Nitrate contamination of surface and groundwater has become a serious concern in many agricultural areas throughout the world. The major source of nitrate contamination is believed to be nitrogen fertilizer from agricultural fields. Best Management Practices have been developed to guide fertilizer use and minimize nitrogen losses, but do not address control of nitrate movement from the crop root zone. It is proposed that an in-situ method, electrokinetics (EK), could be used to control nitrate movement, retaining it near the root zone. Lysimeter experiments were conducted to evaluate the effect of parallel electrodes on pH and nitrate distribution in field soils subjected to an electrical input. However, the expected results, increased nitrate retention, reduced sodium and calcium concentration and lower pH values near the anode, were not attained consistently in the test soils with and without Sudan grass. Small scale experiments in a vertical, partially saturated sandy soil column (25 cm height by 14 cm diameter) were conducted to evaluate the optimal EK parameters. After 80 mA current for 6 h the nitrate was retained near the anode, with the highest measured nitrate concentration of 7155 mg/L within 5 mm of the anode. The nitrate concentration at the cathode was 1/5 of the inflow solute concentration (221 mg/L). The pH was 11 near the cathode, 3.5 near the anode, and showed little changes in intermediate layers. The results demonstrate that in sandy soils nitrate can be strongly retained near the anode, even against gravity effect. As the percentage of illite clay in the soil increased, the EK effect decreased; due to the increase of fine clay particles both the transports of ions and the water were inhibited. The loam soil showed some increase in the nitrate concentration near the anode, but the clay soil showed no change. An increase of pH near the cathode was seen in all soils. The electrical potential analysis showed the sandy soil required the highest electrical potential 97.23 V, loam soil was 18.24 V and clay soil was 14.22 V.

The Alto Rio Lerma Irrigation District (ARLID), located in the state of Guanajuato in Mexico, is an agricultural area whose sustainability depends partially upon groundwater withdrawal for crop irrigation. Because of high pumping demands and current land-management practices, water levels in the regional groundwater aquifers have declined severely, resulting in aquifer overdraft. The potential adverse consequences of this overdraft cannot be overstated, as the long-term economic viability and environmental integrity of the region is threatened. In order to analyze this economic, environmental, and water use problems in this region, simulation of the agricultural system was performed and associated water use impacts quantified under different management scenarios. Linear programming identified the 12 optimal cropping patterns, and then multi-criteria decision-making methodologies were applied to rank and identify the best cropping pattern (satisficing solution). The GLEAMS model was used to simulate the amounts of water, nitrate, and pesticides in both runoff and percolation for each cropping pattern. In order to quantify the economic and environmental impacts of aquifer overdraft, two attributes were used; pumping costs and an aquifer exploitation coefficient. Three multiple criteria methods: Q-analysis, ELECTRE II, and the Range of Value Method, were evaluated and the latter method was selected to analyze the payoff matrix for the ARLID, where 12 alternatives, each with 13 attributes, were considered. The results show the best alternative for effectively balancing environmental with economic considerations was the farming practice, consisting of land leveling, growing vegetables such as red tomato, and controlled groundwater withdrawals to preserve aquifer sustainability. Low water availability does not necessarily reduce farmer's profits, if new water saving alternatives are applied, combined with more profitable crops. Given that ROV method only considers full compensation between objectives, this research contemplate an extension for the nonlinear case in order to assess the whole range of values of the objective function. The final findings suggest that the best methodology was to apply L1 in the lower levels and then L2 for the highest level in the hierarchy. In this manner, the partial compensation between objectives is considered and also the decrease in the uncertainty of alternatives selection.

Diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) in both near infrared (NIR) and mid infrared (MIR) has been previously shown to be effective in quantifying soil nitrogen (N) concentrations when calibrated using numerous field soil samples. However, such an approach provides samples that likely contain substantial correlations between physical and chemical properties. To address these concerns, the performance of DRIFTS coupled with PLS regression in NIR regions, 5,000-4,000 cm⁻¹ (2,000-2,500 nm) and 6,500-5,500 cm⁻¹ (1,540-1,820 nm), and the M1R region, 3,400-2,400 cm⁻¹ (2,940-4,170 nm), was assessed first through analysis of the concentration of mineral N (ammonium (NH₄⁺) (0-50 ppm) and nitrate (NO₃⁻) (0-200 ppm)) artificially incorporated into a series of silica sand and clay samples with a consistent particle size. The influence of the reduction of sand particles to silt was also analyzed quantitatively. Subsequently, the Pima clay loam soil was evaluated and the concentration ranges of 0-200 ppm NH₄⁺ and 180-1,000 ppm NO₃⁻ were added in soil samples. All three regions provided good measurement of NH₄⁺ but the MIR region was significantly more useful for NO₃⁻ measurement in sand. The detection limits for the measurement of mineral N in sand with particle sizes within 212-300 μm using the MIR region were 9 ppm NH₄⁺ (7 ppm NH₄-N) and 36 ppm NO₃⁻ (8 ppm NO₃-N). For silt (particles less than 53 mum), the most effective model was the MIR region for both NH₄⁺ and NO₃⁻ measurements, yielding the detection limits of 15 ppm NH₄⁺ (12 ppm NH₄-N) and 50 ppm NO₃⁻ (11 ppm NO₃-N). The MIR region also performed reasonably well with soil samples but both NIR regions provided poor results. The detection limits for NH₄⁺ and NO₃⁻ measurements in soil were 100 ppm NH₄⁺ (78 ppm NH₄-N) and 330 ppm NO₃⁻ (75 ppm NO₃-N) with the correlation coefficients (R²) of roughly 80% and 90%, respectively. The spectral range of 2,900-2,400 cm⁻¹ was the effective common range for mineral N measurement in sand, silt, and soil samples.

A free water surface finite element model was developed. The method was implemented with the Galerkin approach to solve the Laplace equation in the saturated region. It was developed in the object oriented Visual C ++ computer language to permit easy update and drawing of the adaptive mesh. For each time step, the new water table position was calculated based on flux across the water table, a Brooks-Corey equation mass balance for the unsaturated region, and an equation that calculates water table position for the saturated region. An equation was developed to calculate a drainage transfer coefficient, alpha, based on percentage of perforated area in the drain tube wall. The drainage transfer coefficient was incorporated into the finite element model as a Fourier boundary condition. To validate the finite element model, its results were compared with the Kirkham equation results for steady state recharge of three subsurface drainage systems. The finite element model was used to calibrate a semi-analytical frozen stream tube model for subsurface drainage of heterogeneous soils. The first step in the calibration procedure is to run the finite element model for steady state recharge and calculate the water table height divided by recharge rate (the stream tube resistance to flow) as a function of distance between drains. Least squares regression is used to fit a polynomial logarithmic equation, called the resistance function, to the stream tube resistance to flow vs. distance from the drain curve. A differential equation based on the principle of conservation of mass and application of Darcy's law to the frozen stream tube was solved to obtain an equation that calculates stream tube flow rate and final water table elevation as a function of the resistance function and initial water table elevation. An example was developed for a non-homogeneous subsurface drainage system to illustrate the use of the semi-analytical model to predict water table fall and discharge.

The measurement of sap flow has been sought after for many years. Various methods have been devised to accomplish this task, one of which is the heat balance method. This method is non-invasive and accurate, but its simplifying assumptions were questionable and needed to be critically examined. This study evaluated the heat balance method and sap flow gauges. The method yielded satisfactory results when compared to the calibration system. The satisfactory results were over a limited range, which exemplified the necessity for the gauges to be calibrated. The heat balance method's simplified heat transfer analysis does not reflect the complexity of the physical situation. Sap flow gauge improvements were suggested.

Retractable Roof Greenhouses are a new trend in the greenhouse industry. They allow the improvement of many nursery and crop production practices in semi-arid regions. Hydroponically grown peppers and tomatoes were tested to evaluate possible year-round cultivation in this kind of structure that permits high radiation exposure. Control systems based on radiant surfaces temperatures were developed to integrate, cost effectively, the environmental factors that influence the plants' development and yield, including: air temperature, solar radiation and wind speed. Yields of 7.4 kg m⁻² and 33.0 kg m⁻² were obtained respectively for top quality pepper and tomatoes. These yields were similar or slightly lower than conventional greenhouses in the similar price range and design complexity. This makes the retractable roof greenhouse a mediocre structure for pepper and tomato production in southern Arizona. Radiant surface temperature was found to be a useful parameter for the control of the retractable roof greenhouse climate.

<p> The original ARID (Algae Raceway Integrated Design) raceway was an effective method to increase temperature toward the optimal growth range. However, the energy input was high and flow mixing was poor. Thus, the ARID-HV (High Velocity Algae Raceway Integrated Design) raceway was developed to reduce energy input requirements and improve flow mixing. This was accomplished by improving pumping efficiency and using a serpentine flow pattern in which the water flows through channels instead of over barriers. A prototype ARID-HV system was installed in Tucson, Arizona, and the constructability, reliability of components, drainage of channels, and flow and energy requirements of the ARID-HV raceway were evaluated. Each of the electrical energy inputs to the raceway (air sparger, air tube blower, canal lift pump, and channel recirculation pump) was quantified, some by direct measurement and others by simulation. An algae growth model was used to determine the algae production rate vs. flow depth and time of year. Then the electrical energy requirement of the most effective flow depth was calculated. Channel hydraulics was evaluated with Manning's equation and the corner head loss equation. In this way, the maximum length of channels for several raceway slopes and mixing velocities were determined. Algae production in the ARID-HV raceway was simulated with a temperature and light growth model. An energy efficient design for the ARID-HV raceway was developed. </p>

<p> Pineview Reservoir, near Utah's populous Wasatch Front, could play an important role in modulating water supply as water demands and water uses change in response to increasing population densities. The reservoir is currently mesotrophic but threatens to become eutrophic. Ground water in the shallow water table aquifer that surrounds the reservoir contributes a large proportion of the reservoir's inflows in summer and fall because most of the stream flow is diverted for irrigation. Ground water flow and its subsequent nutrient loading to the reservoir were studied from February 2010 through November 2011. The objectives were to: 1) characterize nutrient transport from the water table aquifer to the reservoir; 2) quantify and characterize the spatial variability of ground water flow and nutrient loading in a mountainous irrigated valley; and 3) estimate nitrate leaching to ground water from cropland, lawns and septic drain fields. </p><p> The first objective was achieved by monitoring stream flows, and modeling ground water flow and nutrient loading towards Pineview Reservoir. Ground water from the water table aquifer contributed 22 percent and 2.6 percent nitrate + nitrite nitrogen and total dissolved phosphorus, respectively, to the annual reservoir loads. The aquifer contributed a total inflow of 3.4 x 10⁶ m³ yr^-1 (2 percent of the total inflows) to the reservoir. Large variations in both ground water nutrient concentrations (6 &ndash; 310 &micro;g P L^-1 as total dissolved phosphorus and 3.3 &ndash; 21 mg N L^-1 as nitrate + nitrite) and ground water flows among aquifer subdivisions were observed. </p><p> Study of the second objective employed GIS-based interpolation techniques in analyzing the spatial distribution of ground water flow and nutrient loading towards the reservoir. Large spatial variations in ground water flows and nutrient loadings were observed. The 67 percent confidence intervals (geometric mean &plusmn; 1 standard deviation) for total dissolved phosphorus ranged from 0.014 - 0.400 kg P d^-1. Nitrate + nitrite nitrogen had a 67 percent confidence interval of 0.954 - 39.1 kg N d^-1. The variations were attributed to agricultural and domestic non-point sources. </p><p> Under the third objective, ground water nitrate loadings in the near-reservoir drainage area of the reservoir's major tributary, the South Fork of the Ogden River, were simulated in the GIS-based Nitrogen Loss and Environmental Assessment Package. Annual leaching rates (kg N ha^-1 yr^-1) from drain-fields and the lawns were, respectively, more than 2.6- and 1.1-fold higher than the croplands. However, differences in the spatial extent of contributing sources resulted in 70- and 50-fold higher total leaching losses from croplands and lawns, respectively, than drain-fields. </p><p> The findings would help water managers, town planners, and stakeholders in their decisions relative to land use, water distribution and use to protect and/or improve water quality in the reservoir.</p>

Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 2008. / Source: Dissertation Abstracts International, Volume: 69-11, Section: B, page: 6956. Adviser: Vijay Singh. Includes bibliographical references (leaves 110-118) Available on microfilm from Pro Quest Information and Learning.

The aim of this study was to investigate two potential beneficial management practices that will reduce the impact of fecal and fertilizers contamination on the environment. The study was conducted in Eastern Ontario on typical small scale agricultural practices. The first part evaluates the impact of a conventional pasture system and an excluding pasture system on surface water quality. The three year study compared water quality endpoints such as: indicator bacteria, pathogens, parasites and nutrients between treatments. Microbial source tracking indicated that livestock was the main source of fecal contamination in the stream. Greater bacteria and nutrient loads were observed in the unrestricted pasture system than the excluding pasture. Moreover, parasite and indicator bacteria concentrations increased after cattle introduction in both systems. The second part compares nitrogen mass balance between managed and conventional subsurface tile drainage. Over two years, nitrogen loads in groundwater, in tile flow, in plants, in soil and denitrification were compared between treatments. Nitrogen was mostly removed from managed tile drainage fields through plant uptake. Compared to nitrogen plant uptake, denitrification, the second greatest nitrogen removing process was 10 times smaller. The denitrification was greater in the unmanaged tile drainage fields. Generally, managed subsurface tile drainage reduces nitrogen mass loads to surface waters and increases nitrogen uptake by plant, which resulted in greater yields.