This study examines literature on subsurface irrigation of turf using published and unpublished sources to determine its relevance for the designer of irrigation systems. It looks at two installed sites to determine current industry practices and then develops a model to assist the designer of these systems. Finally areas in need of further research and technical development are suggested. Literature is not readily available to the designer and it is sometimes contradictory. Case studies show that subsurface irrigation is an effective method of irrigating turf, especially in arid parts of the world. A model to select tubing and emitter spacing is developed by summarizing existing literature and case studies. Virtually all areas of design, installation and management need further research. Two primary areas that need further investigation are specific design issues and benefits to the end user such as cost, water savings and maintenance procedures.

A ground-based remote sensing system was attached to a linear move irrigation system and successfully collected pixels at an approximate density of 1/meter 2. This low-resolution data was used to create 1-meter resolution images in near real time over a 1-hectare cotton field. A new method using GIS and spatial statistics (kriging) was successfully developed for evaluating the 1-meter images and simulate 2 through 7 meter resolution for determining the effects of scale on data collection for crop management as applied to precision agriculture. The images collected reliably predicted nitrogen and water stress in the field and demonstrated how scale from 1 to 7 meters affects reliability of measuring water and nitrogen stress. A 2X2 Latin square water and nitrogen experiment on cotton consisting of optimal and low nitrogen and water treatments was conducted within 4 replicates of the 4 treatments. The remotely sensed data were used to develop images of the plot to ascertain the ability to detecting nitrogen and water stress. Nitrogen stress was evaluated using the canopy chlorophyll content index while water stress was evaluated using the difference between canopy and air temperature. Four days of field images collected in 1999 at a 1-meter resolution were selected for evaluation. The days represent, one day prior to water and nitrogen treatments, two days of little to moderate nitrogen stress, and one day with severe nitrogen stress and moderate water stress. The image analysis incorporated standard statistics, kriging, and fractals. The 1-meter data was used to produce images with grids of 2 through 10 meters. Standard statistics were used to analyze the four days by grid size. The results indicated no difference in the mean in the data for any grid size within a treatment for either water or nitrogen; however, CV generally decreased with grid size. Kriging was used to evaluate the data for pretreatment day and stressed day for one plot representing each of the four treatments. Data for 1, 3, 5, and 7 meters resolution was kriged and compared to the 1-meter grid to determine reproducibility. It was determined that for temperature it is difficult to reproduce finer resolution data, especially in stressed plots. The nitrogen indice was reproducible to a high degree of accuracy for grids as large as 7 meters. Fractal analysis was used to evaluate the kriged data. The results were mixed in that numbers for some plots increased as grid size increased, and decreased as expected for others.

Wastewater reuse for agricultural purposes has been considered as an alternative strategy for water conservation. This study compared subsurface drip irrigation with furrow irrigation in terms of water use efficiency and crop contamination when microbial-contaminated water was used for irrigation. The effects of temperature and moisture on virus survival in soil were assessed quantitatively. Escherichia coli ATCC 25922, Clostridium perfringens, and coliphage PRD-1 served as the study microorganisms. Subsurface drip irrigation used water more efficiently than furrow irrigation due to lower water requirement for similar crop yields. Subsurface drip irrigation performed better for the deep-rooted crops, cantaloupe and bell pepper, compared to the shallow-rooted crop, lettuce. The more water was held by soil and was available for the crop uptake with the deeper root crops than shallow root crops. Overall, significantly greater microbial contamination of produce and soil surface occurred in furrow irrigated plots as compared to subsurface drip irrigated plots. Direct movement of irrigated water to the soil surface appeared to cause crop contamination in subsurface drip irrigation plots. Coliphage PRD-1 demonstrated greater crop contamination and longer survival in the environment compared to E. coli. The smaller size of PRD-1 than that of E. coli seemed to facilitate its movement through soil matrices and increased the chance to contaminate crop produce. The inactivation rate of PRD-1 increased as temperature increased. A soil moisture decrease from 20.9 to 8.9% appeared to be inversely related to the inactivation rate. Further decrease of the soil moisture content to 5.1% increased the inactivation rate. An optimum or a threshold soil moisture level for PRD-1 survival may exist. Evaporation increased the inactivation rate of PRD-1 substantially in higher temperatures but minimally in lower temperatures. A developed model predicted the inactivation rates of PRD-1 in field conditions with an average error of 11.0%. Subsurface drip irrigation with a proper management can be a sustainable strategy to conserve irrigation water as well as to reduce crop contamination when wastewater is used for crop production. PRD-1 survived better at low temperatures and dry soil moisture conditions.

Four types of cable drawn farming systems, a single engine system, a double engine system, a perimeter system, and a double implement system, were analyzed to determine which was best suited for Arizona. The systems were compared in terms of relative cost, reliability/simplicity and field capacity. Field capacity computation variables were implement width, implement speed, tower travel speed, implement carrier travel speed, and implement rotation time. The analysis showed the single engine system was the least expensive, simplest system with a field capacity identical to that of the double engine system, eight percent lower than the double implement system, and approximately thirteen percent higher than the perimeter system. Based on these results, the single implement system was judged superior to the others. The parameters affecting single implement system performance were then examined to optimize performance. The evaluation yielded a recommendation that the system be designed to have a tower speed of 48 ft/min, and a rotation time of 7.5 seconds. A positioning system for the mobile truss of a cable drawn farming system was also developed and tested. The system used a linear move irrigation system's above ground cable guidance system for steering, a wicket positioning system for stopping the machine at the indexing locations, and a wire-alignment system to control inner tower alignment. The system was tested over a length of 280 ft using a five tower, 575 ft long, linear move irrigation system. It was found that the above ground cable guidance system provided ±0.5 ft steering accuracy, the wicket positioning system controlled the power unit and end tower position within ±0.2 ft of the target destination, and that the wire alignment system controlled inner tower position within ±0.3 ft of the target destination. Statistical analysis of the test results showed the probability of position error being controlled to within ±0.4 ft and ±0.8 ft to be at the 99.7% and 99.99% confidence levels, respectively.

This dissertation reviews the process of maize market liberalization in Kenya, investigates a relationship between market integration and price stability, and presents a theoretical foundation for numerical simulations to evaluate effects of agricultural policies. The computer simulations are used to analyze the market under uncertainty. The model examines welfare effects and response to the policies as well as changes in means and coefficients of variation of maize prices and expected income of farmers. The model solves simultaneously indirect utility maximization of individual farmers and a spatial price equilibrium model to give a rational expectations equilibrium land allocation. It takes account of inseparability of consumption and production, stochastic prices and returns, and effects of size and location of farmers. Maize price is endogenously determined as farmers choose a crop mix between maize and a cash crop. It offers a framework in which various agricultural policies, characteristics of farmers, and conditions of markets can be analyzed.

The soil preparation in soil bins must be capable of generating a number of soil density profiles varying from uniform to heavily compacted layers lying below more friable soil. A subsurface rotating rod firmed the soil beneath the rod and repeated passes produced desired profiles. Retrofitting the existing instrumentation with virtual instrumentation methods resulted in measurements that were more precise and improved repeatability. A Wheatstone bridge force transducer measured Cone Index pressure as a function of soil penetration depth. Soil surface elevation and implement depths were located with ratiometric linear transducers. Speed and distance were measured with an optical encoder. Prime mover hydraulic oil temperatures and pressures were gauged with current loop sensors. Three Null Hypotheses were tested: a horizontal subsurface rotating rod will not cause an increase in soil cone index; repeated operation of the horizontal rotating rod will not result in increased soil cone indexes; and soil water content is not relevant to the resultant compaction level. The first two Null Hypotheses were rejected at the 5% level in the overall case although not in each case while the third Null Hypotheses was rejected at the 5% level in all cases.

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An hedonic model of apple prices was developed using data from the three largest producing regions of the United States. Results were used to determine the relative values of selected quality attributes. Specifically, coefficients on the variables produced by the regression represented price premia and discounts for the quality attributes. The variables included in the model were crop year, seasonality, region, variety, size, grade, storage, and a variable designed to measure the impact of the Alar scare on the 1988 crop of Red Delicious apples. Three models were developed. Model I utilized a linear functional form; Model II utilized a log-linear functional form; and Model III utilized a linear functional form with real price as the dependent variable. The results of Model I were used in the final analysis. It was found that size, grade, storage, and seasonality had consistent relationships to the price of an apple. The findings are applied to the Arizona apple industry.

In the analysis of investment and production decisions for perennial crops, expectations play a critical role. This thesis studied three hypotheses about price expectations and reviewed five supply response models for perennial crops. An empirical model for the apple industry was developed to test alternative representations of expected prices. The naive and adaptive expectation model performed well with national data, whereas moving averages of price and the adaptive expectations model performed better with Washington data. To improve estimates of supply response for perennial crops, better data are needed to describe new plantings, removals, the age distribution of trees, production costs, and climatic conditions. Rapid technological change in the U.S. apple industry may cause producers to revise the way they form expected prices, encouraging them to use more historical information and paying more attention to projections of future demand. Rational expectations perspectives may become increasingly relevant.

Previous adoption and diffusion literature had only studied innovations oriented towards operating inputs. This thesis examines the adoption and diffusion of a strategic investment--land leveling. Logit analysis is used to identify the characteristics of adopters of dead level fields. The diffusion of dead level fields is fitted to a logistic function. The data revealed three intra-period diffusion curves that seem to be responses to non-relative price stimuli. The diffusion of the strategic investment--dead level fields--seems to be increased only by government action.