The shared experiences of prospective agricultural education teachers: A phenomenology of supervised agricultural experiences

Whiddon, Ashley Seamon Oklahoma State University 2015 해외박사(DDOD)

소속기관이 구독 중이 아닌 경우 오후 4시부터 익일 오전 9시까지 원문보기가 가능합니다.

The purpose of the qualitative, phenomenological study was to better understand SAE programs through the lived experiences from self-identified future agricultural education teachers in Oklahoma. Phenomenological methods were used to explore eight Oklahoma State University Future Agricultural Education Teachers Academy from each of the five agricultural education districts in the state. The research questions investigated the learning outcomes and experiences regarding SAE programs. Subjects in this study reported learning skills and external factors that attributed their SAE experiences. Four themes were revealed from the reported data to include: (a) subjects attain skills through SAE programs; (b) teachers have a great influence on subjects' SAE programs; (c) subjects have limited and narrow perceptions of SAE; and (d) subjects believe SAE programs diversify their experiences in agriculture. The essence was revealed that teachers determine learning through SAE programs, which provided the greatest opportunity for the acquirement of employability skills in the SBAE program. Recommendations were developed to address the findings and conclusions for each theme.

Soil carbon, nitrogen, and physical properties in cropping systems of Oklahoma

Abreu, Silvano Luiz de Oklahoma State University 2011 해외박사(DDOD)

소속기관이 구독 중이 아닌 경우 오후 4시부터 익일 오전 9시까지 원문보기가 가능합니다.

Soils across the State of Oklahoma where areas of conventional and long term no-till are under similar climate conditions and soil properties (same soil series) were sampled in 4 points of a transect across the field at 110 cm depth and divided in 5 different depths (0--10; 10--20; 20--40; 40--70; and 70--110 cm). Samples were air dried and sieved at 2mm mesh. Sixteen farm fields (eight no-till and eight conventional till) were sampled in the principal agricultural areas of Oklahoma. Also, two tillage experiments that have no-till and conventional till treatments combined with different crop rotations where sampled and compared as well. Organic C and total N were analyzed. Besides, bulk density was determined at each depth and sampling point in order to account for the amount of organic carbon and nitrogen storage in the soil profile. Results were analyzed by LSD comparing tillage system. Organic carbon and total nitrogen was analyzed by LECO analyzer and carbonates were analyzed so the amount of organic carbon can be calculated. Another chapter of the study analyzed the use of cover different cover crops; including forage radish, sunn hemp, pigeon pea, cowpea, and Austrian winter pea in cash crop rotations that included soybean, corn, and wheat. Grain yield, biomass, and soil physical properties were analyzed in two locations in Central Oklahoma. For most Oklahoma studied areas, no-till soils had higher organic carbon and total nitrogen stock in the soil profile than conventional till. Top soils no-till have also more carbon stock in no-till compared to conventional till soils. The increasing of crop intensity and diversity did not affect grain yield in the cash crops, but increased biomass production. After two years of rotations no effect of crop rotation or crop intensity was observed in soil physical properties.

Assessing the Distribution, Abundances, and Ecology of Bobcats (Lynx rufus) in Oklahoma

Proudman, Nathan James Oklahoma State University ProQuest Dissertations & 2023 해외박사(DDOD)

소속기관이 구독 중이 아닌 경우 오후 4시부터 익일 오전 9시까지 원문보기가 가능합니다.

Bobcats (Lynx rufus) are elusive meso-carnivores that are often difficult to study and monitor. Finding a suitable alternative monitoring method, that is independent of fur harvest data, can be useful for their management in Oklahoma. In a project aimed at assessing the distribution, abundances, and ecologies of bobcats, their sympatric meso-carnivores, and their prey in Oklahoma, we deployed a combination of hair-snare cubbies, camera traps, and Sherman live-traps, whilst assessing the efficacy of the hair-snare cubby design as a bobcat monitoring tool. We recruited > 60 wildlife students as citizen scientists, who deployed hair-snare cubbies across the state during Dec – Jan 2018/19 – 2020/21 in a large-scale occupancy study, and deployed 120 hair-snare cubbies and camera traps during Jan – Mar of 2019 – 2021, within three areas of interest that represented distinct ecoregions of the state, in a capture-recapture study. We also deployed Sherman live-trap transects at these study sites Mar – May of 2020 – 2021 to quantify and characterise small mammal prey communities. We found historic harvest rates and environmental variables to be important predictors for bobcat occupancies, but models suffered from high degrees of error. Morphological and genetic identification of hairs proved difficult, with camera traps outperforming hair-snare cubbies and providing the necessary data for density estimation. We found a high degree of spatial, temporal, and spatio-temporal overlap among sympatric meso-carnivores, but bobcats were largely asynchronous temporally with rabbits, with coyotes showing positive spatio-temporal association with bobcats that was nonreciprocal (with even weak evidence to support avoidance of coyotes by bobcats), overriding the presumed effects of using bobcat scent lure in the hair-snare cubbies. We found little differences in the small mammal abundances among study sites but found large differences among habitat types and regrowth levels after prescribed burns. Peromyscus spp. dominated captures, especially at our southwestern study site, where small mammal diversity was low. Our results elucidate some interesting relationships between bobcats and their conspecifics, demonstrate the utility of using wildlife students as citizen scientists, but show hair-snare cubbies may be less effective than camera traps at monitoring bobcats under conditions similar to those in our study.

Optimal nitrogen and choice of reduced tillage systems for wheat production in north western Oklahoma

Bocoum, Kolado Oklahoma State University 2000 해외박사(DDOD)

소속기관이 구독 중이 아닌 경우 오후 4시부터 익일 오전 9시까지 원문보기가 가능합니다.

<italic>Scope and method of study</italic>. Simulation data from the Erosion Productivity Impact Calculator Model (EPIC) and enterprise budget elaborated from the Oklahoma State University Budget Generator were used to study the long-term onsite and offsite effects of soil erosion on wheat production in Garfield County, Oklahoma. It was assumed that the farm has six soil types, and in each, the producer would choose for each of the 100 years of the planning period, a level of nitrogen application and one of four possible tillage systems. The study estimated the functions of erosion, yield, nitrogen carryover, and nitrogen loss functions per soil type. A discrete dynamic economic model was used to determine the private and social optimum rate of nitrogen application and choice of reduced tillage systems under different assumptions of market prices of wheat and nitrogen, cost of erosion and nitrogen loss, and discount rates. Because of the complexity inherent in using dynamic programming for this problem, the study developed a branching method, which is a simpler approach to solving for the optimal solution. <italic>Findings and conclusions</italic>. It was found that the optimal tillage system was different from private versus social choice. The optimum rates of applied nitrogen were almost identical for the sweep systems, varying from 117 kg/ha to 132 kg/ha across all soil types. The corresponding rates were slightly higher for disk chisel. They varied between 124 kg/ha and 135 kg/ha. The plow system required much higher rates of nitrogen application that vary from 136 kg/ha to 145 kg/ha. The net present value of the disk chisel was higher than the other tillage systems for private optimization, and the net present value of sweep system twice was the highest for social optimization where the farmer is responsible for offsite damage costs of soil erosion. The optimal choice of tillage systems and resulting nitrogen application was not sensitive to changes in wheat and nitrogen prices, and discount rates for either private or social optimization. However, the optimum tillage sequence was sensitive to changes in the cost of erosion and nitrogen loss. A 50% reduction in these costs would make farm shift from using sweep systems to using disk chisel. The results imply that policies aimed at reducing soil erosion are bound to be less effective without internalizing the cost of offsite damages.

Optical and human assessment of winter wheat cultivars for competitiveness against jointed goatgrass, and characterizing Oklahoma jointed goatgrass-winter wheat hybrids

Stone, Amanda Elizabeth Oklahoma State University 2003 해외박사(DDOD)

소속기관이 구독 중이 아닌 경우 오후 4시부터 익일 오전 9시까지 원문보기가 가능합니다.

<italic>Scope and method of study</italic>. Characteristics other than mature height contribute to competitive ability of wheat, but the literature has not identified any other useful traits. Twenty-four winter wheat cultivars were seeded with and without jointed goatgrass (<italic>Aegilops cylindrica </italic> Host.) in five environments, 1999–2001. Wheat stand density, forage yield, height at Zadocks 32, 37, and 91, spike density, and yield were measured. Additionally, mature height, spike density, spikelet production, and spikelet density of jointed goatgrass were measured. An Oklahoma State University sensor was used to record incident and reflected wavelengths from the canopy of the 24 winter wheat cultivars grown with and without jointed goatgrass, 1999–2001. Normalized difference vegetative index (NDVI) was calculated. The introduction of imazamox tolerant winter wheat has increased interest in jointed goatgrass-winter wheat hybrids [<italic>Aegilotriticum sanctiandreae</italic> (Degen) Soó]. However, little is known about such hybrids in Oklahoma. Hybrid plants were collected from central Oklahoma, 2000 to 2002, for characterization and germination. <italic>Findings and conclusions</italic>. Yields of the 24 wheat cultivars, at four environments were not affected by jointed goatgrass competition. Cultivars varied substantially in their ability to suppress jointed goatgrass spikelet production. Wheat stand density varied greatly and appeared to be related to competitive ability. Wheat forage production, height at Zadocks 32 and 91, and spike density were minor factors in suppressing jointed goatgrass spikelet production. Wheat height at Zadocks 37 was inversely related and wheat yield was variably related to jointed goatgrass spikelet production. NDVI was useful in estimating spike density, spikelet production, and spikelet density of jointed goatgrass, as well as estimating stand density and forage yield of the wheat cultivars grown without jointed goatgrass. NDVI was variable in estimating wheat height at Zadocks 32, 37, and 91, wheat spike density, and wheat yield. When the published morphological characteristics of the 24 wheat cultivars were considered, estimations improved. When certain stress factors such as plant diseases and late season drought were absent, correlations approached 0.9. Hybrid plants varied in mature height and spike length. Hybrid spike color was darker than mature wheat spike color and mature hybrid spikes disarticulated intact, unlike jointed goatgrass. Wheat cultivars varied in hybrid production ability.

Dynamics of understory shortleaf pine (Pinus echinata Mill.) and hardwood after thinning shortleaf pine forests in the southeastern United States

Kc, Anup Oklahoma State University 2016 해외박사(DDOD)

소속기관이 구독 중이 아닌 경우 오후 4시부터 익일 오전 9시까지 원문보기가 가능합니다.

The shortleaf pine (Pinus echinata Mill.) population is consistently declining in southeastern United States. Shortleaf pine forests are thinned frequently to improve the growth and development of residual stands. But, the effect of thinning on growth and development of understory woody-plants in long term has not been extensively studied. We assessed the effects of thinning, overstory shortleaf pine characteristics, climatic, and topographic factors on shortleaf pine regeneration applying various predictive modeling techniques. We applied decision tree models to predict shortleaf pine regeneration. We also developed, evaluated, and compared the performance of three other predictive models to predict shortleaf pine regeneration. We used understory shortleaf pine data that were collected from shortleaf pine forests of Arkansas and Oklahoma spanning a period of 25 years following thinning and hardwood control treatments. The shortleaf pine densities have declined in every subsequent measurement since the first measurement of understory trees in 1996. Thinning treatments played a significant role on the understory shortleaf pine density. The decision tree model using the Gini criteria as the splitting rule to predict the shortleaf pine regeneration had a low misclassification rate of 7.6 percent. The decision tree model can be an efficient tool to make shortleaf pine stand management decisions. The best performing logistic regression model showed precipitation, plot age, site index, and overstory thinning were the significant inputs affecting shortleaf pine regeneration with validation misclassification rate of 8 percent. The best performing artificial neural network model predicted the shortleaf pine regeneration with validation misclassification rate of 7.6 percent, and cumulative lift of 5, 2.5 and 1.66 at depth of 20, 40 and 60 respectively. An artificial neural network model performed best to predict the shortleaf pine regeneration. Poor shortleaf pine regeneration performance over decades in study sites suggests the future of shortleaf pine dominated forests is questionable unless further regular silvicultural treatments are applied. We recommend continual hardwood removal every 10-15 years to obtain the satisfactory understory shortleaf pine regeneration in shortleaf pine forests of Arkansas and Oklahoma.

Genesis, distribution, and classification of sodic soils in Oklahoma

Jigoulina, Elena Igorevna Oklahoma State University 2001 해외박사(DDOD)

소속기관이 구독 중이 아닌 경우 오후 4시부터 익일 오전 9시까지 원문보기가 가능합니다.

<italic>Scope and method of study</italic>. Aspects of sodic soil spatial distribution, classification, and genesis are studied. The objectives of this study were: (1) to determine the effect of the climate and other factors on the distribution and properties of sodic soils in Oklahoma, (2) to expand sodic soil classification by using soil properties that reflect soil moisture conditions, (3) to analyze selected major types of sodic and leached sodic (Solods) soils to reveal the formation pathways. Fourteen sodic soil series from 19 Oklahoma counties were sampled in 1997. Horizon delineation and in-situ soil descriptions were made using standard techniques. Characterization of each profile was performed by conventional methods. Data on dispersion characteristics for each horizon were obtained from Oklahoma Department of Transportation Testing Laboratory. Classification of soils under study was conducted using Soil Taxonomy. Maps visualizing soil spatial distribution were generated in ArcView/GIS computer software. <italic>Findings and conclusions</italic>. There is a gradual change in sodic soils properties along the Precipitation-Evaporation (P-E) Index and soil moisture regime gradients. Depth and value of salinity (EC), depth to carbonates, depth and values of maximum relative sodium content and SAR, and pH increased with decreasing P-E index. Variability of sodic soils on a local scale was affected by position on the landscape, which influences presence of water table close to the surface. Parent material affected soil occurrence, as well as soil color, texture, chemical composition of soil water solution, and clay mineralogy. The presence of a ground water with relatively large sodium content determines the occurrence of sodic soils in the area. Suggested classification for sodic soils in Oklahoma takes into account soil salinity, which differs significantly between soils with different moisture regimes and landscape positions and is recognized on a subgroup level. Three types of sodic soils, which differ in the amount of salts, SAR values, acidity and pH, are formed under the humid conditions of southeast Oklahoma. The first type, Natrudalfs, has SAR up to 30 and moderate to high salinity (EC > 2) and occur in the lowest position on a landscape. The second type, sodic Hapludalfs, is located on an intermediate landscape position, and has lower salinity and sodium content compared to Natrudalfs. The third type, solodic Hapludalfs, is the leached sodic soils of terraces and uplands.

Remote sensing application in biomass crop production systems in Oklahoma

Foster, Anserd Julius Oklahoma State University 2013 해외박사(DDOD)

소속기관이 구독 중이 아닌 경우 오후 4시부터 익일 오전 9시까지 원문보기가 가능합니다.

This study was conducted to evaluate the combined effects of nitrogen and cropping systems on biomass yield and quality and to describe the spatial variation of biomass yield, soil carbon and nitrogen within a switchgrass field. Field plots at Stillwater and Woodward in Oklahoma consisting of five nitrogen treatments and three cropping systems were used for the nitrogen x cropping system study and an 8 ha switchgrass field at Chickasha, Oklahoma was used to describe the spatial variability at fine (2.5 m sampling distance) and coarse scale (10 m sampling distance). Remote sensing technique was used to monitor biomass yield and quality to better understand N requirement and usage for production. Semivariogram were used to evaluate spatial variability of the soil parameters and biomass yield. The results of this study showed that maximum yield was produced at both locations with less than 84 kg N ha 1 and high biomass sorghum has potential to produce biomass yield > 20 Mg ha 1 under normal conditions in Oklahoma. The study results also showed that perennial grass systems are more reliable sources of biomass yield, especially under adverse climatic conditions of Oklahoma. Final biomass yield of high biomass sorghum could be predicted using both broadband (aerial photograph) and narrowband (GreenSeeker) normalized difference vegetation index (NDVI) from July to close to harvest, while biomass yield in the perennial grass was best predicted during June to July. Comparing simple ratios and best narrowband indices with partial least square regression (PLSR) models suggested that while PLSR calibration models produced significantly lower error and higher r2 for predicting biomass yield and N concentration within a growing season, the simple ratios and best narrowband indices were more stable and reliable when used for prediction across growing seasons. Spatial pattern in switchgrass field was described using both ground and aerial imagery. The NDVI computed from aerial imagery provided good precision at the fine scale in describing the spatial distribution of switchgrass yield. Remote sensing application in biomass production systems can greatly improve prediction models for predicting biomass yield and quality in feedstock materials with use of optimal hyperspectral narrowband.

Effects of multistate species occurrence on community-based inference and applications

Bried, Jason Oklahoma State University 2015 해외박사(DDOD)

소속기관이 구독 중이 아닌 경우 오후 4시부터 익일 오전 9시까지 원문보기가 가능합니다.

Species occurrence is a basic unit of community data, but occurrences tend to have multiple ecological states. Ecologists are often interested in breeding states, such as birds with or without nesting success, frogs with or without mating calls, and plants in flower/fruit vs. vegetative state. My thesis explored the effects of locally resident (autochthonous) vs. immigrant (allochthonous) species occurrence on community inference and applications, using adult Odonata (dragonflies and damselflies) and wetlands as a model system. The primary data came from standardized odonate surveys at non-forested wetlands in New York and Oklahoma, USA. I first had to determine how to split resident and immigrant occurrences (chapter I). The presence of final exuviae (molted exoskeletons of F-0 larvae) definitively indicates local autochthony in odonates. I estimated the probability of exuvia occurrence in relation to readily acquired adult survey information and discovered several indicators of species residency: tenerals (newly emerged) on at least two surveys, adults at any stage on at least four surveys, and counting >20 adults at least once. These criteria were used to separate resident from immigrant occurrences in subsequent chapters. Chapter II explored the general forms of classification analysis in community ecology including the identification of (meta)community structures and site grouping based on variation in species composition. I predicted gradient-structured resident occurrence vs. unstructured (random) immigrant occurrence, and predicted the resident occurrence would more effectively partition community variation than total (resident + immigrant) occurrence. Predictions were well supported, Clementsian-style turnover was prevalent, and species composition of resident adult damselflies appears useful for wetland classification. Chapter III explored additional community approaches including environmental gradient modeling, spatial-environmental hypothesis testing, and biological condition assessment. Resident occurrences reduced model selection uncertainty, enabled detection of environmental and spatial effects, and strengthened the signal of biological impairment. These findings indicate that local autochthony may be determined in standardized adult dragonfly surveys, and that multistate species occurrence can strongly influence community-level inference and applications.

Patch-Burn Grazing and Mixed Grazing as Best Management Practices on Rangelands: A Study Exploring Adoption Behavior, Preferences, and Motivations of Private Landowners in the Southern Great Plains of the United States

Adhikari, Saroj Oklahoma State University ProQuest Dissertations & 2023 해외박사(DDOD)

소속기관이 구독 중이 아닌 경우 오후 4시부터 익일 오전 9시까지 원문보기가 가능합니다.

The Great Plains of the United States' rangelands face a variety of anthropogenic threats including woody plant encroachment and uncharacteristic wildfires. Unfortunately, the situation is worsening due to the conventional land management practices involving limited use of fire, mono-species grazing, and preference for single-forage species. This study is aimed to explore socio-economic issues concerning two best management practices: patch-burn grazing or pyric herbivory and mixed-species grazing.I conducted a mail survey of landowners residing in the southern Great Plains states of Texas, Oklahoma, Kansas, and Nebraska. The study utilized a bivariate probit model to identify various factors affecting the awareness and adoption of patch-burn grazing, a novel approach to maintaining biodiversity in the Great Plains of the United States. Results showed that repeated wildfires, an opportunity to learn from nature conservancy, and university/county extension positively affected the probability of being aware of patch-burn grazing awareness. Likewise, larger landholding size, management objectives that focus on controlling blackberry, repeated wildfires, and the opportunity to learn from university/county extension positively influenced the likelihood of patch-burn grazing adoption. Additionally, landowners' preferences for non-traditional management practices were studied, and their willingness to pay was estimated through the Best-Worst Choice (BWC) experiment. The study found that ensuring higher forage utilization, lower level of fire risk, wildlife promotion, and the lower cost was likely to persuade landowners to conduct best management practices on their lands. Finally, the study explored the role of landowner values, attitudes, and norms on their behavioral intentions to adopt best management practices that promote wildlife abundance. The results emphasized the need for innovative communication and non-traditional outreach methods to educate rangeland owners on the ecological and production benefits of the best management practices.