Browsing by Subject "Herbicides"
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Item A study of five methods to re-treat sprayed mesquite(Texas Tech University, 1969-08) Weddle, Jon PaulNot availableItem Community response to use of prescribed grazing and tebuthiuron herbicide for restoration of sand shinnery oak communities(2012-05) Zavaleta, Jennifer; Boal, Clint W.; Haukos, David A.; Cox, Robert D.; Perry, GadThe sand shinnery oak (Quercus havardii) mixed-grass community is an isolated, relict habitat located within short-grass prairie of the Southern High Plains. With the introduction of center-pivot agriculture, unmanaged grazing, oil and gas exploration and suppression of the natural fire regime, the vegetation composition of the shinnery oak community has changed during the past century. While some areas have become dominated by a monoculture of shinnery oak, the absolute amount of shinnery oak has been drastically reduced. This is particularly disconcerting not only because native biodiversity is lost, but also because this area is home to a number of species of conservation concern including the lesser prairie-chicken (Tympanuchus pallidicinctus), sand dunes lizard (Sceloporus arenicolus), and Cassin’s sparrow (Aimophia cassinii). Land managers have used herbicides (e.g., tebuthiuron) and a variety of grazing systems as tools to manage shinnery oak. However, very little research has been done to test how these tools can be used to restore an altered shinnery oak-grass community to pre-settlement standards of species composition. This thesis tests the community response in terms of abiotic factors; plant composition, structure and production; and mammal, herptile, and invertebrate community responses in terms of abundance, dominance, and diversity to a designed restoration effort from 2000-2011. The primary objectives were to (1) determine the variable response to tebuthiuron and grazing treatments, (2) assess the temporal response of the variables to the use of four treatment combinations over a 12-year period, and (3) compare resultant vegetation composition to historical standards. In Roosevelt Co, New Mexico, on the Southern High Plains, 532 ha of private land were treated with tebuthiuron (rate of 0.60 kg/ha with dune avoidance) in 2000. The state of New Mexico owned 518 ha of adjacent land, representing extant shinnery oak community (experimental control). This application rate was approximately 50% of previously recommended rates because the goal was to reduce shinnery oak to historical levels, not to eliminate it. A moderate grazing treatment was designed to take a maximum of 50% of the annual herbaceous production. To allow for inference beyond the study site, the experimental design was a combined completely randomized design with a systematic application of treatments following random assignment of initial treatment combination. The four treatments were treated/grazed, treated/not grazed, not treated/grazed, and not treated/not grazed. There were four replicates for the four treatments, totaling 16 plots. To remove the variation of year-to-year precipitation on the effect of tebuthiuron and grazing, I first ranked precipitation variables (based on two winter, growing and annual precipitation indices) and then used an analysis of variance with precipitation as a covariate. Plant and abiotic variables include soil moisture; line intercept data that was used for percent composition of shrubs, grasses, forbs, litter, bare ground, percent shinnery oak and sand bluestem (Andropogon gerardii) grass; Robel pole heights to measure visual obstruction; angle of obstruction to measure overhead obstruction; herbaceous production; and seed production for dropseed species (Sporobolus spp.), bluestems (Andropogon spp.), sand paspalum (Paspalum maritimum), and gramas (Bouteloua spp.). Small mammals and herptiles were trapped from May to September with 800 trap nights and 960 trap nights per plot per year from 2002-2010. Mammals were trapped with Sherman live traps and herptiles were trapped with pitfall and funnel traps. Abundance, dominance, diversity and the three most abundant mammals - kangaroo rat (Dipidomis ordii), spotted ground squirrel (Spermophilus spilosoma), and pocket mouse species (Perognathus spp.) - and herptiles (prairie lizard (Sceloporus lecontei), Great Plains skink (Eumeces obsoletus), and coachwhip (Masticophis flagellum)) were variables used in analyses. Invertebrates were collected in April and June with a terrestrial vacuum sampler. Invertebrate abundance, biomass, and number of taxonomic families as well as biomass of the three most abundant (grasshoppers (Acrididae), treehoppers (Acrididae), and caterpillars (Lepidoptera larvae) were variables used in analysis. My results show that at relatively low levels of tebuthiuron (0.60 kg/ha) and subsequent moderate grazing system, sand shinnery oak can be reduced and maintained at near historical levels without reapplying tebuthiuron because the tested management approach allowed grasses to remain competitive in the system. Over the ten years, there was 91% less shinnery oak in untreated areas. The removal of shinnery oak made environmental soil moisture more available for grasses and forbs to germinate and grow. Indeed, grasses increased by 149% and forbs increased by 257% in treated areas as compared to untreated areas throughout the study period. In terms of visual obstruction, there was both an herbicide and grazing effect in April such that visual obstruction increased by 30% in treated areas as compared to untreated and decreased by 6.5% in grazed areas as compared to non-grazed areas. Similarly, there was an herbicide and grazing interaction effect such that treated areas had a 14% decrease in overhead obstruction in grazed areas and non-treated areas had only 10% less in grazed areas as compared to non-grazed areas. These changes in plant composition and structure increase biodiversity such that there are more available niches to fill. The results from mammal, herptile, and invertebrate data indicated that species react on an individual basis to herbicide and grazing combinations, so the treatments yielded mixed results. I found no significant herbicide effect of overall abundance of small mammals. However, there was a significant grazing effect such that there was 23% more abundance of small mammals in grazed areas as compared to non-grazed areas, which was likely driven by kangaroo rats. In terms of herptile abundance, there was an interaction effect such that more lizards were found in treated/non-grazed and not treated/grazed areas. This mixed result indicates that species act individually in response to herbicide and grazing. Invertebrates, for the most part, responded positively to herbicide treatment and negligibly in terms of grazing, presumably due to increases in forbs. Areas that were treated with tebuthiuron and had moderate grazing statistically reached historical standards only during one year, but showed trends that were comparable to historical standards throughout the study compared to other treatment combinations. The largest difference between treated areas and historical standards was that treated areas had more forbs. This may not necessarily be interpreted as a bad thing because increase in invertebrates due to forb presence indicates good habitat quality and increases food sources for animals higher on the food chain. With low rates of tebuthiuron (0.60 kg/ha) and moderate levels of grazing, shinnery oak communities can approach historical standards and provide the most plant composition diversity. With moderate levels of grazing, shinnery oak will not need to be re-treated as grasses remain competitive in the system. With the removal of shinnery oak, there is increased soil moisture such that grasses and forbs can establish. The change from a shrub monoculture to a mixed-grass prairie changes the plant composition and structure and provides more niches for invertebrates, mammals and herptiles to fill. Treatment with tebuthiuron at low doses is the first step in managing shinnery oak communities; however, given the incredible, absolute loss of shinnery oak managers should be cautious about treating all shinnery-oak dominated areas.Item Cotton and grain sorghum response to drift rates of glyphosate(Texas Tech University, 2004-08) Lyon, Leanna LNot availableItem Crop and Weed Response to Application Rates and Dates of Dinitroaniline Herbicides(Texas Tech University, 1977-12) Keeling, WayneNot Available.Item Differential responses of perennial weeds to glyphosate(Texas Tech University, 1979-08) Chykaliuk, Peter BohdanNot availableItem Dimethyl sulfoxide and chemical bud stimulation to increase herbicide activity in mesquite(Texas Tech University, 1969-12) George, Melvin RNot availableItem Effects of benefin on lettuce grown at varying levels of Nob3s, C1 and SOb4s(Texas Tech University, 1973-08) Christie, Charles JNot availableItem Efficacy and crop tolerance to diclosulam in west Texas peanut(Texas Tech University, 2002-05) Karnei, Jarred RNot availableItem Efficacy and persistence of five dinitroaniline herbicides.(Texas Tech University, 1975-08) Berner, Richard CarlNot availableItem Enhanced control of mesquite with NAA following shredding.(Texas Tech University, 1974-08) Beck, Danny LeeNot availableItem Evaluation of weed control and economic benefit of a light-activated sprayer in cotton(Texas Tech University, 2003-12) Peters, D AlanField experiments were conducted from 2000-2002 to evaluate weed control and economic performance of a light-activated sprayer (LAS) m cotton. Herbicide treatments were applied with a broadcast sprayer, a conventional hooded sprayer (OS) or LAS. Treatments included prometryn at 1.34 kg ai/ha preemergence followed by (fb) cultivation as needed (ASN); glyphosate at 1.12 kg ai/ha applied postemergence over-the-top (POT) at the four-leaf growth stage of cotton fb glyphosate at 1.12 kg ai/ha applied with CS ASN; glyphosate at 1.12 kg ai/ha applied POT at the four-leaf stage fb glyphosate at 1.12 kg ai/ha applied with LAS ASN; and glyphosate at 1.12 kg ai/ha applied in a 36-cm band over the row at the four-leaf stage plus glyphosate at 1.12 kg ai/ha applied with LAS fb glyphosate at 1.12 kg ai/ha applied with LAS ASN. Weed control was evaluated 14 and 28 days after the last treatment was applied (DAT). Herbicide savings were calculated by measuring the amount of spray solution in the tank before and after treating each LAS-treated plot. Economic analysis included total specified expenses and fixed expenses (irrigation maintenance and hooded sprayer cost); and returns above total specified expenses, derived from the sale of cotton lint and seed. The light-activated sprayer generally controlled weeds similar to the conventional sprayer and better than cultivation, regardless of whether a band or broadcast application of glyphosate was made at the 4-leaf growth stage of cotton. The additional cost of LAS was offset by reductions in herbicide use; however, net returns were not increased when compared to a conventional sprayer. Additional research was conducted to investigate the potential for plant species differentiation by spectral reflectance. Reflectance was measured using sixteen wavelengths for two crops and four weed species at two growth stages. When small plants were measured, wavelengths 600, 630, 650, 670, 700, 1600, and 1700 nm revealed no similarities between species. At wavelengths 450,470, 630, 650, and 670 nm, data revealed that reflectance of large cotton plants was different from every weed species evaluated. Wavelengths were identified that have potential for use in species differentiation by spectral reflectance measurements.Item Foliar and soil activity of four selective grass herbicides(Texas Tech University, 1983-08) Bean, Brent W.Not availableItem Follow-up spraying on burned and shredded mesquite(Texas Tech University, 1971-08) Karr, Bob LewisNot availableItem Glufosinate-tolerant cotton: tolerance and weed management(Texas Tech University, 1999-12) Blair, Lesli KristenField studies conducted in 1997 and 1998 examined plant growth and development, yield and fiber quality of glufosinate-tolerant cotton. Regardless of glufosinate application rate, number of applications, or cotton growth stage at application, no visual injury nor adverse effects on cotton development, yield or fiber quality were observed. Amaranthus palmer! and Proboscidea louisianica control in glufosinate-tolerant cotton using preplant incorporated, preemergence and postemergence-topical herbicide applications with and without cultivation was examined also. Amaranthus palmeri and Proboscidea louisianica was controlled at least 90% when trifluralin preplant incorporated followed by prometryn preemergence followed by glufosinate postemergence was applied. These weeds were controlled 0 to 100% following soil applied herbicides alone and 47 to 99% following glufosinate alone. This research indicated that the transformation events for glufosinate-tolerance in Gossypium hirsutum L. cv. 'Coker 312' were successful and the gene expressing glufosinate-tolerance was expressed throughout the growing season. In addition, Amaranthus palmeri and Proboscidea louisianica control was greater when glufosinate was used in combination with soil applied herbicides as opposed to glufosinate applied alone.Item Herbicidal control of individual honey mesquite trees(Texas Tech University, 1988-05) Dumesnil, Mark JNot availableItem Herbicide fallow considerations on sandy soils(Texas Tech University, 1983-12) Armstrong, Rachel BordenNot availableItem Movement and persistence of two substituted phenylurea herbicides in selected High Plains soils(Texas Tech University, 1970-08) Fickle, James SNot availableItem Movement and persistence of two substituted phenylurea herbicides in selected High Plains soils(Texas Tech University, 1970-08) Fickle, James SNot availableItem Oenothera elata: Economics and best management practices for commercial production(2012-05) Bonds, Amber N.; McKenney, Cynthia B.; Wester, David B.; Henry, Gerald M.; Montague, David T.; Johnson, JeffOenothera elata Kunth, Hooker’s evening primrose, is a biennial to short-lived perennial found in a variety of habitats ranging from xeric to mesic. Currently it has limited use in landscapes. A similar species, Oenothera biennis L. or common evening primrose, is currently grown as a nutraceutical crop. The seed oil contains gamma linolenic acid (GLA), which has been used to treat ailments including eczema, arthritis, auto-immune disorders, and high cholesterol. Most primrose production is in China, because of the cooler climates which allow for increased GLA in the seed. Hooker’s evening primrose is found in warmer climates and has a similar oil profile to that of common evening primrose when grown in Lubbock, TX. This may mean there is potential for Hooker’s evening primrose production as a niche crop in this area. Best management practices must be established and cost of production must be determined before production can increase. Therefore, objectives of this research were 1) to determine spacing, irrigation, and fertility requirements for this species, 2) to evaluate several pre- and postemergence herbicides for use in O. elata production, 3) to determine most efficient harvest practices by evaluating different harvest methods and defoliants, and 4) to determine cost of production. Research was conducted at the Texas Tech University Greenhouse complex and the Texas Tech University Plant and Soil Science Research Farm in Lubbock, TX. All experiments were replicated twice throughout the 2009-2011 growing seasons. To determine irrigation, spacing, and fertility needs an experiment was set up as a split-split plot design with irrigation (33%, 66% or 100% ET) as the main plot, spacing (0.3 m, 0.6 m, or 0.9 m) as the sub-plot, and fertility (133.79 kg N ha-1, 89.19 kg N ha-1, 44.60 kg N ha-1, and 0 kg of N ha-1) as the sub-sub plot. This experiment had six blocks and every combination was represented once in each block. Data taken included: yield, visual appearance on a criterion reference scale of 1-10, number of flowers, plant growth index (PGI), and percent floral density. Pre- and postemergence herbicide trials were set up as a randomized complete block design with five replications. These experiments were conducted in the greenhouse. Data were recorded for O. elata phytotoxicity, plant biomass, and PGI. For the postemergence herbicide experiment 4 month old seedlings were placed in containers and acclimatized for 28 days before treatment with one of the following herbicides: glyphosate, glufosinate, fenoxaprop, fluazifop, sulfosulfuron + non-ionic surfactant, quinclorac + methylated seed oil, mesotrione, and quinclorac + mecoprop + dicamba + methylated seed soil. For preemergence herbicide studies applications of oxadiazon, isoxaben, oryzalin, prodiamine, dithiopyr, metolachlor, pendimethalin, and isoxaben + trifluralin were applied two days prior to the transplanting of four month old O. elata seedling. To determine harvest practices, two different experiments were set up as a randomized complete block design. Both experiments had 4 blocks and each treatment was represented once within a block. One experiment compared yield after the use of three defoliants [Paraquat, (Ethephon + Cyclanilide) + (Thidiazuron + Diuron), and Ethephon] to a non-treated control. The other compared yield of two different harvest methods (hand and Hege combine). Cost of production was determined using best management practices investigated in the previous trials. Data suggest Hooker’s evening primrose planted at 0.9 m spacings will increase appearance, flower number, PGI, and floral density. This spacing will not decrease yield. Irrigation equivalent to 66% reference evapotranspiration (ETo) increased appearance, PGI, and number of flowers in times of drought, but will not influence yield. Fenoxaprop and fluazifop may be used as postemergence herbicides without excessive phytotoxicity or reduction in growth. All preemergence treatments except trifluralin + isoxaben exhibited low phytotoxicity and will not reduce growth. Machine harvesting does not decrease yield and should reduce the cost of production. Defoliants can be used to harvest this species without a loss in yield. Paraquat and (Ethephon + Cyclanilide) + (Thidiazuron + Diuron) may be preferred over Ethephon alone. Cost of production is estimated at $1906.89 per acre. Growers will need to receive approximately $0.48 per pound in order to break even.Item Performance and economics of cotton weed management systems for the Texas Southern High Plains(Texas Tech University, 1998-05) Asher, Brady ScottIn the United States, approximately 30 plant species that infest cotton fields are economically important weeds. Nearly three-fourths of the losses m cotton can be attributed to 10 types of weed species: momingglory species (Ipomoea spp.), common cocklebur (Xanthium strumarium), pigweed species (Amaranthus spp.), Johnsongrass (Sorghum halepense), nutsedge species (Cyperus spp.), bermudagrass (Cynodon dactylon), prickly sida (Sida spinosa), silverleaf nightshade (Solanum elaeagnifolium), croton species (Croton spp.), and sicklepod (Cassia obtusifolia). AU of these weeds except prickly sida, croton species, and sicklepod are found in the southwest United States (Frans and Chandler 1989). Without herbicides, United States cotton producers could face a 32% yield reduction due to weed competition (Abemathy 1981). Current preplant and preemergence herbicides control many small-seeded broadleaf weeds and annual grasses, but weeds not effectively controUed by current herbicides are an increasing problem. The development of transgenic cotton varieties and the registration of a new postemergencetopical (FT) herbicide offer improved potential for effective and economical control of many troublesome weeds on the Texas Southern High Plains. Weed management systems utUizing glyphosate(Roundup Ultra) along with existing herbicides provide options to control weeds in conventional and reduced tillage, make applications during a wide window of cotton development, economically control a broad spectmm of weeds, and control weeds m an environmentally sound manner (Vidrine et al. 1996). Glyphosate is a non-selective herbicide that wiU control both annual and perennial grass and broadleaf weeds. Roundup Ready cotton varieties, which are resistant to glyphosate, were first available for wide-spread commercial planting in 1997. These new transgenic varieties aUow fanners to apply glyphosate PT through the 4-leaf stage and postemergence-duected (PD) until 20% open bolls.