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Doctor of Philosophy / Department of Horticulture, Forestry, and Recreation Resources / Dale J. Bremer / Turfgrass covers 1.9% of the nation’s surface area and is the largest irrigated crop in the USA. Developed urbanized land is projected to double by 2025, which will increase turf’s environmental impact. Studies were conducted to evaluate environmental impacts by characterizing nitrogen, carbon, and water fluxes in turfgrass ecosystems. Emissions of nitrous oxide (N[subscript]2O), a major greenhouse gas and ozone depleter were measured from bermudagrass (Cynodon dactylon L. Pers. x C. transvaalensis Burtt-Davy) (bermuda), perennial ryegrass, (Lolium perenne L.) (rye), and zoysiagrass, (Zoysia japonica Steud.) (zoysia) under regional N management. In a separate study, N2O fluxes were measured from bermuda fertilized with controlled-release N fertilizers including polymer-coated and organic-N, and quick release urea. Emissions of N2O were measured using static surface chambers and gas chromatography. Zoysia, with less N requirements, had lower emissions than bermuda. Cumulative N[subscript]2O emissions were similar among N types. To measure water and carbon fluxes, a portable non-steady state chamber was designed and tested. The chamber had minimal affects to the canopy during field measurements: leak values averaged <1.5 micromol CO[subscript]2 m[superscript]-2 s[superscript]-1; average chamber pressure was 0.09 Pa ±0.01 Pa; temperature rise inside the chamber averaged 0.74C; and the chamber had 90% photosynthetically active radiation transmittance. Using the chamber, differences were detected in net photosynthesis (Pnet), gross photosynthesis (Pg), evapotranspiration (ET), canopy stomatal conductance (gc), and water use efficiency (WUE) in well-watered tall fescue (Festuca arundinacea Schreb.), Kentucky bluegrass (Poa pratensis L.) (KBG), zoysia, and bermuda. Irrigation requirements, visual quality ratings, and genetic rooting potential of 28 KBG cultivars and 2 Texas bluegrass hybrids (P. pratensis x P. arachnifera Torr.) were quantified in greenhouse and rainout facility studies. Average water applied ranged from 23.4 to 40.0 cm among cultivars. Bedazzled, Preakness, and Bartitia required less water and had higher average quality than other cultivars. Compact America and Mid-Atlantic phenotypes exhibited greatest potential for success in integrating reduced water inputs with maintenance of acceptable visual quality. Results indicated that turfgrass management could mitigate N[subscript]2O emissions and conserve water while maintaining healthy turfgrass, and the new chamber will enhance turfgrass studies by providing rapid measurements of photosynthesis.

Masters of Science / Department of Agricultural Economics / Jeffrey M. Peterson / The expansion of the biofuels industry, world demand, and various other factors are having a historic impact on the price of grains. These high prices have been creating a large increase in production of many water intensive crops such as corn. As corn is among the most input-intensive crops, this extra production has raised concerns about environmental impacts and pressures on water resources in particular. While water quality has been a longstanding concern in the cornbelt, much of the new production is in nontraditional corn regions including the southeast, the High Plains, and the western states. In these areas, there is mounting concern over depletion of already stressed water supplies. In the High Plains, the chief water source is the Ogallala aquifer, one of the largest water resources in the world that underlies eight states from South Dakota to Texas. The Ogallala has enabled many agricultural industries, such as irrigated crops, cattle feeding, and meat processing, to establish themselves in areas that would not be possible otherwise. A consequence is that the economy of this region has become dependent on groundwater availability. Continued overdrafts of the aquifer have caused a long-term drop in water levels and some areas have now reached effective depletion. This thesis seeks to estimate the impact of the rising commodity prices on groundwater consumption and cropping patterns in the Kansas portion of the Ogallala. The economy of this region is particularly dependent on water and irrigated crops, with more than 3 million head of feeder cattle and irrigated crop revenues exceeding $600 million annually. Sheridan (northwestern Kansas), Seward (southwestern Kansas), and Scott (west central Kansas) counties have been selected as representative case study regions. These counties have a wide range of aquifer levels with Seward having an abundant supply, Sheridan an intermediate supply, and Scott nearing effective depletion. Cropping patterns in these counties are typical of the western Kansas region, with most irrigated acreage being planted to corn and with dominant nonirrigated rotations of wheat-fallow and wheat-sorghum-fallow. A Positive Mathematical Programming (PMP) model was developed and calibrated to land- and water-use data in the case counties for a base period of 1999-2003. The PMP approach produces a constrained nonlinear optimization model that mimics the land- and water- allocation decision facing producers each year. The choice variables in the model are the acreages planted to each of the major crops and the water use by crop. The model was run for each of the case counties. The PMP calibration procedure ensures that the model solutions fall within a small tolerance of the base period observations. Once calibrated, the models were executed to simulate the impacts of the emerging energy demand for crops over a 60-year period. After the baseline projections were found, the model was then run under increased crop prices that reflect the higher prices observed in 2006 and after. The thesis found that under the high price scenario, both irrigated crop production and water application per acre increased significantly during the early years of the simulated period in all modeled counties. The size of the increases depended on the amount of original water available in each county. The increases generally diminished in magnitude toward the end of the simulation period, but led to smaller ending levels of saturated thickness as compared to the base price in all counties. Finally, in two of the three counties, it was observed that initial increases in irrigated crop acres and water application forces a decline in the aquifer such that less water can be applied per acre in the final years of the simulation. This suggests that high commodity prices forces a higher emphasis on early production levels than later production levels. Additionally, the higher prices have a significant effect on the rate of decline of the Ogallala aquifer.

Master of Science / Department of Agronomy / Clenton E. Owensby / Currently there are no model inputs for eastern gamagrass [Tripsacum dactyloides (L.) L] for use in the National Research Council's (NRC) beef cattle model. This study was conducted to determine model inputs for two eastern gamagrass varieties for use with the forage database of the NRC model. Cattle producers in the Midwestern US will be able to evaluate eastern gamagrass in a forage system and estimate net energy for maintenance (NEm), metabolizable protein (MP), and degradable intake protein (DIP) balance for various production scenarios. Eastern gamagrass varieties 'Iuka' and 'Pete' were arranged in a split-plot randomized complete block experiment with four replications. Varieties were whole plots with harvest maturities as split plots. Plant tissue was harvested from both varieties at four maturities: vegetative/early elongation, anthesis, seed shattering and dormancy. Various compositional attributes were determined on forage samples to enable the determination of model inputs for predicting energy and protein balances. A slight difference between varieties was found for crude protein concentration (p<0.05). Differences (p<0.05) due to maturity were found for all analyses used in the model, corroborating the decline in nutritive value of eastern gamagrass with advancing maturity. Neutral detergent fiber (NDF) ranged from 593 g kg-1 at the vegetative/early elongation stage of maturity to 731 g kg-1 at dormancy. Assumed animal and environmental inputs were used for beef cattle at two stages: nonlactating 160 d prepartum and 60 d peak lactation. Energy and protein balance were estimated using level I of the model. The vegetative/early elongation stage of development supplied the greatest amount of MP. Digestible intake protein declined as plant tissue matured. All but the vegetative/early elongation stage of maturity were limited in DIP for cows in both stages of production. Soybean meal was used as a protein supplement in amounts ranging from 0.8 kg to 1.4 kg to meet nutritional demands of cattle grazing eastern gamagrass at anthesis, seed shattering and dormancy. In the simulations conducted, eastern gamagrass would be an acceptable forage source for beef cattle provided that appropriate protein supplementation was given when the forage was at more advanced stages of maturity.

Doctor of Philosophy / Department of Entomology / Larry L. Buschman / C. Michael Smith / Several studies were conducted to develop soybean management options that could provide protection from the soybean stem borer, Dectes texanus LeConte. Selected soybean genotypes were screened for host plant resistance against D. texanus. Soybean plants were grown in a footprint that could be covered by a field cage. When beetles were flying in the fields they were collected and placed in the field cages to increase the insect feeding pressure on the test plants. A susceptible commercial soybean variety treated with the systemic insecticide fipronil was used as a positive antibiosis check. Both commercial soybean varieties and plant introductions (PIs) obtained from the USDA National Soybean Germplasm Collection in maturity groups (MG) VI to VIII were tested over a four-year period. Since the number of ovipositions per plant could not be controlled, the ratio of oviposition punctures (OP’s) per live larvae (OP/ Lv) was used as a novel index of potential plant antibiosis to D. texanus. Field evaluations identified PI165673 as a genotype with a very high OP/ Lv ratio - similar to that for the fipronil antibiosis control. PI165673 appears to be potential source of resistance to D. texanus. Factorial analysis indicated that soybean maturity group was not significant factor in the expression of resistance. The OP/ Lv ratio appears to be more sensitive means of identifying antibiosis than other more conventional damage indices. The use of field cages demonstrated consistent plant responses from year to year during the multi-year study. Greenhouse-grown soybean plants, including transgenic plants containing the Manduca sexta chitinase gene, were not morphologically appropriate for successful D. texanus oviposition because the greenhouse-grown plants were poorly developed and had not produced enough pith in petioles. Therefore the greenhouse results were inconclusive. Analysis of the vertical distribution of D. texanus oviposition on soybean plants revealed that D. texanus oviposition was most likely to occur on leaf petioles on the upper five nodes of the plant canopy. Histomorphological observations of plant petioles indicated that the proportion of the petiole perimeter occupied by vascular bundles might be related to D. texanus oviposition. Both foliar and seed applications of fipronil suppressed D. texanus larval damage on soybean plants. The efficacy of these treatments was sustained for long periods, even until adult beetles were present in early August. The effects of the fipronil seed-treatment and harvest date on grain yield were both significant while the interaction was not. A physiological yield loss of 8.2% and plant lodging losses of 2.9% were associated with D. texanus infestation.

Doctor of Philosophy / Department of Agronomy / Johanna A. Dille / Challenges in weed management include occurrence of multiple weed species in the field, variable emergence among weed species, different spatial distribution and weed densities, which leads to the persistence of weed patches. The overall objective of this research was to understand the interaction of weed emergence, weed density, herbicide choice, and herbicide rate in soybean. Specific objectives were 1) to characterize the seedbank and emergence patterns of shattercane (Sorghum bicolor L.), prickly sida (Sida spinosa L.), and ivyleaf morningglory (Ipomoea hederacea Jacq.) including initial, peak, end, and duration of emergence in response to crop and herbicide treatments in soybean, and 2) to evaluate large crabgrass (Digitaria sanguinalis L.), shattercane, Palmer amaranth (Amaranthus palmeri S.), and velvetleaf (Abutilon theophrasti Medik.) mortality and dry weight reduction in response to herbicide rates across varying weed densities as well as to determine the influence of velvetleaf growth stage and density on herbicide efficacy. In the emergence study of 2006 to 2008, four treatments were nocrop, no-residual herbicide, half-rate of residual herbicide and full-rate of residual herbicide. Reduction in weed emergence was observed over the years in the same species patch. Species emerged in mid-May in both years, coinciding with soybean planting. Extended emergence was observed for shattercane when moisture was low and temperature high, while for prickly sida and ivyleaf morningglory, extended emergence was observed when moisture was high and temperature low. Applying residual herbicide decreased weed emergence. Herbicide choice was the whole plot, herbicide rates were subplots and weed densities were sub-subplots in field experiments conducted in 2006 and 2007. Shattercane was more susceptible to both glyphosate and clethodim than large crabgrass. Increasing large crabgrass density reduced percent mortality with clethodim, while with glyphosate, density did not affect both species mortality. Shattercane dry weight was reduced to 0 g per plot with 0.1X labeled rate of clethodim or glyphosate while 0.5X of the labeled rate reduced dry weight of large crabgrass to 0 g per plot. For broadleaf weeds, higher percent mortality was observed with glyphosate than with lactofen at high densities. Palmer amaranth was more susceptible than velvetleaf. Velvetleaf response was density dependent, such that increasing density did not increase dry weight. Velvetleaf growth stage was of importance, as stage affected herbicide efficacy, with higher mortality achieved at the two-leaf stage than the four- and six-leaf stages. For glyphosate, 0.125X of labeled rate on velvetleaf density of 5 seedlings per pot achieved more than 90% mortality when applied at the two-leaf stage, but dropped to 60 and 50% mortality when applied at the four- and six-leaf stage, respectively. The trend was the same for velvetleaf at a density of 30 seedlings per pot, which had 80, 60, and 55% mortality for the two-, four-, and six-leaf stages, respectively. Weed managers and farmers have the opportunity to better select herbicide choice and rate based on weed species, weed emergence patterns, and weed density.

Master of Science / Department of Agronomy / Walter H. Fick / Rough-leaved dogwood (Cornus Drummondii Meyer) is one of the most invasive woody plants in rangeland of Kansas. Reduced prescribed burning due to drought and urban encroachment probably has contributed to its spread. Herbicides are commonly recommended for control of rough-leaved dogwood, but minimal data exists for recommendation development. Ten herbicide treatments were applied in June during late flowering at two locations in northeast Kansas in 2005 and 2006. Each treatment was replicated three times in a randomized complete block design with individual plot sizes of 3 x 3 m. Herbicides were applied with hand sprayers in 1017 L/ha solution. Visual evaluations of defoliation were made about 1 and 12 months after treatment (MAT) and mortality was estimated about 1 year after treatment (YAT). Defoliation 1 MAT varied among herbicides with significant location by year and herbicide by year interactions. Treatments providing greater than 70% defoliation 12 MAT both years were triclopyr + 2,4-D (1.12 + 1.06 kg ae/ha), triclopyr + fluroxypyr (1.83 + 0.61 kg ae/ha), picloram + fluroxypyr (0.41 + 0.41 and 0.82 + 0.82 kg ae/ha), and picloram + 2,4-D + triclopyr (0.66 + 2.44 + 2.44 kg ae/ha). Rough-leaved dogwood is difficult to control with a single herbicide application, but treatments exist that will substantially reduce stands. Tebuthiuron pellets (Spike 20P) are another control measure recommended for rough-leaved dogwood. Treatments of 4.4 kg ai/ha (3/4 oz per 100 square feet) tebuthiuron pellets were applied in December 2004. A visual estimate of control indicated tebuthiuron reduced dogwood cover by 65% compared to a 3% decrease on untreated plots. Dogwood density was reduced by 2.2 stems/m2 (P<0.08). Total woody plant cover increased on untreated plots by 6.2 percentage units, but was decreased by 20.9 percentage units on tebuthiuron treated plots. Other woody plants decreased in both treated and untreated plots. Shading by a large elm tree likely caused variation between replications including increases in cover and density of rough-leaved dogwood on treated plots. Tebuthiuron is a photosynthetic inhibitor that often is not effective on shaded plants. Tebuthiuron pellets applied at 4.4 kg ai/ha was an effective control option for unshaded rough-leaved dogwood.

Master of Science / Department of Agronomy / Walter H. Fick / Patch-burn grazing is a relatively new concept in terms of rangeland management. While numerous benefits have been associated with this system, in the tallgrass prairie of Kansas, cattle production and sustainability of rangeland are critical. In 2006, 253 ha at the KSU Bressner Range Research Unit in Woodson County, Kansas were subjected to spring patch-burn grazing (using one-third portions) and traditional full-burn grazing. Each treatment within the split-block design was replicated four times for 3 years. The objectives were to evaluate whether livestock performance would be compromised under this grazing system, to monitor the health of the rangeland, and to observe the usefulness of this tool as a potential control of the invasive plant sericea lespedeza [Lespedeza cuneata (Dumont) G. Don]. In regards to cattle performance, burn treatments had no significant difference in average daily gain (p≥0.10) in any of the 3 years. On average, cattle utilized 61% of the current year’s forage production in patch-burned portions, which was higher (p≤0.10) than that of unburned (30%) and full-burn (41%) portions. Results of the botanical composition show forb and woody plant composition did not differ between treatments, however differences (p≤0.10) were present in grass composition. Total annual grasses increased 19.1 percentage units under patch-burn and 2.1 units under full-burn, while total perennial grasses decreased 18.4 and 1.1 units, respectively. When evaluated by treatment area (one-third portion), results indicated that the 3-year cycle did allow enough time for recovery. At 2 years after treatment (2-YAT), no significant difference in composition(p≥0.10) was present between initial patch-burn portions and the full-burn pastures. Finally, in only 1 year of the study did cattle statistically consume a greater percentage of sericea lespedeza plants (p≤0.10) in the patch-burned portions (92%) than in full-burned pastures (35%). Biomass utilization did not differ (p≥0.10) between burn treatments. Surprisingly, there was a trend for the number of plants in the sampled areas of the patch-burn portions to decrease throughout the cycle. However, at the conclusion of the 3-year cycle, sericea densities did not differ(p≥0.10) between treatments. Patch-burn grazing shows promise as a potential management tool for Kansas land managers.

Doctor of Philosophy / Department of Agronomy / Scott A. Staggenborg / Grain sorghum yield has notably increased from the beginning of hybrid production and commercialization in the late 1950s. The yield increases were the result of improved agronomic practices and hybrid advancement. The objectives of my research were: (1) to determine the magnitude of yield change in the hybrid era in irrigated and rain fed sorghum production, (2) to determine the contribution of agronomic and hybrid changes for yield in the hybrid era, (3) to investigate changes in sorghum morphology, physiology, and water use that contributed to yield increases, (4) to investigate changes that accompanied yield increase with hybrid improvement, and (5) to understand sorghum water and nutrient use and variations between hybrids in these regards. Fifty-two years of grain sorghum hybrid performance trial data (1957-2008), were analyzed and greenhouse and field studies were conducted on five selected hybrids to meet our objectives. The greenhouse and field studies were conducted from the summer of 2007 to the fall of 2009 on five selected hybrids, each representing a decade from the past fifty years. Results indicated that there was an increase in hybrid yield of nearly 50 kg ha-1 yr-1 in dryland sites over the 52 yrs (1957-2008) analyzed. Irrigated grain sorghum yields, however, remained unchanged over the same period. Agronomic practices such as planting date, phosphorus fertilizer use, and planting density changed over these years but were not found to contribute to increased dryland sorghum yields. There was no difference found between old and new hybrids tolerance to different densities. Hybrid advancement and increased nitrogen fertilizer application were responsible for changes in dryland yields. Total water use changed with hybrid advancement. New hybrids used the greatest total water and also had greater root-to-total biomass ratio than the old hybrids. Leaf biomass was also greater for the newest hybrid. There was a difference in amount of total nutrients extracted by hybrids, and there were differences among hybrids in allocation of nutrients to different tissues. In general the yield focus of sorghum hybrid development was effective in dryland sorghum production, likely because of intentional or inadvertent selection of hybrids with better drought tolerance. Results indicated that breeding programs created hybrids with improved morphological characteristics that might have resulted in better resource use (water and nutrient) and ultimately increased yield.

Master of Science / Department of Agronomy / Michel D. Ransom / Many soils in southeastern Kansas are characterized by high clay contents and high shrink-swell potentials. Their vertic properties and claypan characteristics cause soil management to be difficult and pose problems for agricultural, environmental, and engineering uses. Thus, collecting more information and improving our understanding of these soils is an important step towards bettering our soil management techniques. The objectives of this study were to examine the morphology, processes of soil genesis, clay mineralogy, micromorphology, and potassium fixation potential of the soils of interest and how these characteristics varied between and within individual pedons. Ten pedons expected to represent varying degrees of vertic expression were selected. Methods included the use of field descriptions, routine soil laboratory characterization, micromorphological investigations, the determination of clay mineralogy by X-ray diffraction, and the measurement of potassium fixation potential. Field morphology reflected the geologic parent materials available in the region. The fine sediments that compose these clayey soils are primarily provided by the Pennsylvanian and Permian shales and limestones underlying this region and the Flint Hills to the west. Dominant pedogenic processes currently at work are clay illuviation and shrink-swell processes. Silty, non-expansive surface soils at all but sites 6 and 7 are thought to buffer the rapid wetting and drying cycles needed for maximum vertic expression. Four of the soils were dominated by smectitic minerals in the clay fraction while the rest exhibited a more mixed mineralogy. Disruption of illuvial clay features by shrink-swell movement was evident in thin section. Striated b-fabrics dominated the micromorphology except in non-expansive surface soils. K fixation of the soil surface was found to be negative in all soils, thus K fixation potential is considered very low. In subsurface horizons, K fixation generally increased with increasing vermiculite content. In addition to limited quantities of K-fixing clay minerals, naturally high K levels limited the amount of K fixation in this study. The information presented can be used to improve our understanding and management of high clay, vertic and claypan soils in southeastern Kansas.