• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 177
  • 7
  • Tagged with
  • 187
  • 187
  • 113
  • 34
  • 29
  • 29
  • 27
  • 24
  • 24
  • 20
  • 20
  • 20
  • 17
  • 17
  • 16
  • 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.

Palmer amaranth control in established alfalfa and documentation of glyphosate-resistant Amaranthus species in Kansas

Putman, Joshua Adam January 1900 (has links)
Master of Science / Department of Agronomy / Dallas Peterson / Palmer amaranth is a troublesome weed that competes for water, nutrients, and sunlight in many cropping systems throughout the United States. It is a serious production problem for alfalfa growers in the southern Great Plains region because of extended germination and impact on forage quality and yields. Glyphosate has been used extensively to control Palmer amaranth but control has become difficult. The objectives of this research were to (1) evaluate various herbicide treatments for Palmer amaranth control in established alfalfa, (2) confirm the presence and scope of glyphosate-resistance in common waterhemp and Palmer amaranth populations in eastern Kansas, and (3) to characterize glyphosate-resistance in two Palmer amaranth populations from south central Kansas. Residual Palmer amaranth control in alfalfa varied among herbicide treatments. The best late season Palmer amaranth control was accomplished with sequential treatments that included flumioxazin at 140 g ha-1 or diuron at 2,690 g ha-1 as dormant applications followed by a between cutting treatment of flumioxazin at 70 g ha-1, which was still providing 85 to 96% control in late summer. Several other treatments provided good early season Palmer amaranth control, but control diminished as the season progressed. Palmer amaranth emerges throughout the growing season and therefore, sequential herbicide treatments with good residual activity may be necessary for season-long control. Greenhouse studies indicated that glyphosate-resistant common waterhemp is present throughout eastern Kansas with several populations that survived glyphosate up to two times the suggested use rate. Glyphosate-resistant Palmer amaranth was documented in several populations collected from various counties throughout Kansas. Two populations collected in south central Kansas in 2011 survived up to eight times the typical field use rate of glyphosate. Six more populations collected in 2012 displayed similar resistance characteristics with three populations surviving up to four times the typical rate of glyphosate. Shikimate assays on susceptible and resistant Palmer amaranth biotypes confirmed resistance to glyphosate.

Productivity and quality of smooth brome pastures under continuous, rotational, and mob grazing by sheep

Humerickhouse, Natalie January 1900 (has links)
Master of Science / Department of Agronomy / Peter J. Tomlinson / In recent years, an alternative grazing method to continuous and rotational methods has gained popularity among producers and has been termed mob grazing. Mob grazing uses high animal densities grazing for a short period of time. The objectives of this study were to determine the impact of continuous, rotational, and mob grazing on forage production and the quality of smooth bromegrass (Bromus inermis Leyss), along with soil dissolved organic carbon (DOC), microbial biomass carbon (MBC), and dehydrogenase enzyme activity. Twelve paddocks, 4 continuous (40 X 10 m), 4 rotational and 4 mob (15 X 10 m), were designated at the Kansas State University Sheep and Meat Goat Center in Manhattan, KS. Forage quality samples were collected by hand clipping randomly throughout the paddock. Neutral detergent fiber (NDF) and acid detergent fiber (ADF) were determined using ANKOM technology and crude protein (CP) content was calculated by multiplying total nitrogen determined by combustion by 6.25. Soil samples were extracted with 0.5 M K2SO4 and analyzed for DOC and MBC using the chloroform-fumigation-extraction method and soil dehydrogenase activity using the colorimetric method. Forage quality declined as the spring grazing season progressed in all treatments. Sheep grazed higher quality forage in the continuous and rotational treatments in the period prior to the spring mob grazing event. No treatment differences were found for DOC, MBC, dehydrogenase, or total forage biomass accumulation. Dissolved organic carbon and soil biological parameters have not been altered by the grazing management. Forage quality was found to be poorest in the mob treatment at the time of grazing. The mob treatment accumulated the greatest amount of aboveground biomass prior to grazing, however season-long total biomass accumulation was not different from the other treatments. Based on this research, in the short-term, there are no advantages of mob grazing over rotational grazing.

Growing crops for biofuel and forage while conserving soil and water

Evers, Byron J. January 1900 (has links)
Master of Science / Department of Agronomy / Humberto Blanco / The use of renewable feedstocks to produce cellulosic ethanol is quickly becoming a reality as facilities to produce cellulosic ethanol are scheduled to open in the upcoming years. Initial feedstocks for these facilities are thought to be crop residues such as corn (Zea mays L.) and wheat (Triticum aestivum L.) residues. However, additional feedstocks, such as perennial warm-season grasses (WSG), maybe needed to meet the demands of these bioenergy facilities. Thus, the development of regional dedicated energy crop systems is a high priority. Our objectives were to: a) assess the impacts of growing WSG on water storage, soil physical and hydraulic properties, soil organic carbon (SOC) dynamics, and water and wind erosion as compared with row crops, b) assess the impacts of growing WSG on biomass and forage production and quality and c) determine the most adaptable WSG species to dryland conditions. A number of dedicated energy crops and their performance across three different moisture regimes in Kansas were studied. Biomass yield, soil physical and hydraulic properties, and soil water and wind erosion parameters were measured between August 2010 and August 2012. Additionally, forage quality under two cutting systems (biofuel and forage) and two harvest heights (0.1 m and 0.2 m) and water infiltration was determined in 2011. Differences in bulk density, water retention, infiltration and SOC were found to be minimal. However, differences in wind and water erosion parameters indicate that WSG can protect soil from erosion. Furthermore, soil water data indicate that WSG are better suited to use early season moisture to accumulate biomass than annual row crops. Yield results indicate that a two cut hay system with a 0.1 m cutting height can produce more biomass compared with a one cut biofuel system. Additionally, the hay system improved forage quality parameters. Data collected from this project provided insights into the viability of growing various dedicated energy crops across the region during the first five years of production.

Effect of genotypes and nitrogen on grain quality of sorghum

Diallo, Sory January 1900 (has links)
Master of Science / Department of Agronomy / P.V. Vara Prasad / Sorghum (Sorghum bicolor L. Moench) is cultivated as an important food grain in the semi-arid regions of Africa. Processed grain sorghum is traditionally consumed as porridge, couscous, traditional tô or beer. The quality of such foods is highly dependent upon grain characteristics. Sorghum grain quality traits mainly include kernel hardness, kernel weight, kernel size, protein content and kernel color. Grain quality traits are often influenced by environment, genotypes, fertilizer management and their interaction. The objective of this study was to determine the impact of different levels of nitrogen application (0, 45, and 90 kg ha[superscript]-1) on grain quality of selected sorghum genotypes. The field experiment was conducted at three locations in 2010 (Manhattan, Ottawa, and Hays) and at two locations in 2011 (Manhattan and Ottawa). The experiment was laid in split plot randomized complete bloc design and replicated four times. The main plots were assigned to three N regimes: control (0 kg N ha[superscript]-1), half recommended rate (45 kg N ha[superscript]-1) and recommended rate (90 kg N ha[superscript]-1). The subplots were assigned to twelve genotypes (six hybrids and six inbred lines). Plot size was 6.1 m x 3.0 m with a row spacing of 0.75 m. After harvest, grain quality traits (hardness, weight, diameter and protein content) were evaluated using standard procedures and the data subjected to statistical design using SAS. There were significant effects of genotype for most grain quality traits across both locations in Manhattan. Inbred lines SC35 and SC599 had maximum hardness at all locations while hybrid 95207, had the lowest hardness for all locations. Also, Inbred lines SC35 and Tx340 had maximum protein content at all the locations. While hybrids 95207, 26056, 23012 had the lowest protein content. Genotypes Tx430, SC35, had higher hardness and with higher protein content were classified as high quality. We conclude that application of N (45 or 90 kg ha[superscript]-1) significantly improved grain protein, but not other quality traits. There are opportunities to improve grain protein through fertilizer management and plant breeding.

Kochia control with preemergence herbicides in soybeans, dose response of three Kochia populations to glyphosate, and response of corn, soybean, and grain sorghum to saflufenacil

Hulse, Brandon Michael January 1900 (has links)
Master of Science / Department of Agronomy / Dallas Peterson / Kochia (Kochia scoparia (L.) Schrad) is a troublesome and highly competitive weed in many cropping systems in the Great Plains region. It has traditionally been controlled using postemergence (POST) applications of glyphosate, however control is becoming inconsistent. Use of preemergence (PRE) herbicides may help to control kochia. Objectives of this research were to (1) Evaluate the efficacy of selected PRE herbicides in combination with POST applied glyphosate for controlling kochia in soybeans, (2) evaluate a kochia population (Norton) response to various rates of glyphosate compared to previously characterized highly susceptible (Syracuse) and moderately resistant (Ingalls) kochia populations, and (3) quantify the effects of herbicide rate, planting depth, soil pH, and soil type on corn, soybean, and grain sorghum tolerance to saflufenacil. Field studies showed that glyphosate applied alone did not always provide adequate season-long kochia control. In general, PRE herbicide treatments provided effective kochia control. These data suggest that a sequential herbicide program with a PRE herbicide treatment followed by POST glyphosate will provide the most consistent kochia control in soybeans and help minimize the risk of developing herbicide resistant kochia. Greenhouse studies confirmed great variability in kochia susceptibility to glyphosate across three different kochia populations. In general, as glyphosate rates increased, kochia control increased with all three populations. At the field use rate of glyphosate, the Syracuse kochia population was controlled 94% 21 days after treatment (DAT), whereas the Ingalls and Norton populations were controlled 26 and 41% respectively. Nonlinear regression analysis for each population indicated the glyphosate rate required to cause 50% visible control (GR50) was 1.6, 1.1, and 0.31 times the field use rate of 870 g ae/ha for the Ingalls, Norton, and Syracuse kochia populations. Greenhouse studies indicated that soil type had the greatest impact on saflufenacil injury to corn, soybeans, and sorghum, with crop injury consistently being greater on a fine sandy loam soil with 0.9% organic matter than a silt loam soil with 3.9% organic matter. Soil pH, saflufenacil rate, and seed depth also may influence the risk of crop injury from saflufenacil, but were less important than soil type.

Variation among grain sorghum genotypes in response to nitrogen fertilizer

Mahama, George Yakubu January 1900 (has links)
Master of Science / Department of Agronomy / P.V. Vara Prasad / Grain sorghum [Sorghum bicolor (L.) Moench] is an important crop in the semi-arid regions of Africa, Asia and United States. Productivity of grain sorghum is limited by soil fertility, especially nitrogen (N). Sorghum genotypes are known to vary in their response to nitrogen, however, the information on nitrogen use efficiency (NUE) is limited. The objectives of this research were to (a) determine the response of sorghum genotypes (hybrids and inbred lines) to nitrogen fertilizer (b) quantify genotypic differences in NUE; and (c) determine physiological and morphological basis of NUE. Field experiments were conducted at three locations in Kansas (Hays, Ottawa and Manhattan) during 2010 and 2011. Six hybrids and six inbred lines of grain sorghum were grown with 0, 45 and 90 kg N ha-1.The experimental design was a split-plot design with N regimes as main plots and genotypes as sub-plot, with four replications. Planting was done in May and June across all the locations, and nitrogen fertilizer (Urea, 46% N) was applied at emergence. Data on N concentration in the leaves, stems and grain were determined. NUE and components of N use were computed for Ottawa and Manhattan as follows: Nitrogen use efficiency (NUE): Grain weight / N supplied; Nitrogen utilization efficiency: Grain weight / N total in plant; Nitrogen uptake efficiency: N total in plant / N supplied; Percent fertilizer recovery = [uptake (fertilized plot) – N uptake (un- fertilized plot)] / [ N applied ] x 100; and Nitrogen harvest index (NHI) = Grain N / N total in plant. Where N supplied = Rate of N fertilizer applied + soil N supplied. Growth and yield data were collected at all locations. There were significant effects of genotypes (P < 0.05) and nitrogen (P < 0.05) on biomass and grain yield across all locations. Performance of hybrids was generally superior to the inbred lines of all traits. Sorghum hybrids 26506 and 99480 produced maximum grain yield across all locations. While inbred lines B35 and SC35 had the lowest grain yield. Maximum biomass and grain yield was obtained at 90 kg N ha-1, followed 45 kg N ha-1, and lowest in 0 N kg ha-1. There were significant differences among genotypes for all NUE traits at Ottawa and Manhattan. Across genotypes, total NUE ranged from 17.2 to 42.6 kg kg-1, utilization efficiency from 24.3 to 60.2 kg kg-1, N uptake efficiency ranged from 56.1 to 82.5%, recovery from 2 to 52%, and NHI from 43.6 to 81.3%. Among the genotypes, 99480 and 26506 both known to be post–flowering drought tolerance were high in NUE and component of N use. While genotypes B35 and SC35 were the lowest in NUE and components of N use. Overall, our data suggest that there were significant differences for NUE traits in sorghum hybrids and inbred lines. There are opportunities to breed for higher NUE in grain sorghum.

Early season applications of fungicides to control diseases in winter wheat

Rich, Jonathan K. January 1900 (has links)
Master of Science / Department of Agronomy / Allan K. Fritz / Reducing plant disease pressure in wheat (Triticum aestivum L.) is an important management goal for producers. Over the last 10 years, steadily increasing adoption of no-till management has resulted in both over wintering as well as increased inocula levels for many diseases associated with straw residue. Reduced rates of fungicide, applied at early stages of plant development were investigated to measure their effect on reducing inocula density, controlling disease pressure and ultimately increasing grain yield in both no-till and conventionally planted wheat in Kansas from 2004-2008. Different cultivars were chosen based upon their resistance or susceptibility to specific diseases. The main diseases of interest were leaf rust (Puccinia triticina), speckled leaf blotch (Septoria triticii), tan spot (Pyrenophora tritici-repentis), and powdery mildew (Blumeria graminis (DC.) E.O. Speer f.sp. tritici). Two different studies were conducted. In 2004-2007, studies focused on the impact of spraying 133g/ha, half the normal rate, of propiconazole at Feekes 4.0. Disease levels and grain yields were evaluated. In 2008, four fungicide treatments and six cultivars were evaluated at 6 locations. Grain yield, measurements of green leaf duration, and grain yield components were also evaluated. No statistical differences were found in the 2004-2006 studies, but trends were apparent with grain yield increasing by 10.9%. The 2006-2007 growing season was a failure due to a late spring freeze. In the 2007-2008 growing season, statistically different grain yields were observed among some cultivars at two locations. At Partridge, KS and Salina, KS, Jagalene treated with an early-season application of propiconazole yielded significantly more than the untreated check, providing 11.4% and 9.5% increases, respectively. Early fungicide treatments also increased green leaf duration and reduced disease pressure. Further, larger scale studies need to be conducted to more accurate quantify the benefits of early applications of fungicides.

Effect of phosphorus placement in reduced tillage crop production

Martin, Kent Lee January 1900 (has links)
Doctor of Philosophy / Department of Agronomy / David B. Mengel / A number of questions are being raised concerning phosphorus (P) management as producers switch to minimum or no-tillage cropping systems. Benefits of P application are site specific and potential advantages need to be evaluated for each location. Deep band application effects on crop yield and soil P distribution have been studied, but conclusive results are lacking because of the complexity of environment and P placement interactions, particularly in moisture limited environments. Challenges in soil test sampling and interpretation have also affected P management in these reduced and no-tillage systems because of decreased confidence in soil test P data. The objectives of this research were to evaluate crop responses to P application rate and placement and to study the distribution of soil P concentration, both vertically and laterally at a number of locations in Kansas. This research shows that crop growth at the sites evaluated was not negatively affected by P stratification, which was present at all sites at the beginning of the study. Phosphorus placement methods (broadcast and deep band) did not have significant effects on P responses. However, P application was required to achieve maximum yields at sites with low soil P, but high P sites did not consistently respond to P application. When P fertilizer was broadcast, shallow soil depths continued to have high soil test P, while deep band application increased soil P in the 7.6 to 15 cm depth. The addition of starter application with deep banding of P generally resulted in a more even vertical distribution of soil P. Soil test P data also demonstrated that the presence of bands can be confirmed through soil sampling, but the confidence of soil test P data in a vertical and lateral stratified soil was decreased. Soil samples taken from the band area had highly variable P (high coefficient of variation) concentrations likely due to an inability to sample from within the P band or variability in P application. Soil sampling in these management systems proves to be challenging and will need further research to identify improved methods for soil test P sampling and interpretation.

Postemergence weed management in acetolactate synthase (ALS) resistant grain sorghum

Hennigh, David Shane January 1900 (has links)
Doctor of Philosophy / Department of Agronomy / Kassim Al-Khatib / Field experiments were conducted to evaluate the efficacy of nicosulfuron and nicosulfuron + rimsulfuron applied alone or in combination with various broadleaf herbicides in acetolactate synthase (ALS)-resistant grain sorghum. Herbicides were applied when weeds were 5 to 15 cm in height. Overall weed control was greater when nicosulfuron + rimsulfuron were applied with other herbicides than when it was applied alone. Results indicated that postemergence (POST) application of nicosulfuron and nicosulfuron + rimsulfuron is effective at controlling grasses including barnyardgrass, green foxtail, and giant foxtail. The research also showed that broadleaf weed control was more effective when nicosulfuron + rimsulfuron were applied with other broadleaf herbicides. A field study was conducted to evaluate the differential response of ALS-resistant grain sorghum to POST applications of nicosulfuron + rimsulfuron at three growth stages. Grain sorghum was treated with nicosulfuron + rimsulfuron at the 3- to 5-leaf, 7- to 9-leaf, or 11- to 13-leaf collar stage. Nicosulfuron + rimsulfuron injured grain sorghum when applied at the 3- to 5-leaf, and 7- to 9-leaf collar stage, however, sorghum yields and plant height were only reduced for the 3- to 5-leaf collar stage. Results indicated that nicosulfuron + rimsulfuron application at the 3- to 5-leaf collar stage injured ALS-resistant grain sorghum, but application at 7- to 9-leaf and 11- to 13-leaf collar stages did not result in grain yield reduction. Greenhouse experiments were conducted to evaluate the efficacy, absorption, and translocation of nicosulfuron, rimsulfuron, and nicosulfuron + rimsulfuron. Barnyardgrass, green foxtail, longspine sandbur, and large crabgrass were treated at 5 to 10 cm in height. Barnyardgrass GR[subscript]50 was the lowest and was the most susceptible to all herbicides whereas, large crabgrass had the highest GR[subscript]50 for all herbicides and was the most tolerant. Barnyardgrass and large crabgrass were treated with [superscript]14 C-nicosulfuron, [superscript]14 C-rimsulfuron, or both and radioactivity was recovered at 7 DAT. Barnyardgrass absorption and translocation of nicosulfuron, rimsulfuron and nicosulfuron + rimsulfuron was higher than large crabgrass. Results may indicate that greater absorption and translocation of the herbicides may attribute to the differential response of the species to nicosulfuron, rimsulfuron, and nicosulfuron + rimsulfuron.

Winter cover crops in corn and forage sorghum rotations in the Great Plains

Freeman, Oliver W., II January 1900 (has links)
Doctor of Philosophy / Department of Agronomy / Mary Beth Kirkham / In Kansas, winter cover crops have a new interest with the development of summer crops for biofuel. When a crop is harvested for bioenergy, the residue is removed leaving the soil prone to erosion during the winter. It is possible that the use of winter cover crops may allow for more residue to remain in a field while keeping the soil from blowing. Therefore, the objective of this research was to determine the effect of two winter cover crops on the growth of two biofuel crops, corn (Zea mays L.) and forage sorghum [Sorghum bicolor (L.) Moench] in a corn-forage sorghum rotation. The two cover crops were a legume, Austrian winter pea (Pisum sativum var. arvense Poir.) and winter wheat (Triticum aestivum L.). Control plots were fallowed. The experiment was done for two years (2010 and 2011) at two locations: under rain-fed conditions in Manhattan in the northeastern part of Kansas, where the soil was a Belvue silt loam (coarse-silty, mixed superactive non-acid, mesic Typic Udifluvents) and under irrigated conditions in Tribune in the western part of Kansas, where the soil was a Richfield silt loam (fine, smectitic, mesic Aridic Argiustolls). Two levels of nitrogen were added to the soil: 0 and 101 kg ha[superscript]-1 N. Grain and stover yields of the corn and forage sorghum were determined at harvest of the crops in the fall, and dry matter production of the cover crops was determined at their termination in the springs of 2011 and 2012. Additional nitrogen fertilizer increased grain and stover yields in both growing seasons at both locations, except for Manhattan in 2010. During the second winter of the study, Austrian winter pea did not emerge in Manhattan, probably due to a combination of cold temperatures and drought. Austrian winter pea survived both winters at Tribune. Corn yielded more grain than did the forage sorghum in Manhattan in 2011 and in Tribune in 2011. This suggests that, under both rain-fed and irrigated conditions in Kansas, corn would potentially be more productive for bioenergy production than forage sorghum. The results of the study also showed that winter wheat for both Manhattan, Kansas, and Tribune, Kansas, should be the cover crop chosen, because of its ability to grow well during the off-season of the bioenergy crops and to provide soil cover during winter.

Page generated in 0.0243 seconds