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The Effect Of Salinity Level Upon The Yield, Root Growth, And Water Extraction Of Contrasting Rooting Subpopulations Of Alfalfa (Medicago Sativa) Under Conditions Of Zero Leaching, Laura A. Vincent

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

A major problem in irrigated agriculture in the Western U.S. is the gradual accumulation of salinity in the plant root zone. These nonuniformly saline soils contain increasing amounts of salinity with depth, and salt accumulation is accelerated in situations where leaching is minimized. Root growth and thus plant yield is limited in these soils due to decreased water uptake. We studied the root growth of two subpopulations of alfalfa differing in their ability to produce fibrous roots to determine if altering root morphology would increase plant yield and water extraction, in an irrigated saline soil.

Soil profiles for a control …

The Effects Of Osmotic Potential On Ammonification, Immobilization, Nitrous Oxide Production, And Nitrification Rates In Penoyer Soil, Andrew P. Low

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

An isotopic dilution method was used to test the effects of osmotic potential, (𝛹_s), upon nitrification, ammonification, N-immobilization, and nitrous oxide production rates in soil at solute concentrations encountered in Penoyer soil. A nitrification potential assay was also performed to approximate maximum nitrification rates.

Nitrification potential rates in soil slurries exponentially declined in response to decreased osmotic potential. However, nitrification was independent of salt concentration at the ambient NH₄⁺ concentrations of the soil. The differential response was attributed to the variable NH_4⁺ substrate quantities. The effects of osmotic potential were secondary to NH_{4 …}

Livestock As Seed Disseminators For Reseeding Degraded Rangelands: The Role Of Dung In Gap Formation And Plant Establishment, Brian S. Auman

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

Livestock (cattle and sheep) were examined as seed disseminators for reseeding degraded Intermountain rangelands. "Hycrest" crested wheatgrass [Agropyron desertorum (Fisch. ex Link) Schult. X A. cristatum (L.) Gaert.] seed was fed to yearling Holstein steers and Suffolk ewes. Dung was collected from each animal type and deposited on plots of high and low densities of an annual [cheatgrass (Bromus tectorum L.)] and perennial [squirreltail (Sitanion hystrix Nutt.)] grass species. The experiment evaluated the ability of the dung to suppress the resident vegetation, and the recruitment and establishment of Hycrest seedlings emerging from the dung.

Sheep dung had …

Growth Responses Of Great Basin Plant Species To Variation In Nitrogen Availability, Carol J. Bilbrough

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

For this dissertation, I examined the ability of field-grown plants to capture N presented in enriched patches or in whole-plant pulses. I assessed root proliferation in N-enriched patches when Agropyron desertorum plants had been previously fertilized or shaded. All plants responded with increased root growth rates in N-enriched patches. However, root proliferation by shaded plants was 50% less than unshaded plants. Unexpectedly, plants with higher N status had greater root growth rates in enriched patches than plants that had not received N supplement. I concluded that plants already under competitive pressure above ground for light and below ground for nutrients …

Ecological Amplitude And Invasion Of Diffuse Knapweed At Yakima Training Center, Washington, Donna Denise Wilcox

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

Diffuse knapweed (Centaurea diffusa) is an introduced annual or short-lived perennial from Eurasia that has become a threat to native rangelands in the Pacific Northwest. Military training activities on the Yakima Training Center (YTC) increase the likelihood that knapweed will expand its range at YTC. This study, conducted in a major watershed at YTC, focused on: 1) how a variety of environmental variables influences knapweed distribution, 2) the use of Landsat Thematic Mapper (TM) imagery to map existing knapweed populations, and 3) the use of a logistic regression model and geographical information systems (GIS) to create a potential …

An Integration Of Tillage And Herbicides To Control Jointed Goatgrass (Aegilops Cylindrica Host.) In Winter Wheat, Troy M. Price

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

An integrated management approach for jointed goatgrass control was investigated at two farms in northern Utah using three tillage regimes and tree herbicides. The tillage regimes included no tillage, conservation tillage, and conventional tillage. Each regime was composed of different tillage practices common in the Intermountain West. A preemergence herbicide, clomazone, and two postergance herbicides, 2, 4-D and glyphosate, were investigated. Greenhouse studies were also conducted to investigate clomazone efficacy and depth of planting of winter wheat and jointed goatgrass.

Differential sensitivity to clomazone between jointed goatgrass and winter wheat did not occur in the greenhouse for the rates tested. …

Superoptimal Co2 Reduces Seed Yield In Wheat, Timothy P. Grotenhuis

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

Although projected terrestrial CO₂ levels will not reach 1000 μmol moI^-1 (0.1%) for many decades, CO₂ levels in growth chambers and greenhouses routinely exceed that concentration. CO₂ levels in life support systems in space can exceed 10,000 μmol moI^-1 (1%) CO₂. Numerous studies have examined CO₂ effects up to 1000 μmol mol^-1, but theoretical and some experimental evidence indicates that the beneficial effects of CO₂ continue past 1000 μmol mol^-1 and are near-optimal for wheat at about 1200 μmol mol^-1.

We studied the effects of near-optimal …