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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Drought Resistance Response of Tall Fescue Established in Disturbed Urban Soils Utilizing Biosolids

Boyd, Adam Philip 18 February 2016 (has links)
Urban soils are typically degraded due to land disturbance. The poor quality physical and chemical properties of the soil can benefit from application of organic amendments. Local sources of such amendments are biosolids, which are treated domestic wastewater sludges. The objective of this experiment was to compare effects of various high quality biosolids-based soil amendments with synthetic fertilizer on the growth and quality of tall fescue (Schedonorus arundinaceus) under two different soil moisture regimes. The research site was a disturbed soil at the Virginia Tech Turfgrass Research Center in Blacksburg, Virginia. The experimental design was a split plot with irrigation regime as the main factor and soil amendments as the split factor. All treatments were arranged in four randomized complete blocks. The study was established in late summer 2013. Soil amendment treatments, applied prior to seeding in September 2013, were: 1) inorganic N, P, K applied according to soil test laboratory recommendations; 2) anaerobically digested, dewatered biosolids to supply agronomic N rate; 3) anaerobically digested, dewatered biosolids blended with sand and sawdust to supply agronomic N rate; 4) anaerobically digested, dewatered biosolids blended with sand and sawdust to supply agronomic P rate; and 5) composted biosolids to supply agronomic N rate. The agronomic N rate for the turfgrass was 224 kg of estimated plant available nitrogen (PAN) ha-1. Inorganic fertilizer was applied to supply annual P and K requirements prior to seeding in late summer, and the N was split into three application timings (September 2013, April 2014, and June 2014). Supplemental fertilizer N to achieve full agronomic N rate was applied to the treatment plots that received the agronomic P rate of blended biosolids-sand-sawdust. The area was seeded on September 13, 2013 with a tall fescue blend at a rate of 488 kg ha-1. Following full tall fescue establishment, in June 2014, two irrigation regimes, consisting of 0% and 80% evapotranspiration replacement every three days, were initiated. The study had three phases denoted as the pre-drought, drought, and recovery phases which started in April and concluded in August of 2014. Turfgrass color and quality, volumetric soil moisture percentage to a 5 cm depth, normalized difference vegetative index (NDVI), clipping yield, and turfgrass N uptake were measured bi-weekly throughout the growing season. During the first May through July 2014 irrigation season, results were that the fertilizer control consistently provided improved responses relative to the biosolids amended treatments. Clipping yield, quality, and NDVI were all significantly greater in the inorganic fertilizer treatment, but volumetric soil moisture percentages were slightly greater in the biosolids treatments. Turfgrass responses appeared to have been associated with plant available nitrogen, which was lower in the biosolids treatments than in the fertilizer treatment. Calculated PAN for the biosolids products was too low to achieve ideal turfgrass growth and quality. Improving the estimated PAN and/or splitting the organic amendment application times should improve the growth and quality of the turfgrass. / Master of Science
2

A Quasi-Experimental Study of Inter-rater Reliability When Awarding Exceptional Quality Points on the Texas Teacher Appraisal Instrument

Dobbs, Louann 08 1900 (has links)
This study investigates the inter-rater reliability of appraisers who award exceptional quality points on the Texas Teacher Appraisal Instrument. Inter-rater reliability was measured when appraisers scored exceptional quality points after viewing a videotaped lesson. Comparisons were made between appraisers when grouped according to elementary or secondary certification, sex, years of administrative experience, and type of training. A total of 707 subjects from 56 school districts participated in the study. Five research hypotheses were formulated with the .05 level of significance for acceptance. All hypotheses were tested by correlation of coefficients, multiple response procedures, frequencies, and percentages. The data measuring inter-rater reliability of the appraisers in training imply that there is very little reliability in the awarding of exceptional quality points on the Texas Teacher Appraisal Instrument. The findings of this study are that certification, sex, administrative experience, and type of training made no significant differences when scoring the instrument. Therefore, it is concluded that the scoring of exceptional quality points is a subjective, professional judgment made by each appraiser when observing a teacher. Since no significant reliability was found, the scoring of exceptional quality points cannot be supported as a reliable means of determining the quality of teaching in Texas schools. Generally, elementary certified appraisers awarded fewer exceptional quality points than secondary appraisers, males awarded slightly more points than females, appraisers indicated no noticeable trend because of years of administrative experience, and less experienced appraisers had the tendency to award more points than experienced appraisers. Therefore, inter-rater reliability in awarding exceptional quality points cannot be expected on a consistent basis. Each appraiser, regardless of certification, sex, years of administrative experience or training, will use his or her own professional judgment when scoring the instrument.
3

Assessment of Exceptional Quality Biosolids for Urban Agriculture

Alvarez-Campos, Odiney Maria 28 March 2019 (has links)
Biosolids have been used as soil conditioners and fertilizers in agriculture and mine land reclamation, but application of Exceptional Quality (EQ) biosolids to rehabilitate anthropogenic soils for urban agriculture is recent and requires greater study to ensure their appropriate use. The objectives were: 1) to quantify plant available nitrogen (PAN) of new EQ biosolids in a greenhouse bioassay; 2) to quantify PAN of EQ biosolids applied to an urban degraded subsoil via tall fescue N fertilizer equivalency, and compare field results to laboratory tests; 3) to investigate EQ biosolids and inorganic fertilizer effects on urban soil properties, vegetable yields, and potential N and phosphorus (P) loss. Biosolids evaluated were products of thermal hydrolysis plus anaerobic digestion (BLOOM), blending with woody mulch (BM) and sand/sawdust (BSS), composting (LBC), and heat-drying (OCB). Organic N mineralization of new blended biosolids products ranged between 20-25% in the greenhouse bioassay. Products BLOOM, BM, and OCB had the highest organic N mineralization as estimated by the 7-day anaerobic incubation, and this test and soil nitrate-N had the highest correlations with tall fescue N uptake (r=0.49 and r=0.505, respectively). We conducted a two-year field study with four growing seasons (fall 2016-2017 and summer 2017-2018) in an urban disturbed subsoil where EQ biosolids were applied seasonally at agronomic N rates, and yearly at reclamation rates (5x agronomic N). Cabbage yields were greater with reclamation rates (~3.0 kg m-2) and bell pepper yields were greater with BLOOM reclamation rate (~1.0 kg m-2) than with the inorganic fertilizer (1.0 kg m-2 and 0.2 kg m-2, respectively) during second year growing seasons. Soil carbon (C) accumulation (%C remaining in the soil) two years after biosolids additions ranged between 37 to 84%. Soil N availability and mineralization were limited most likely due to lack of residual soil C and N, and high clay content. Nitrogen leaching losses from reclamation rates were not greater than agronomic N rates. Leachate P was below detection during most of the experiment. Despite limiting soil conditions, biosolids amendment at reclamation rates showed greatest potential to increase vegetable yield and improve soil properties after two years of application, while not impairing water quality. / Doctor of Philosophy / Exceptional Quality (EQ) biosolids are by-products of wastewater treatment plants that have been processed to destroy pathogens, reduce attraction by disease-spreading organisms (e.g. flies, mosquitoes, rodents, etc.), and limit heavy metal concentrations. These characteristics make EQ biosolids safe for use by home gardeners for growing food crops. There is limited information on optimal recommended rates at which these products should be applied to urban gardens. The purpose of our research was to determine optimum application rates of EQ biosolids to urban gardens based on their essential plant nutrient (esp., nitrogen and phosphorus) availability. We learned that the EQ biosolids we studied are less concentrated in plant available nitrogen and phosphorus than biosolids applied to conventional agricultural fields. This is because we diluted our biosolids with sawdust, sand, and woody mulch to facilitate their storage, handling, and ease of application. We learned that high EQ biosolids application rates reduce soil compaction and increase essential plant nutrient availability and crop yields for agriculture practiced in urban soils. The high application rates of EQ biosolids accomplished such soil-improving and yield-increasing benefits without impairing local water quality.

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