Thesis (Ph. D.)--University of Tennessee, Knoxville, 2009. / Title from title page screen (viewed on Nov. 2, 2009). Thesis advisor: Thomas C. Mueller. Vita. Includes bibliographical references.

Thesis (MS)--Montana State University--Bozeman, 2009. / Typescript. Chairperson, Graduate Committee: Alan T. Dyer. Includes bibliographical references.

Master of Science

Current Virginia soft red winter wheat (Triticum aestivum L.) management strategies have been in place for over 20 years. A new advanced intensive management (AIM) system has been evaluated in order to improve Virginia wheat yields and attempt to bring state average wheat yields of 4288 kg ha⁻¹ more closely in-line with the maximum yield achieved in the Virginia Tech Official Soft Red Winter Wheat Trials of 7400 kg ha⁻¹. Increases in nitrogen (N) fertilizer application rates and splits, a chelated micronutrient blend, increased seeding rates, and a "no tolerance" pest control methodology were compared to current intensive management practices in this study. Additional fall N application and an increased seeding rate resulted in an increased number of tillers m-2 at growth stage (GS) 25 and biomass at GS 30. This increased number of tillers may lead to a greater amount of viable grain head production and increased wheat yields. Higher seeding and N application rate resulted in dramatically increased lodging in 2009 with resultant yield loss. Grain yield was significantly affected by management type in three of six instances. The number of heads m-2 was the yield component factor most influenced by factors tested in these studies. / Master of Science

Doctor of Philosophy / Department of Agronomy / Kraig L. Roozeboom / Previous research has revealed that winter wheat (Triticum aestivum L.) yields are often reduced following grain sorghum [Sorghum bicolor (L.) Moench] compared to wheat after other summer crops. The objectives of the study were to: (a) evaluate grain sorghum residue management strategies to improve the performance of a following winter wheat crop in no-till systems; (b) determine grain sorghum hybrid characteristics that facilitate planting wheat following grain sorghum, and identify winter wheat cultivars that are suitable for planting after grain sorghum; (c) evaluate effect of environment, sampling time, and grain sorghum hybrid plant pigmentation on phenolic acid concentration in sorghum residues. Experiments were conducted in environments suitable for planting winter wheat following a summer crop. Treatments for objective one were: glyphosate (pre-harvest application, post-harvest, none), residue (removed, chopped, left standing), and nitrogen (34 kg ha⁻¹ applied to residue, none). Treatments for objective two and three were grain sorghum hybrids representing three maturities (early, medium, medium-late) and two plant pigmentations (red, tan), wheat cultivars occupying significant planted acreage and having favorable performance within the region. Wheat yields increased in two environments by 217 and 630 kg ha⁻¹ when glyphosate was applied to the sorghum pre-harvest. Residue chopping or removal either had no effect or a negative effect on wheat yields compared to residue left standing. Nitrogen applied to the sorghum residue increased wheat yields in only one environment. Grain sorghum hybrid characteristics did not influence winter wheat yields in any environment, but winter wheat cultivar did influence grain yields of the winter wheat in three of the four environments. Breakdown of phenolic acids depended on environment. Results for these studies indicate that wheat yield after a grain sorghum crop can be maximized by planting a red-pigmented sorghum hybrid of an early or medium maturity, desiccating the sorghum crop with pre-harvest glyphosate if it can be applied to the sorghum roughly 45 to 50 days before a frost, and with a wheat cultivar that is well suited to no-till planting.

Pheasant Eye (Adonis annua L.), a native of Europe, is commonly cultivated as an ornamental, but ocasionally escapes into fields and waste places. It is prevalent in certain area in the United States, especially southward, on heavy soils that are inadequately drained (20). This Plant is one of a number of early maturing winter annual weeds that infests dryland wheat in northern Utah, and it has become a problem in certain lowland areas.

Large sums of money are spent annually for herbicides to control weeds in fall sown wheat. Many of these weeds are killed by such treatments while others survive and mature seed. Viability of seeds produced by weeds injured by systemic or growth regulator type herbicides has long been a matter of great interest, much speculation, and very little research. Data on this subject are needed in order to intelligently use chemicals for weed control.

The objective in wheat hybridization primarily is to obtain new varieties which are of a greater agronomic value than existing varieties. Frequently, however, crosses which obviously will not produce superior commercial types are made and studied in order to obtain genetic information which may be useful to the breeder. This latter phase of breeding, i.e., the accumulation of genetic information, provides the basis for this study.

Graduation date: 2000

Winter wheat is commonly grown in dryland cropping systems in the Pacific Northwest region of semi-arid eastern Oregon. For agronomic, economic, and environmental reasons, it is important to understand the long-term sustainability of such dryland systems. The objective of this study was to evaluate the long-term effects of tillage, nitrogen (N), soil depth, and the influence of precipitation on wheat yields in dry land cropping systems of eastern Oregon. Data were taken from the Tillage/Fertility or "Balenger" experiment, which was established in 1940 by a Soil Conservation employee, and is one of the oldest replicated research experiments in the western United States. The experiment consisted of a winter wheat-summer fallow rotation arranged in a randomized block design with three replications. The main plot consisted of three primary tillage treatments (moldboard plow, offset disk, and subsurface sweep) and subplots consisted of six nitrogen treatments that changed over time and most recently ranged from 0 to 180 kg ha�����. Soil depth of individual plots ranged from 1.2- to 3.0-m. The study was divided into four main time periods (1940-1951, 1952-1961, 1962-1987, and 1988-1997) within which experimental treatments were consistently maintained. The moldboard plow tillage treatment significantly increased yields by more than 300 kg ha����� over the subsurface sweep tillage treatment in all four time periods. Yields with the moldboard plow system were significantly higher than with the offset disk system in time periods 3 and 4. The same trend was evident for mean yield in time periods 1 and 2, but differences were not statistically significant. In time periods 1, 2, and 3, mean yields were higher with the offset disk tillage treatment than the subsurface sweep tillage system, although the differences were not statistically significant. In time period 4, mean yield was higher for the subsurface sweep system than the offset disk treatment, but differences were not statistically significantly. The optimum amount of N for winter wheat differed from year to year, within, and between experiment periods. This was apparently in response to rainfall patterns and improved management factors, specifically more N responsive semi-dwarf varieties. For time period 1, the maximum fertilizer rate was 11.2 kg N ha�����, which tended to produce higher mean grain yields than an application rate of than 0 kg N ha�����, regardless of the quantity or distribution of precipitation. For time period 2, the maximum fertilizer rate was 33.7 kg N ha�����, which produced significantly higher grain yields than an application rate of than 0 kg N ha�����, regardless of the quantity or distribution of precipitation. For time period 3 (1962-1987), which had below-normal annual and growing season precipitation, yield increased with the addition of 45 kg N ha�����. For time period 4 (1988- 1997), which had above-normal annual and growing season precipitation, yield increased with the addition of 90 kg N ha�����. Yield increases at greater rates of N were insignificant. For time periods 3 and 4, maximum mean yield was obtained at an application rate of 135 kg N ha�����. The response of wheat yield to N during dry years was greater for deep (> 2.8 m) soils than for shallow soils. In addition to amount, rainfall distribution during the winter (October to March) and growing (April to June) season significantly affected yield. Results demonstrate the importance of rainfall and nitrogen to winter wheat production in eastern Oregon, and that the most environmentally sound tillage systems are not necessarily the most profitable from farmers' point of view. / Graduation date: 2000