Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 2007. / Source: Dissertation Abstracts International, Volume: 68-06, Section: B, page: 3456. Adviser: John A. Juvik. Includes bibliographical references (leaves 117-153) Available on microfilm from Pro Quest Information and Learning.

Agricultural production is vulnerable to climate change. However, this vulnerability can be reduced by adapting food crops to a hotter climate. Many studies have ignored adaptation when quantifying the effect of climate change on crop yield, which has likely overestimated yield losses. Therefore, it is necessary to quantify agriculture's adaptive potential to climate change. Such work is challenging because there are no historical analogues to current or future warming. In place of such a precedent this work explores the varying sensitivity of maize yield to elevated temperatures through a suite of multiple linear regression models. These models use high resolution yield and crop development data available since 1981 in the United States to account for overlooked features of maize physiology and agricultural management. The results of these models substantially alter estimates of how crops will respond to a warming environment. The studies here illustrate how finer scale details can be incorporated into broader regional models. Temperature sensitivity is found to vary with local climatology indicating that maize cultivars are adapted to their particular environment. Incorporating this historical adaptation into estimates of yield loss substantially reduces the effect of a modest warming. A physiological basis for spatial adaptation is apparent when maize development data are incorporated into the model -- cooler regions accelerate through sensitive development phases faster than hotter areas. The development data also suggest that crop development has been adapted to the seasonal cycle and that a non-trivial portion of the temporal trend in maize yield has resulted from management adjustments. Finally, the importance of spatio-temporal variation in temperature sensitivity is highlighted through case studies of recent years with record-setting yield losses. Spatial and/or temporal variation in temperature sensitivity is necessary to reduce bias in estimates of yield loss in these years. This work builds from previous conclusions regarding the negative effects of hot temperatures, and suggests that while hotter temperatures will harm maize yields there are steps that farmers might take to manage and reduce these losses. Taken together these results quantify how extant adaptation may help to ameliorate yield losses in a hotter future. / Earth and Planetary Sciences

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The estimation of chlorophyll content is an essential biochemical parameter to track the main developmental stages and yield of cereals relevant for precision agriculture. Traditional techniques for chlorophyll content measurements are time consuming, expensive and laborious. Measurements at field level have proven to be a good alternative, but their use is limited due to extensive sampling designs and techniques. Several spectral chlorophyll indices have been developed to estimate chlorophyll content both at the leaf and canopy level using remote sensing data. A methodology of using spectral chlorophyll indices to estimate chlorophyll content from laboratory and satellite hyperspectral data was carried out in this study for wheat crops. The application of this technique under agricultural field conditions has been very limited and not rigorously validated for wheat crops. The main objective of this study is to validate the chlorophyll content estimation using spectral chlorophyll indices, and to examine the potential for chlorophyll content estimation using hyperspectral remote sensing data in the context of precision agriculture. (Abstract shortened by UMI.)

Soil loss in eastern Ontario is of great concern. The objective of this study is to map soil loss risk in Eastern Ontario for 2001. The universal soil loss equation (LISLE), the universal soil loss equation 2 dimensions (USLE2D), and the unit stream power erosion deposition (LISPED) models are applied within a Geographic Information System (GIS) to calculate soil loss within agricultural fields. Hourly precipitation, soil survey, digital elevation, field boundary, and satellite imagery data are main inputs used to generate model parameters at non-depositional areas. These datasets are integrated to compute mean annual and monthly soil loss at multiple scales. For precision agriculture purposes, results are given as a number of high precision, high accuracy soil loss grids and associated summary tables under a variety of farming practices and erosion processes. Results indicate that: (1) soil loss is occurring at intolerable levels (>6 t ha-1 yr -1) in the region, particularly in the southeastern study region, (2) slope steepness followed by the cropping and management factor affect soil loss to the greatest extent, and (3) under no tillage systems, a considerable amount of soil is lost at intolerable levels in high slope areas. (Abstract shortened by UMI.)

The apple maggot fly, Rhagoletis pomonella (Walsh), is a key pest attacking apple fruit in eastern and midwestern North America. Sticky-coated 8-cm spheres baited with fruit odor (butyl hexanoate) have been the mainstay of a behavioral approach to direct maggot fly control. Improvements upon the red sphere trapping system are needed, however, if it is to be feasible and cost-effective for widespread commercial use. Several aspects of visual and odor stimuli influencing apple maggot fly captures on sticky red spheres were investigated. Results indicated that the efficacy of spheres in capturing adults was not improved by increasing sphere size to a diameter greater than that of 8-cm or by using more synthetic fruit odor (butyl hexanoate). Significant improvement was attained by using synthetic food odor (ammonium carbonate) together with butyl hexanoate. Distance (15-60 cm) of a butyl hexanoate source from a red sphere had no significant effect on fly captures. Semi-natural (field cage) conditions were used to examine response patterns of females to red spheres in relation to fly age and prior ovipositional experience. As fly age increased from a reproductively immature stage to a mature stage, the probability of a fly finding a sphere hung in a host tree increased. Simultaneously, the likelihood that a fly would deposit eggs in host fruit before encountering a sphere increased. Prior experience with different species or cultivars of host fruit did not have significant effect on the ability of flies to find red spheres but reduced the likelihood of oviposition in unfamiliar fruit. Prior experience with the same species or cultivar of host fruit had no apparent effect on fly ability to find a red sphere trap or to oviposit in familiar fruit. Various feeding stimulants, pesticides, and residue-extending agents were evaluated in laboratory and field cage experiments for suitability in developing a nonsticky lethal sphere. Spheres treated with a mixture containing 1.05% (a.i.) dimethoate (insecticide), 58.95% corn syrup (feeding stimulant) and 40% latex paint (residue extending agent) and not exposed to weather killed a great majority of alighting flies. However, these spheres became ineffective after exposure to weather (rainfall). Retreating weather-exposed spheres with feeding stimulant restored effectiveness. Studies conducted in commercial orchards showed that pesticide-treated spheres, like the sticky spheres, had much potential for eliminating insecticide sprays against the flies. Current necessity of retreating pesticide-treated spheres with feeding stimulant after each rainfall compromises present utility for commercial use. Development of a polymer to protect residual effectiveness of feeding stimulant is key to further widespread commercial use of this simpler behavioral approach to controlling apple maggot flies.

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.

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.

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.