Doctor of Philosophy / Department of Horticulture, Forestry, and Recreation Resources / Jack D. Fry / 'Meyer' zoysiagrass (Zoysia japonica Steud.) has been the predominant cultivar used in the transition zone since its release in 1952, primarily because of its excellent freezing tolerance. Six hundred and nineteen zoysiagrass progeny were evaluated over 3 years, and 31 were identified from which one or more cultivars may be released with a finer texture and/or faster establishment and recovery rate compared to Meyer, but with comparable freezing tolerance. DALZ 0102 (Z. japonica), a selection tested in the 2002 National Turfgrass Evaluation Program (NTEP) Zoysiagrass Study has exhibited a faster establishment and recovery rate than Meyer; however, a lower percentage of living rhizomes and nodes was observed in DALZ 0102 compared to Meyer at temperatures [less than or equal to]-15 C in a controlled freezing chamber experiment. Physiological contributors to freezing tolerance, including lipid and fatty acid composition, and endogenous abscisic acid (ABA) levels, were monitored in 'Cavalier' [Z. matrella (L.) Merrill] (cold sensitive, LT[subscript50] = -9.6 C) and Meyer (cold tolerant, LT[subscript50] = -16.2 C) rhizomes during cold acclimation over two years. The most abundant lipids in Zoysia rhizomes were digalactosyl diacylglycerol (DGDG), monogalactosyl diacylglycerol (MGDG), phosphatidylcholine (PC), phosphatidylethanolamine (PE), and phosphatidic acid (PA). It has been suggested that DGDG and PC adopt bilayer structure; whereas MGDG, PE and PA have higher tendency to form a nonbilayer, hexagonal II (HII) phase, which compromises bilayer structure and cell function. Greater fluctuations in PC, PA, and the ratio of PC to (PE + PA) were observed in Zoysia rhizomes during cold acclimation compared to the galactolipids (DGDG and MGDG). Changes in PC and PA levels and the ratio of PC to (PE + PA) were more gradual in Meyer than in Cavalier in one year of the two-year study. There was no clear relationship between double bond indices (DBI) and LT[subscript50] in Cavalier and Meyer; thus, DBI might not be a good indicator of freezing tolerance. Abscisic acid (ABA) levels were higher in Meyer than in Cavalier on all sampling dates and were significantly correlated with LT[subscript50] (r = -0.65, P = 0.01).

Doctor of Philosophy / Department of Agronomy / David B. Mengel / Corn (Zea mays) is an important cereal crop in Kansas primarily used as livestock feed for cattle in the feedlots, and there has been increased use of corn for ethanol production as well. According to the USDA National Agriculture Statistics approximately 1.7 million hectares of corn is planted each year in Kansas, with an average yield ranging from 5,750-7,750 kg ha[superscript]-1 within the last five years (2005-2009). With this variability in yield and volatility of crop and fertilizer prices over that same period, it seems logical that optimum nitrogen or N rates may vary. A series of 14 field experiments were conducted across Kansas from 2006 through 2009 to address this issue. Specific experiments included: evaluating optimum N rates from side-dressing nitrogen fertilizer; timing of nitrogen application, pre-plant vs. split applications and normal side-dress V-6-V-9 vs. late side-dress V-14-V-16; N response of corn to a late side-dress of nitrogen fertilizer; and the evaluation of optical sensors for making in season N recommendations. The specific objectives of this research were to: a. Determine the optimum N application rate and timing to optimize corn grain yields in different corn producing regions in Kansas. b. Confirm or revise the current K-State soil test based N recommendation system for corn. c. Evaluate N management strategies using the GreenSeeker, Crop Circle, and SPAD meter, crop sensors. d. Develop draft GreenSeeker, Crop Circle, and SPAD sensor algorithms for producers to use. Grain corn yields were responsive to N at all but 3 sites. Grain yields obtained at the sites ranged from 3,460 to 15,480 kg ha[superscript]-1. Optimum N rates varied from 0 to 246 kg N ha[superscript]-1. This work suggests that current K-State N fertilizer recommendations for corn need revisions due to over recommendation of N. Including different coefficients for irrigated and dry land corn along with N recovery terms would create a more accurate N recommendation system that more closely reflects the results obtained in these experiments, and provide a significant improvement over the current system. The optical sensors used in this study were effective at making N recommendations for corn. These sensors can be a valuable tool for producers to use and determine in season N status of corn.

Master of Science / Department of Agronomy / Kassim Al-Khatib / Kochia (Kochia scoparia (L.) Schrad) is a troublesome weed throughout the western United States and Great Plains. It is an aggressive warm season annual dicot plant that exhibits protogynous flowering and facultative open pollination. The aggressive growth habit and prolific seed production enable kochia to spread and compete well for light, moisture, and nutrients. Kochia is ranked as one of the most problematic weeds in cultivated fields including corn, sorghum, wheat, soybean, and sugarbeet. Kochia has been found to lower yields as well as hinder mechanical harvest. Glyphosate is a nonselective herbicide that is widely used in controlling kochia in no-till cropping systems. With rapid adoption of no-till systems where glyphosate is used for weed burndown treatment before planting and extensive use of glyphosate resistant crops, it is common that glyphosate is frequently applied on the same field during the growing season. In 2007, poor control of kochia was observed in three fields in Western Kansas. Greenhouse experiments were conducted with 10 kochia populations to determine the efficacy of glyphosate on kochia when applied at 10 different rates and at 3 plant heights. Herbicide rates included 0, 0.0625, 0.125, 0.25, 0.50, 1, 1.5, 2, 4 and 6 times a typical use rate of 870 g ae/ha. Resistance to glyphosate was identified in three kochia populations. The glyphosate resistant populations from Ingalls, Norton, and Moscow Kansas were 4.6, 3.3, and 2.8 times more resistant to glyphosate than a susceptible population, respectively, based on the rate required for 50% control. Glyphosate injury symptoms included stunting, and chlorosis, followed by some necrotic tissue but resistant plants generally recovered from injury, or were slow to show symptoms. In general, the level of resistance is greater in more developed plants compared to younger plants. Experiments also were conducted on the different kochia biotypes to evaluate glyphosate absorption and translocation, and any differences in mineral content of the plants that might be detrimental to glyphosate activity. Differences in glyphosate absorption and translocation and kochia mineral content were not sufficient to explain the resistance to glyphosate.

Master of Science / Department of Agronomy / Michel D. Ransom / Soil Taxonomy is the official soil classification system used in the United States and many other countries. Any soil in the world can be classified from the order to the family level using a set of classification keys that are currently in an eleventh edition. The classification system is quite complex and can be too complicated for beginning soil science students to understand and use. Thus, a national advisory working group of the National Cooperative Soil Survey developed an abbreviated guide called the Simplified Guide to Soil Taxonomy. The goal of the simplified guide is to help reduce the complexity of soil taxonomy and aid in the classification of soils from the order to the great group level. The purpose of this study was to evaluate the effectiveness of the simplified guided when used by students in soil science courses to classify soils as compared to traditional methods using the more detailed keys. Classes at Kansas State University were used in the study and included the laboratory sections of AGRON 305 (Soils) and AGRON 515 (Soil Genesis and Classification). Student learning was evaluated using pre and post-test scores, assignments, and evaluation surveys. Results from the fall and spring semesters of AGRON 305 vary based on pre and post test scores and the assignment. Written evaluations indicated that both methods were easy to understand, especially as the lab progressed, but students responded more favorably to the abbreviated descriptions of taxa, pictures, and hyperlinks associated with the simplified guide. The Simplified Guide to Soil Taxonomy can be used in introductory soils courses. However, it is more suited for mid to upper level soil science courses, such as AGRON 515, where students responded favorably to the shorter and more comprehensible descriptions of taxa at the order, suborder, and great group level.

Master of Science / Department of Agronomy / DeAnn Presley / In the Midwest there has been an increase in the number of vertical tillage (VT) implements sold and a large push in marketing these newer implements to producers. Vertical tillage is defined as shallow tillage, usually in the top 5 to 7.5 cm of the soil and results in no horizontal disturbance of the soil. The objective was to determine the short-term (one growing season) effects of a vertical-tillage operation on seedling emergence, crop growth and development, yield, residue decomposition, disease incidence and severity, quantification of pathogen propagules in soil and crop residue, and effects on the near-surface soil physical properties. The study was conducted during the 2010 and 2011 growing seasons at nine locations total for the two years throughout Kansas. The study compared vertical tillage against the producer’s current practice of no-till (NT), strip tillage (ST), or conventional disk (CD). Few significant differences were observed when studying soil properties, however not one treatment continuously had significant results and no trend was observed. Residue cover at all sites and across both years was significantly greater in the NT treatments. The residue cover also impacted the disease incidence and severity of Cercospora zea-maydis also known as gray leaf spot (GLS). Other diseases such as Marcophomina phaseolina and Fusarium spp. were not significantly impacted by one treatment or another. Overall, any differences in the soil, plant, and pathogen indicators have not resulted in significant yield improvements at any of the nine site locations of the two years of this study, but more site years will be needed to assess any potential benefits of VT. Information gained from this project will be disseminated to extension clientele including extension educators, producers, commodity groups, and agricultural professionals.

Doctor of Philosophy / Department of Agronomy / Allan Fritz / Wheat breeders are constantly working to develop new wheat varieties with improved performance for agronomically important traits such as yield and disease resistance. Identifying better ways of phenotyping germplasm, developing methods for predicting performance based on genetic information, and identifying novel sources of genetic disease resistance can all improve the efficiency of breeding efforts. Three studies relating to these research interests were conducted. Synthetic hexaploid wheat lines were screened for resistance to root-lesion nematodes, an economically important pest of wheat. This resulted in the identification of three lines resistant to the root-lesion nematode species Pratylenchus thornei. Grain yield data from multi-location yield trials and average yields for counties in Kansas were used to identify wheat production areas in Kansas. Knowledge obtained from this study is useful for both interpreting data from yield trials and deciding where to place them in order to identify new higher yielding varieties. These data also aided the final research study, developing a genomic selection (GS) model for yield in the Kansas State University wheat breeding program. This model was used to assess the accuracy of GS in conditions experienced in a breeding project. Available measurements of GS have been constructed using simulations or using conditions not typical of those experienced in a wheat breeding program. The estimate of accuracy determined in this study was less than many of the reported measurements. This measure of accuracy will aid in determining if GS is a cost efficient tool for use in wheat breeding.

Master of Science / Department of Agronomy / Kraig L. Roozeboom / Interest has grown regarding management options to improve and stabilize dryland corn production (Zea mays L.) in challenging environments. Grain sorghum (Sorghum bicolor L.) has been documented to produce more consistent grain yields than corn in dryland production in Kansas. In periods of reduced water availability, sorghum can delay growth and development, allowing the plant to capture water later in the season for flowering and grainfill. Delaying planting in corn can serve a similar purpose. In central Kansas, planting corn earlier so pollination occurs before periods of extreme stress has been successful, but little research has investigated delayed planting or its long-term effect. The objectives of this study were to evaluate plant growth and yield response to delayed planting through field research and to quantify its long-term effects through crop model simulations. Field trials with delayed planting dates and hybrids of varying maturity revealed that yield at Manhattan, KS, did not decrease significantly until the final planting date in 2007 and did not decrease at all with delayed planting in 2008. At Belleville, yield increased with later planting in 2007 and was not affected by planting date in 2008. At Hutchinson, yield decreased significantly with each planting date until the third in 2007. However, in 2008, yield increased significantly from the second to fourth planting dates. Simulations in CERES-Maize over 51 years revealed no difference in yield between planting dates at Manhattan and Belleville, but showed a significant decrease between the first planting date and the third and fourth planting dates at Hutchinson. Chi-squared tests indicated that all planting date x hybrid combinations at Manhattan and Belleville produced economically profitable yields at frequencies significantly greater than 0.5. At Hutchinson, all but two of the twelve planting date x hybrid combinations produced profitable yields at frequencies significantly less than 0.5. The two remaining combinations produced profitable yields at frequencies that were not different than 0.5. One of these combinations was observed at the fourth planting date. These results suggest that the economical viability of delayed planting of corn is heavily dependent on location.

Master of Science / Department of Agronomy / P. V. Vara Prasad / Drought is the single most limiting factor in crop production. This study was conducted to investigate if a cell viability assay could serve as an effective, efficient screen to determine post-anthesis drought tolerance in sorghum (Sorghum bicolor [L.] Moench) and maize (Zea mays [L]). The assay measured decline in chlorophyll fluorescence (Fv/Fm) over time from leaf punches collected from plants grown under optimum environmental conditions and placed in an incubator under high respiratory demand. A total of 300 lines of sorghum and 197 lines of maize were screened using this assay and potential post flowering drought tolerant staygreen lines and non-stay green lines were identified. Further testing of potential lines was done in both controlled and field environments, under drought conditions, to evaluate genotype performance for physiological, yield, and staygreen traits. Standard known staygreen and non-staygreen checks were also included in these studies for comparisons. Some relationships existed between results from the cell viability assay and performance measures under controlled environment and field conditions for both sorghum and corn. However, controlled experiments were limited due to space and time constraints, and field experiments were limited due to an absence of drought during the growing season. These studies showed that the staygreen trait was not clear in the known standards under controlled environment conditions. Few of the selected lines performed better under field condition. Further testing needs to be conducted to investigate the effectiveness of a cell viability assay as a feasible indicator of drought tolerance. Experiments under field conditions at different locations and with more replications would be necessary to evaluate relations between cell viability assay and expression of drought tolerance in field conditions.

Master of Science / Department of Agronomy / Nathan O. Nelson / Glyphosate-resistant (GR) soybean cultivars are widely accepted in the United States. Glyphosate-resistance provides many benefits to production agriculture, yet GR soybeans may require some additional management practices. The objectives of this research are to (a) determine response of GR and conventional (CV) soybean near isoline to manganese fertilization, (b) determine nutrient concentration and uptake in GR and CV soybean, (c) determine differences in yield of GR and CV soybean varieties, (d) quantifying Mn uptake when glyphosate is and is not applied to glyphosate-resistant soybean, and (e) determine glyphosate effect on soybean response to Mn treatments. A field study was conducted at 5 locations in Kansas from 2006 through 2007. Manganese soil test levels ranged from 4 to 52 mg Mn/kg. Soybean (near isoline) varieties were planted at each location in a split-block design with 4 replications. Manganese treatments consisted of soil-applied MnSO[subscript]4 at 0, 2.8, 5.6, and 8.4 kg Mn/ha and foliar applied Mn at 0.22 and 0.45 kg Mn/ha. Leaf tissue and whole plant samples were taken at approximately R1, R3, and R6 growth stages and analyzed for N, P, K, Mn, and other nutrient concentrations. Few significant differences were found between varieties for concentration of any nutrient. Overall nutrient uptake under optimal growth conditions was greater in GR soybean than CV soybean varieties. There were no yield differences between GR and CV soybean varieties at low yielding locations (< 3.3 Mg/ha). In high yielding environments, CV soybean yield was greater than GR soybean yield for the 0 kg Mn/ha rate. However, granular Mn additions increased yield of GR soybean but did not affect CV soybean yield while foliar Mn treatments at high yielding locations increased yields in GR and CV soybean. In addition, a greenhouse study was conducted with a completely randomized block design having 5 blocks. Manganese treatments in the greenhouse study consisted of soil-applied MnSO[subscript]4 at 0, 8.5, 17, and 25.5 mg Mn/pot and foliar applications of 0.66 and 1.33 mg Mn/pot. Treatments were with and without glyphosate applications. Glyphosate applications did not alter Mn concentrations or total Mn uptake in the soybean biomass.

Master of Science / Department of Agronomy / Dorivar Ruiz Diaz / Two studies were conducted to evaluate phosphorus response. The first study focused on genetic improvements in corn (Zea mays) for water limited scenarios on phosphorus uptake. The object of the first study was to evaluate plant response to fertilizer and soil phosphorus for contrasting corn hybrids, including a drought tolerant (DT) and conventional hybrid. This study was established at seven locations for two years (2011 and 2012). Four locations were rain fed and three locations were under irrigation. Fertilizer treatments included phosphorus fertilizer at various rates and placements for the two different hybrids. The experimental design randomized complete block with factorial arrangement in four replications. Early growth biomass, early season whole plant tissue concentration (V6), ear leaf tissue concentration, and grain yield was measured throughout the season. Results showed differences in all measurements between hybrids. Differences in most measurements were also significant with fertilizer application. The DT hybrid had less early growth and P uptake but had higher ear leaf P concentration as well as higher yields. The second study focused on P placement, P stratification may be a concern for producers using reduced tillage systems. The objective of this study was to evaluate different placements and rates of P fertilizers in two crops, corn and soybean (Glycine max). This study is currently ongoing; however, here we are presenting data from three locations and four years (2009-2012). Two of the locations were rain fed and one was irrigated. There were four different fertilizer rates with three different placements as well as various combinations of those placements. The experimental design was randomized complete block with four replications at two locations and three replications at one location. Corn early growth biomass, whole plant tissue concentration, ear leaf tissue concentration, soybean uppermost fully open trifoliate P concentration, and yield for both crops were evaluated throughout the season. Results showed response to the phosphorus treatments in all the measured parameters. Results also showed differences in all measured parameters except yield, were significantly affected by placement.