. Soil moisture levels were controlled by watering at 2 days (2D), 5 days (5D) and 8 days (8D) intervals. The results revealed that soil moisture influenced the tiller number, plant height, chlorophyll index, and tissue dry weight of switchgrass plants more significantly than nitrogen application. Tiller number and plant height of Alamo were significantly higher than that of Blackwell. Tiller number and plant height could be enhanced by increasing the nitrogen application rate and watering interval. Effects of nitrogen application and soil moisture on the tiller number and plant height were more prominent on Alamo than those on the Blackwell. Tiller number and plant height are considered as the evaluation factors for indicating the biomass yield to be harvested. The results showed that the effects of nitrogen application and soil moisture on the dry weight of aboveground tissues were more pronounced on Alamo than on Blackwell. On the other hand, the biomass yield of underground tissues of both the cultivars was influenced by the watering intervals; the dry weight of underground tissues was significantly increased with the increase in soil moisture levels resulting from frequent watering. Moreover, Alamo yielded more dry weight of underground tissues than Blackwell. Establishment of Alamo would be more beneficial for soil carbon sequestration than that of Blackwell. However, nitrogen application rate did not dshow a consistent positive response on the dry weight of underground tissues harvested. In conclusion, the morphological growth pattern and biomass yield of Alamo cultivar showed its strong ability to be a successful candidate for biofuel feedstock production in Taiwan, but the Blackwell cultivar has limited usefulness in teams of biofuel production because of low biomass yield.

MSCAGR (Soil Science)
Department of Soil Science
Maize (Zea mays L.) is widely grown in the semi-arid regions of South Africa mainly for its grain that is used for direct human consumption, feed for animals and raw materials for the industries. The challenges of soil infertility, water supply, and availability of high yielding cultivars remain a major constraint for its production in this environment. These constraints are a major threat to sustainable crop production and food security. Maize/lablab Zea mays L.\ L. purpureus) intercropping system could thus become an option for food security among small scale maize producers in dry environments. Preliminary studies show the huge potential of maize/lablab intercropping in the semi-arid environments of the North-Eastern South Africa. Therefore, this study aimed to assess the effects of maize/lablab intercropping on soil water content, nitrogen dynamics and crop productivity based field experiments and crop simulation modeling using the model APSIM. The trials were conducted at two sites (Univen and Syferkuil) in Limpopo province, South Africa, for two seasons (2015/2016) and 2016/2017). The treatments consisted of; (i) sole maize (ii) sole lablab (iii) maize and lablab planted at the same time (Maize+lablab-ST) and (iv) maize with lablab planted 28 days after maize (Maize+lablab-28).The treatments were laid out in an RCBD replicated 4 times, with individual plots size measuring 4.5 m × 4 m (18 m2) and the layout of the field as consisting of 4 plots per block giving a total of 16 plots in 4 blocks. The following parameters were determined: soil water content, soil NO3--N and NH4+-N levels, dry matter and grain yield. The APSIM-model (version 7.7) was then used to simulate maize grain yield and dry matter production to assess risks associated with the production of maize/lablab intercropping. The results obtained from this study showed that maize/lablab intercropping had significant effects on measured parameters (grain, biomass yield soil water content, and N-minerals). Maize+lablab-28 produced 46 % higher grain yield than sole cropping (24%) and maize+lablab-ST) (30%). The results also showed variation in soil water content at different depths among the treatments. The soil water content was increased with depth. The intercropped plots and lablab sole had significantly higher soil water content than the sole maize. At all depths, the highest soil water content was obtained under sole lablab followed by maize+lablab-ST and maize+lablab-28. It was notable however that maize/lablab intercropping showed a higher NO3--N and NH4+-N levels at all depths. At both sites, the soil NO3--N showed a sharp drop at V7 sampling time. The results showed the benefits of intercropping in comparison to sole cropping as demonstrated by positive land equivalent ratios of >1 for both cropping systems in both years and sites. Modelling exercises showed that APSIM was able to simulate the results sufficiently. In the simulation experiment, a stronger negative effect of planting lablab with maize simultaneously was found. Hence, delayed planting of lablab should be a standard practice
NRF

In the semi - arid Mediterranean - type environments of southern Australia, soil and water resources largely determine crop productivity and ultimately the sustainability of farming systems within the region. The development of sustainable farming systems is a constantly evolving process, of which cropping sequences ( rotations ) are an essential component. This thesis focused on two important soil resources, soil water and nitrogen, and studied the effects of different crop sequences on the dynamic of these resources within current farming systems practiced on the upper Eyre Peninsula of South Australia. The hypothesis tested was that : continuous cropping may alter N dynamics but will not necessarily alter water use efficiency in semi - arid Mediterranean - type environments. Continuous cropping altered N - dynamics ; increases in inorganic N were dependent on the inclusion of a legume in the cropping sequence. Associated with the increase in inorganic N supply was a decrease in WUE by the subsequent wheat crop. Overall, estimates of water use efficiency, a common index of the sustainability of farming systems, in this study concur with reported values for the semi - arid Murray - Mallee region of southern Australia and other semi - arid environments worldwide. Soil water balance and determination of WUE for a series of crop sequences in this thesis suggests that the adoption of continuous cropping may increase WUE and confer a yield benefit compared to crop sequences including a legume component in this environment. No differences in total water use ( ET ) at anthesis or maturity were measured for wheat regardless of the previous crop. Soil evaporation ( E [subscript s] ) was significantly affected by crop canopy development, measured as LAI from tillering until anthesis in 2002, however total seasonal E [subscript s] did not differ between crop sequences. Indeed in environments with infrequent rainfall, such as the upper Eyre Peninsula, soil evaporation may be water - limited rather than energy limited and the potential benefits from greater LAI and reduced E [subscript s] are less. Greater shoot dry matter production and LAI due to an enhanced inorganic N supply for wheat after legumes, and to a lesser degree wheat after canola, relative to continuous cereal crop sequences resulted in increases in WUE calculated at anthesis, as reported by others. Nonetheless the increase in WUE was not sustained due to limitations on available soil water capacity caused by soil physical and chemical constraints. Access to more soil water at depth ( > 0.8m ) through additional root growth was unavailable due to soil chemical limitations. More importantly, the amount of plant available water within the ' effective rooting depth ' ( 0 - 0.8m ) was significantly reduced when soil physical factors were accounted for using the integral water capacity ( IWC ) concept. The difference between the magnitude of the plant available water capacity and the integral water capacity was approximately 90mm within the ' effective rooting depth ' when measured at field capacity, suggesting that the ability of the soil to store water and buffer against periodic water deficit was severely limited. The IWC concept offers a method of evaluating the physical quality of soils and the limitations that these physical properties, viz. aeration, soil strength and hydraulic conductivity, impose on the water supply capacity of the soil. The inability of the soil to maintain a constant supply of water to satisfy maximal transpiration efficiency combined with large amounts of N resulted in ' haying off ', and reduced grain yields. A strong negative linear relationship was established between WUE of grain production by wheat and increasing soil NO₃ - N at sowing in 2000 and 2002, which conflicts with results from experiments in semi - arid Mediterranean climates in other regions of the world where applications of N increased water use efficiency of grain. Estimates of proportional dependence on N₂ fixation ( % N [subscript dfa] ) for annual medics and vetch from this study ( 43 - 80 % ) are comparable to others for environments in southern Australia ( < 450mm average annual rainfall ). Such estimates of fixation are considered low ( < 65 % ) to adequate ( 65 - 80 % ). Nevertheless, the amount of plant available N present at sowing for subsequent wheat crops, and the occurrence of ' haying off ', suggests that WUE is not N - limited per se, as implied by some reports, but constrained by the capacity of a soil to balance the co - limiting factors of water and nitrogen.
Thesis (Ph.D.) -- University of Adelaide, School of Earth and Environmental Sciences, 2005.

In the semi - arid Mediterranean - type environments of southern Australia, soil and water resources largely determine crop productivity and ultimately the sustainability of farming systems within the region. The development of sustainable farming systems is a constantly evolving process, of which cropping sequences ( rotations ) are an essential component. This thesis focused on two important soil resources, soil water and nitrogen, and studied the effects of different crop sequences on the dynamic of these resources within current farming systems practiced on the upper Eyre Peninsula of South Australia. The hypothesis tested was that : continuous cropping may alter N dynamics but will not necessarily alter water use efficiency in semi - arid Mediterranean - type environments. Continuous cropping altered N - dynamics ; increases in inorganic N were dependent on the inclusion of a legume in the cropping sequence. Associated with the increase in inorganic N supply was a decrease in WUE by the subsequent wheat crop. Overall, estimates of water use efficiency, a common index of the sustainability of farming systems, in this study concur with reported values for the semi - arid Murray - Mallee region of southern Australia and other semi - arid environments worldwide. Soil water balance and determination of WUE for a series of crop sequences in this thesis suggests that the adoption of continuous cropping may increase WUE and confer a yield benefit compared to crop sequences including a legume component in this environment. No differences in total water use ( ET ) at anthesis or maturity were measured for wheat regardless of the previous crop. Soil evaporation ( E [subscript s] ) was significantly affected by crop canopy development, measured as LAI from tillering until anthesis in 2002, however total seasonal E [subscript s] did not differ between crop sequences. Indeed in environments with infrequent rainfall, such as the upper Eyre Peninsula, soil evaporation may be water - limited rather than energy limited and the potential benefits from greater LAI and reduced E [subscript s] are less. Greater shoot dry matter production and LAI due to an enhanced inorganic N supply for wheat after legumes, and to a lesser degree wheat after canola, relative to continuous cereal crop sequences resulted in increases in WUE calculated at anthesis, as reported by others. Nonetheless the increase in WUE was not sustained due to limitations on available soil water capacity caused by soil physical and chemical constraints. Access to more soil water at depth ( > 0.8m ) through additional root growth was unavailable due to soil chemical limitations. More importantly, the amount of plant available water within the ' effective rooting depth ' ( 0 - 0.8m ) was significantly reduced when soil physical factors were accounted for using the integral water capacity ( IWC ) concept. The difference between the magnitude of the plant available water capacity and the integral water capacity was approximately 90mm within the ' effective rooting depth ' when measured at field capacity, suggesting that the ability of the soil to store water and buffer against periodic water deficit was severely limited. The IWC concept offers a method of evaluating the physical quality of soils and the limitations that these physical properties, viz. aeration, soil strength and hydraulic conductivity, impose on the water supply capacity of the soil. The inability of the soil to maintain a constant supply of water to satisfy maximal transpiration efficiency combined with large amounts of N resulted in ' haying off ', and reduced grain yields. A strong negative linear relationship was established between WUE of grain production by wheat and increasing soil NO [subscript 3] - N at sowing in 2000 and 2002, which conflicts with results from experiments in semi - arid Mediterranean climates in other regions of the world where applications of N increased water use efficiency of grain. Estimates of proportional dependence on N [subscript 2] fixation ( % N [subscript dfa] ) for annual medics and vetch from this study ( 43 - 80 % ) are comparable to others for environments in southern Australia ( < 450mm average annual rainfall ). Such estimates of fixation are considered low ( < 65 % ) to adequate ( 65 - 80 % ). Nevertheless, the amount of plant available N present at sowing for subsequent wheat crops, and the occurrence of ' haying off ', suggests that WUE is not N - limited per se, as implied by some reports, but constrained by the capacity of a soil to balance the co - limiting factors of water and nitrogen.
Thesis (Ph.D.)--School of Earth and Environmental Sciences, 2005.

Emergent macrophytes are an integral part of prairie marshes and involved in many of the services that make these ecosystems valuable. Water depth and hydroperiod are two environmental variables that can influence the growth and nutrient content of emergent macrophytes. This study looked at the growth and nutrient content response of hybrid cattail (Typha x glauca) to water depth and hydroperiod in two prairie marshes in southern Manitoba, Canada. Above- and belowground samples of hybrid cattails were collected along a water depth gradient at Oak Hammock Marsh, Canada, and analyzed for biomass, total phosphorus, total nitrogen, total Kjeldahl nitrogen content, shoot height, and density. A second dataset was obtained from the Marsh Ecology Research Program (MERP) experiment, and used to determine the biomass and nutrient content response of the hybrid cattail following one or two years of drawdown.
October 2015

In Southern Manitoba, potato producers are experiencing wetter and drier conditions within the soil profile during the growing season leading to poor quality and inconsistent yields. Russet Burbank Potato cultivar was grown in Southern Manitoba on fine sandy loam soil in a two year (2013-2014) study using two water management treatments: (i) overhead irrigation and (ii) no-irrigation. The main objectives of the study were (i) to assess the impact of overhead irrigation on water table depth and potato yield (ii) to estimate the shallow groundwater contribution to potato water requirement through upward flux (iii) to track the nitrogen dynamics within the potato root-zone under overhead irrigation and no-irrigation scenarios (iv) to examine the effects of no-irrigation and overhead irrigation system at critical growth stages on marketable yield and quality of potatoes. In 2013, water was applied using a linear move irrigation system and in 2014 a rain gun irrigation system was used for the irrigated treatment. Volumetric soil water content, precipitation, irrigation depth, water table depth, nitrate concentration and electrical conductivity in potato root-zone, groundwater electrical conductivity, weather variables, total potato yield, marketable yield, and quality parameters were measured. The total yield was not significantly different between the two treatments in both years. The marketable yield of the irrigated treatment (36.89 MT/ha) was 20% higher (p = 0.017) compared to the non-irrigated treatment (30.74 MT/ha) in 2013. However, no significant difference was found between the irrigated (39.0 MT/ha) and non-irrigated (43.7 MT/ha) treatments in 2014. Potato yields from both treatments were significantly correlated with the average groundwater depth. Water balance analysis within the root-zone during rainy and rain-free periods showed that nitrate rich groundwater may have contributed to some of the crop water demand. The lack of rainfall and high temperature during tuber initiation and tuber bulking stages resulted in the accumulation of high concentration of nitrates within the root-zone by the late release of nitrates from the polymer-coated urea and the upward migration of groundwater containing 55 ppm and 70 ppm of nitrates in the 2013 and 2014 growing seasons, respectively. Overhead irrigation was found to be economically advantageous to produce better quality potatoes with higher marketable yields.

Indiana University-Purdue University Indianapolis (IUPUI)
The characterization of the nutrients nitrogen, phosphorus and carbon (NPC) export to streams during storms is an integral part of understanding processes affecting water quality. Despite the fact that excessive levels of these nutrients in the Mississippi River basin adversely affects water quality in the Gulf of Mexico, little research has been conducted on NPC dynamics during storms on larger (>20 km2) agriculturally dominated Midwestern watersheds. This project examined the storm export of nitrate, ammonium, total phosphorus, and dissolved organic carbon (DOC) in the upper Eagle Creek Watershed (UECW) (274 km2) in Central Indiana, USA. Water samples were collected during five winter and spring storms in 2007 and 2008 on the rising and falling limb of the hydrograph, in order to characterize NPC dynamics during storm events. Stream discharge and precipitation was monitored continuously, and major cations were used to examine changes in source water over the duration of the storm and assist in the determination of potential flowpaths. DOC, total P, and TKN (Total Kjeldahl Nitrogen) tended to peak with discharge, while nitrate usually exhibited a slight lag and peaked on the receding limb. Total phosphorus, NH3-, TKN, and DOC appear to be delivered to the stream primarily by overland flow. NO3--N appear to be delivered by a combination of tile drain and macropore flow. Overall UECW displayed smoother nutrient export patterns than smaller previously studied watersheds in the area suggesting that scale may influence nutrient export dynamics. Further research is underway on a 3000 km2 watershed in the area to further examine the role scale may play in nutrient export patterns.

The Calapooia River, a major tributary of the Willamette River in western Oregon, is a watershed typical of many found in the Willamette Basin. Public and private forested lands occur in the steep Upper Zone of the watershed, mixed forest and agriculture lands are found in the Middle Zone, and the Lower Zone of the watershed is comprised primarily of grass seed agriculture on relatively flat topography with poorly drained soils. High levels of dissolved nitrogen (DN) have been identified as a water-quality concern within the Calapooia River. To gain a better understanding of the relationship between landuse/landcover (LULC), soil drainage, and DN dynamics within the watershed on a seasonal basis, we selected 44 sub-basins ranging in size between 3 and 33 km² for monthly synoptic surface water-quality sampling from October 2003 through September 2004. We selected an additional 31 sample locations along the length of the Calapooia River to determine relative influence of the 44 sub-basins on DN concentrations in the river. T-tests were used to analyze differences between zones (Upper, Middle and Lower) and regression analysis was used to determine relationships between DN and LULC or soil drainage class. The agriculture-dominated sub-basins had significantly higher (< 0.05) DN concentrations than the predominantly forested sub-basins. Winter concentrations of nitrate-N were 43 times higher in agriculturally dominated sub-basins than in forested sub-basins, whereas in the spring, the difference was only 7-fold. High DN concentrations associated with the predominantly agriculture sub-basins were substantially reduced once they mixed with water in the Calapooia River, highlighting the likelihood that water draining the relatively nutrient-poor, forested sub-basins from the Upper Zone of the watershed, was diluting DN-rich water from the agriculture sub-basins. Relationships between DN and agriculture, woody vegetation or poorly drained soils were moderate to strong (0.50 < R² > 0.85) during the winter, spring and summer seasons. Results indicated an exponential increase in DN concentration when proportion agriculture or poorly drained soils increased, whereas an increase in woody vegetation was related to an exponential decrease in DN concentration. The high variability in DN concentration in the agriculture-dominated sub-basins suggests factors in addition to LULC and poorly drained soils influence DN in surface water. Seasonal relationships were developed between DN and proportion of poorly drained soils, agriculture, and woody vegetation at differing scales (10 m, 20 m, 30 m, 60 m, 90 m, 150 m, 300 m, and entire sub-basin), which we defined as Influence Zones (IZs), surrounding the stream network. Correlations between DN and proportion LULC or poorly drained soil at each IZ were analyzed for significant differences (p-value < 0.05) using the Hotelling-Williams test. Our results show strong seasonal correlations (r > 0.80) between DN and proportion of woody vegetation or agriculture, and moderate-to-strong seasonal correlations (r > 0.60) between DN and proportion of sub-basins with poorly drained soils. Altering scale of analysis significantly changed correlations between LULC and DN, with IZs < 150 m generally having higher correlations than the sub-basin level. In contrast, DN correlations with poorly drained soil were generally higher at the sub-basin scale than the 60- through 10-m IZs during winter and spring. These results indicate that scale of analysis is an important factor when determining relationships between DN concentration and proportion LULC or poorly drained soils. Furthermore, seasonal shifts in significant differences among IZs for correlations between LULC and DN suggest land management proximity and its influence on DN concentration changes temporally. DN relationships with poorly drained soil suggest that during winter and spring, when rainfall is highest, sub-basin scale soil drainage properties have a greater influence on DN than soil properties within IZs in close proximity to the stream network.
Graduation date: 2006

Spatially explicit ecosystem service valuation (ESV) allows for the identification of the location and magnitude of services provided by natural ecosystems to human activities along with a measure of their significance based upon economic valuation. While ESV has been used to provide new insight into land use management, few studies have identified the connections between the values of ecosystem services and ecological sensitivity to nitrogen loading despite a growing body of ecosystem service literature. This research combines a GIS-based, value transfer approach to map ecosystem services in the Lower Yakima River Basin (LYRB), Washington, USA, along with estimates of nitrogen loading to identify how nitrogen management may affect ecosystem services in the basin. This analysis combines values of ecosystem services with estimates of nitrogen loading and identifies subwatersheds and specific parcels within a Groundwater Management Area (GWMA) most susceptible to reductions in ecosystem services due to excess nitrogen loading. Based on the benefit transfer analysis, wetlands and forested areas have disproportionately high values of ecosystem services when compared to their land area in the LYRB, while pasture and cultivated crops contribute much less to the total value of ecosystem service flows in proportion to the total area in the LYRB. Across the study area estimated nitrogen loads are strongly driven by the location of concentrated animal feeding operations (CAFOs) and cultivated crops. Areas of particularly high nitrogen loading and high ESV may highlight specific areas for achieving immediate success in increasing or maintaining ecosystem services through appropriately focused regulatory mechanisms. The land cover analysis however, completely neglects the values and importance of subsurface processes and groundwater resources in ecosystem service assessment, and therefore an econometric model is applied to estimate willingness to pay (WTP) to maintain safe nitrate levels in private wells. Through the incorporation of WTP estimates for groundwater quality, a more complete economic and ecological perspective on the effects of landscape N loading in the study site is highlighted. The results of these estimates clearly indicate that ecosystem services from groundwater should be considered to have significant value in the LYRB. Further economic valuation data on specific land cover types and the value of groundwater quality, whether from primary studies or meta-analysis, is needed to refine relative measures of ecosystem service values and more confidently describe these values in specific dollar amounts. Additionally, limits in spatial data resolution may contribute to errors in location and magnitude of ecosystem services, and is an area in need of further development. Despite these potential limitations, this analysis highlights a promising direction for combining spatially explicit ecosystem service valuation with nutrient loading data to identify the location and potential magnitude of effects on ecosystem services from management practices.
Graduation date: 2013

The increased demand for wood and fiber from a continually shrinking land base has resulted in the use of intensively managed forest plantations. The concentration of timber production on the most suitable sites allows the world's demand for forest products to be met on less land and enable native forests to be conserved. Because much of the water flowing in rivers in the U.S. originates as precipitation in forests, there is a justified concern about the impacts of forest management on water quality. Nutrient concentrations were measured in eight streams from October 2002 to September 2011 to assess nutrient response to contemporary forest practices at the Hinkle Creek Paired Watershed Study in the Oregon Cascades. This period of time included a two-year pre-treatment calibration between control and treatment watersheds, a fertilization treatment of both basins in October 2004, and a post-treatment period from 2005 to 2011. A treatment schedule comprised of two temporally explicit harvest entries was used to assess the effects of clearcutting at the non-fish-bearing headwater scale and the fish-bearing watershed scale. Stream water samples were analyzed for nitrogen, phosphorus, calcium, sodium, potassium, magnesium, sulfate, chloride, and silicon as well as specific conductance, pH, and alkalinity. Programmable water samplers were used to take water samples during fall freshets in November 2009 to assess the stream water discharge versus NO₃ + NO₂ concentration relationship. All treatment watersheds showed a statistically significant increase in NO₃ + NO₂ concentrations after clearcutting (p < 0.001). The slope of the streambed through the disturbance was a stronger predictor of the magnitude of the response than was the magnitude of disturbance. Ammonia and organic nitrogen displayed notable increases after harvest treatment, but these increases were attributed to increases in the control watersheds. Phosphorus showed a response to timber harvest in one headwater stream. The remaining nutrients showed a small decrease in the control and treatment watersheds for the period after harvest. There was some evidence to suggest that the addition of urea nitrogen to both basins may have caused an increase in in-stream biota uptake of these nutrients. The storm response results showed that NO₃ + NO₂ concentrations in stream water increase with discharge during small storms that occur after periods of negligible precipitation. Concentrations of NO₃ + NO₂ observed during the calibration period were similar to concentrations observed in an old-growth forest in the H.J. Andrews, suggesting that nutrient processing within the Hinkle Creek watershed had returned to levels that existed prior to its initial harvest sixty years ago. This finding helps to assess long-term impacts of shorter rotation timber harvest of regenerated Douglas-fir stands characteristic of industrialized timber harvest in Oregon.
Graduation date: 2012