Browsing by Subject "Precision farming"
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Item A comparison of the performance and perceptions of students receiving live versus web-based horticultural instruction(Texas Tech University, 2003-12) Teolis, IginoThe primary purpose of this dissertation was to examine whether the level of student learning in horticulture was equivalent in both web-based and traditional live instruction and to compare perceptions of students towards different modes of instruction. The research also investigated whether performance and perception were related to students' learning styles and other characteristics. The study in Chapter II addressed whether student performance and perceptions differed between the web-based and traditional versions of an introductory horticulture course. The increase in quiz scores from pre- to post-course surveys suggested that students receiving traditional instruction acquired more knowledge than did web-based students. Traditional course students felt that their course was more of an adequate learning experience than did web-based students. Web-based students' preference for instructional mode changed from web-based to traditional during the semester. Preferences towards reflective, factual, verbal and linear learning styles were positively correlated with final grades in the traditional course. Pre-course quiz score, GPA, age, and distance living from campus were correlated with final grades in both instructional modes. The study in Chapter III investigated whether students were able to identify plants after studying the plants online just as well as after studying them traditionally at the greenhouse. Students in the traditional group had greater total quiz scores than web-based students. Students were able to identify plants from photos just as well as from live plant specimens. In Chapter IV, the experiment addressed whether student comprehension was different among three methods of delivery after receiving a lesson on a topic that was either predominantly text-based (photosynthesis) or object-based (plant identification). The three delivery methods were: (1) independent learning using a text handout, (2) traditional learning involving a summary lecture and a text handout, and (3) independent web-based learning with the lesson on the computer. There were no differences in student performance (where multiple choice tests and concept mapping tests were treated as a within-subjects factor) among the three delivery methods and no interaction between topic and delivery method. Participants generally had greater scores on the multiple choice tests than on the concept mapping tests where they had difficulty recalling the concepts they learned. The study in Chapter V addressed whether student performance and perceptions were equivalent between disabled and non-disabled students receiving traditional or web-based horticultural instruction. Non-disabled students had greater final grades, expressed less frustration and found the course more acceptable than did their non-disabled counterparts in both modes of instruction. Non-disabled learners preferred factual and linear learning styles to a greater extent than did the disabled students within both modes of instruction. The higher grades and lower frustration levels of non-disabled students may be due to the instruction being more suited to their learning styles than those of disabled students, regardless of the instructional mode.Item Economic and environmental evaluation of precision farming practices in irrigated cotton production(Texas Tech University, 2000-05) Yu, ManNot 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 Influence of varying replacement of potential evapotranspiration on water use efficiency and nutritive value of three Old World bluestems (Bothriochloa spp.)(Texas Tech University, 2004-05) Philipp, DirkForage systems offer alternatives to traditional cropping systems in the Texas High Plains, but information on water management is lacking. This research investigated whether differences in water use efficiency (WUE; kg total seasonal dry matter [DM] yield ha"' mm"' water [precipitation, irrigation, and soil water depletion]) existed among species of old world bluestems (Bothriochloa spp.). Additionally, effects of irrigation amounts on forage nutritive value and plant morphology were explored. Established stands of three Bothriochloa species ('Dahl' [bladhii]; 'Caucasian' [caucasica]; and 'Spar' [ischaemum]) were surface drip-irrigated weekly during the growing season to replace: 1) 0% (dryland); 2) 33% (low); 3) 66% (medium); and 4) 100% (high) of potential evapotranspiration minus precipitation during 2001,2002, and 2003. Soil organic carbon as influenced by irrigation level and optimum metabolic temperature for growth were investigated in 2003. Each species and water treatment was replicated three times in a complete randomized block design with a split plot treatment arrangement. In 2001 and 2002, no differences in water use efficiencies among species were found. Averaged across these 2 yr, WUE of 19.0, 19.3, and 15.3 kg ha"' mm"' were observed for Caucasian, Dahl, and Spar, respectively. In 2003, Caucasian produced 16.9 kg ha" mm', differing (P < 0.05) in slope fi-om Spar (7.4 kg ha"' mm"') but Dahl (12.4 kg ha"' mm"') was not different in slope from either Caucasian or Spar. Maximum seasonal DM yield was obtained with Caucasian under high irrigation (18.0 Mg ha"') vs. Dahl (15.2 Mg ha") and Spar (12.55 Mg ha"') averaged over all years. Percentage dry matter digestibility (DMD) was higher (P < 0.05) in all forage species irrigated at a low level (58% DMD) than for other water treatments (57, 56, and 55% DMD for dryland, medium, and high irrigation, respectively). Dahl generally averaged higher (P < 0.05) percentage crude protein (CP) than other species during the growing season. More differences in percentage CP were observed between dryland and irrigated forages than within the irrigated treatments but CP would have met nutritional needs of most livestock only in May. In all species, percentages total nonstructural carbohydrates (TNC) and DMD and leaf: stem ratio declined while percentage cell wall increased with increased irrigation amount in the first half of the growing season. Effects of irrigation on cell wall, TNC, and DMD appeared related to changes in plant morphology (leaf:stem) and to an increase in physiological age as indicated by growth stage (mean stage count and mean stage weight). Leaf:stem ratio following hay harvest in July showed fewer effects of irrigation treatments but ratios of live:dead plant material generally increased during the growing season in response to increased irrigation (linear effects; P < 0.05). Soil organic carbon was higher (P < 0.05) in all irrigated soils (5.5 g 100 g"') compared with dryland (4.6 g 100 g"') but did not differ among irrigation treatments. Optimum metabolic temperatures for growth of Caucasian, Spar, and Dahl old world bluestems were 24, 24, and 28°C, respectively. Our data suggest that differences in WUE among Bothriochloa species can be identified, and that yield, chemical composition, and morphology can be manipulated through irrigation management to optimize total nutrient yield and nutritive value.Item Potential efficacy of mite resistant genes in corn topcrosses and improvement of resistance in crosses with specific resistance traits(Texas Tech University, 2003-12) Bynum, Edsel DSpider mites significantly reduces yield of maize, Zea mays L., grown in the Great Plains States. Determining the genetic performance of mite-resistant lines is important in developing resistant hybrids. Studies were conducted at either Lubbock, TX or Halfway, TX in 1997, 1998, 2001, and 2002 to evaluate the efficacy of resistance and agronomic performance of testcrosses with B73 and Mo 17. Resistant inbred lines (SI, S2, S3, S4, S5, S7, and S9), testcrosses, check inbred lines (B73 and Mo 17), and check hybrids (B73 X Mo 17 and Pioneer 34K77) were arranged in randomized block design with three replications. Analysis showed that the effects of environment, entry, environment x entry interaction was significant for mite density. Environment and entry effects were significant for damage ratings and mite per damage (M/D). Heritability on a mean basis was 73%, 80%, 86%, and 87% for total mite density, M/D, total damage rating, and seasonal damage ratio, respectively. Testcrosses had less damage than check hybrids. Testcrosses (SI x B73, S2 x B73, S5 x B73, S2 x Mol7, and S3 x Mol7) significantly reduced damage, and S7 x B73 and S7 x Mol7 had highly significant reductions in damage. All testcrosses, except SI x Mol7, S5 x Mol7, and S9 x Mol7, had grain yields statistically similar to check hybrids. A Griffmg's diallel mating design was used to evaluate range of resistance, combining ability and agronomic traits of resistant F1 crosses. Analysis of DR was significant for environments, entry, and environment x entry interaction. Mite density and M/D was significant for entry x environment interaction. Seasonal damage ratios were significant for environment and entry, but not interactions. Heritability showed that > 90% of the damage was associated with genotypic effects. Crosses with SI, S2, and S9 had more mites, but had higher M/D values than S3, S4, S5, and S7, indicating greater tolerance to mite feeding. Crosses between tolerant lines or tolerant x antibiotic lines resulted in better resistance than crosses between antibiotic lines. S1 and S2 had the highest general combining ability for reduce damage. SI x S4, SI x S7, S3 x S5, and S4 X S7, were the best crosses for specific combining ability for resistance to spider mites.Item The economics of precision farming in the Texas High Plains(Texas Tech University, 2002-12) Watson, Susan ElizabethNot available.Item Transformation of cotton plants through an alternate DNA delivery approach(Texas Tech University, 2003-12) Xiang, ZhixinThe objective of this research was to introduce chitinase and â-l,3-glucanase genes into cotton to improve resistance to fungal pathogens through the pollen tube pathway-mediated transformation (PTP). To confirm the success of this method, DNA of a plasmid pRTL2-GUS containing uidA (coding sequence for â-glucuronidase) was introduced into cotton (Gossypium hirsutum L.) 'Paymaster HS26', 'Stovepipe', and 'CA3048'. Seeds formed from treated flowers were allowed to mature on the plants. Seedlings grown from seeds harvested from treated flowers were screened for the presence of uidA by PCR and GUS (â-glucuronidase) expression by histochemical assay. The overall transformation frequency was 11.7 %. Southem hybridizations of T1 progeny confirmed that the uidA transgene was integrated into the cotton genome. GUS expressions were detected in the plants of two generations. In T2 progeny, GUS segregation of uidA followed the expected 3:lMendelian genetic ratio. Our results confirmed transformation of uidA via PTP. Chitinases and â-1,3-glucanases have been used in transgenic plants to improve resistance to pathogens. In this study, fertile, transgenic cotton (Gossypium hirsutum L.) plants expressing a bean chitinase and an Arabidopsis â-l,3-glucanase were generated using pollen tube pathway-mediated transformation system. Ch5b from Phaseolus vulgaris L. and bg2 from Arabidopsis thaliana L. were cloned into plasmid pRTL2 driven by the CaMV 35S promoter. The transgenes ch5b and bg2 were successfully delivered into two breeding lines of cotton. Southern blot and slab blot analyses of DNA isolated from T2 progeny demonstrated that the transgenes were stably integrated into the genome of transgenic cotton plants and inherited by the offspring. Expression of the chitinase and â-1,3-glucanase gene was detected in transgenic T2 cotton plants. Transgenic T2 and T3 plants examined for resistance to the fiingal pathogen Rhizoctonia solani Kuhn in a growth chamber exhibited less root rot and fewer hypocotyl lesions than non-transgenic control plants. Greenhouse screening tests indicated that the ability to resist the fungal pathogen R. solani increased in these plants. Our results suggest that the chitinase and â-l,3-glucanase genes functioned in cotton and were expressed in fertile plants. The pollen tube pathway transformation strategy may be useful for the control of other fungal diseases of plants.