Master of Science / Department of Agronomy / Dorivar A. Ruiz Diaz Suarez / An effective nutrient management plan is essential for optimum wheat (Triticum aestivum) yields. The objectives of the first study were to: i.) evaluate changes in concentration of nitrogen (N), phosphorus (P), potassium (K), sulfur (S), copper (Cu), manganese (Mn), and zinc (Zn), within separate plant parts, throughout the growing season, ii.) evaluate the uptake pattern and redistribution of each of these nutrients within the plant throughout the season, and iii.) evaluate the impact of micronutrient and S fertilization on concentration and uptake of nutrients and the potential use of fertilization for biofortification. Three locations were established and sampled every 7 to 10 days during the spring. Samples were divided into leaf, stem, head, spike and grain fractions and analyzed for nutrient concentration. Concentration levels tended to decrease throughout the season in non-grain plant fractions and stay relatively constant in the grain. Harvest grain concentration of Zn was significantly higher with micronutrient fertilization at all locations, suggesting the possibility of Zn biofortification through fertilization. S, Cu, and Zn showed nutrient accumulation increases in all plant fractions until the time period around anthesis (Feekes 10.5.1), at which point leaf and stem fractions decreased in total accumulation while nutrients were remobilized to the grain. N, P, K and Mn showed a similar trend although timing of remobilization varied between locations and treatments. The objectives of the second study were to i.) evaluate the interaction of wheat grazing management and soil and fertilizer N requirements with emphasis on dual purpose wheat, ii.) assess the use of NDVI sensors for N management and forage quantity assessment in wheat grazing systems, and iii.) evaluate forage quality and quantity interactions with N management. Three locations were established and fertilized with N application rates of 0, 34, 67, and 101 kg ha⁻¹ in the fall, followed by simulated grazing. Spring topdress applications were made at rates of 0 and 90 kg ha⁻¹, or a sensor based rate. The impact of grazing on grain production varied by location. NDVI readings correlated with biomass at two of three locations and N recommendations using NDVI sensors resulted in significantly lower N rates and similar yield results to high N application rates. Forage dry matter and N concentration increased with higher N rates.

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Reverse osmosis (RO) desalination plants enable the production of high-quality freshwater from seawater, explaining the increasing global use of this technology. However, a major operational challenge for RO is biofouling, caused by excessive biomass accumulation. Membrane fouling simulators (MFSs), downsized membrane systems, were demonstrated to be suitable for biofouling studies using tap water. There is a need to investigate biofouling using natural seawater. The seawater MFS studies involved (i) an exploratory study to evaluate the MFS setup, (ii) long-term operation without feed water nutrient dosage, (iii) impact of nutrient concentration, and (iv) a comparison of biofouling development with freshwater. MFSs were operated parallel at constant feed flow (0.2 m/s), with feed spacer and RO membrane, at varying biodegradable organic nutrient concentrations (0, 50, and 200 µg C/L). The relative pressure drop (RPD) was monitored over time, and biofilm development was characterized through the MFS window applying optical coherence tomography (OCT). Results demonstrated for seawater that (i) the developed setup had a reliable operation and provided reproducible data, (ii) biofouling development presented a minimal effect when nutrient concentration was quadrupled, (iii) there was no correlation between the nutrient concentration and growth rate for seawater experiments, suggesting biofilm development under conditions close to the maximum growth rate. Compared to tap water at the same nutrient concentrations, seawater showed much faster biofilm development, pressure drop increase, and strongly different biofilm morphology. This research provides new insights, new research directions and underlines the importance of doing MFS research with natural seawater.

The previously developed watershed hydrological and water quality model for St. Louis Bay watershed by Kieffer (2002) was refined and calibrated. The aspects of model development refinement included development of fertilization-related nutrient input parameters, evaluation of nutrient input methods, development of plant uptake-related nutrient input parameters, non-cropland simulation using PQUAL module, and recalibration of hydrology in Jourdan River. The related information of typical cropland management practice based on consultation from Mississippi State University Extention Service personnel was integrated into the watershed model. In addition, the Mississippi Department of Environmental Quality (MDEQ) observed water quality data were analyzed to evaluate the appropriateness of current watershed delineation and assess the health of the stream based on the MDEQ proposed numerical water quality target. The refined watershed model was calibrated in Wolf Rover and Jourdan River using both USGS and MDEQ observed water quality data. The concentrations of water quality constituents calculated from the developed watershed model will be provided as boundary conditions for the developed Bay hydrodynamic and water quality model for Total Maximum Daily Load studies.

Nutrient removal is one of the primary goals of wastewater treatment and large amounts of ammonia are present throughout the wastewater treatment process. Conventional ammonia removal technologies are energy intensive and do not result in recoverable forms of the nutrient. Anaerobic dewatering side-streams are the liquid recovered during the biosolids dewatering processes following anaerobic digestion. The dewatering side-streams contain high concentrations of ammonia (~1000 mg/L NH4-N) making them an excellent candidate for resource recovery technologies. In this study electrodialysis (ED) was investigated for ammonia (NH4-N) recovery from anaerobic dewatering side-streams with an emphasis on fouling and scaling control on ion exchange membranes (IEMs). The experimental set-up consisted of 3 bench-scale electrodialyzers operating in parallel. The dewatering side-stream (centrate) was collected directly from centrifuges at a local WWTP and pretreated using a 0.3-mm screen. Electrodialyzer operation over 2.25 hrs achieved 95% NH4-N removal and the ammonia separation rate was slowed down by the concentration gradient between concentrate and diluate streams. A combined 269 hrs of operation during fouling experiments showed that electrodialysis (ED) performance decreased over time due to IEM fouling and thus clean-in-place (CIP) procedures was conducted every 60-120 hrs to restore the ED effectiveness. The two stage CIP procedures consisted of a NaCl Clean (5% NaCl, 2 hrs recirculation) and an Acid Clean (5% v/v HCl, 2 hrs recirculation). The NaCl Clean targeted organic fouling and the Acid Clean removed scales that precipitated on the IEMs. CIP procedures were able to recover 84-90% of the initial separation efficiency, the permanent loss in separation efficiency indicating that a portion of IEM fouling (10-16%) is irreversible. The higher applied voltage condition (7.5 V) showed faster fouling rates compared to low voltage conditions (4.5 V), while the degree of irreversible fouling was independent of the applied voltage. Organic fouling and inorganic scaling were individually quantified during CIP procedures using electrochemical impedance spectroscopy (EIS). While both fouling and scaling contributed significantly to the overall increase in the IEM stack resistance (63% scale formation, 37% organic fouling), inorganic scaling was found to play a more important role in reducing the separation rate in ED. ICP and SEM-EDS analysis identified the scale that formed on the surface of the IEMs as mostly of CaCO3 precipitation with smaller amounts of struvite. This finding indicates that the pretreatment of dewatering side-streams should be more focused on removing divalent cations (Ca2+ and Mg2+), but also still consider organic foulant removal for its treatment in ED. Since organic fouling primarily affects anion exchange membranes (AEMs), the impacts of fouling were investigated on two types of AEMs (AR908, AR204). Fouling experimentation showed minor differences in current density and separation efficiency over 269 hrs of operation, with AR204 AEMs showing signs of worse irreversible fouling. Particle size analysis of centrate suggested that large suspended particles could obstruct electrodialyzer chambers. Screening pretreatment (0.3 mm) effectively removed large particles and mitigated clogging issues without having to increase intermembrane distances. The experimental results suggest that ED is a promising technology for recovering ammonia from nutrient rich wastewaters. ED was able to efficiently achieve high levels of ammonia separation from centrate, while fouling was shown to be manageable using CIPs at reasonable intervals. Overall ED was shown to be an effective way to recover ammonia from dewatering side-streams, but pretreatments targeting scaling and organic fouling could better mitigate performance losses due to fouling and further improve the process. / Thesis / Master of Applied Science (MASc)

The objective of the first study was to characterize amino peptidase N (APN), peptide (PepT1), amino acid (ASCT1, bo,+AT, CAT1, EAAT3, LAT1, y+LAT2), and sugar transporter expression (GLUT2, GLUT5, SGLT1) in the small intestine of male and female turkeys. Small intestine samples were collected during embryonic development (E21, E24) and DOH. In a separate experiment during post-hatch development (DOH, D7, D14, D21, D28). APN, bo,+AT, PepT1, y+LAT2, GLUT5 and SGLT1 were expressed most on DOH. Post-hatch, all genes except GLUT2 and SGLT1 were expressed greater in females than males. SGLT1 was expressed greater in males. Basolateral transporters were expressed more during early development; while there was more expression of brush border transporters EAAT3, GLUT5 and SGLT1 later in development. In chickens, there are alternatively spliced exons of the PepT2 gene that encode proteins with four different N-termini (Variants 5-8). The objective of this study was to characterize the patterns of expression of these PepT2 variants. Brain, kidney, liver and intestine were analyzed at E18 and D7 (n=5). Expression of Variant 5 was most prominent in the brain and variant 6 was most prominent in the kidney. Variant 8 appeared in all tissues on E18 and D7. Variant 7 was only expressed in late embryonic development in the ileum. Results from these studies demonstrate that there are differences in gene expression of nutrient transporters in two agriculturally important avian species from the same order Galliformes. These differences can be used to improve feed efficiency and enhance the growth of both species. / Master of Science

We sampled forest stands in upland forests of the Southeastern US along a chronosequence of a replicated successional forest sere (1, 6, 10, 25, and 80 years) to elucidate the temporal changes in soil spatial heterogeneity. Samples were collected from loblolly pine plantations representing reorganization through aggradation phases of succession, and from one set of oak-hickory stands to signify the steady-state phase of the model. These trends are characterized and compared to a conceptual model of pattern dynamics. Variability in soil properties (NO3, NH4, pH, Total N, Total C) and forest floor litter at scales relevant to individual plants was quantified using univariate and geostatistical procedures. Global variation (using both coefficient of variation and standard deviation), patch size and proportion of spatially structured variation were examined for individual variables at each successional stage. These patterns were also averaged to produce a generalized model of spatial heterogeneity change during succession. Individual variables often showed differing patterns. However, when patterns from individual variables were averaged, overall patterns emerged. Early in succession global variability was largest and patch sizes were smallest. As succession progressed, trends in the data showed that global variability decreased and patch sizes increased to the middle stage of succession. Both of these trends fit our conceptual model of pattern dynamics. However, the slopes in these trends were not significant at alpha=0.05. / Master of Science

In this study, biogeochemical regimes of Marguerite Bay and the adjacent part of the West Antarctic Peninsula (WAP) continental shelf were delineated through integration of nutrient, hydrographic, and biological measurements obtained during the LTER and SO GLOBEC studies during austral summer, autumn, and winter of 2001 and 2002. Marguerite Bay biogeochemical regime was found to differ from those of the adjacent WAP continental shelf. In terms of Treguer and Jacques (1992), Marguerite Bay is a combination of Coastal Continental Shelf Zone (CCSZ) and Seasonal Ice Zone (SIZ) distinguished by shallow mixing regime, high primary production and export production. At the end of the growing season (autumn) in both years, waters in Marguerite Bay were strongly depleted in nutrients (the deficits of total inorganic nitrogen (NO3-+NO2-+NH4+) and silica were >0.6 mol m-2 and >2.5 mol m-2, respectively). Observed ΔN/ΔP removal ratios of 10-12.5, lower than that of Redfield et al. (1963), and ΔSi/ΔN removal ratios as high as 4-5 indicated the dominance of diatoms. High autumnal ammonium stocks (>0.25 mol m-2) were observed in Marguerite Bay and were co-located with the areas of the highest nutrient deficits suggesting spatial coupling between primary and heterotrophic production during both years. Consistency of this feature was not disrupted by significant interannual variability of biological production in Marguerite Bay that resulted in ~30-50% reduction in nutrient deficits and ammonium stocks from the first year to the next.The other two biogeochemical regimes were at the central part of the continental shelf characterized by mixed phytoplankton community and at the outer shelf dominated by diatoms. Both regimes were characterized by considerably lower depletion of nutrients compare to those of the Marguerite Bay regime and were consistent between the two years. Interannual variability of biological production and possible sources of high ammonium stocks in Marguerite Bay were studied with a one-dimensional model, a modification of that of Walsh et al. (2001). The model attributed the decline in nutrient deficits to the difference in sea ice cover dynamics between two years. The greater sea ice presence led to the somewhat lower primary production during the second year compare to the fist one. Moreover, model's tight coupling between primary and bacterial production resulted in a decline of bacterial ammonification between the two years. Bacteria were found to be the primary source of ammonium in the Marguerite Bay model. Yet, 3-4-fold fluctuations in macro- and mesozooplankton biomass might have led to 15-25% variability in model's autumnal ammonium stocks.

The nutrient status of the soils in Shenchong Basin and the effects of soil erosion were examined during the summer of 1987. Eight raingauges and two thermographs provided meteorological data. Soil samples were collected from different land use categories in the uplands and lowlands, including agricultural areas. Water and sediment samples were collected from 1) surface discharge from the upland slope, rills and a gully during storms and 2) surface and ground waters during dry weather. Analysis was carried out on water samples to determine ammonia-nitrogen, nitrate-nitrogen, orthophosphate, soluble iron, calcium and potassium concentrations. The soil and sediment samples were analyzed for nitrate-nitrogen, available phosphorus, exchangeable potassium, calcium, magnesium and iron. Concentrations of nitrate and orthophosphate in the water samples were very low. Potassium showed the highest concentrations. Ammonia was the dominant inorganic nitrogen species in water and possibly the soils. The soils were highly acidic (pH < 5) and the soluble iron concentrations were high in the upland soils. Total aluminum concentrations were also high. Potassium concentrations were high in soils from vegetated areas. The higher levels of calcium and magnesium in the agricultural soils were were related to lime additions. Available phosphorus concentrations were very low. Nitrate showed no spatial trend except for the high concentration in the cassava field which was attributed to the peanut plants that were previously planted there. In general, nutrient concentrations were low compared to other tropical areas in the world. / Thesis / Master of Science (MSc)

The transporters primarily responsible for transporting important nutrients involved in energy metabolism have a wide substrate specificity setting up the potential for drug-nutrient transporter interactions. Pharmacological inhibition of nutrient transport across the lactating mammary and neonatal intestinal epithelial barrier can directly and indirectly affect growth and maturation of the developing neonate by either reducing the uptake of important nutrients by the neonate or by disrupting epithelial barrier integrity. My thesis focused on two transporters, OCTN2 and MCT1, expressed in immortalized intestinal and mammary epithelial cell cultures to assess the effects of their pharmacological inhibition on L-carnitine and butyrate flux, respectively, and polarized epithelial barrier integrity. Human colorectal adenocarcinoma (Caco-2) and bovine mammary (BME-UV) cell lines were grown into monolayers on 12-well tissue culture plates and subsequently exposed to the presence or absence of OCTN2 and MCT1 inhibitors for 6, 12, and 24 hours as well as 7 days. Failure to obtain a polarized mammary monolayer prevented the analysis of the direct effects of nutrient transport inhibition on nutrient flux forcing the focus on the indirect effects. To assess polarized epithelial barrier integrity, transepithelial electrical resistance and Lucifer yellow rejection rates were measured at each time point. No trend was noted between control and treated groups. To assess the acute and chronic effects of pharmacological exposure on polarized epithelial function, a limited appraisal of nutrient transporter expression and cellular homeostasis parameters was conducted. Following exposure at each time point, mRNA expression of OCTN1, OCTN2, MCT1, MCT2 and GADPH were measured using qPCR. Low mRNA yields resulted in an inability to assess transporter expression levels in the epithelial systems. Cellular homeostasis parameters were analyzed using the CellTiter-Glo Luminescent Cell Viability Assay, pH-Xtra Glycolysis Assay and MitoXpress Xtra Oxygen Consumption Assay. These assays measured ATP synthesis, glycolytic flux and cellular respiration, respectively. No significant trend was noted in ATP synthesis between control and treated groups. An upward trend in both glycolytic flux and cellular respiration was noted in treatment with both inhibitors in both cell lines. Complications in obtaining polarized monolayer forced the focus on the indirect affects, therefore, obtaining and utilizing a more accurate portrayal of the lactating mammary and neonatal intestinal epithelium is critical in answering this research question as both of these systems are highly synthetic and complex. By doing so, a more accurate representation of the effects of pharmacological inhibition of nutrient transporters essential for energy metabolism can be identified.