This dissertation deals with modeling the radiative regime in vegetation canopies and the possible remote sensing applications derived by solving the forward and inverse canopy transport equation. The aim of the research is to develop a methodology (called "end-to-end problem solution") that, starting from first principles describing the interaction between light and vegetation, constructs, as the final product, a tool that analyzes remote sensing data for precision agriculture (ripeness prediction). The procedure begins by defining the equations that describe the transport of photons inside the leaf and within the canopy. The resulting integro-differential equations are numerically integrated by adapting the conventional discrete-ordinate methods to compute the reflectance at the top of the canopy. The canopy transport equation is also analyzed to explore its spectral properties. The goal here is to apply Case's method to determine eigenvalues and eigenfunctions and to prove completeness. A model inversion is attempted by using neural network algorithms. Using input-outputs generated by running the forward model, a neural network is trained to learn the inverse map. The model-based neural network represents the end product of the overall procedure. During Oct 2002, an Unmanned Aerial Vehicles (UAVs) equipped with a camera system, flew over Kauai to take images of coffee field plantations. Our goal is to predict the amount of ripe coffee cherries for optimal harvesting. The Leaf-Canopy model was modified to include cherries as absorbing and scattering elements and two classes of neural networks were trained on the model to learn the relationship between reflectance and percentage of ripe, over-ripe and under-ripe cherries. The neural networks are interfaced with images coming from Kauai to predict ripeness percentage. Both ground and airborne images are considered. The latter were taken from the on-board Helios UAV camera system flying over the Kauai coffee field. The results are compared against hand counts and parchment data to evaluate the network performances on real applications. In ground images, the error is always less than 11%. In airborne image, the error bound is 20%. The results are certainly adequate and show the tremendous potential of the methodology.

For chemigation of nonsoluble pesticides, small oil-pesticides droplets (dmax tend to wash-off from foliage while large droplets tend to stick. Large droplets (dmax are buoyant, tend to rise in the irrigation pipeline and exit at the beginning of the pipeline; thus, uniformity and efficacy are poor. For this research, a new chemigation system was proposed. The system removes water from the irrigation pipeline, injects the oil-pesticide into the water stream, increases dispersion velocity in successively smaller tubing diameters, and finally injects the dispersion back into the irrigation pipeline. The higher velocity flow with high turbulent shear forces breaks the oil-pesticide into desired size droplets. Droplet break-up research was reviewed, and a model developed to predict maximum droplet size and size distribution. A maximum relative error of 40% was observed when dmax predicted by the model was compared against literature data. Equations to predict friction factor in helically coiled pipes and effective viscosity of oil-in-water dispersions were evaluated. The friction factor predicted by the Ito equation was in good agreement with the experimental data. Effective viscosity of soybean oil- and kerosene-in-water dispersions was predicted satisfactorily by the Richardson equation with k₄ = 2.5. Finally, center pivot field experiments were conducted using the new and conventional chemigation systems. For the conventional system, the soybean oil uniformity coefficient along the lateral was 61%, and oil applied over the last tenth of irrigated area was 9% of the initial concentration. For the new system, the uniformity coefficient was 73% and 98% for dmax of 875 mum and 98 mum, respectively; oil applied over the last tenth of the area was 27% and 90% of the initial concentration. Field data were compared with those predicted from a pipeline transport model for nonsoluble pesticides. Agreement between the model and the field data was excellent for both experiments using the new chemigation system. Based on the field results and simulation analyses, droplets < 150 μm should be desirable to keep the discharge uniformity coefficient over 97%, for 0.92 ≤ ρ(d)/ρ(c) ≤ 1.04.

The broad objective of this research was to develop a spatial model which provides both timely and quantitative regional maize yield estimates for real-time Early Warning Systems (EWS) by integrating satellite data with ground-based ancillary data. The Food and Agriculture Organization (FAO) Crop Specific Water Balance (CSWB) model was modified by using the real-time spatial data that include: dekad (ten-day) estimated rainfall (RFE) and Normalized Difference Vegetation Index (NDVI) composites derived from the METEOSAT and NOAA-AVHRR satellites, respectively; ground-based dekad potential evapo-transpiration (PET) data and seasonal estimated area-planted data provided by the Government of Kenya (GoK). A Geographical Information System (GIS) software was utilized to: drive the crop yield model; manage the spatial and temporal variability of the satellite images; interpolate between ground-based potential evapo-transpiration and rainfall measurements; and import ancillary data such as soil maps, administrative boundaries, etc. In addition, agro-ecological zones, length of growing season, and crop production functions, as defined by the FAO, were utilized to estimate quantitative maize yields. The GIS-based CSWB model was developed for three different resolutions: agro-ecological zone (AEZ) polygons; 7.6-kilometer pixels; and 1.1-kilometer pixels. The model was validated by comparing model production estimates from archived satellite and agro-meteorological data to historical district maize production reports from two Kenya government agencies, the Ministry of Agriculture (MoA) and the Department of Resource Surveys and Remote Sensing (DRSRS). For the AEZ analysis, comparison of model district maize production results and district maize production estimates from the MoA (1989-1997) and the DRSRS (1989-1993) revealed correlation coefficients of 0.94 and 0.93, respectively. The comparison for the 7.6-kilometer analysis showed correlation coefficients of 0.95 and 0.94, respectively. Comparison of results from the 1.1-kilometer model with district maize production data from the MoA (1993-1997) gave a correlation coefficient of 0.94. These results indicate the 7.6-kilometer pixel-by-pixel analysis is the most favorable method. Recommendations to improve the model are finer resolution images for area planted, soil moisture storage, and RFE maps; and measuring the actual length of growing season from a satellite-derived Growing Degree Day product.

In the mid-1980s, a new biotype of Bemisia tabaci was introduced into the southern U.S. causing extensive damage to agricultural crops throughout the region. An augmentative biological control project was initiated using a native parasitoid, Eretmocerus eremicus to determine its efficacy against B. tabaci infesting cotton in the desert areas of California and Arizona. A series of experiments were conducted in 1992-1995: release rate studies in cages and open fields; parasitoid dispersal within fields to determine movement rates after point release; and experiments to determine the parasitoid-host spatial relationship. Cage release rate studies, demonstrated that rates of parasitism could be increased 61 to 79% in the highest release treatments, with reductions in whitefly densities of 80 to 100% relative to control treatments. Cotton yields in the high release treatments peaked at 2.5 bales/ac and were 2.6 to 4.2 times greater than in control treatments. Effective release rates were estimated to be equivalent to 770,000 to 1.1 million parasitoids/ha. Field releases equivalent to 7.9 million parasitoids/ha resulted in a peak rate of parasitism of 42% but there were no statistical differences in parasitism, whitefly densities, or cotton yield; relative to no-release plots. High levels of whitefly immigration from surrounding crops, and parasitoid dispersal from release plots, diluted the effects of release. In a second field release rate study, releases equivalent to 2.0 to 3.0 million parasitoids/ha increased levels of the percentage of discovered leaves to greater than 80%. Parasitoid dispersal was analyzed with mark-recapture experiments and data were fit to a diffusion model. One female wasp flew 82 m in one day though the majority of wasps flew a few meters or less. Estimated diffusion rates and median dispersal distances were 0.40 to 0.71 m²/min and 2.4 to 4.4 m/(4 to 8) days respectively. Analysis of dispersal data suggested that releases on 20 m centers would provide effective coverage within a field. Density independent parasitism was common at the spatial scale of leaves and plants. There was positive density dependence for the percentage of discovered leaves suggesting that parasitoids aggregate to high density patches of whitefly but fail to achieve high levels of parasitization possibly due to egg limitation or mutual interference.

Irrigation scheduling using the soil water balance approach has been recommended to irrigators for many years. Reasonably good results are normally obtained by researchers using carefully quantified inputs. Irrigators in production agriculture may estimate inputs and then question the validity of the method when the irrigation recommendations conflict with present irrigation schedules. By associating each input with an interval representing possible bias based on the way the input was estimated, and solving the irrigation scheduling model using the intervals as inputs, the output was associated with an interval representing possible bias. This method was also used to evaluate possible bias associated with growing degree day based crop coefficient curves developed from Arizona crop consumptive use measurements. For comparison purposes, roughly estimated inputs based on irrigation system type, soil type, area weather data and available crop coefficient curves were used as default intervals. Improved input intervals consisted of observed irrigation system performance, soil property measurements, local weather data and theoretical improvements in crop coefficient curves. For surface irrigation, field observation of plant stress and soil water content showed the greatest potential to improve irrigation date predictions. For buried drip under a row crop, accuracy of the predicted daily irrigation rate was most improved by a better estimate of irrigation efficacy.

Aquaculture has great potential to help supply the nutritional needs of a growing population. To date, however, the benefits that aquaculture can have, have largely been overshadowed by the environmental degradation some segments of the industry have caused. The following body of work describes my efforts to help reduce the environmental impacts of aquaculture. By integrating aquaculture production into traditional agriculture, the impact of farming on already limited water resources and the reliance on chemical fertilizers can be reduced. Recent expansion of the aquaculture industry in Arizona has made it possible to study the integration of olive groves with marine shrimp culture. In chapter 3, I describe the characterization and evaluation of the effluent from an inland, low-salinity shrimp farm as a potential source of irrigation water. I found that 0.41 kg of ammonia-nitrogen, 0.698 kg of nitrite-nitrogen, 8.7 kg of nitrate-nitrogen and 0.93 kg of total phosphorus (TP) were made available as fertilizer each day in the effluent water. Based on the results of this first study, I decided to conduct a farm trial to quantify the effects of these shrimp farm effluents on olive trees. This work is described in chapter 4. Trees in all treatment groups grew an average of 40.1 cm over the four month study period. While growth of trees irrigated with shrimp farm effluent did not improve in respect to the other treatments, our results do indicate that irrigating with low-salinity water had no noticeable negative effects. Chapter 5 describes work conducted in Idaho, as part of a larger study aimed at reducing the effluent loads of phosphorus (P) from high density, flow-through aquaculture facilities. Research steps were taken to establish a relationship between TP and the carbon 12/13 isotope ratio (δ¹³C) and/or the nitrogen 14/15 isotope ratio (δ¹⁵N). Our findings suggest that both δ¹⁵N and δ¹³C are good better proxies for P, after correcting for P retention. A linear regression of %P (corrected) on δ¹³C and δ¹⁵N resulted in R2 values of 0.843 and 0.8622, respectively. This suggests that by tracking δ¹⁵N and/or δ¹³C through a high-density, flow-through aquaculture facility over time I will be able to determine the residence time of P with a high degree of accuracy.

Nitrate movement under simultaneous influence of hydraulic, electric and chemical gradients was investigated. A one-dimensional ion migration model was developed and compared with laboratory column experiments. Operation of subsurface drainage with an electrode was discussed as an application. The ion transport equation was developed utilizing non-equilibrium thermodynamics. Onsager's reciprocal relations were applied to reduce the number of linear phenomenological coefficients that relate flux to driving forces. Then phenomenological coefficients were expressed using known or measurable physical, chemical and electrical properties of solute and porous media. Developed equations were numerically solved by the Integral Finite Difference Method in one dimension. The numerical results were validated with analytical solutions of simple boundary conditions as well as the results obtained from laboratory column experiments for two or three applied gradients. Without water flow, nitrate concentration increased at the anode by 2.5 times after 100 hrs of 30 V application. Three initial concentrations, 10, 100 and 500 ppm NO₃-N, were tested. A log normal relation between elapsed time and relative concentration increase at the anode was obtained. Two flux rates (0.112 and 0.225 cm min⁻¹), and three inflow concentrations (100, 500 and 1000 ppm NO₃-N) were used to evaluate nitrate transport in the column. Nitrate concentration at the anode increased by 10 to 20% at the end of all experiments. However, the concentration in the column was same as inflow concentration. The application of electrokinetic nitrate removal by installed subsurface drainage with on-off (no flow then flush out) operation is recommended over a continuous flow approach. The numerical model results showed very low flux rates (i.e. 2.68 x 10⁻³ cm min⁻¹) are required for nitrate accumulation in a sand column, and the experimental results confirmed no accumulation at a flux rate of 0.112 cm min⁻¹.

Analysis indicates that the Blasius equation yields accurate estimates of head loss in small diameter plastic tubing and larger diameter PVC pipe for Reynolds numbers upto 100,000. The Hazen-Williams equation with suitable roughness parameter values also predicts head loss accurately. The results of laboratory experiments reveal that the undulations which are created during field installation are the primary cause of air locking in the delivery hose. The additional head needed to release the trapped air was found to be equal to the sum of heights of all the undulations. If the sum of their heights exceeds the design head loss in the delivery hose, air locking will result. The capital investment for bubbler system under study was comparable to that of a pressurized drip system. Long term savings in terms of energy and maintenance make low head bubbler systems an attractive alternative to pressurized drip systems for irrigating orchards or vineyards.

Low-head bubbler irrigation systems are particularly well-suited for the irrigation of orchard crops, and these systems differ from other micorirrigation systems because they are based on gravity-flow, can operate at pressures as low as 1 meter (3.3 ft), and do not require elaborate filtration systems. A design procedure for low-head bubbler systems is described in detail, and example designs for bubbler systems located on level ground and gradual slopes are also presented. The design procedure utilizes head loss gradient charts based on the Darcy-Weisbach equation to size the pipe diameters, and the delivery hose elevations are calculated by using a personal computer with spreadsheet software. The causes of air locks in the laterals and delivery hoses are also investigated, and minimum design flow rates for various pipe diameters are recommended to ensure flow velocities are high enough to prevent air locks from occurring within the delivery hoses.

Performative Landscapes examines and strategizes the production of artificial wetlands, port facilities, and recreational/commercial fishing areas by utilizing the excess dredge material generated by the Houston Ship Channel. Performative Landscapes seeks to propose a developmental tool kit and set of logics that will guide the growth of new wetlands and foster the production of integrated, not fragmented, program along Galveston Bay. The primary goal of the project then is to produce a design method, a generative seed, that can be used in the genesis of new and integrated man-made and natural systems along the coast, and in Galveston Bay. What I primarily advance in this thesis is a design analytic and a design method geared towards ecological and relational thinking. These two tools are derived and inspired by the concept of self-organization in material systems and the operational searching method of the genetic algorithm as defined by David E. Goldberg.