Yellow bluestem (Bothriochloa ischaemum (L.) Keng.) cultivars are used in conservation plantings in New Mexico, Texas and Oklahoma. The recommended cultivar in southern Arizona is Ganada. However, a population from Saudi Arabia P.I. 237110, may be better adapted to the Sonoran Desert environment. This study was conducted to determine why P.I. 237110 may be better adapted to this environment than Ganada. Morphological and physiological characteristics of P.I. 237110 and Ganada were compared in five experiments. Evaluations revealed significant differences in combined stomate densities on both leaf surfaces, leaf surface area, and water use efficiency but not in apparent photosynthesis or dark respiration. Combined average stomate density was significantly lower for P.I. 237110 than Ganada (107 vs. 136 stomates mm⁻²). P.I. 237110 had a significantly higher leaf surface area (40.5 cm²) than Ganada (25.3 cm²). Apparent photosynthetic rates were not significantly different between the populations (Ganada: 12 mumol m⁻² s-1 and P.I. 237110: 10 mumol m⁻² s⁻¹). Dark respiration rates for Ganada were not significantly different (1.4 mumol m⁻² s⁻¹) from those of P.I. 237110 (1.9 mumol m⁻² s⁻¹). P.I. 237110 required 88.9 g of water per 1 g of dry matter than Ganada which required 52.3 g of water.

Field and laboratory experiments were conducted with the following ten cultivars of rice: Lebonnet, Lemont, Dawn, Katy, Della, IR36, Mars, Brazos, Labelle and Jasmine. For each variety, components of biomass, root porosity and methane emission were observed throughout the entire growing season and yield was determined at harvest. Methane emission differed among cultivars by as much as a factor of 2.4 and resulted in two distinct emission groups. Significant differences were also found for biomass among cultivars, although these differences did not coincide with the differences that were observed for emission among cultivars. Methane emission correlated strongly with aboveground live vegetative biomass within most varieties until heading and among cultivars within emission groups to heading. Emissions showed less correlation with biomass during ripening and may have been affected by other factors within the system at this time. Methane emission appeared to be consistently proportional to grain production among cultivars, when determined per gram biomass, and may be related through processes of carbohydrate partitioning. Root porosity did not appear to be associated with observed differences or trends in methane emission.

There has been recent interest in the possible carcinogenic potential of vegetable fibers (plant fibers) containing amorphous silica. These fibers referred to as Biogenic Amorphous Silica Fibers (BAS) are the normal constituents of number of plant species such as sugar cane, wheat, barley, oats, rice etc. Exposure to fibers within the respirable range has been documented during sugar cane and rice farming and processing operations. Some studies have suggested that such exposure could increase the risk for lung cancer while others have suggested the contrary. In countries like India, sugar cane farming is the major occupation in a number of provinces. A large workforce is involved in its farming and processing. In order to investigate the risk for lung cancer among one such population in Western Maharashtra, we carried out a hospital-based case-control study in the region. As part of this study we measured the exposures to BAS fibers during the harvesting of the sugar cane and the processing of the cane in the mills. / Cases of lung cancer were ascertained from 6 cancer treatment centers and matched to controls who had other types of cancers on age, sex, area of residence and timing of diagnosis. After controlling for potential confounding variables such as smoking, asbestos exposure, family history of lung cancer, income, education and farming of other crops, the risk for lung cancer was elevated in workers involved in the farming of the sugar cane, Odds ratio (OR) 1.92; 95% Confidence Interval (CI) 1.08--3.40. Specifically, the risks were elevated for those involved in the preparation of the farm (OR: 1.81; 95% CI: 0.99--3.27) and in the burning of the farms after harvesting (OR: 1.82; 95% CI: 0.99--3.34). Risks were moderately elevated for those involved in the harvesting of the crop (OR: 1.41; 95% CI: 0.70--2.90) and in the processing of the crop in the sugar mills (OR: 1.70; 95% CI: 0.20--12.60). Smoking modified the relationship between sugar cane farming and lung cancer. Sugar cane farmers who smoked had a 6-fold higher risk compared to those who never farmed and did not smoke. / Environmental measures both during harvesting and processing of the crop in the mills showed exposure to vegetable fibers. Some of these fibers contained silica and resembled BAS fibers in morphology. However a majority of the fibers lacked mineral content and were unlikely to be those of BAS. / The epidemiological study showed increased risk for lung cancer among sugar cane farmers but the limited exposure data did not show high concentration of BAS fibers. The role of polynuclear aromatic hydrocarbons and crystalline silica in particular needs to explored in future studies.

<p>The goal of the Mississippi State University Extension Service (MSU-ES) is to improve the quality of life for all Mississippians. One specific group that agricultural change agents work with at the county level is beef producers. Grazing lands have received much attention over the last few years regarding environmental concerns and Best Management Practices (BMPs) for beef cattle operations. </p><p> The adoption of these practices was voluntary during the time this study was conducted, however; adoption was highly encouraged by the MSU-ES and the Natural Resources Conservation Service (NRCS). By knowing the level of adoption of BMPs that Mississippi beef producers have implemented, change agents can more effectively plan educational programming efforts for producers to better understand the importance of BMP adoption. </p><p> The purpose of this study was to describe the adopter categories of Mississippi beef producers as determined by Rogers (2003) adopter characteristics generalizations based on their (1) socioeconomic status, (2) personality values and communication behavior, and (3) opinions. It also examined the correlations between the adopter categories to predict the level of the three BMPs being studied. </p><p> The adopter categories were innovator, early adopter, early majority, late majority, and laggard. The three BMPs that were the focus of the study were rotation grazing, riparian buffers, and pasture renovation. </p><p> The results of the study indicated that Mississippi beef producers could be correctly identified in the adopter categories. By identifying the adopter categories of the Mississippi beef producers and then examining the correlations among the variables, prediction of BMP adoption of rotational grazing and riparian buffers was possible. </p><p> The relationships between MSU-ES agents and their programming efforts, as well as the relationships between NRCS district conservationist and their programs, were studied. Non-adoption, though not an adopter category, was also examined and the reasons for it were cited. </p>

Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 2006. / Source: Dissertation Abstracts International, Volume: 67-11, Section: B, page: 6119. Adviser: Stephen P. Long. Includes bibliographical references (leaves 89-99). Available on microfilm from Pro Quest Information and Learning.

Doctor of Philosophy / Department of Agronomy / Charles W. Rice / Atmospheric concentrations of the greenhouse gases (GHG) carbon dioxide (CO2), nitrous oxide, and methane have been increasing since the Industrial Revolution. An expanding human population, increased fossil fuel use, extensive ecosystem disturbance, and intensive production agriculture have contributed to this increase. Storing carbon (C) in soil in natural and agricultural ecosystems has the potential to offset a portion of the future atmospheric increases in CO2 levels. Laboratory and field studies were conducted to evaluate basic mechanisms of C sequestration. The research reported here focuses on identifying strategies to reduce C loss from soil by (1) slowing plant residue decomposition rates, or (2) increasing soil fungal dominance and physical protection of soil C. Grain sorghum (Sorghum bicolor) hybrids were used in a laboratory experiment to determine the effect of varied amounts of lignin on plant residue C mineralization. The different levels of lignin in the hybrids was not strongly correlated with plant residue C mineralization. Another laboratory experiment investigated larger differences in lignin content between crop plants. Plant residue exhibiting the natural mutation referred to as brown midrib (bmr) also had lowered total lignin and different lignin chemistry. The bmr plants decomposed faster than the normal isolines, and the addition of nitrogen lowered overall mineralization. Nitrogen additions also significantly impacted the microbial community by lowering total phospholipid fatty acids (PLFA) and shifting fungal energy storage physiology. A field experiment was conducted to measure the soil microbial response to adding grain sorghum residue in both tillage (CT) and no-tillage (NT) agricultural ecosystems. The residue mineralized similarly in both systems, but the NT microbial population was stimulated significantly greater than CT. The fungal PLFA in NT 0-5 cm was higher than NT 5-15 cm, CT 0-5 cm, or CT 5-15 cm. A significantly greater amount of plant residue C was found in soil macroaggregates, as compared to microaggregates, at the conclusion of the experiment, regardless of tillage. More N was found in NT macroaggregates than in CT macroaggregates. The experiment identified two mechanisms for increased C storage in NT soils, as compared to CT soils.

Doctor of Philosophy / Department of Agronomy / Johanna A. Dille / This dissertation has two complementary components: educational, in a survey of students in Weed Science and their perception of the Kansas State University Agronomy Learning farm, and research, regarding interactions between mesotrione and sulfonylurea herbicides. The Learning Farm serves as a resource where undergraduate students at KSU can develop agronomic skills through hands-on field site experiences and investigations. Students’ perceptions of experiential learning activities in the development of problem-solving and critical thinking skills were studied as a result of the Learning Farm. Activities included: undergraduate students in Weed Science (AGRON 330) developing a weed management recommendation, and Undergraduate Research Assistants (URAs) conducting weed science research projects at the Learning Farm. Students stated that experiential learning activities increased their critical thinking skills, required effective time management, and presented concepts that could be used in other situations. Pre- and post-project evaluation questionnaires showed that URAs had an increased interest in agronomy, weed science, and research following the completion of their project. For the research project, field and greenhouse studies were conducted from 2003 to 2006 to evaluate the efficacy of various sulfonylurea herbicides when applied with mesotrione or mesotrione + atrazine. Research demonstrated that the addition of mesotrione to sulfonylurea herbicides decreased efficacy of sulfonylurea herbicides on green foxtail, yellow foxtail, and shattercane. The addition of atrazine to the tank mix, or increased mesotrione rates, resulted in additional decrease in sulfonylurea herbicide efficacy on shattercane and foxtail species. Additional studies were performed to determine if absorption, translocation, or metabolism was the basis for the reduction in sulfonylurea herbicide efficacy when mixed with mesotrione or mesotrione + atrazine. Results indicated that the cause of antagonistic interaction between mesotrione and sulfonylurea herbicides in green and yellow foxtail was reduced absorption and translocation of the sulfonylurea herbicides. Producers who choose to apply mesotrione and sulfonylurea herbicides to corn should apply the herbicides sequentially to achieve maximum control of weedy grass species.

Doctor of Philosophy / Department of Agronomy / Michel D. Ransom / Upland soils in east central Kansas have a complex genesis, often contain one or more paleosols, and form in multiple parent materials including loess, colluvium, residuum, and alluvium. Quaternary loess/paleosol investigations have largely ignored this region of Kansas, as the total loess thickness on uplands is <2 m thick. In this study, the objectives are to examine the morphology and genesis of the soils of interest and how these characteristics vary within soil profiles, across landscapes, and throughout the current series mapping extent. The series of interest include the Irwin, Konza, Dwight, and Ladysmith soil series. Methods used in this study include field descriptions and sampling, terrain analysis, micromorphological investigations, and laboratory characterization, including silt and clay mineralogy. Accelerator mass spectrometry (AMS) was used for numerical dating and determination of stable carbon isotope values (δ13C) for selected paleosols. Radiocarbon ages ranged from 24,000 to 19,000 yr BP and δ13C values were between -19 and -17 ‰ (PDB), indicating that the paleosols were formed in Gilman Canyon loess or the Severance formation, under a mix of C3 and C4 vegetation. Terrain analysis results illustrated that, in given drainage areas, the soil series were mapped on a wide range of slope positions. Field observations and terrain analysis confirmed no relationships between mollic epipedon thickness, solum thickness, paleosol thickness, or depth to the paleosol with respect to landform. Micromorphological investigations revealed increasing soil development with depth, i.e., the presence of two paleosols beneath the modern soil. Mean particle size and mineralogy vary geographically within individual series. Pedogenic carbonate accumulations and redoximorphic concentrations are common features of the soils of interest, and less common features include sodium and gypsum accumulations, slickensides, and redoximorphic depletions. Results from this study will be provided to the USDA-NRCS for use in future soil survey updates, and will contribute to Quaternary loess/paleosol knowledge in Kansas and the Great Plains.

Doctor of Philosophy / Department of Agronomy / Johanna A. Dille / Palmer amaranth is a competitive weed and has caused variable corn yield losses in diverse environments of Kansas. The objectives of this study were to 1) determine corn and Palmer amaranth growth, development, and grain (seed) production, 2) determine soil water content throughout the growing season, and 3) evaluate the performance of the modified ALMANAC model for simulating monoculture corn yield and corn yield loss from Palmer amaranth competition when corn and Palmer amaranth were grown alone or in competition under dryland and irrigated environments. For the first objective, field experiments were conducted in 2005 and 2006 with whole-plots of dryland and furrow irrigation arranged in a side-by-side design. Within each soil water environment, sub-plot treatments were monoculture Palmer amaranth at one plant m-1 of row, and corn with zero, one, and four Palmer amaranth plants m-1 of row. Corn height, leaf number, LAI, and total plant dry weight were reduced with increasing water stress and were reduced further in the presence of Palmer amaranth. Corn yield losses were similar with increasing Palmer amaranth density across soil water environments in each year, except for 2006 dryland corn. Palmer amaranth growth and development were negatively impacted by corn interference and weed density. For the second objective, Time Domain Reflectometry measurements documented seasonal trends of volumetric soil water content at the 0 to 15 and 0 to 30 cm soil profile depths for treatments in dryland and irrigated environments each year. The soil water depletion rate increased as water received prior to a drying period increased at the 0 to 30 cm soil depth in the dryland and irrigated environments. For the third objective, the modified ALMANAC model was parameterized based on monoculture corn and Palmer amaranth growth data. The model underestimated monoculture corn yield but overestimated corn yield with Palmer amaranth competition. The model performance was not consistent when comparing simulation results to dryland and irrigated experiments conducted across Kansas. Overall, the experiment provided an improved understanding of corn yield loss risks associated with water management and Palmer amaranth competition.

Master of Science / Department of Agronomy / Kassim Al-Khatib / Field experiments were conducted near Manhattan, KS in 2005 and 2006 and Sabetha, KS in 2005 to determine the efficacy of S-metolachlor tank mixed with fomesafen on common waterhemp in soybean. Preemergence treatments included S-metolachlor + fomesafen at 0.91 + 0.22, 1.21 + 0.28, 1.52 + 0.36, and 1.82 + 0.43 kg ha-1 and S-metolachlor + metribuzin at 0.55 + 0.14 kg ha-1. These treatments were applied alone or followed by a postemergence glyphosate application at 0.88 kg ha-1. Ratings were taken 2, 4 and 8 weeks after treatment. The study showed that S-metolachlor + fomesafen gave excellent early season control of common waterhemp at both Sabetha and Manhattan. S-metolachlor + fomesafen at the 1.52+0.36 kg ha-1 rate gave greater weed control than S-metolachlor + metribuzin. A separate study was conducted to determine the competitiveness and fitness of a protox-resistant common waterhemp biotype. Protox-resistant and protox-susceptible biotypes of common waterhemp were grown under noncompetitive and competitive arrangements in the greenhouse. In the noncompetitive study a single plant of both biotypes was planted in 15-cm-diam pots. Photosynthesis, leaf area, and plant biomass were measured 10, 20, 30, and 40 day after transplanting (DATP). In general, photosynthesis rate and plant biomass was similar between biotypes. However, the protox-resistant biotype had higher leaf area then the susceptible biotype at 20, 30, and 40 DATP. Under competitive conditions, a replacement series study, photosynthesis, leaf area, plant height, and plant biomass were measured 7, 14, 21, and 28 DATP. In general protox-resistant and –susceptible common waterhemp values were similar 28 DATP. Relative crowding coefficient values 28 DATP were 0.86, 0.89, 1.09, and 1.13 for photosynthesis, leaf area, plant height, and plant biomass, respectively. Suggesting, protox resistance did not change the ability of common waterhemp to grow normally under competitive conditions.