Graduation date: 2000

Nitrogen availability in agricultural soils from fertilizer, plant residue inputs, and soil organic matter has important implications beyond crop yield. Legume winter cover crops and one fourth the recommended N rate on sweet corn resulted in yields equivalent to those at the recommended rate in the Willamette Valley of western Oregon. Cereal rye winter crops absorbed an average of 40 kg N/ha that otherwise would have been leached, but did not effectively replace fertilizer N. Cereal rye as a cover crop therefore shows an ability to immobilize N from fertilizer. This was further confirmed in an experiment with "N labeled urea where results showed that N derived from fertilizer in sweet corn or cereal rye plant residue was less available for crop uptake and loss from the system than inorganic N or N directly immobilized from fertilizer. Losses of N from fertilizer ranged from 40 to 73% of that which was in the soil over winter. Mineralization of organic matter N is an important process in N availability, especially when cover crops are used to replace fertilizer. Finding a general indicator or predictor of N mineralization in soils would help in reducing fertilizer N costs and leaching of inorganic N that is applied in excess of crop needs. In a screening of 17 biological and chemical properties of 19 differently managed soils from around the state of Oregon, a model using total soil N and ��-glucosidase activity provided the best model of mineralized N uptake by ryegrass. Biological activity is primarily responsible for the transformations that result in N availability in soils. Management of soils directly impacts soil biology, and results from multivariate analyses of biological and chemical parameters in differently managed soils showed that disturbance creates an overriding common biochemical state in soils. Beyond disturbance, vegetation and the nature of organic inputs also impart recognizable multivariate patterns in soils managed differently. These results suggest that indicators independent of soil type may be used to discern effects of management on agricultural soils. / Graduation date: 1999

Graduation date: 1999

The study was conducted to evaluate the use and perceived effectiveness of occupational safety and health consultative services among Oregon corporations. The three types of consultative services examined: workers' compensation insurance; private; and Oregon Occupational Safety and Health. The research examined if corporations, categorized by corporation size, within the four high-risk industry classes used each of the three types of consultative services. The four high-risk industry classes included: agriculture; construction; manufacturing; and wood products. Based on the results of the study, fewer than one-half of the respondents reported they had used consultative services; however, two out of three respondents indicated they were aware that consultative services were available. Of the three types of consultative services, workers' compensation insurance consultative services were used most frequently. In contrast, private consultative services were used least frequently even though respondents were most aware of the availability of the services. Overall, small corporations, primarily from the agriculture industry class, used consultative services the least whereas large corporations were most likely to use consultative services. Almost half of all respondents, who were aware of the availability of the consultative services and indicated that they had not used or would not use these services in the future, reported that they believed these services were unnecessary for their corporation. In addition, over half of the respondents cited cost as a prohibitive factor in requesting private consultative services. Among those respondents who implemented the recommendations of occupational safety and health consultants, over 84 percent of the respondents felt that the recommendations were either very effective or somewhat effective for all three types of consultative services. Although this percentage of perceived effectiveness was high, the percentage of respondents who reported that consultative services were instrumental in loss reduction was considerably lower than the perceived effectiveness. This finding indicates that respondents' perceived effectiveness of occupational safety and health consultative services include more than loss reduction elements. Future studies need to discern what these additional elements include. / Graduation date: 2000

Estimations of plant water use can provide great assistance to growers, irrigators, engineers and water resource planners. This is especially true concerning the introduction of a new crop into irrigated agriculture. Growing hybrid poplar trees for wood chip stock and veneer production under agronomic practices is currently being explored as an alternative to traditional forestry practices. To this author's knowledge, no water use estimates or crop coefficients, the ratio of a specified crop evapotranspiration to a reference crop evapotranspiration, have been verified for hybrid poplars grown under drip irrigation. Four years of weekly, neutron probe measured, soil water data were analyzed to determine averaged daily, monthly and seasonal plant water use, or crop evapotranspiration. The plantation studied was located near Boardman, Oregon on the arid Columbia River Plateau of North-Central Oregon. Water was applied by periodic applications via drip irrigation. Irrigation application data, weekly recorded rainfall and changes in soil water content permitted the construction of a soil water balance model to calculate weekly hybrid poplar water use. Drainage was estimated by calculating a potential soil water flux from the lower soil profile. Sites with significant estimated potential drainage were removed from the analysis so that all sites used in the development coefficients were calculated using reference evapotranspiration estimates obtained from a nearby AGRIMET weather station. Mean crop coefficients were estimated using a 2nd order polynomial with 95% confidence intervals. Plant water use estimates and crop curves are presented for one, two and three year old hybrid poplars. Numerical simulation of irrigation practices was attempted using weekly soil water content and soil physical characterization data. Parameter optimization and numerical simulations were attempted using the HYDRUS-2D Soil Water and Solute Transport model. Parameter optimization and numerical simulations were largely unsuccessful due to lack of adequate soil physical and root zone system representation and dimensional differences between drip irrigation processes and the model design used in this study. / Graduation date: 1998

Despite the fact that fishing is an inherently uncertain business, risk has rarely been formally recognized in fisheries science or management. Few fishery management plans include any form of risk assessment and those that do focus on minimizing risk caused by uncertainty associated with markets and environmental conditions. Fishermen's attitudes towards risk, whether they are risk-neutral, risk-averse, or risk-prone, have rarely been considered. Although fishermen's attitudes towards risk have been shown in theory to have an impact on fish populations, none of the previous investigations precisely identified whether fishermen are risk-neutral, risk-averse, or risk-prone. This research attempted to identify fishermen's attitudes towards risk from an analysis of their decisions about where to fish. The research applied risk-sensitive foraging theory to an analysis of data from the Oregon trawl fishery for 1991. The data were provided by the Oregon Department of Fisheries and Wildlife. One file contained tow-by-tow information for each fishing trip on landings by species, time spent fishing, type of gear, and fishing locations. A corresponding file contained trip-by-trip information on landings and price by species. The two data files were screened for inconsistencies and then classified into small homogeneous categories based on port, fishing gear, fishing area, and boat size. Various variance-discounting models were fitted to each category to determine fishermen's attitudes toward risk. The models describe the expected utility of fishing at a given distance from port as a linear function of the mean, variance, and third moment of the dollar value per hour of the retained catch. The unknown parameters were estimated from the data using logistic regression techniques. The results of the analysis indicated that in two of fifteen categories the fishermen were risk-averse, and in four categories they were risk-neutral. However, for the remaining nine categories the results were inconclusive and in some cases the fishermen's choice of fishing locations appeared illogical. Instead of preferring fishing grounds that generated higher profits, it appeared that fishermen actively avoided such grounds. The inconclusive and sometimes illogical results may have been due to inappropriate assumptions about the data and about the factors motivating fishermen's decisions. Additionally, there might have been some factors that could have affected the analysis which this research overlooked. For example, this research only accounted for monetary rewards, but fishermen may have preferences other than revenues and costs that influence their choice of fishing grounds. / Graduation date: 1995

The Oregon Employment Division (ES) and Job Training Partnership Act (JTPA) funded agencies frequently provide employment and training services to the same populations, resulting in increased demands to coordinate the two systems efforts and avoid duplications of service. This study examined coordination between local ES offices and JTPA agencies in eight Oregon communities. A literature survey was utilized to supplement the information acquired from 193 responses to a cooperation and coordination questionnaire which was developed and administered to ES and JTPA staff in the eight communities studied. Frequency distributions were analyzed using a mean statistic at the individual, organization and system level to determine that the two systems were moderately coordinated. / Graduation date: 1991

Graduation date: 1999

This research examined the diets of angora goats on a sagebrush bunchgrass rangeland. Research objectives were to 1) determine the effects of a positive conditioning method on both mature and immature angora goats; and 2) to quantify plant selection and provide preliminary information as to the potential for using goats to rehabilitate degraded sagebrush rangelands. Goat diets were ascertained using focal - animal bite-count observations during five consecutive seasons, summer 1990 through summer 1991. Treatment group goats were conditioned for 8 months by including ever- increasing amounts of sagebrush (Artemisia tridentate subspp. wyomingensi) in their daily ration, up to 25% of their total intake. Conditioning effects were evaluated in a rangeland setting by comparing relative amounts of sagebrush consumption between groups. Our results indicate that while conditioning did not significantly impact sagebrush consumption, young animals consumed significantly more sagebrush than adults. Additionally, learning throughout the first year altered dietary selection by the second summer. Both does and kids were primarily gramnivorous, however there was strong seasonality in species preference and a significant age difference in diets selected. Age differences in the plant species selected persisted throughout the study until the summer of 1991 when kids were eighteen months old. / Graduation date: 1993

Mentor teachers are currently seen as a solution to education's dilemma of how to orient beginners into the profession and provide educational advancement for its most capable, experienced teachers. One goal of Oregon's mentor program is to have mentors provide their proteges with instructional assistance through an observation process. The purpose of this study was to explore the quantity and types of observations being conducted by mentors and discover what factors most affect their ability to complete observations for instructional assistance. In order to determine the possible need for differentiation in training, comparisons were made between elementary and secondary level mentors for the quantity and types of observations conducted and for needs related to attitude, skills, and context. A literature survey provided an initial list of needs and attitudes previous researchers have found to be critical to mentors' success. This list was refined through the work of a Delphi Panel. The resulting survey gathered observation-related information from a random sample of two hundred and twenty-five Oregon mentors distributed throughout the state. Data was analyzed using Analysis of variance and Chi square tests at the .05 level to determine if there were significant differences between elementary and secondary level mentors and between twenty-four observation-related factors. A significant difference was found between observation-related factors, the most important being trust between the mentor and protege, availability of release time, the mentor's teaching in the same building as his/her protege, and the protege's willingness to be observed. No significant differences were found between elementary and secondary level mentors in either the quantity and types of observations conducted or in the perceived importance of various observation-related factors. / Graduation date: 1991