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Master of Science / Department of Horticulture, Forestry, and Recreation Resources / Jack Fry / Zoysiagrass (Zoysia spp.) is more heat and drought resistant and requires fewer cultural inputs than cool-season (C3) turfgrasses; however, its widespread use may be limited by an extended period of winter dormancy, the disease Rhizoctonia large patch (Rhizoctonia solani Kühn AG-2-2 LP), and lack of cold hardiness. Objectives of these 2012-2014 field studies were to evaluate: 1) turfgrass colorants and overseeding for color enhancement; 2) three colorant application volumes on color persistence; 3) colorants applied at two volumes, once or sequentially, on buffalograss (Buchloë dactyloides) and zoysiagrass; 4) the impact of nitrogen source and application timing on large patch severity; and 5) winter hardiness and turf quality of new experimental lines. The colorants Ultradwarf Super and Green Lawnger provided acceptable lawn-height ‘Chisholm’ zoysiagrass color for 7 to 9 and 19 to 24 weeks after treatment (WAT), respectively. Chisholm receiving a sequential application of either product in mid-winter (14 WAT) maintained an acceptable color level after that point until mid-May (28 WAT). Overseeding with annual ryegrass did not provide acceptable color for more than 4 weeks. Evaluation of the colorants Green Lawnger, Endurant, and Wintergreen Plus showed that acceptable Chisholm color at lawn-height occurred for 8 to 14 WAT at 80 gallons per acre (GPA) and 16 to 26 WAT at 240 GPA. Buffalograss at lawn-height receiving a single autumn colorant application had acceptable color for 8 to 12 WAT at 100 GPA or 8 to 14 WAT at 160 GPA. ‘Meyer’ zoysiagrass maintained at a 0.5 inch height receiving a single autumn colorant application had acceptable color for 8 to 18 WAT at 100 GPA or 14 to 18 WAT at 160 GPA. No differences in large patch occurred between spring and fall applications of ammonium sulfate and calcium nitrate, nor between those treatments and summer-applied urea. Applying fertilizer in spring when soils reached 21 ºC increased green cover on some rating dates compared to applications in fall when soil temperatures fell to 21 ºC but differences were minimal. Out of 985 experimental zoysiagrass lines planted in the field, about 25 were identified for further evaluation for cold hardiness, large patch resistance, and turf quality.

Doctor of Philosophy / Department of Horticulture, Forestry, and Recreation Resources / Jack Fry and Megan Kennelly / Rough bluegrass (RBG, Poa trivialis L.) is a difficult-to-control weed that commonly infests cool-season turfgrass swards after movement of vegetative propagules or contamination from seed lots. Rough bluegrass is less tolerant of heat stress than desirable cool-season species such as tall fescue (TF, Festuca arundinacea Schreb. Syn [italicize]Schedonorus [italicize]arundinaceus Schreb.), and often declines during mid-summer due to biotic or abiotic stresses. The objectives of these 2011-2013 controlled environment and field experiments were to: 1) observe growth and physiological differences between ‘Laser’ and ‘Pulsar’ RBG and TF; 2) differentiate between physiological and pathological contributors to RBG decline; 3) determine the effects of TF seeding rate and mowing height on TF/RBG establishment when RBG is a seed contaminant; 4) evaluate herbicide combinations for selective RBG control; and 5) evaluate seasonal timing of glyphosate for nonselective RBG control. Tall fescue was less affected by elevated temperature than RBG. At 35°C, Laser and Pulsar experienced similar reductions in quality, gross photosynthesis (Pg), shoot and root biomass, and root length density compared to when grown at 23°C, but maximum electrolyte leakage was greater for Pulsar (63%) than for Laser (49%). Cell membrane thermostability could contribute to the better heat tolerance of Laser RBG. Evaluation of RBG foliage and roots did not reveal a fungal pathogen associated with RBG decline. Still, repeated applications of azoxystrobin (610 g a.i. ha⁻¹) or pyraclostrobin (556 g a.i. ha⁻¹) increased RBG quality, cover, and Pg during summer compared to untreated RBG, possibly due to poorly understood non-target physiological effects of the fungicides. Mowing TF at 7.6 or 11.4 cm reduced RBG incidence up to 57% compared to mowing at 3.8 cm. Tall fescue seeding rate had no effect on RBG incidence. Several herbicides and herbicide combinations resulted in some RBG injury in the field, but bispyribac-sodium was the only treatment that provided RBG control (16 to 92%) in Manhattan, KS; Hutchinson, KS; and Mead, NE. Spring-applied glyphosate resulted in the lowest RBG coverage (1 to 31%) among field studies in Manhattan and Mead, followed by late-summer applications (6 to 58%), and mid-summer applications (9 to 86%).

Doctor of Philosophy / Department of Horticulture, Forestry, and Recreation Resources / Dale Bremer / Greg Davis / In 2005, turfgrass was estimated to cover approximately 20 million ha of urbanized land. That area is increasing with rapid urbanization, stressing the importance of water conservation in the lawn and landscape industry. Turfgrasses have been identified for replacement by presumably more water-efficient ornamental plant species to conserve water. However, research comparing drought resistance and evapotranspiration (ET) of turfgrasses with ornamental landscape plants is limited. Two studies were conducted to evaluate water use and performance under drought stress of several ornamental and turfgrass species. An online course was developed to educate students about critical water issues related to irrigation in urbanizing watersheds. In a field study, ET was measured using lysimeters and plant water status was evaluated under deficit irrigation (100%, 60%, and 20% ET) in Festuca arundinacea Schreb., Buchloe dactyloides (Nutt.) Engelm. ‘Sharps Improved’, and Ajuga reptans L. ‘Bronze Beauty’. Evapotranspiration was similar between A. reptans and F. arundinacea, and was 32 and 35% greater than ET of B. dactyloides. In a greenhouse study, the performance of one turfgrass (Poa pratensis L. ‘Apollo’) and eight landscape species (Achillea millifolium L., Ajuga reptans L. ‘Bronze Beauty’, Liriope muscari Decne., Pachysandra terminalis Siebold and Zucc., Sedum album L., Thymus serpyllum L., Vinca major L., and Vinca minor L.) was evaluated during a severe dry down and subsequent recovery. S. album, L. muscari, and P. terminalis performed the best, requiring 86 to 254 d to decline to a quality rating of one (1-9 scale: 1=dead/dormant, 9=best quality). The remaining species required 52 to 63 d. The only species to recover were P. pratensis [46% pot cover (PC) after 60 days], S. album (38% PC), and V. major (35% PC). A survey was developed to measure student learning as it relates to the level of sense and meaning present in the content of a new online course entitled “Water Issues in the Lawn and Landscape.” Survey results were compared with student learning as measured through a post-test. Post-test scores declined as the difference between sense and meaning increased (r =-0.82; P=0.03), indicating student learning is higher when both sense and meaning are present.

Common bermudagrass [Cynodon dactylon (L.) Pers.] and hybrid bermudagrass [C. dactylon (L.) Pers. X C. transvaalensis Burtt-Davy] are some of the most common turfgrasses used on athletic fields. Subsequently, the traffic tolerance of commercially available cultivars and the effects of trinexapac-ethyl (TE) on bermudagrass athletic fields with or without perennial ryegrass are often limited. A two year study at the University of Tennessee was conducted under simulated athletic field traffic to evaluate the performance of bermudagrass cultivars as affected by TE and overseeding. Bermudagrass cultivars evaluated were Tifway, Riviera, Patriot, and Celebration. TE treatments consisted of an untreated control, TE at 76.3 g a.i. ha-1 every 14 days until 14 days prior to trafficking (TE A), and TE at 76.3 g a.i. ha-1 every 14 days until 14 days after trafficking (TE B). Overseeding treatments consisted of no overseeding and overseeding at 670 kg ha-1 of perennial ryegrass (Lolium perenne L.). Plots were rated for percent green cover using digital image analysis after every 5 traffic events. Soil physical characteristic measurements were performed after every traffic season. Morphological data was determined by measuring number of leaves, internode lengths, leaf angle, and leaf width of the bermudagrass. Cultivar was significant for percent green cover for both years of this study with Tifway and Celebration having the highest ratings and Patriot having the lowest rating. TE was also significant for percent green cover for the first 10 traffic events with TE treatment B having lower percent cover values. Morphological characteristic was significant for leaf angle for both years of the study. A more vertical leaf angle to the shoot occurred in the more traffic resistant cultivars Tifway and Celebration. Finally, both TE treatments yielded higher percent green cover values in 2008 when morphological characteristic data was collected and a more vertical leaf angle to the shoot occurred compared to the untreated control. Tifway, Celebration, and Riviera when applied with trinexapac-ethyl before the traffic season and overseeded with perennial ryegrass would be beneficial for athletic field managers.

A total maximum daily load (TMDL) assessment in the Upper North Bosque River (UNBR) has mandated reductions of soluble reactive phosphorus (SRP). The large concentrations of dairies in the UNBR watershed have been identified as a source of the SRP. Agricultural best management practices (BMPs) can be used to reduce in-stream loads of manure nutrients from confined dairy feeding operations (CAFOs). A new BMP utilizes turfgrass sod to export composted dairy manure nutrients out of the impaired watershed in a sustainable manner. Previous plot-scale experiments have showed that 46 to 77% of applied phosphorus (P) and 36 to 47% of applied nitrogen (N) were removed in a single sod harvest. Two, 1.4 ha turfgrass fields were instrumented to measure runoff flow and sediment and nutrient transport. One turfgrass field was topdressed with composted dairy manure and fertilizer N and the other with fertilizer N only. A total of 3.5% of the applied manure P and 3.1% of applied manure N were lost in the surface runoff over a 1.5 year period. The runoff data from the experimental fields were used to calibrate and validate Soil and Water Assessment Tool (SWAT) model simulations of flow, sediment, organic, and mineral nutrients. The Nash-Sutcliffe model fit statistic was greater than 0.6 for flow, sediment, and nutrients during the calibration period and greater than 0.3 during the validation period. Research results indicated that turfgrass sod can be used to export composted dairy manure out of impaired watersheds to improve water and soil quality.

Concentrated animal feeding operations (CAFOs) have caused water quality concerns in many rural watersheds, sometimes forcing the State of Texas to conduct Total Maximum Daily Load (TMDL) assessments of stream nutrients such as nitrogen (N) and phosphorus (P). One suggested Best Management Practice (BMP) is the export of phosphorus (P) through turfgrass sod produced with composted dairy manure from an impaired rural watershed to an urban watershed. The manure-grown sod releases P slowly and would not require additional P fertilizer for up to 20 years in the receiving watershed. This would eliminate P application to the sod and improve the water quality of urban streams. The Soil and Water Assessment Tool (SWAT) was used to model a typical suburban watershed that would receive the transplanted sod. The objective of the modeling was to determine the water quality changes due to the import of sod transplanted from turf fields and grown with composted dairy manure. The SWAT model was calibrated to simulate historical flow and sediment and nutrient loading to Mary's Creek. The total P stream loading to Mary's Creek was lower when manure-grown sod was imported instead of commercial sod grown with inorganic fertilizers. Yet, flow, sediment yield, and total N yield increased equally for both cases at the watershed outlet. The SWAT simulations indicate that a turfgrass BMP can be used effectively to import manure P into an urban watershed and reduce in-stream P levels when compared to sod grown with inorganic fertilizers.

The Upper North Bosque River (UNBR) watershed is under a Total Maximum Daily Load (TMDL) mandate to reduce Phosphorus (P) due to excess nutrients in the watershed. To address these problems, Texas A&M University researchers have developed a turfgrass sod Best Management Practice (BMP) to remove excess nutrients from impaired watersheds. Turfgrass harvest of manure fertilized sod removes a thin layer of topsoil with most of the manure applied P. Plot and field scale research has demonstrated the effectiveness of turfgrass to remove manure phosphorus (P). In order to assess the impact of the turfgrass BMP on a watershed scale, the Soil and Water Assessment Tool (SWAT) was used to predict water quality in the UNBR watershed. The SWAT model was modified to incorporate turfgrass harvest routines to predict manure and soil P export through turfgrass sod and soil during harvest. SWAT simulations of the BMP predicted stream load reductions of 20 to 36% for P loads in the UNBR depending on the implementation scenario, an average reduction of 31% for total N and 16.7% for sediment for all the scenarios, at the watershed outlet. The SWAT model also predicted up to 176 kg/ha P removed per sod harvest when fertilized with 100 kg manure P/ha, and 258 kg/ha of P removed per sod harvest when the manure P application rate was 200 kg/ha. In addition, depending on the implementation scenario, the turfgrass BMP could export between 262 and 784 metric tons of P out of the UNBR watershed every year. Manure fertilized turfgrass has the advantage of slow releasing nutrients from the composted dairy manure, so it would not require any additional P for life. This means reduced urban non-point source pollution and lower maintenance cost compared to regular sod. These modeling simulations complement the wealth of research that shows the effectiveness of the turfgrass BMP.

A total maximum daily load (TMDL) assessment in the Upper North Bosque River (UNBR) has mandated reductions of soluble reactive phosphorus (SRP). The large concentrations of dairies in the UNBR watershed have been identified as a source of the SRP. Agricultural best management practices (BMPs) can be used to reduce in-stream loads of manure nutrients from confined dairy feeding operations (CAFOs). A new BMP utilizes turfgrass sod to export composted dairy manure nutrients out of the impaired watershed in a sustainable manner. Previous plot-scale experiments have showed that 46 to 77% of applied phosphorus (P) and 36 to 47% of applied nitrogen (N) were removed in a single sod harvest. Two, 1.4 ha turfgrass fields were instrumented to measure runoff flow and sediment and nutrient transport. One turfgrass field was topdressed with composted dairy manure and fertilizer N and the other with fertilizer N only. A total of 3.5% of the applied manure P and 3.1% of applied manure N were lost in the surface runoff over a 1.5 year period. The runoff data from the experimental fields were used to calibrate and validate Soil and Water Assessment Tool (SWAT) model simulations of flow, sediment, organic, and mineral nutrients. The Nash-Sutcliffe model fit statistic was greater than 0.6 for flow, sediment, and nutrients during the calibration period and greater than 0.3 during the validation period. Research results indicated that turfgrass sod can be used to export composted dairy manure out of impaired watersheds to improve water and soil quality.

Common bermudagrass [Cynodon dactylon (L.) Pers.] and hybrid bermudagrass [C. dactylon (L.) Pers. X C. transvaalensis Burtt-Davy] are some of the most common turfgrasses used on athletic fields. Subsequently, the traffic tolerance of commercially available cultivars and the effects of trinexapac-ethyl (TE) on bermudagrass athletic fields with or without perennial ryegrass are often limited. A two year study at the University of Tennessee was conducted under simulated athletic field traffic to evaluate the performance of bermudagrass cultivars as affected by TE and overseeding. Bermudagrass cultivars evaluated were Tifway, Riviera, Patriot, and Celebration. TE treatments consisted of an untreated control, TE at 76.3 g a.i. ha-1 every 14 days until 14 days prior to trafficking (TE A), and TE at 76.3 g a.i. ha-1 every 14 days until 14 days after trafficking (TE B). Overseeding treatments consisted of no overseeding and overseeding at 670 kg ha-1 of perennial ryegrass (Lolium perenne L.). Plots were rated for percent green cover using digital image analysis after every 5 traffic events. Soil physical characteristic measurements were performed after every traffic season. Morphological data was determined by measuring number of leaves, internode lengths, leaf angle, and leaf width of the bermudagrass. Cultivar was significant for percent green cover for both years of this study with Tifway and Celebration having the highest ratings and Patriot having the lowest rating. TE was also significant for percent green cover for the first 10 traffic events with TE treatment B having lower percent cover values. Morphological characteristic was significant for leaf angle for both years of the study. A more vertical leaf angle to the shoot occurred in the more traffic resistant cultivars Tifway and Celebration. Finally, both TE treatments yielded higher percent green cover values in 2008 when morphological characteristic data was collected and a more vertical leaf angle to the shoot occurred compared to the untreated control. Tifway, Celebration, and Riviera when applied with trinexapac-ethyl before the traffic season and overseeded with perennial ryegrass would be beneficial for athletic field managers.