Browsing by Author "Qian, Yaling, advisor"
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Item Open Access Analysis of root growth in two turfgrass species with minirhizotron and soil coring methods(Colorado State University. Libraries, 2015) Young, Jason Scott, author; Qian, Yaling, advisor; Comas, Louise, advisor; Ocheltree, Troy, committee memberIn this study root growth of a turf-type variety of inland saltgrass (Distichlis spicata L. Greene) (a native grass with varieties in development by Colorado State University) and Kentucky bluegrass (Poa pratensis L.) (a common turfgrass planted in the arid and semi-arid west) was examined under saline conditions in a pot experiment and non-saline conditions in the field. Since turfgrass is a high user of water, the turf industry is interested in using native species that use less water and also salt-tolerant species, which may allow the industry to use marginal water (grey water) for irrigation. However, plants with different root distributions will need to have irrigation managed differently. These experiments examined root growth differences in saltgrass and Kentucky bluegrass to begin exploring how these species might need to be managed differently in saline and non-saline conditions. Two separate experiments were conducted to answer the two objectives of this research: (I) to evaluate root growth of inland saltgrass under saline conditions in a growth chamber and (II) observe unrestricted root growth in the field both over time with a minirhizotron camera system, and in stands of differing age with a soil coring method. In the first experiment, root growth in container grown saltgrass under salt stress showed increased flushes of fine root growth in response to moderate levels of salinity (8 dS/m) compared to the control. Root growth increased about 3 weeks after salt treatments began, suggesting that this time frame was long enough for ionic stress to occur in the shoots root responses were seen. In-growth root tubes placed in the soil of the salt stressed saltgrass showed trends of increasing root and rhizome growth with increasing salt stress, this was opposite the trends seen in Kentucky bluegrass. In experiment II, field-grown saltgrass plots of varying stand age (1, 4, 5, and 8 years) had less root biomass in soil layers less than 30 cm compared to bluegrass. Kentucky bluegrass root biomass was nearly zero below 30 cm, whereas saltgrass had roots down to 275 cm in stands that had been growing longer than 4 years. In soil layers up to 1.8 m, saltgrass root mass was greater with increasing stand age. Minirhizotron observations showed that 15°C was the soil temperature at which root growth began in saltgrass and dramatically slowed in Kentucky bluegrass which had a growth range of 0 to 15°C. When soil temperatures were above 15°C saltgrass roots continued to grow at a slow but steady rate during the summer months. Findings that saltgrass produced roots deeper in the soil profile and was responsive to saline soil may impact where and when it is used. If stored moisture is present deep within the soil, saltgrass has a unique ability to mine this water that would be out of reach of shallower rooted turfgrasses. Deep rooting can also have implications for slope stabilization which can be important in the arid west where bare slopes can be stripped of soil during heavy and infrequent rainstorms. The responsiveness of rooting in saline soils may be the underlying mechanism explaining the enhanced growth of saltgrass under mild saline conditions. Increased surface area from new fine root production can enhance root water uptake providing more water to growing shoots. More studies are needed to explore root responsiveness in many types of plants, including saltgrass, to discover the true benefit of fluctuations in root system architecture.Item Open Access Changes in golf course fairway soils under effluent water irrigation(Colorado State University. Libraries, 2010) Skiles, David John, author; Qian, Yaling, advisor; Andales, Allan A., committee member; Koski, Tony, committee memberAs the use of effluent irrigation increases, salinity and sodicity issues associated with its use continue to be of great concern to the golf course industry. The purpose of our research was to (i) observe salinity accumulation patterns on 4 fairways of two effluent water irrigated golf courses using 2 different types of sensors and to (ii) determine long-term changes in soil chemistry in soils under effluent water irrigation on golf course fairways. Temporal and spatial accumulation patterns were measured using a network of in-situ soil sensors located at two depths 15 and 30 cm for 5TE sensors and 8 and 19cm for Turf Guard sensors (TG2). Sensors measured electrical conductivity (EC), volumetric soil water content (SWC), and soil temperature data were collected continuously during the 2008 and 2009 growing seasons. Correlation was observed between 5TE sensor-measured soil salinity vs. saturated paste extracted soil salinity (r = 0.77). A significant exponential relationship was observed between TG2 sensor-measured soil salinity vs. saturated paste extracted soil salinity (R² = 0.97). In-ground measurements indicated that salinity can vary widely across a seemingly homogenous golf course fairway in a manner reflective of the underlying soil physical characteristics. Plots exhibiting low and high salinities presented opposite seasonal trends at Heritage Golf Course. Strong correlation was observed between average soil salinity and mean soil water content (r =0.76), soil salinity and the percentage of sand in the soil texture composition (r = -0.63) for Heritage fairway 1. High salinity was found on fairway 19 at Common Ground Golf Course. However, the salinity level as high as 10.6 dS/m is not a result of water reuse, but a historical geological contribution. Drainage appears to be vital in maintaining low soil salinity levels under effluent irrigation in clay soils. Slow to infiltrate, percolate and difficult to leach; predominately clay soils irrigated with effluent water can accumulate soil salinity over time. Our data suggested that a robust drainage network in predominantly clay soils irrigated with effluent could better manage salinity accumulation associated with poor drainage. To determine long-term changes in soil chemistry in soils under effluent water irrigation on golf course fairways, soil testing data was provided by the superintendent for the years of 1999, 2000, 2002, 2003, and 2009 for Heritage Golf Course in Westminster, Colorado. Soil samples were tested by Brookside Laboratories, Inc, New Knoxville, OH. Parameters of each soil sample tested included pH, extractable salt content (calcium, magnesium, potassium, sodium, iron, manganese, copper, zinc, phosphorus, and boron), base saturation percent of calcium, magnesium, potassium and sodium, soil organic matter (SOM), and cation exchange capacity (CEC). Regression analysis was used to evaluate the changes in individual soil parameters over time after the use of effluent water for irrigation. Soil pH, CEC, extractable aluminum, copper, manganese and iron along with both base saturation percentages and exchangeable percentages of calcium and magnesium did not change over time. The strongest indications of change are seen for extractable boron (R² = 0.56), Bray II extracted phosphate (R² = 0.56), and sodium base saturation percentage (R² = 0.44). The regression analysis indicated that B, P, and sodium increased linearly during the 8 year's irrigation with effluent water. Further studies are needed to determine if these parameters would continue to increase or would stabilize. Continued accumulation of sodium could eventually result in loss of soil structure.Item Open Access 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 memberIn 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).Item Embargo Drought and salinity tolerance of cool-season turfgrasses(Colorado State University. Libraries, 2024) Li, Jizhou, author; Qian, Yaling, advisor; Burcham, Daniel C., committee member; Ham, Jay, committee member; Zhang, Yao, committee memberDue to the water scarcity and increased use of recycled water/saline water for turfgrass irrigation in arid and semi-arid climates, there is an increasing demand for drought and salt tolerant turfgrass. Kentucky bluegrass (Poa pratensis L.), tall fescue (Festuca arundinacea Schreb.), and perennial ryegrass (Lolium perenne L.) are the most commonly used cool season turfgrass species in the northern regions of the United States. The thesis includes two separate studies evaluating entries in National Turfgrass Evaluation Program (NTEP) trials. These two trials were conducted to identify the most drought tolerant lines of Kentucky bluegrass and tall fescue grown in a field study, and the most salt tolerant lines of perennial ryegrass grown in a greenhouse study, respectively. The drought tolerance trial is presented in Chapter 1. In it, the drought tolerance of thirty-five cool-season turfgrasses, including 15 Kentucky bluegrass lines, 19 tall fescue lines, and 1 perennial ryegrass line were evaluated under three deficit irrigation treatments, 40%, 60% and 80% evapotranspiration (ETo) from 2018 to 2020. Overall turfgrass quality, minimum irrigation requirement for maintaining the acceptable quality, and length of time to maintain acceptable quality were determined for each entry. The amount of irrigation needed to maintain acceptable quality for tall fescue was 71% - 95% ETo, and for Kentucky bluegrass, it was 81% - 110% ETo under three-year deficit irrigation. Based on turf quality and irrigation requirement to maintain acceptable quality during the three-year deficit irrigation period, we have identified the most drought tolerant entries. Among Kentucky bluegrass entries, "PST-K13-141" has emerged as the top performer, demonstrating an 81% ETo rate to maintain acceptable quality. Among tall fescue lines, the most drought-tolerant entries include "PST-5SDS," "Kingdom," "DLFPS 321/3679," and "Thor," requiring 71%, 74%, 74%, and 72% ETo, respectively, to uphold satisfactory turf quality. The results of this study suggest that selecting species and entries that use less water while maintaining acceptable quality could mitigate irrigation demands. In Chapter 2, the salt tolerance of eighty-three perennial ryegrass lines was evaluated in two separate greenhouse experiments. Eighty-three lines were grown in cone-shaped containers that were soaked in increasingly saline nutrient solution for 1 hour per day. The solution began with an electrical conductivity (EC) of 6.0 dS·m-1 and was subsequently increased by 4.0 dS·m-1 (in Experiment I) or 6.0 dS·m-1 (in Experiment II) every 3 weeks until reaching the next targeted salinity level. The final targeted salinity level was 22 dS·m-1. Grasses were grown under each of the 4 or 5 targeted salinity levels for a period of 3 weeks. Clipping yield reduction, overall turf quality, leaf firing, and density were determined at each salinity level. Regression analysis was conducted to determine the relationship between clipping yield and salinity. The salinity level causing a 25% reduction in clipping yield was used as an indicator of salinity tolerance level in different entries. We found that entries "SGP4", "PPG-PR 667", "PVF-SGS5", "BAR LP 22262", "GO-RUS21", "PPG-PR 610", "DLF-PR 3727", and "PPG-PR 639" were the most salt-tolerant, evidenced by the best turfgrass quality and the highest salinity levels at which there was a 25% clipping yield reduction in two experiments. We observed that the salinity levels that caused a 25% clipping yield reduction ranged from 5.0-8.8 dS·m-1 in experiment I and 5.7-10.7 dS·m-1 in experiment II. The entries with better salt tolerance identified in this study would hold the potential to be utilized on sites with marginally elevated saline soil. Additionally, they could be beneficial for locations where irrigation involves waters with elevated salinity, such as recycled water.Item Open Access Effects of topdressing established Kentucky bluegrass with composted manure(Colorado State University. Libraries, 2005) Johnson, Grant A., author; Qian, Yaling, advisor; Davis, Jessica, advisor; Koski, Anthony J., committee memberConcerns about water quality issues surrounding nutrient loading into surface and ground water from agricultural manure applications have contributed to the increasing interest in composting manure and topdressing it on turfgrass to alleviate manure pollution. Little information is available regarding the effects of composted dairy manure topdressings on established turfgrass. The objectives of this research were to evaluate the effects that topdressing composted manure has on: (i) turfgrass growth and quality, (ii) soil physical and chemical properties, (iii) turfgrass quality and soil moisture content during periods of dry down, and (iv) nutrient runoff and leaching during simulated rainfall event. Compost was topdressed onto three cultivars ('Nuglade', 'Livingston', and 'Kenblue') of established Kentucky bluegrass (Poa pratensis L.) at rates of 0, 33, 66, and 99 m3 ha-1, twice in 2003 and once in 2004. A synthetic fertilizer (Urea 46-0-0) was added to help balance inorganic N rates among treatments. Compost treatments had 6-10% higher quality than the control during the growing seasons, produced 18-56% higher clipping yields in late summer months, and helped retain turfgrass color longer into the fall and allowed for faster spring green up. Compost treatment 99 m3 ha-1 reduced surface soil (0-3 cm) bulk density by 5.3% and increased water retention by an average of 14.2% over all tensions tested. Compost treatments increased soil P, K, Fe and Mn in the 0-10cm depth. During 10-day dry down periods, compost treatment increased soil moisture in the 15-30 cm soil depth during the first 2-3 days, which in turn, increased soil moisture in the 0-15 cm depth towards the end of dry down and led to 1.2-3.3 °C lower canopy temperatures compared to the control. Runoff collected revealed no differences in NO3-N or total phosphorus concentrations among treatments, and mean NO3-N concentrations (6.5 mg L-1) were below the EPA standards, while mean TP concentrations (1.1 mg L-1) slightly exceeded EPA standards. No differences in leaching potential occurred among treatments. From these results it is recommended that manure compost be topdressed to Kentucky bluegrass at an optimal rate 66 m3 ha-1, which provided good quality throughout most of the year.Item Open Access Environmental stress aspects of saltgrass [Distichlis spicata (L.) Greene](Colorado State University. Libraries, 2002) Shahba, Mohamed Ahmed, author; Qian, Yaling, advisor; Hughes, Harrison G., advisor; Wallner, Steven J., committee member; Brick, Mark A., committee memberSaltgrass [Distichlis spicata (L.) Greene] is undergoing preliminary evaluation at Colorado State University for use as a turfgrass in adverse environments. Furthermore, it has a potential as a range species in saline-alkali basins and many of the salt marsh areas in addition to its importance for wildlife. In cooperation with a saltgrass breeding project, the objectives of this dissertation work were to: (a) determine freezing tolerance of saltgrass; (b) determine the relationship between freezing tolerance and nonstructural carbohydrate content; and (c) determine nitrogen requirements and to evaluate the nutritive value of saltgrass as affected by N levels. Stolons of saltgrass accessions were sampled at monthly intervals from October 1999 to April 2000 and from October 2000 through April 2001 and subjected to laboratory freezing tests. Parts of the sampled stolons were used to assess soluble carbohydrates, including sucrose, fructose, glucose, raffinose and stachyose using gas chromatography (GC). Results indicated significant differences among accessions in LT50 (subfreezing temperature resulting in 50% mortality) and carbohydrate content. Ranking of accessions for LT50 (°C) during January, 2000 was A29 = 48 (-20.0) > 55 (-17.0) ≥ 32 (-15.5) ≥ A65 = C66 (-14.0). In January, 2001 they were ranked with 48 = 55 (-26.0) > A65 = 32 (-23.0) > A29 (-20.0) = C66 (-18.5). Sucrose was the predominant sugar, but did not show a clear seasonal trend and had no correlation with freezing tolerance. Fructose, glucose, raffinose and stachyose exhibited clear seasonal changes, showing highest concentrations during mid-winter. Higher fructose, glucose, or raffinose concentrations were frequently observed in accessions 48, 55, and A29, which coincided with their lowest LT50. In contrast, C66 had the lowest sugar concentrations overall, which related to its sensitivity to lower temperatures. Accessions A24 and A138 were planted in the field at the Horticulture Research Center, Fort Collins, CO. to determine the nitrogen requirements for these accessions during establishment and to evaluate their nutrient content as related to nitrogen level. Results indicated positive linear relationships between cover %, productivity, tissue nitrogen and protein contents with applied nitrogen levels in both seasons. Ca, P and Fe had a positive association while Na, S and Mg had a negative association with nitrogen levels. Establishment in terms of cover and productivity, and nutritive value of the two tested saltgrass accessions increased with increasing N fertilization rate. However, nitrogen had no effect during the first month of establishment on cover when water was critical. Plots which received total of 450 kg/ha showed the best cover percentage.Item Open Access Physiological, morphological, and spectral reflectance characteristics of Kentucky bluegrass, Texas bluegrass, and their hybrids in response to water stress(Colorado State University. Libraries, 2002) Ploense, Mary Rebecca, author; Qian, Yaling, advisor; Hoffer, Roger, committee member; Koski, Anthony, committee member; Cardon, Grant, committee member; Wallner, Stephen J., committee memberDemands on fresh water resources, especially throughout the arid and semi-arid western USA, have resulted in escalation of government regulations to force water conservation. Such measures have included limitations on the permissible area devoted to turfgrass, restrictions on the quantity of potable water relegated to turfgrass irrigation, and mandates on the types of turfgrass permitted. As a result, identification and development of turfgrasses exhibiting improved drought resistance as well as those able to withstand secondary irrigation waters high in soluble salts has become paramount. Towards this end, three studies were conducted. In Study 1 Kentucky bluegrass (Poa pratensis L.) (KBG), Texas bluegrass (Poa arachnifera Torr.) (TBG), and their hybrids (HBG) were evaluated for salt tolerance. A broad range of variability in leaf firing and shoot and root growth reduction in response to salinity was found to exist within and among these Poa spp. and their hybrids, indicating that improvement in the salt tolerance of bluegrasses may be possible. In study 2 HBG and KBG water use characteristics and response to drought were compared. Hybrid bluegrass exhibited a lower inherent ET rate, as well as the ability to moderate its ET as evaporative demand increased, relative to KBG, thereby reducing water loss. Hybrid bluegrass also exhibited lower leaf water content and slower shoot growth than KBG under non-limiting soil moisture conditions, characteristics advantageous to reduce water use. Additionally, HBG possesses a significantly deeper, more extensive root system than KBG enabling water extraction from a greater volume of depth when surface soil water is depleted. These factors combined contributed significantly to the drought avoidance ability observed in HBG. In study 3 we found spectral reflectance within the far-red region of the visible portion of the spectrum to be most sensitive to, and highly correlated with, progressive dehydration. These wavelengths might effectively be used as an irrigation management tool in nondestructively monitoring leaf water status. Computation of reflectance difference between non-stressed and dehydrated leaves of HBG, KBG, and perennial ryegrass (Lolium perenne L.) revealed consistent differences in their reflectance sensitivity to dehydration. This sensitivity ranking was comparable with previous reports of drought resistance among these grasses, suggesting that the magnitude of reflectance change may be used as an indicator of drought resistance.Item Open Access Salinity tolerance and associated salinity tolerance mechanisms of four turfgrasses(Colorado State University. Libraries, 2001) Alshammary, Saad Farhan, author; Qian, Yaling, advisor; Wallner, Stephen J., advisor; Brick, Mark A., committee member; Stushnoff, Cecil, committee memberThe need for salinity tolerant turfgrasses is increasing because of the increased use of effluent or other low quality water for turfgrass irrigation. Greenhouse container and hydroponic experiments were conducted to determine the relative salinity tolerance, growth characteristics, and physiological responses (especially water and ion relations) of 'Challenger' Kentucky bluegrass (Poa pratensis L.) (KBG), 'Arid' tall fescue (Festuca arundinacea Schreb) (TF), 'Fults' alkaligrass (Puccinellia distans (L.) Parl.) (AG), and saltgrass (Distichlis spicata (Torr.) Beetle) (SG). Salinity treatments were applied for 8 weeks using 1NaCl:1CaCl2 solution at 2.0, 4.7, 9.4, 14.1, 18.8, and 23.5 dS/m. Based on data on shoot dry mass, KBG, TF, AG, and SG experienced a 50% shoot growth reduction at 5.5, 14.2, 23.0, and 34.5 dS/m, respectively, suggesting the ranking of salinity tolerance was SG > AG > TF > KBG. Leaf firing of KBG, TF, and AG increased as salinity increased, but no injury was noticeable in SG. Salinity caused root cortex cells to collapse in KBG at 14.1 dS/m and in TF at 23 .5 dS/m. Alkaligrass and SG only had a few cell collapses even at 23.5 dS/m. Osmotic adjustment (OA) occurred in all species under salinity stress. However, in KBG and TF, the contribution of Na+ and Cl- to OA increased and became the major contributors at high levels of salinity, whereas Na+ and Cl- contributions to OA in SG were maintained at stable levels as salinity increased from 4.7 to 23 .5 dS/m. As salinity increased, the contribution of unidentified osmolytes to OA increased in SG and decreased in KBG and TF. The proportion of K+ to OA in AG and TF was lower than SG but higher than KBG. The ability to maintain a K+/Na+ ratio close to or above 1 appeared to be important for these grasses to tolerate high salinity. Saltgrass, AG, TF, and KBG could maintain a shoot K+/Na+ ratio of 1 when salinity levels were less than 22.3, 13.6, 7.4, and 3.7 dS/m, respectively. Salt glands present in SG, root growth stimulation of SG and AG, maintenance of high root to shoot ratio in TF, synthesis of compatible solutes, regulation of ion concentrations, and maintenance of high K+/Na+ ratio in shoots are important salinity tolerance mechanisms among these grasses.Item Open Access Saltgrass revegetation of saline soils(Colorado State University. Libraries, 2010) Nickell, Kory James, author; Qian, Yaling, advisor; Fenwick, Jack R., committee member; Koski, Anthony J., committee member; Hansen, Neil, committee memberSaltcedar (Tamarix spp.) invasion into riparian areas in southwestern US, including Colorado, is threatening native biodiversity and riparian geomorphic and hydrologic processes. Great effort and resources have been invested to eliminate and control saltcedar invasion. However, due to salt redistributions, saltcedar-affected sites typically have high salts content at the soil surface. Ecological restoration of sites impacted by invasion ( and subsequent control) of saltcedar presents technical and conceptual challenges. Inland saltgrass (Distichlis spicata L. Greene) is a warm-season, rhizomatous, perennial, halophyte with worldwide distributions. It may have potential to use as a revegetation species for salinity affected soil, including saltcedar cleared areas. Therefore, the objectives of my first study are to: 1) Collect native saltgrass germplasms on riparian sites with saltcedar present along major river systems in the western US; 2) Evaluate the collections for establishment and long-term persistence in Colorado climate by determining coverage, vigor, density, and biomass over 3-4 year period. We collected saltgrass ecotypes along major rivers in the western U.S. from 2004 to 2006. Ninety-two ecotypes were planted in 2006 and 2007 for field observation. Data obtained for this study were: establishment as indicated by saltgrass coverage, density, height, yield, and spring green-up. Data showed significant differences among saltgrass ecotypes. Vegetative coverage was correlated to plant height and density in both years' plantings. From ecotypes planted in 2006, C30, C35, C25, C32, and C2 had the fastest establishment with good persistence. In considering all data collected, ecotype C30 is best suited for revegetation purposes; C30 exhibited the fastest establishment, and it was among the ecotypes that exhibited the highest density and yield. The growth and coverage of C30 persisted over the duration of this experiment (from 2006 to 2009). From ecotypes planted in year 2007, C51, C52, C62, C70, C115, C117, C133, C134, C135, and C137 have the best promise for revegetation purposes. Information from this study can be used to further develop saltgrass for revegetation purposes. Two experiments were conducted in the field with the objective to determine saltgrass seed germination and establishment as affected by salinity and seed treatment chemicals (Proxy and/or Thiourea). As the average soil EC salinity increased from 3.5 to 7.6 dS m- 1, saltgrass seed germination was not affected. However, lower germination and plot coverage were observed in plots with soil salinity at 12.4 dS m- 1 than the control plots. Our results indicate that Proxy solution at 5 mM a.i. enhanced saltgrass seed germination better than the other treatments at all salinity levels. The ecotypes selected in this study can be valuable to further develop saltgrass for revegetation purposes. The information on saltgrass germination as affected by salinity and proxy treatment can be integrated into development of protocols for revegetation of saline areas.Item Open Access Simulations of carbon and nitrogen dynamics in turfgrass systems using the DAYCENT model(Colorado State University. Libraries, 2012) Zhang, Yao, author; Qian, Yaling, advisor; Parton, William J., committee member; Koski, Anthony J., committee memberEcosystem modeling offers an opportunity to better understand the carbon and nitrogen dynamics in a certain ecosystem. Modeling provides a way for researchers to expand their research to larger scales or other situations where field measurements are difficult or costly to conduct. In this study, the DAYCENT ecosystem model was parameterized and validated under home lawn conditions. Long-term effects of irrigation and fertilization on turfgrass quality, soil carbon and nitrogen sequestration, and nitrous oxide (N2O) emissions were investigated. The DAYCENT model was also used as a tool to develop best management practices (BMPs) for a Kentucky bluegrass lawn. Clipping yields, evapotranspiration (ET), deep percolation, nitrate leaching, and soil temperature of a Kentucky bluegrass lawn were simulated and compared with the measured values from a three-year lysimeter study. Parameters that control damping factors of soil temperature and nitrate leaching rate were modified to reflect the unique properties of turfgrass ecosystems. The prediction of weekly ET and deep percolation of the three years was acceptable (r > 0.6). The simulated clipping yield was improved compared to the monthly time step CENTURY ecosystem model, with the r value increased from -0.32 to 0.74. Modeled N2O emissions were validated for Kentucky bluegrass (Poa pratensis L.) and perennial ryegrass (Lolium perenne L.). The annual cumulative N2O emissions predicted by the DAYCENT model were close to the measured emission rates of Kentucky bluegrass sites in Colorado (within 16% of the observed values). For the perennial ryegrass site in Kansas, the DAYCENT model overestimated the N2O emissions for all treatments by about 200% (urea and ammonium sulfate at high rate and urea at low rate). After including the effect of biological nitrification inhibition (BNI) in the root exudate, the DAYCENT model properly simulated the N2O emissions for all treatments (within 8% of the observed values). After calibration and validation, the DAYCENT model was further used to predict best management practices (best irrigation and nitrogen fertilization rates) for a Kentucky bluegrass lawn. Irrigation that decreases from 100% potential evapotranspiration (PET) to 60% PET is predicted to reduce 50-percent of annual net production in the semi-arid region. The model simulation suggested that gradually reducing fertilization as the lawn ages from 0 to 50 years would significantly reduce long-term nitrate leaching and N2O emissions when compared to applying nitrogen at a constant rate (at 150 kg N ha-1 yr-1). Our simulation indicates that a Kentucky bluegrass lawn could change from a sink to a weak source of greenhouse gas (GHG) emissions about 20 to 30 years after establishment.Item Open Access The Colorado golf carbon project(Colorado State University. Libraries, 2014) Gillette, Katrina, author; Qian, Yaling, advisor; Follett, Ronald F., committee member; Delgrosso, Steven J., committee member; Koski, Anthony, committee member; Conant, Rich, committee memberThere is concern regarding the rise of greenhouse gas (GHG) emissions and the impending effects of global climate change. Soils are the largest pool of C on earth with small changes having potentially significant effects on atmospheric carbon dioxide (CO2) concentrations. Soil emits a substantial portion of nitrous oxide (N2O), and is an important sink for balancing atmospheric methane (CH4) through microbial oxidation. Anthropogenic management of soil is therefore critical in mitigating the effect of climate change by increasing biological sinks and reducing GHG emissions. Due to recent rapid urban expansion and the common use of turfgrass as ground cover and its associated management, these areas are becoming increasingly important for regional accounting of GHG budgets. Golf courses in particular are important economical green spaces that are intensively managed with common practices that include frequent irrigation, mowing and fertilization. Such management practices increase biogeochemical cycling of C and N fine quality turfgrass system and may therefore help mitigate atmospheric CO2 through increase soil organic carbon (SOC) sequestration. However, intensive management of turfgrass may also increase emissions of N2O and reduce CH4 oxidation potentials, and therefore it is critical to have a complete account of GHG fluxes in the system. The objective of this dissertation was to estimate the carbon balance of golf courses using a multifaceted approach that included survey data, ecosystem modelling of C and N dynamics in turfgrass, and a two year field study measuring trace gas fluxes from a golf course using different urea fertilizers. Survey information was collected from Colorado golf courses regarding energy use from clubhouses, management facilities, and fertilizer and irrigation management, and land use. Further calculations were made from published literature for fertilizer production, N2O emissions and C offsets through SOC sequestration in regards to land use type. Survey information was also used to evaluate the effects of different management scenarios reported by turfgrass managers in order to simulate SOC accumulation and N2O fluxes using the DAYCENT biogeochemical model on a near (25 yr) and long (50 yr) term time scale. Finally, soil GHG fluxes were monitored using a modified version of the closed chamber method over the course of a two year field study, where the effects of fertilizer treatment, turfgrass site, and soil drainage potential were evaluated. Soil organic C and N were also measured for future analysis from all field plots. Through these efforts we have encompassed critical components required to calculate an overall C balance of golf course facilities maintained in the state of Colorado. Energy consumption from clubhouse and maintenance facilities and irrigation pumping stations were the largest sources of emissions, therefore increasing energy efficiency may significantly reduce annual emissions from golf courses. Of the twenty-two golf courses around the state of Colorado that participated in the survey, most had similar areas of managed turfgrass and nearly all maintained alternative land use types apart from turfgrass. Increasing the area of natural grassland and trees that have minimal management inputs is important to offset the C intensive management required to maintain the aesthetics of fine quality turfgrass. Alternative land use types contributed to C offsets through SOC accumulation not only for turf management, but offset approximately 40% of CO2 emissions from building and irrigation systems. In our second analysis we used the DAYCENT model to make projections of SOC and N2O emission over several periods of time; simulations were based on fertilizer rates reported in the survey to evaluate different management scenarios. The model projected rapid SOC sequestration rates when turfgrass was newly established, but these rates decreased and N2O emissions substantially increased after 25 yr if best management practices were not used. Field trials were the third and final part of our study, and we observed greater N2O emissions from fairways than from the rough turfgrass sections for all fertilizer treatments; a likely result of taller mowing height that increased plant water transpiration as well as from an increased layer of thatch on the Kentucky Bluegrass rough that partially immobilized N applications. Of the fertilizer treatments, Polyon with advanced coated technology was the most effective in restricting N substrate to control N2O emissions, especially following summer fertilizer applications. Using fertilizer technologies that reduce the risk of loss is important both economically and environmentally. Soil water and temperature were important abiotic variables affecting N2O and CH4 emissions, with emissions increasing as high soil water content depleted soil oxygen and rising summer temperatures reduced C3 turfgrass physiological activity. Observations collected in the field signify important GHG mitigation strategies in managing turf irrigation and fertilizer, as well as effective fertilizer technologies to reduce N2O emissions. If turfgrass managers are to employ the best GHG mitigation strategies to fine quality turf, there must be a complete understanding of the variables effecting soil GHG emissions that include N substrate availability, soil water and temperature, and plant physiology.Item Open Access Trait evaluation of second generation lines of Distichlis spicata(Colorado State University. Libraries, 2014) Additon, Tess Katherine, author; Qian, Yaling, advisor; Holm, David, committee member; Barbarick, Ken, committee memberConverting to more drought-tolerant, low-input turfgrass varieties that can help conserve water in the landscape is critical for the future of turf in the arid portions of the western United States. This study attempts to address the growing demand for native, low-input turfgrass by breeding a turf-type variety of inland saltgrass (Distichlis spicata) that is well adapted to grow in arid and salty sites while maintaining acceptable quality. Two breeding cycles have been completed for improving the turf quality of inland saltgrass and the current elite lines were selected out of the second-generation nursery to initiate Cycle 3. The goal of this thesis is to evaluate turf-type traits in all second-generation lines. Objectives of this research are three-fold: (1) document, analyze, and report the second-generation nursery of 2,933 saltgrass plots grown at the Horticulture Research Center between 2006-2009, (2) compare improvements of saltgrass through cycles of selections, and (3) maintain and evaluate Cycle 3 crossing blocks for survival, seed yield, and spread. Seed yield increased through cycles of selection and over half the flowering females in the second-generation elite population showed the ability to produce commercially acceptable levels of seed (448-673 kg/ha). Selecting for short canopy height and greater spread/fill was effective and second-generation lines were unique from the wild types and first-generation breeding populations in both of these traits. Nearly 50% of second-generation elite lines showed no signs of leaf rust (Puccinia aristidae) infection in 2008 and roughly 38% showed no signs of leaf shredding and/or browning after mowing. The top 5 elite lines recommended for potential vegetative variety releases from the second-generation were: A37-15x84-6 (M), A37-15xA50-20-1 (F), 84-8x84-6-1B (F), 84-8x84-6-2A (M) and A37-28xA34-18-4B (M). The variability observed in leaf shredding (relating to mowing quality) suggests that more work needs to be done before a uniform, seeded turf-type may be released; however, there is potential to release improved seed for native revegetation projects owing to the increased seed yield and spread in the second-generation lines. Third generation seed was harvested in 2013 and is available for future progeny evaluations.Item Open Access Warm season turfgrasses as potential candidates to phytoremediate arsenic pollutants at Obuasi Goldmine in Ghana(Colorado State University. Libraries, 2012) Owusu Ansah, Koduah, author; Qian, Yaling, advisor; Koski, Tony, committee member; Pilon-Smits, Elizabeth, committee memberGhana, originally known as the Gold Coast prior to March 6, 1957, has generally had a very long history of gold mining dating back over 1000 years. Gold is one of the largest contributors to the economy, including cocoa (Gavin, 2002), accounting for about 38% of total merchandise and 95% of total mineral exports as well as about 80% of all mineral revenue. Arsenic enters the environment from a variety of sources associated with gold mining, including waste soil and rocks, tailings, atmospheric emissions from ore roasting, and bacterially enhanced leaching. The combination of opencast mining by multi-national mining companies and heap leaching generates large quantities of waste soil and rock (overburden) and residual water from ore concentrations (tailings) into various water bodies in and around Obuasi. Arsenic constitutes the major trace element problem in the Obuasi area. Extremely high concentrations of this element have been observed in ponds (2250μg/L (USEPA)) and drinking water (1400μg/L). These high levels are far above recommended United States Environmental Protection Agency's (USEPA) drinking water guideline of 10μg/L for Arsenic. At least 10% of rural populations rely on Ghana's borehole wells that have Arsenic concentrations exceeding 10μg/L (USEPA). The basic idea that plants can be used for environmental remediation is very old and cannot be traced to any particular source. However, a series of scientific discoveries combined with an interdisciplinary research approaches have allowed the development of this idea into a promising, cost-effective, and environmentally friendly technology (Pilon-Smits, 2005). This paper reviews the physiological characteristics of five selected native turfgrasses and one exotic grass found in Ghana and their ability to phytoremediate arsenic pollutants at Obuasi mines.