Master of Science / Department of Agronomy / Kraig Roozeboom / High soybean [Glycine max.] commodity prices in recent years have led to an increase in use of yield enhancing and protecting products. These products need to be evaluated to determine if the use of multiple inputs has a positive impact on yield and how these inputs interact with agronomic practices. The objectives of this study were to evaluate products individually and collectively in input systems, examine interactions between varieties and input systems (IS), seeding rates (SR) and IS, and row spacing (RS) and IS. Field experiments were conducted at high-yielding locations in Kansas and Minnesota in 2012 to 2014 to meet these objectives. Sixteen treatments consisting of individual inputs and inputs combined in systems were evaluated in one experiment. A second experiment evaluated the variety by IS interaction by constructing 18 treatments from a factorial combination of six glyphosate [N-(phosphonomethyl) glycine] resistant varieties and three IS’s: untreated control (UTC), SOYA (combination of possible yield-enhancing products representative of those currently being marketed), and SOYA minus foliar fungicide (SOYA – foliar F). A third experiment evaluated the SR by IS interaction by constructing 12 treatments from a factorial arrangement of six SR’s and two IS’s: UTC and SOYA. A fourth experiment evaluated the RS by IS interaction by constructing 12 treatments from a factorial arrangement of three RS’s and four IS’s: UTC, fungicide and insecticide seed treatment plus foliar fungicide (STFF), SOYA, and SOYA – foliar F. Very few interactions between IS and agronomic practices were detected in any of the experiments. Varieties had an effect on multiple growth parameters but yield differences were marginal; linear-plateau and non-linear models found that seeding rates that maximized yield in this study were similar to University recommendations; and in general, narrow rows produced the greatest yields. The use of inputs and IS’s typically increased seed mass and yield above the UTC across all experiments. However, given current costs and soybean prices, yield response to IS’s was not great enough to cover the additional costs. Overall, it appears producers would be better served by focusing on agronomic practices rather than implementing input systems.

Master of Science / Agronomy / Mithila Jugulam / Common waterhemp (Amaranthus rudis) is a problematic weed species of cropping systems throughout the Midwestern states, including Kansas. Recently, waterhemp populations from Kansas were found to have evolved resistance to the widely used herbicide glyphosate as a result of amplification of the 5-enolpyruvylshikimate-3-phosphate synthase (EPSPS), the enzyme target of glyphosate. The objectives of this research were to 1) perform glyphosate dose-response study and determine the relationship between relative EPSPS genomic copies and EPSPS gene expression in glyphosate-resistant waterhemp, and 2) characterize the genomic configuration and distribution of EPSPS copies using florescence in situ hybridization (FISH) in three glyphosate-resistant waterhemp populations. Waterhemp populations from eastern Kansas were screened with 868 g ae haˉ¹ (field used rate) of glyphosate, and genomic DNA and total RNA was isolated from the survivors to determine the EPSPS genomic copies and EPSPS gene expression relative to the acetolactate synthase (ALS) gene using qPCR. Furthermore, waterhemp specific EPSPS probes were synthesized to perform florescence in situ hybridization (FISH) on these glyphosate-resistant plants. Results of these experiments indicate a positive correlation between level of glyphosate resistance, EPSPS copies, and their expression. As expected, a negative correlation was found between shikimate accumulation and EPSPS copies. Sequencing of the EPSPS gene showed no presence of the proline 106 mutation, which is known to be associated with glyphosate resistance suggesting that an insensitive EPSPS enzyme was not involved in the mechanism of glyphosate resistance. FISH analysis of resistant plants illustrated presence of amplified EPSPS copies on two homologous chromosomes, likely near the centromeric region. . This is the first report demonstrating a positive relationship between EPSPS copies and expressions, as well as chromosome configuration of EPSPS copies in glyphosate- resistant waterhemp from Kansas.

Master of Science / Department of Plant Pathology / Bernd Friebe / Bikram S. Gill / Common, bread, or hexaploid wheat, Triticum aestivum L. (2n=6x=42, AABBDD), has several relatives in the Triticum/Aegilops complex of the Poaceae family in the Triticeae tribe, which are valuable sources for broadening genetic diversity and may provide genes for disease and pest resistance and general wheat improvement. Other wild relatives of wheat also may be exploited for wheat improvement, such as Haynaldia villosa (L.) Schur. (2n=2x=14, VV). It is a diploid species with resistance to powdery mildew, wheat curl mite colonization, cereal eyespot disease, rust diseases, and wheat spindle streak mosaic virus. H. villosa may harbor many other as yet unidentified traits for wheat improvement. The polyploid nature of bread wheat allows tolerance to genomic changes, because homoeologous chromosomes from other genomes compensate for missing wheat chromosomes. In this experiment, we crossed the disomic alien addition line DA4V (2n=6x=44) with a pair of H. villosa chromosomes added to the wheat chromosome complement with wheat monosomic for chromosome 4D (2n=41) to produce 4D/4V double monosomic plants. According to centric breakage-fusion mechanisms, univalents tend to break at their centromeres at meiotic metaphase I producing telocentric chromosomes with unstable or “sticky” ends that can fuse with the sticky ends of other newly formed telocentric chromosomes. This fusion results in Robertsonian whole-arm translocations that may be compensating if a short arm of one chromosome fuses with a long arm of another. Double monosomic plants were screened cytogenetically and further visualized by genomic in situ hybridization (GISH). Five transfers were identified, including T4DS.4VL and T4VS.4DL translocations, and a T4VS-W.W transfer of unknown wheat origin. These results were confirmed by GISH. The T4DS.4VL and T4VS.4DL translocations are genetically compensating and should be exploited in wheat improvement.

Master of Science / Department of Horticulture, Forestry, and Recreation Resources / Steven J. Keeley / Non-structural carbohydrates (NSC) are important for plant health and recovery from stress. Controlled-release N sources may moderate turfgrass vegetative growth, thereby maximizing NSC levels. Three studies were conducted to determine the effect of N source/timing on NSC levels, turfgrass visual quality, and color of ‘Midlawn’ bermudagrass and turf-type tall fescue. Additionally, the effect on low temperature tolerance of bermudagrass and brown patch incidence on tall fescue was investigated. Nitrogen sources included two polymer-coated ureas (PCU), a polymer-sulfur coated urea (SCU) and urea formaldehyde (UF). Total annual N was applied in either late summer or spring for bermudagrass, and either late summer or split between late summer and spring for tall fescue. Urea, applied at traditional timings, was a control in all studies. NSC status was determined at regular intervals by extracting two cores from each plot, defoliating, and measuring regrowth in a dark growth chamber. Turfgrass color, visual quality and brown patch incidence were rated monthly during the growing season. Bermudagrass low temperature tolerance was evaluated by subjecting plugs to a freezing regime and evaluating regrowth. Over the 2-yr study, N source did not have a significant effect on bermudagrass or tall fescue NSC levels, color, or visual quality. Timing of application, by contrast, did have a significant impact. For bermudagrass, August-applied N resulted in higher overall NSC levels and improved fall color. For tall fescue, split Sept/March applications improved color; but split Sept/ May applications reduced NSC compared to a single Sept application. Brown patch incidence was unaffected by N source or timing, though disease pressure was low. Timing of PCU application did not affect low temperature tolerance of bermudagrass, but PCU improved low temperature survival compared to urea.

Master of Science / Department of Agronomy / Charles W. Rice / Biotic interactions among mycorrhizal fungi, nematodes, plants and other microbial communities can have significant effects on the dynamics of C and nutrient cycling. The specific objectives of this study were (1) to evaluate the effects of grazing and mycorrhizal symbiosis on the allocation and storage of C, especially for plant above-and belowground biomass, (2) evaluate the biotic rhizosphere interactions and their role in C cycling, (3) determine the soil microbial community structure as a result of the plant-mycorrhizal symbiosis, and (4) determine the effect of mycorrhizal fungal abundance on soil aggregation. The soil for the experiment was sampled from the Ap horizon of a fine-silty, mixed, superactive, mesic Cumulic Hapludolls located at Konza Prairie Biological Station, Manhattan KS. The experiment was a three-way factorial in a complete randomized block design with four replications. The three factors were mycorrhizae (M), nematodes (N), and phosphorus (P). In a greenhouse study, 96 microcosms (52×32×40cm) were planted to Andropogon gerardii Vit. so that a third of the microcosms could be destructively sampled at the end of each growing season for three years. Plant biomass was separated into aboveground, rhizomes, and roots. All components were dried and weighed at harvest. Mycorrhizal fungi and P increased plant aboveground biomass, while nematodes decreased plant aboveground biomass compared to non-inoculated controls. As expected, P increased plant root biomass, while mycorrhizae increased plant rhizome biomass. Nematodes decreased both above- and belowground biomass. Phospholipid and neutral lipid fatty acid (PLFA and NLFA) analysis were determined for both soil and roots. Water-stable aggregates were separated using a modified Yoder wet-sieving apparatus and analyzed for mass, total C and N, and the isotopic composition of C. There was a positive relationship between AM fungal abundance in the soil and the mass of the largest macroaggregates (>2000µm) after the 3rd year (r=0.67). The effect of roots on the macroaggregate (>2000µm) fraction was not apparent. Phosphorus significantly increased smaller macroaggregates (250-2000µm), along with significantly enhanced plant root biomass, which indirectly demonstrated the effect of roots on the formation of macroaggregates (250-2000µm). The addition of P induced more plant derived C into the aggregates than the non-P amended microcosms as suggested by the [superscript]13C content of the aggregates. Our results confirmed the importance of biotic and abiotic interactions among mycorrhizae, nematodes, and phosphorus on plant growth and the resulting effect on the soil C cycle and soil aggregation.

Master of Science / Department of Grain Science and Industry / Jeffrey A. Gwirtz / Variation in wheat kernel hardness is influenced by several factors including genetic expression and environmental conditions. However, these factors explain only a portion of the observed variation. Thus, there are unknown contributors to this important physical property. The following experiments investigated growing locations between farms and within the spike as a source of variation. Four commercial varieties of Hard Red Winter (HRW) wheat were chosen for evaluation; Jagger, Jagalene, Overley, and 2137. In total, 374 wheat spikes were collected from three farms participating in the Kansas State University Research and Extension- 2007 Crop Performance Tests (KSCPT). For analyses, each kernel was removed and cataloged by spikelet and floret position. A total of 10,240 kernels were uniquely identified by variety, farm, plot, spike, spikelet and floret position. Using the single kernel characterization system (SKCS), kernels were crushed to determine the hardness, diameter, weight, and moisture content. The variability of each measured attribute was greatest between spikes of a given variety. Measured attributes exist in gradients along the spike, with the top and bottom portions being most variable. This research broadens our knowledge of wheat kernel variation, and results from this experiment may contribute to improved methods for single kernel analysis.

Doctor of Philosophy / Department of Agronomy / Gerard J. Kluitenberg / The Parsons soil has a sharp increase in clay content from the upper teens in the A horizon to the mid fifties in the Bt horizon. The high clay content continues to the parent material resulting in 1.5 m of dense, slowly permeable subsoil over shale residuum. This project was designed to better understand soil-water management needs of this soil. The main objective was to determine a comprehensive hydrologic balance for the claypan soil. Specific objectives were a) to determine effect of tillage management on select water balance components including water storage and evaporation, b) to quantify relationship between soil water status and crop variables such as emergence and yield, and c) to verify balance findings with predictions from a mechanistic model, specifically HYDRUS 1-D. The study utilized three replicates of an ongoing project in Labette County, Kansas in which till and no-till plots had been maintained in a sorghum [Sorghum bicolor (L.) Moench] – soybean [Glycine max (L.) Merr.] rotation since 1995. Both crops are grown each year in a randomized complete block design. The sorghum plots were equipped with Time Domain Reflectometry (TDR) probes to measure A horizon water content and neutron access tubes for measurement of water throughout the profile. Precipitation, evaporation, and perched water depth were determined at the field scale. Drainage was estimated as negligible after performing hydraulic conductivity measurements on the clayey subsoil. Runoff was determined as the residual in this water balance. Cumulative differences in the hydrologic balances as a result of tillage management were found to be minimal over an entire growing season. However, tillage treatment differences were seen in early season evaporation, surface water content, and the resulting residual runoff values. The chisel-disk treatments had greater evaporation leading to reduced runoff when compared with no-till. There was interaction between tillage treatment and time for surface water content measurements. No effect of tillage treatment was found for whole-profile water content. Crop variables were unaffected by tillage other than the first days emergence, and first days tillering being greater for chisel-disk treatments. No correlation between stored water and crop variables could be found. All aspects of field measurement were well supported by the predictions of the HYDRUS 1-D model.

Master of Science / Department of Agronomy / Scott A. Staggenborg / Volatile energy prices, energy independency, and environmental concerns have increased the demand for renewable fuel production in the United States. The current renewable fuel industry in the United States has developed around the conversion of starch into ethanol fuel, supplied mainly by corn (Zea mays L.) grain. Future energy demands cannot be met by corn grain alone; therefore greater amounts of biomass from traditional and alternative crops must be utilized. Nutrient removal by selected biofuel crops is important in order to determine biomass quality, required fertilizer inputs, and economic viability of biofuel cropping systems. The objectives of this study were to evaluate grain, stover, total biomass, and estimated ethanol yields of annual and perennial C4 crops grown under the same soil and weather conditions; and fermentable carbohydrate (FC) yields from extracted sweet sorghum juice. In addition, nitrogen (N), phosphorus (P) and potassium (K) concentrations of biomass were evaluated to determine total nutrient removal for annual and perennial crops. Field trials, at two locations in northeast Kansas, included corn, sorghum [Sorghum bicolor (L.) Moench] and perennial warm-season grass cultivars. Yields and nutrient removal were greater for annual crops than perennial grasses. Annual crop yields varied among cultivars, but were similar between locations and years. Perennial grass yields improved significantly from the 2007 establishment year to 2008, however nutrient removal was not affected by the yield increase. The highest grain yield and grain nutrient removal amounts were observed for corn across both years and locations. Total biomass yields were greatest for sweet and photoperiod sensitive sorghum cultivars. Average extracted sweet sorghum FC yields were 4.8 Mg ha[superscript]1. Estimated ethanol yields of sweet sorghum were greater than all other crop cultivars. Overall, nutrient removal was most affected by biomass yield variation among crop cultivars; however P concentrations, and subsequent removal, were dependent upon soil P levels at individual locations. These results suggest that annual crops can achieve the greatest biomass yields for multiple renewable fuel conversion processes, but are associated with high nutrient removal levels which must be considered when evaluating biofuel energy cropping systems.

Master of Science / Department of Agronomy / Charles W. Rice / The sequestration of atmospheric CO[subscript]2 into soil through no-till management is an economic and viable method for reducing greenhouse gases, but maintaining no-till practices are necessary to sequester C in the long-term. Our study focused on the effects of a single tillage operation on soil organic C and N and aggregation in no-till soils when no-till practices are immediately resumed after tillage. Three locations in western Kansas were selected that had been in continuous dryland no-till for at least 5 years – Wallace, Tribune, and Spearville. Tillage treatments were administered in 2004 and consisted of no-till (NT), disk plow (DP), sweep plow (SwP), and chisel plow (CP). Treatments were arranged in a randomized complete block design with four replications. Soil samples were taken at 0-5, 5-15, and 15-30 cm depths. Composite samples were taken from each block prior to tillage and tested for whole soil organic C and N. Further soil samples were collected in spring 2005 at approximately nine months after tillage (MAT) and again in fall 2005 at approximately 12 MAT and tested for whole soil organic C and N and aggregate size distribution. Bulk density was measured for each plot and depth prior to sampling at 12 MAT. Twelve MAT samples were also tested for aggregate-associated C and N. The DP tillage had a greater C concentration than NT and CP when averaged over depth and time, but C mass did not vary between tillage systems. Changes in whole soil C and N over time varied by location, but the differences were similar between tillage treatments. Tillage treatments DP and SwP also had a greater mass of macroaggregate (250-1000 [Mu]m) associated C relative to CP (but not to NT) for Wallace in the surface 0-5 cm at 12 MAT. No other differences between tillages in aggregate-associated C were observed. A single tillage event did not have a significant impact on aggregate size distribution. The greatest amount of aggregate-associated C and N existed in the large microaggregate (53-250 µm) fraction. Changes in aggregate distribution or aggregate-associated C or N did not directly correlate to changes in whole soil C and N. We therefore conclude that a single tillage operation using these implements will not result in a measurable loss in sequestered C over time for dryland soils in a semi-arid climate such as western Kansas.

Master of Science / Department of Agronomy / David B. Mengel / Grain Sorghum (Sorghum bicolor) is one of the most drought and stress tolerant crops grown in Kansas. For this reason, much of the sorghum is grown in high risk environments where other crops are more likely to fail or be unprofitable. Efficient sorghum cropping systems should not only produce high yields and use inputs such as nitrogen efficiently, but they should also remove as much risk as possible for a successful crop, and give farmers more flexibility in making input decisions. The price of nitrogen (N) fertilizer has increased substantially in recent years. Current retail prices for commonly used N fertilizers range from $0.88 to $1.50 per kilogram of N in Kansas. Thus, a farmer could easily invest $50-$100 per hectare in N, depending on the rate of N needed and the source used. Practices which allow farmers to assess crop potential as late as possible after planting before applying costly inputs like fertilizer, can increase the potential for a profitable return on those inputs in risky environments. Currently, most sorghum growers routinely apply all the N fertilizer prior to planting, sometimes as much as 6 months prior. The current Kansas State University (KSU) nitrogen recommendation is yield goal based and performs well when the grower is able to predict yield six months or more in advance of harvest. However, yield is quite variable and difficult to predict. Because long range weather and yield predictions are not very reliable, could deferring making N application decisions until later in the season when yield can be more accurately predicted reduce risk? Can the use of active sensors provide a better estimate of yield potential and nitrogen needs sometime after planting? If they can, how late can the decision be made and how best should the fertilizer N be applied? Several studies were conducted throughout Kansas to look at the effect of N rate, N application timing (pre-plant, side dress, or combinations of the two) and method of application on sorghum yield and N use efficiency. The studies were also designed to examine the potential of using optical sensors to predict optimum N rate for post-planting applications as a means of avoiding the use of soil tests to estimate soil N contributions. The objectives of this research were: a. to validate the KSU N fertilizer recommendations for grain sorghum grown in rotation with crops such as soybeans and wheat, b. to determine the effect of both preplant and midseason N applications on the growth and yield potential of grain sorghum, and to determine the optimal timing and method for midseason N applications on grain sorghum, and, c. to assess the potential of optical sensing of the growing crop to refine N recommendations using in-season applications during the growing season. This thesis will summarize the results from the various experiments we completed to achieve these objectives. The KSU N fertilizer recommendations for grain sorghum may need some revisions. This research suggests that including coefficients relating to N use efficiency may be necessary to get more accurate N recommendations. Both pre-plant and midseason N applications increased the yield of grain sorghum whenever a response to N was observed. There was no negative effect of applying all the nitrogen midseason at 30-40 days after planting when compared to pre-plant applications. Injecting nitrogen fertilizer below the soil surface had higher yields than other methods of midseason N applications such as surface banding or surface broadcasting, especially when a significant rainfall event did not occur within a few days of application. The optical sensors used in this study were very effective at making N recommendations 30-40 days after planting. These sensors will provide for more accurate N recommendations compared to the current soil test and yield goal method.