Graduate Thesis Or Dissertation
 

Irrigation Innovations to Increase Efficiency and Sustainability

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https://ir.library.oregonstate.edu/concern/graduate_thesis_or_dissertations/cv43p4074

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  • The first part of the dissertation chronicles irrigation technology changes to progressively improve water application efficiency, water use efficiency, irrigation water productivity and crop production. Technological innovation in irrigation, from 6000 BC to present, has been driven by an unchanging need to provide support for growing populations. The first irrigation approaches remain in use today but are the least efficient. Ancient civilizations irrigated with water channeled from highland springs and rivers to the dryland. These first flood and basin irrigation fall into the category of surface irrigation. The advent of pressurized irrigation technologies (micro and sprinkler) dramatically improved irrigation efficiency. The per capita agricultural area and the per capita irrigated area declined sharply after the advent of pressurized irrigation technologies. Despite this, the total area of agriculture and irrigated agriculture has increased sharply since the turn of the century. Today, the mix of employed irrigation technologies is ~75% surface, ~20% sprinkler, and ~5% micro. The hypothetical redistribution of irrigation methods, away from surface irrigation to sprinkler irrigation and micro irrigation, would either reduce irrigated agriculture’s water footprint or increase irrigated agriculture’s land footprint. These shifts in technology motivate the study and improvement of sprinkler and drip irrigation systems presented in the following chapters. For sprinkler irrigation, this study assesses the potential of dynamic nozzle height adjustment for overhead irrigation systems. This system maintains the nozzle or emitter a constant distance above the crop canopy throughout the growing season and would dynamically respond to variability in canopy height across the field. Within such systems, nozzle height would no longer be fixed in space and time. Nozzle heights would instead vary across space and time. This dynamic system response may therefore have adverse impacts on water application uniformity. The impact of dynamic elevation adjustment on application uniformity was assessed in three steps. First, changes in individual sprinkler patterns for pressure, nozzle type, flow rate and nozzle height were measured in controlled experiments. Next, parametrized equations of the individual sprinkler patterns and how they are altered by nozzle height are developed. Next, the Center Pivot Evaluation and Design software was used to simulate theoretical uniformity, and these simulations were tested against field measurements of the coefficient of uniformity. Finally, we use the parameterized equations within the Center Pivot Evaluation and Design software to simulate the coefficient of uniformity for pivots with constant nozzle heights with a random distribution of nozzle heights, which simulate a dynamic elevation system. It was found that the uniformity coefficient decreased by 4-6% as the distribution of heights throughout the pivot become more variable, due to localized dynamic height adjustment. Systems equipped with nozzles with triangular spray patterns were less impacted than systems equipped with nozzles with elliptical spray patterns. Following upon uniformity tests and simulations, the third part of the thesis investigates the technical feasibility of dynamic nozzle height adjustment. The key data input required to achieve dynamic elevation spray application (DESA) is the plant canopy height; however, this measurement is challenging to acquire in real time due to canopy heterogeneity and potential interference from active water spray. An ultrasonic sensor was evaluated for this purpose. Both lab and field evaluations were conducted. Lab evaluations used view angles ranging from 0º to 35º at increments of 5º, and heights ranging from 0.5 m to 1.75 m for corn, clover, and potato. Field evaluations, informed by laboratory tests, used view angles of 0º and 5º, and heights from 0.5 m to 1.25 m for green beans, green peppers, eggplants, grass, and ground. Regardless of plant type and height, results from the lab suggests that acoustic sensor accuracy decreases about 0.5% with one-unit increase in angle’s degree. When corn was used, the sensor accuracy dropped almost 9%. Results for the field showed that the lowest accuracy (92%) was observed at the green beans with 1.25 height. Field tests with active water spray yielded significantly different measurements from without water spray, but still had accuracies >97%. These findings give confidence in the technical feasibility of DESA under field conditions and could help growers to reduce water losses by using DESA where the nozzle elevation is automatically adjusted with a microcontroller in response to changes canopy height. An innovation in drip irrigation, Variable Rate Drip Irrigation (VRDI), is proposed and evaluated in the fourth part of the dissertation. A VRDI emitter that monitors individual water drops was designed, built, and tested. Just as in the sprinkler innovation tests of chapter 1, uniform water application is critical. In drip irrigation systems this is controlled indirectly by pressure compensation and operational times. Pressure compensated emitters are assumed to have a constant flow rate and are operated for a set period. This approach leaves no possibility to verify the applied amount of water applied at each water outlet. The new VRDI emitter self-monitors the total volume of water applied and halts the flow once the desired total water application has been achieved. Laboratory tests verify that the integrated volume measurements of the VRDI system are independent of pressure. Conversely, the flow rates of a commercial pressure compensated drip lines were not. Significant differences were found in flow rate per time between commercial drip and VRDI. The result found flow rate decreased 90% with VRDI compared to commercial drip. Significant differences in the water volume per drop were found between designs that had outside diameters of 3.5mm and 3mm. These results demonstrate that this form of VRDI is technically feasible and has advantages over current commercial pressure compensated drip emitters. Remaining challenges include cost reduction and miniaturization.
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  • Intellectual Property (patent, etc.)
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  • 2020-12-16 to 2023-01-16

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