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Department of Horticulture & Landscape Architecture

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https://hdl.handle.net/10217/100453
These digital collections include theses, dissertations, faculty publications, and student publications from the Department of Horticulture & Landscape Architecture. Due to departmental name changes, materials from the following historical departments are also included here: Recreation Resources; Natural Resource Recreation and Tourism; Horticulture.

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Browsing Department of Horticulture & Landscape Architecture by Author "Andales, Allan, committee member"

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    Comparison of soil properties and Kentucky bluegrass shoots mineral composition prior to and after 10-11 years irrigation with recycled water
    (Colorado State University. Libraries, 2016) Lin, Yuhung, author; Qian, Yaling, advisor; Davis, Jessica, committee member; Klett, James E., committee member; Andales, Allan, committee member
    In Colorado, fresh water is one of the most valuable and limited natural resources. Due to population growth, an increase of fresh water withdrawal has been reported by U.S. Geological Survey. Irrigation with recycled water has been utilized as a means to alleviate the stress on potable water supplies and facilitate the reuse of treated wastewater. Recycled water irrigation is taking place at landscape sites such as public parks, golf courses, and school playgrounds. Research information is needed to better understand the long-term effects of recycled water irrigation on urban landscapes. Therefore, the objectives of this research were to: 1) assess changes in soil chemical properties after 5 and 11 years of recycled water irrigation, 2) determine if there is any heavy metal accumulation in soil after 11 years of recycled water irrigation, 3) evaluate Kentucky bluegrass (Poa pratensis L.) (KBG) turf quality grown on golf courses irrigated with recycled water, and 4) determine the relationship of turf quality to shoot mineral concentrations and soil chemical properties. To address Objectives 1 and 2, soil samples were collected and analyzed at the commencement (in 2004) and 11 years after recycled water irrigation on three golf courses, 5 metropolitan parks, 1 school ground, and 1 zoo. Samples were taken at 0-20, 20-40, 40-60, 60-80, and 80-100 cm depths on golf courses and at 0-20 and 20-40 cm depths at other locations. Soil was analyzed for texture, soil pH, soil organic matter, soil salinity [soil electrical conductivity (EC)], exchangeable sodium percentage (ESP), cation exchange capacity (CEC), nitrate-N, chloride (Cl), boron (B), and AB-DTPA extracted phosphorus (P), iron (Fe), manganese (Mn), arsenic(As), chromium (Cr), cadmium (Cd), cobalt (Co), nickel (Ni), lead (Pb), zinc (Zn) and copper (Cu). Averaging over all sites, soil pH was 0.25-0.3 higher in 2015 and 2009 than in 2004. The increase was greater at deeper depths. Soil salinity (EC) was 0.84, 0.88, and 0.98 dS m-1in 2004, 2009 and 2015, respectively. The magnitude of increase in ESP after recycled water irrigation indicated potential sodicity problems. Calcium based product applications reduced ESP at soil surface depths. In contrast, significant increase in ESP was found at deeper soil depths. No increase in soil nitrate-N was observed over 5 and 11 years with recycled water irrigation, therefore, leaching of nitrogen to the groundwater was not a great concern. AB-DTPA extracted As, Co, and Ni decreased after 11 years of recycled water irrigation. Soil Cd, Cr, Cu, Pb, and Zn did not show significant change from 2004 to 2015. Results revealed that there was no sign of heavy metal accumulation. To address Objectives 3 and 4, research was conducted on eight golf courses, including three courses in Denver after 10 years of recycled water irrigation, three courses in the nearby cities receiving recycled water for more than 10 years, and two courses receiving fresh surface water for irrigation. Results indicated that Na concentration in KBG shoot tissues increased by 4.3-9.9 times, Cl by 1.5-1.3 times, B by 1.3-3.5 times whereas K/Na ratio was reduced by 74-90%. Multiple regression analysis indicated shoot Na accumulation had the highest association to turf quality decline (R2= 0.65). Soil sodium adsorption ratio (SAR) in 0-20 cm depth was highly associated with KBG shoot Na concentration (R2= 0.70).
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    Irrigation effects on growth, stress, visual quality and evapotranspiration of ornamental grasses
    (Colorado State University. Libraries, 2016) Hagopian, Sam R., author; Klett, James E., advisor; Qian, Yaling, committee member; Andales, Allan, committee member
    Deficit irrigation research has proven extremely effective for reducing the amount of irrigation applied to various types of landscape plants including trees, shrubs, and herbaceous ornamental plants. This research has yet to delve into one of the most common classes of drought tolerant plants, ornamental grasses. Deficit irrigation treatments were based on evapotranspiration of a short reference crop (Kentucky bluegrass evapotranspirtation, ETo). In 2012 three ornamental grass species were planted, and an on-site atmometer was used to estimate ETo. The three species used for trialing were Panicum virgatum ‘Rotstrahlbusch’ (Rotstrahlbusch Switchgrass), Schizachyrium scoparium ‘Blaze’ (Blaze Little Bluestem), and Calamgrostis brachytricha (Korean Feather Reed Grass). Treatments were applied and data was collected in 2014 and 2015 on two separate studies. The first study was in-ground and consisted of four treatments based on ETo (0%, 25%, 50%, and 100%). The second study was a mini-lysimeter and consisted of three treatments based on ETo (25%, 50%, and 100%). Only Schizachyrium scoparium ‘Blaze’ (Blaze Little Bluestem) was used in the lysimeter study. Data collected in both studies included plant water potential, biomass accumulation, green up date, flowering date, height, width, circumference, floral impact, landscape impact, overall habit, self-seeding, and color. The in-ground component also measured infrared canopy temperature and soil water content, while the lysimeter study included daily weight measurements which were then transferred to evapotranspiration readings. Plants in the 0% treatment were smaller and not considered visually suitable for landscape use. All three species in the 25% treatment performed equivalent to the 50% and 100% treatments in all categories. The only exception was plants in the 25% mini-lysimeter study were more stressed than the 50% or 100% treatments during periods of drought. These plants were all considered visually suitable for landscape use based on visual ratings. This suggests that as long as ornamental grasses are kept on a strict weekly regiment of 25% ETo, and are never exposed to periods of drought, they will be physiologically as well as aesthetically usable in the landscape trade. A weekly amount of 0.25 inches of irrigation on weeks without precipitation was determined to be a usable number for those installing and maintaining ornamental grasses.