• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 738
  • 566
  • 153
  • 54
  • 50
  • 17
  • 15
  • 12
  • 10
  • 9
  • 9
  • 6
  • 5
  • 5
  • 3
  • Tagged with
  • 2036
  • 491
  • 262
  • 246
  • 238
  • 209
  • 202
  • 184
  • 176
  • 166
  • 163
  • 142
  • 140
  • 138
  • 135
  • 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.
101

Control of Dodder in Alfalfa Seed Crops

Lee, William Orvid 01 May 1954 (has links)
Dodder (Cuscuta spp.) is a parasitic weed which attacks alfalfa, clovers, lespedeza and many other species of plants. This pest is especially troublesome when these crops are grown to produce seed.
102

Small Burnet (Sanguisorba minor Scop.) Response to Herbicides Applied Postemergence

Nelson, Ryan Lee 01 May 2013 (has links)
Small burnet (Sanguisorba minor scop.) Is a hardy, relatively long lived evergreen forb native to Eurasia that has potential to improve grazinglands and extend grazing into late fall and winter. Trials evaluating small burnet tolerance to spring and fall postemergence herbicide applications were conducted at the Utah State University Evans farm in Millville, UT. Two small burnet genotypes were grown in a randomized complete block design with a split-plot arrangement. Twelve treatments, clethodim, clopyralid, imazamox, 2,4DB, metribuzin, aminopyralid, pendimethalin, dimethenamid-P, bromoxynil, dicamba, quinclorac, and an untreated were applied at moderate field use rates either spring or fall of the establishment year. Plots were rated for visual injury on a 0 to 100 scale where 0 = no injury and 100 = complete mortality. Ratings were done 7, 14, 60 days after treatment (DAT) and the spring following treatment. Seed yield, seed viability, and dry matter yield (DMY) were determined. Fall treatments of aminopyralid reduced seed yield 65%, seed germination 43%, and DMY 67%. Fall applied imazamox treatments reduced DMY by 36%, and seed yield by 33%, but did not impact germination. Visual injury was greatest from spring and fall applied aminopyralid treatments with ratings of 24% and 79%. Spring applied treatments did not impact seed yield or seed germination. Results suggest that clethodim, metribuzin, quinclorac, clopyralid, dimethenamid-P, bromoxynil, and pendimethalin cause little or no injury to small burnet.
103

Revegetation of Bulrushes Bolboschoenus Maritimus, Schoenoplectus Acutus, and S. Americanus in Great Salt Lake Wetlands: Seed Biology and Influence of Environmental Factors on Rhizomes

Marty, James 01 May 2016 (has links)
A primary goal of ecological restoration is to establish desirable plant species. This goal is particularly important following the removal of invasive plants. Understanding biological traits of plant species important to revegetation is crucial to plant establishment. In the globally important Great Salt Lake (GSL) wetlands, native habitat-forming bulrushes Bolboschoenus maritimus, Schoenoplectus acutus, and S. americanus are frequently displaced by the invasive grass Phragmites australis. Successful revegetation of bulrushes relies on improving our understanding of seed dormancy break, seed germination requirements, and the environmental factors affecting rhizome emergence and growth. We used a series of germination chamber and greenhouse experiments to examine effective seed dormancy break treatments and germination conditions for multiple collection sites of bulrushes B. maritimus, S. acutus, and S. americanus. We also performed a greenhouse experiment to investigate how water depth, nutrient, and salinity levels affect B. maritimus and S. acutus emergence and growth from rhizomes. Cold, moist stratification and bleach scarification were effective dormancy break treatments for all species, though magnitude of effect varied by species and source site. Soaking the seeds after application of dormancy break treatments improved germination for all species. Rhizome emergence of S. acutus was negatively affected by high water depth, likely due to oxygen limitation. Bolboschoenus maritimus was salinity tolerant relative to S. acutus. GSL wetland managers can use these findings to improve revegetation projects via seeding and planting.
104

The Genetic Basis for Seed Coat Polymorphisms In Lupinus Perennis

Wilson, Rachel Erin 26 November 2019 (has links)
No description available.
105

Impacts of a Seed Predator on Sundial Lupine

Shimola, Jennifer 27 August 2013 (has links)
No description available.
106

Cultural Thinning of Native Sagebrush Stands to Increase Seed Yields

Elder, Kurt David 13 December 2012 (has links) (PDF)
Wyoming big sagebrush (Artemisia tridentata Nutt.) is an important native shrub in the Great Basin because of its wide distribution where it dominates over 60 million ha and provides essential habitat and forage for many varied species. The hand collection of sagebrush seed often results in seed scarcity and the available seed quantities are at times inadequate to revegetate large areas that have been disturbed, resulting in a demand for sagebrush seed. Study locations were selected near Scipio and Sahara sand dunes of Utah, and treatments were 1-) control, no treatment applied area left undisturbed 2-) general chemical strip thinning 3-) general chemical thinning of entire stand, 4-) general mechanical strip thinning, and 5-) general mechanical thinning of the entire stand. Significant differences among treatments in seed yields were collected in 2011 at Scipio but not at Sahara. At Scipio, the mechanical strip of competing sagebrush in 3m strips was the most effective of all treatment and produced 2.47kg/ha compared to 4.624kg/ha in the control, but the mechanical land area was only utilizing half the compared control area. The chemical treatments produced 1.819kg/ha and 1.31kg/ha. The percent of sagebrush mortality by each treatment determined the level of competition killed in treatment areas. All treatments at both locations killed at least 57% of the sagebrush. Chemical treatments had a consistent kill rate at both locations, although lower than anticipated, but mechanical kill was the highest at 93% in Scipio. Both mechanical and chemical treated plots had increased cover levels of cheatgrass when compared to the control plots.
107

Use of Seed Coating Technologies to Improve Cercocarpus ledifolius (Curl-Leaf Mountain Mahogany) Seed Germination and Emergence to Reclaim Mine Lands

Nielson, Emily M. 04 August 2022 (has links)
Globally, mining is vital to human interests, but its practice can cause landscape alteration which may look unnatural or engineered. The reintroduction of native plants to these areas is needed to restore the visual appeal and ecological function back into these altered mine lands. Cercocarpus ledifolius (curl-leaf mountain mahogany) is one desirable native species in the Intermountain West that is prized for its potential to grow on step and rocky hillsides and for the habitat it provides for wildlife. Unfortunately, C. ledifolius does not establish well from seed, which has been attributed to seed dormancy. The first objective of this study was to determine if scarification and gibberellic acid (GA3) treatments improve germination by alleviating seed dormancy. We also aimed to determine if a combination of fungicide and hydrophobic seed coatings increased emergence and establishment of C. ledifolius seedlings in mine overburden by reducing loss from fungal pathogens and premature germination. We found that two treatments, GA3 and GA3 + hydrophobic coatings, improved emergence compared to untreated seed, producing 1.8 (P = 0.0682), and 2.2 (P = 0.0751) more seedlings per meter, respectively. The second objective of this study was to make improvements in the laboratory to treatments explored in the field trial. We found that C. ledifolius seed responded inconsistently to treatments applied in the lab. The 15-minute acid scarified seed in combination with various GA3 seed coatings had significantly higher germination than untreated seed in one trial but had no difference in a second trial. Overall, these results indicate that seed enhancement technologies have the potential to improve C. ledifolius emergence in reclaimed mine lands, but additional research is needed to understand the species' dormancy characteristics better and improve the efficacy of the applied seed treatments.
108

Influence of Seed Treatment on Tobacco Mosaic Virus Incidence in Tobacco Seedlings and Virus Distribution in Greenhouse Transplant Production

Loveday, Rachel Ellen Leonard 25 April 2007 (has links)
Tobacco mosaic virus (TMV) is an economically important pathogen that has been studied for over one hundred years. Seedlings, seed coats, and nutrient solution were assayed for the presence of the virus and seed treatments were tested on seeds. Double antibody sandwich enzyme-linked immunosorbent assay (DAS ELISA) and biological local lesion assay data were collected. Seed coats from seed collected from TMV infected plants were always positive for TMV regardless of chemical treatment. Seed from infected source plants have lower germination than seed from healthy plants. Trisodium phosphate and hydrochloric acid treatments reduced virus infection of seedlings when grown under controlled conditions. Virus particles were serologically and biologically detected in both the leaves and roots of seedlings mechanically inoculated with TMV. Nutrient solution collected from 28 day old seedlings, 12 days post inoculation, tested positive for biologically active TMV by ELISA and infectivity assay. Infected water in float bed production could facilitate viral movement to all seedlings sharing nutrient solution. Seed transmission of TMV was shown to occur at a rate of 0.2%. This is in contrast to other research attempting to demonstrate seed transmission where visual symptoms on seedlings have been used to assess seed transmission. / Master of Science
109

Biology and ecology of Ambrosia Trifida L. seedling emergence

Schutte, Brian J. 16 July 2007 (has links)
No description available.
110

Harvest Weed Seed Control: An Integrated Weed Management Strategy for Organic and Conventional Production Systems

Haring, Steven C. 07 September 2017 (has links)
Harvest weed seed controls (HWSC) destroy weed seeds that are retained by the plant at crop harvest, which would typically be spread by the harvester along with other field residues. HWSC exploits coincidental maturity between crops and weeds, so an experiment was designed to collect weed seeds as they shatter throughout the growing season and through a simulated harvest delay. This experiment monitored four economically important broadleaf species and two grass species in a soybean (Glycine max (L.) Merr.) field. Results indicated that broadleaf species shattered seed at rates accelerating through the growing season, while grass species shattered more seed early in the growing season. Field experiments in organic and conventional winter wheat (Triticum aestivum L.) fields infested with Italian ryegrass (Lolium perenne L. ssp. multiflorum (Lam.) Husnot) compared two HWSC techniques to grower-standard weed management programs in each system, including both no-till and full-till standard treatments in the conventional system. Italian ryegrass populations were monitored, and wheat yield was measured both before and after HWSC application. In both organic and conventional cropping systems, HWSC treatments did not provide better Italian ryegrass control than the grower-standard treatments. The conventional program including tillage boosted Italian ryegrass populations. These results suggest that HWSC treatments did not enhance Italian ryegrass control compared to grower-standard practices in either the organic or conventional systems. Additionally, broadleaf weeds may retain enough seeds to be viable targets for HWSC. Incorporating best practices, such as a timely crop harvest, is key for understanding and optimizing HWSC. / Master of Science / Harvest weed seed controls (HWSC) destroy weed seeds that the weed plant retains at the time of crop harvest. On a typical farm, these weed seeds pass through the crop harvester and get spread across the field along with other plant materials. HWSC directly targets weed seeds, differentiating itself from normal weed management practices, such as herbicides, that kill emerging or emerged weed plants. With HWSC, weed seeds never enter the soil seed bank, thus depleting weed populations over time. HWSC works through mechanical means, such as crushing, burning, or removal. For conventional farmers battling herbicide resistant weeds, HWSC can provide effective weed management by diversifying weed management programs. HWSC also has promise as a new chemical-free weed management for organic farmers. HWSC relies on crops and weeds having coincidental maturity; seeds released from the plant (shattered) before crop harvest cannot be targeted by HWSC. An experiment was designed to collect weed seeds weekly as they shatter throughout the growing season, continuing until three weeks after the ideal date to harvest crops, thereby simulating a situation where weather or logistical factors prevented a timely crop harvest. This experiment monitored four broadleaf species and two grass species that infest soybean fields. Broadleaf species shattered seeds at increasing rates throughout the soybean growing season, with each species shattering over 50% of captured seed during the simulated harvest delay. Compared to broadleaf weeds, grass species shattered relatively more seed early in the growing season. This experiment indicates that broadleaf weeds may be more suited to control by HWSC. HWSC was also used in organic and conventional winter wheat fields infested with Italian ryegrass. These experiments compared two HWSC techniques, windrow burning of field residue and residue removal to standard weed management programs in each system. Windrow burning incinerates field residues, eliminating weed seeds within. Residue removal takes all field residues off the field for disposal elsewhere. While the standard organic weed management program involved tillage by default, the conventional cropping system featured both no-till and full-till standard weed management programs. Italian ryegrass populations were monitored through population counts, biomass collections, and counting of seed remaining at harvest. Wheat yield was also recorded. These measurements were taken both before HWSC application and after the first year of HWSC, to compare year-to-year changes. In the organic cropping system, Italian ryegrass populations grew and wheat yield decreased at similar rates for both HWSC treatments and the standard weed management program. In the conventional cropping system, Italian ryegrass populations declined and wheat yield increased for HWSC and the no-till standard treatments. Tillage, however, boosted Italian ryegrass populations, keeping them at similar levels to the previous growing season. These results suggest that HWSC treatments did not enhance Italian ryegrass control compared to standard practices in either the organic or no-till conventional systems. Though these results indicate that broadleaf weeds may retain enough seeds to be viable targets for HWSC, more research is needed to optimize HWSC for Italian ryegrass control, especially for organic growers. Incorporating best agricultural practices, such as a timely crop harvest, is key for improving HWSC’s efficacy. Commercial implementation of HWSC depends on further understanding of how specific HWSC practices, such as windrow burning, interact with the agricultural landscape, including effects on landscape aesthetics and soil nutrition. HWSC holds promise for diversifying weed management and limiting reliance on herbicides, but its true potential is yet to be revealed.

Page generated in 0.0441 seconds