Improved Turf Quality Research Articles

Using Humus on Golf Course Fairways to Alleviate Soil Salinity Problems

Increased use of recycled water along with inherent soil salinity problems on golf courses make salinity an important issue for golf course management. The objective of this study was to investigate if using humus on golf fairways by topdressing or spraying can alleviate soil salinity problems and improve turf quality. The study was conducted from 2015 to 2017 at Aurora, CO, and Medora, ND. Treatments included an untreated control, topdressing (sand, sand + peat), and spraying of humic acid. Our results showed that the application of humus increased the soil microbial biomass and improved turf quality on fairways either with a soil salinity problem or irrigated with recycled water. The effects on turfgrass health and turf quality were dependent on the rates of humus applied. Humic acid at 3 gal/acre was equivalent to topdressing sand + peat (80/20 v/v) and consistently showed improved turf quality over the untreated control. Soil properties also were affected by the application of humus. Soil pH, electrical conductivity (EC), bulk density, water infiltration, and microbial biomass may have had an indirect contribution to turf quality.

Soil Salinity of an Urban Park after Long‐Term Irrigation with Saline Ground Water

Core Ideas Changes in soil salinity after 46 yr of irrigation. Using electromagnetic induction to map soil salinity and sodicity. Correlate soil salinity with irrigation system distribution uniformity. Chamizal National Park, located in El Paso, TX, extends over 140,000 m2 and has been irrigated with saline water for 46 yr. In recent years, turf areas in the park have severely degraded and bare spots have developed. Root zone salinity and sodicity were suspected to be the main reasons for the turf conditions. Developing salinity management and remediation strategies to improve turf quality requires information on the distribution of salinity (ECe) within the turf root zone. Electromagnetic induction (EMI) uses apparent electrical conductivity (ECa) to delineate salinity distribution, and is reportedly superior to traditional wet chemistry analyses. This study was conducted to investigate the spatial distribution of soil salinity and sodicity using the EMI technique. In addition, we assessed irrigation distribution uniformity and compared findings with root zone salinity and sodicity. The EMI data correlated well with saturated paste results and indicated that root zone salinity ranged from <1 to 43 dS m−1. In several parts of the park, ECe exceeded the threshold values for bermudagrass of 15 dS m−1. Root zone sodium adsorption ratio values ranged from <1 to 21 mmol1/2 L−1/2 and in areas where increased runoff and surface ponding were observed, values exceeded the threshold level of 12 mmol1/2 L−1/2. Correlation analysis between irrigation uniformity parameters and standard deviation of ECe and SAR values revealed that more than 90% of the variability of EC and SAR in the top 30 cm of the root zone could be explained by irrigation uniformity.

Evaluation of Herbicides and their Tank‐Mixes for Suppression of Bermudagrass in Zoysiagrass

Zoysiagrass (Zoysia spp.) is a popular turfgrass species for use on lawns, sod farms, and golf courses in the transitional and southern climatic zones of the United States. One common problem in managing zoysiagrass is the contamination and subsequent removal of bermudagrass (Cynodon spp.). Various herbicides and herbicide tank‐mixes may be utilized for bermudagrass control in zoysiagrass. Research was conducted in Fayetteville, AR, and Auburn, AL, to evaluate aminocyclopyrachlor, fluazifop, fenoxaprop, triclopyr, and their combinations for bermudagrass suppression in zoysiagrass. Fluazifop at 0.105 kg active ingredient (a.i.) ha–1 suppressed bermudagrass most, but this application caused unacceptable injury and quality reduction to zoysiagrass. Tank‐mixing fluazifop or fenoxaprop at 0.14 kg ai ha–1 with triclopyr at 0.56 kg acid equivalent (a.e.) ha–1 reduced zoysiagrass injury and improved turf quality over fluazifop or fenoxaprop alone. Fluazifop + triclopyr provided more bermudagrass suppression than fenoxaprop + triclopyr. Aminocyclopyrachlor (0.026 or 0.071 kg a.e. ha–1) did not reduce herbicide injury from fluazifop or fenoxaprop applications to zoysiagrass and did not provide significant bermudagrass suppression. Results suggest that fluazifop + triclopyr and fenoxaprop + triclopyr remain the best treatments for bermudagrass suppression in zoysiagrass because they provide bermudagrass suppression without reducing zoysiagrass quality.

Effects of Cytokinin and Nitrogen on Drought Tolerance of Creeping Bentgrass.

Cytokinin (CK) is a vital plant hormone that controls many aspects of growth and development in plants. Nitrogen (N) is the indispensable macronutrient needed in plants and also one of the most important limiting factors for plant growth. This study was designed to investigate the simultaneous effects of CK and N on the visual turf quality and antioxidant metabolism of drought-stressed creeping bentgrass (Agrostis stolonifera L.). ‘PennA-4’ creeping bentgrass treated with trans-zeatin riboside at three rates of CK concentrations of 0, 10 and 100 μM (designated by CK0, 10, and 100) and two nitrogen rates with 2.5 and 7.5 kg N·ha-1 every 15 days (designated by low and high N) in a complete factorial arrangement was grown under two soil moisture regimes: well-watered and drought stress. Exogenous CK improved turf quality and delayed leaf wilting under drought stress, especially under high N. The grasses treated with CK10 and CK100 had lower O2- production and H2O2 concentration than those without CK treatment. The CK100 treatment enhanced the activities of superoxide dismutase (SOD), ascorbate peroxidase (APX), catalase (CAT), and guaiacol peroxidase (POD) by 25%, 22%, 17% and 24%, respectively, relative to CK0. Moreover, the activity changes of the antioxidant enzyme isoforms were more significant under high N condition relative to low N condition. Our results demonstrated the beneficial impacts of CK and N on physiological reactions, especially antioxidant metabolism, and foliar application of CK at 10 or 100 μM plus 7.5 kg ha-1 N biweekly may improve drought stress resistance of creeping bentgrass.

Turf Manager Response to Changing Pesticide Regulations

A mail survey was distributed to school turfgrass managers throughout Connecticut focusing on the differences between turfgrass management practices for kindergarten through eighth-grade (K-8) school grounds before, during, and after a 2010 ban on pesticide use at these facilities. The results indicate that as turf care protocol transitioned from an integrated pest management (IPM) program to new pesticide-free regulatory requirements, school grounds/athletic field managers did not significantly adjust their management programs. The percentage of managers applying pesticides on K-8 grounds decreased, as expected, with the implementation of the new pesticide ban; however, pesticide applications on high school grounds/athletic fields also decreased. Furthermore, it was observed that there had been minimal adoption of minimum risk 25(b) products, the suggested alternative to traditional synthetic pesticides. With respect to other cultural practices, we found that few changes have been made to other cultural practices that would improve turf quality. Budgetary issues facing school grounds/athletic field managers may have limited their ability to implement potentially costly management practices necessary to offset the loss of pesticides. Educational efforts to promote new management practices have the potential to inform school grounds/athletic field managers about new methods, thereby, potentially increasing adoption.

개량 가축분뇨발효액비의 시비주기에 따른 켄터키블루그래스의 생육효과 및 양분흡수

개량SCB저농도액비(DSCB)를 친환경적인 잔디관리에 이용하기 위하여 시비간격에 따른 켄터키블루그래스의 엽색지수, 엽록소지수, 잔디생육, 양분흡수 및 이용율을 바탕으로 DSCB의 적절한 시비방법을 평가하였다. 시험을 위한 처리구는 무처리(NF), 대조구(CF), 15일 간격으로 시비한 DSCB 처리구 (DSCB), 30일 간격으로 시비한 DSCB처리구(2DSCB), 4월부터 60일 간격으로 시비한 DSCB처리구(4DSCB-1), 그리고 5월부터 60일 간격으로 시비한 DSCB처리구(4DSCB-2)으로 구분하였다. 잔디의 엽색지수는 DSCB와 2DSCB가 CF보다 높았고, 엽록소지수는 CF와 비슷하였다. 질소와 칼리의 흡수량 및 이용율과 예지물량은 2DSCB와 4DSCB에서 CF보다 증가하였다. 이러한 결과들로 종합할 때, DSCB는 월 1회 시비하는 것이 잔디의 양분흡수와 이용을 증가시켜 잔디생육과 품질을 향상시키는 것으로 알 수 있었다. A developed slurry composting and biofiltration (DSCB) liquid fertilizer could be used for eco-friendly turfgrass management in golf course. This study was conducted to evaluate the growth effect of application intervals of DSCB in Kentucky bluegrass based on turf color index, chlorophyll index, clipping yield and uptake and availability of nutrient. Treatments were designed as follows; non-fertilizer (NF), control (CF) and DSCB treatments which were applied a every 15 days (DSCB), every 30 days (2DSCB) and 60 days (4DSCB-1: April, June, August; 4DSCB-2: May, July, September). Turf color indexes of DSCB and 2DSCB were higher than CF, but these chlorophyll indexes similar to CF. The clipping yield and uptake and availability rate of nitrogen and potassium in turfgrass were increased in 2DSCB. These results suggested that application of DSCB improved turf quality and growth by prompting an uptake and availability of nutrients in Kentucky bluegrass and its application interval was 1time per month.

Overexpression of ubiquitin-like LpHUB1 gene confers drought tolerance in perennial ryegrass.

HUB1, also known as Ubl5, is a member of the subfamily of ubiquitin-like post-translational modifiers. HUB1 exerts its role by conjugating with protein targets. The function of this protein has not been studied in plants. A HUB1 gene, LpHUB1, was identified from serial analysis of gene expression data and cloned from perennial ryegrass. The expression of this gene was reported previously to be elevated in pastures during the summer and by drought stress in climate-controlled growth chambers. Here, pasture-type and turf-type transgenic perennial ryegrass plants overexpressing LpHUB1 showed improved drought tolerance, as evidenced by improved turf quality, maintenance of turgor and increased growth. Additional analyses revealed that the transgenic plants generally displayed higher relative water content, leaf water potential, and chlorophyll content and increased photosynthetic rate when subjected to drought stress. These results suggest HUB1 may play an important role in the tolerance of perennial ryegrass to abiotic stresses.

In vitro chemical mutagenesis improves the turf quality of bahiagrass

Bahiagrass (Paspalum notatum Flugge) is a warm season, low-input, perennial turfgrass used for residential lawns and sides of road ways. The turf quality of bahiagrass is limited by its open growth habit, light green color, and prolific production of tall seedheads. Genetic improvement of the tetraploid bahiagrass turf cultivar ‘Argentine’ by conventional breeding is difficult due to its apomictic mode of reproduction. Our objective was to explore the potential of in vitro chemical mutagenesis for the generation of uniform, mutant seed progeny with improved turf quality. Scarified, surface sterilized bahiagrass seeds were treated with different concentrations of the chemical mutagen ‘sodium azide’. Callus was induced from these seeds and 19,630 plants were regenerated via somatic embryogenesis. 2,035 of these plants were selected based on their morphological characteristics and transferred to soil. Wildtype bahiagrass and 46 mutant lines (M1 lines) with reduced stem lengths, higher tiller densities or reduced or delayed seedhead formation were established under field conditions. Mutant lines with improved traits and production of viable apomictic seeds were identified and their apomictic M2 progeny was evaluated. A superior line displayed higher density, finer leaves, an upright growth habit, dark green color, reduced seedhead formation and uniform seed progeny in replicated, two location field trials. Beside this improved turf quality, this line also retained the superior drought tolerance and persistence that make bahiagrass a popular low-input turfgrass.

Effects of Biosolids on Root Growth and Nitrogen Metabolism in Kentucky Bluegrass under Drought Stress

Biosolids are valued as a source of plant nutrients, soil organic matter, and biologically active substances. This greenhouse study was designed to examine if application of biosolids can improve plant drought tolerance by affecting nitrogen (N) and hormone metabolism as well as root growth in kentucky bluegrass (Poa pratensis L.; KBG). The three treatments, which provided N rates equivalent to 75 mg plant-available N/kg soil, included: 1) biosolids at 1× agronomic (Ag) N rate (75 mg N/kg soil completely provided with biosolids); 2) biosolids at 0.5× Ag N rate (37.5 mg N/kg soil provided with biosolids and 37.5 mg N/kg soil provided with NH4NO3); and 3) control (75 mg N/kg soil completely provided with NH4NO3). The treated KBG was grown under either well-watered (90% container capacity) or drought stress (≈25% container capacity) conditions. Biosolids application improved turf quality and delayed leaf wilting under drought stress. The grass treated with biosolids at 1× N rate had higher leaf proline and amino acid content and greater nitrate reductase activity than the control under drought stress. Biosolids treatments also increased leaf and soil indole-3-acetic acid (IAA) content. Moreover, biosolids at 1× N rate increased root length density by 23% compared with the control under drought stress. The results of this study suggest that biosolids may enhance plant drought tolerance by improving N and hormone metabolism and root growth in KBG.

Flucarbazone–Sodium Absorption, Translocation, and Metabolism in Bermudagrass, Kentucky Bluegrass, and Perennial Ryegrass

Perennial ryegrass is overseeded in bermudagrass and Kentucky bluegrass to improve turf quality, but selective control may be warranted for transition back to monostand turfgrass. Flucarbazone–sodium controls perennial ryegrass in bermudagrass and Kentucky bluegrass, but the physiological basis of selectivity has received limited investigation. Greenhouse and laboratory experiments were conducted to evaluate efficacy, absorption, translocation, and metabolism of flucarbazone–sodium in these grasses. Flucarbazone–sodium reduced perennial ryegrass shoot mass from the nontreated an average ≈ 22 times and 3 times more than bermudagrass and Kentucky bluegrass at 4 wk after treatment, respectively. In laboratory experiments, foliar and root absorption of14C–flucarbazone–sodium were similar among species. Bermudagrass distributed ≈ 25% more foliar-absorbed14C to nontreated shoots than Kentucky bluegrass and perennial ryegrass. From root applications, all grasses averaged 84% distribution of14C to shoots. Bermudagrass and Kentucky bluegrass metabolized 100% and 74% of14C–flucarbazone–sodium at 1 d after treatment (DAT), whereas perennial ryegrass metabolism measured 44, 58, and 65% at 1, 3, and 7 DAT, respectively. Bermudagrass, Kentucky bluegrass, and perennial ryegrass had 4, 4, and 2 metabolites after 7 d, respectively. Results suggest differential metabolism of flucarbazone–sodium is attributed to selectivity for controlling perennial ryegrass in bermudagrass and Kentucky bluegrass.

Lightweight Rolling Effects on Anthracnose of Annual Bluegrass Putting Greens

Lightweight rolling can be effectively used to increase ball roll distance (BRD) and influence anthracnose development on annual bluegrass (ABG) [Poa annua L. f. reptans (Hausskn) T. Koyama] putting green turf. The objective of this 3‐yr field trial was to evaluate the influence of roller type (i.e., sidewinder, triplex mounted vibratory, and nonrolled) and location (center or perimeter) of equipment traffic on anthracnose severity, turf quality, and BRD of ABG turf maintained at 3.2 mm. Both roller types either had no effect or reduced disease 3 to 13% compared to nonrolled turf under moderate disease pressure in 2006, 2007, and 2008. Disease severity was not different between the roller types on most dates; however, the heavier sidewinder roller did result in less disease than the triplex mounted vibratory roller on 4 of 13 rating dates in 2007 and 2008. Interestingly, perimeter plots had slightly less disease compared to center plots on 6 of 13 rating dates. The current study shows that the practice of rolling does not explain field observations that greater anthracnose can often occur and is most severe within the perimeter of putting greens. Alternatively, this research indicates that rolling can be used to increase BRD and improve turf quality without exacerbating the severity of anthracnose disease on ABG putting green turf.

Overexpression of phytochrome A and its hyperactive mutant improves shade tolerance and turf quality in creeping bentgrass and zoysiagrass

Phytochrome A (phyA) in higher plants is known to function as a far-red/shade light-sensing photoreceptor in suppressing shade avoidance responses (SARs) to shade stress. In this paper, the Avena PHYA gene was introduced into creeping bentgrass (Agrostis stolonifera L.) and zoysiagrass (Zoysia japonica Steud.) to improve turf quality by suppressing the SARs. In addition to wild-type PHYA, a hyperactive mutant gene (S599A-PHYA), in which a phosphorylation site involved in light-signal attenuation was removed, was also transformed into the turfgrasses. Phenotypic traits of the transgenic plants were compared to assess the suppression of SARs under a simulated shade condition and outdoor field conditions after three growth seasons. Under the shade condition, the S599A-PhyA transgenic creeping bentgrass plants showed shade avoidance-suppressing phenotypes with a 45% shorter leaf lengths, 24% shorter internode lengths, and twofold increases in chlorophyll concentrations when compared with control plants. Transgenic zoysiagrass plants overexpressing S599A-PHYA also showed shade-tolerant phenotypes under the shade condition with reductions in leaf length (15%), internode length (30%), leaf length/width ratio (19%) and leaf area (22%), as well as increases in chlorophyll contents (19%) and runner lengths (30%) compared to control plants. The phenotypes of transgenic zoysiagrass were also investigated in dense field habitats, and the transgenic turfgrass exhibited shade-tolerant phenotypes similar to those observed under laboratory shade conditions. Therefore, the present study suggests that the hyperactive phyA is effective for the development of shade-tolerant plants, and that the shade tolerance nature is sustained under field conditions.

Poa pratensis or Lolium perenne for establishment and overseeding of Scandinavian football (soccer) pitches

Scandinavian football pitches are sometimes sodded because of slow establishment of Kentucky bluegrass (KB, Poa pratensis) from seed. Sodding is fast but expensive and brings with it thatch and sometimes annual bluegrass (AB, Poa annua). Perennial ryegrass (PR, Lolium perenne) is used for overseeding and often becomes an important component of the turf. Triggered by experiences in SW Norway and predictions for milder winters, our objectives were (1) to compare KB sod and PR seed for establishment of football pitches in three climatic regions; and (2) for both types of turf to document the effect of overseeding PR or KB in spring, summer or fall on turf cover, botanical composition, and wear tolerance. Field trials with sodded KB and seeded PR on main plots and overseeding on subplots were conducted from June 2008 to Nov. 2011 at the Bioforsk units Landvik (58 °N, coast), Apelsvoll (61 °N, inland) and Kvithamar (64 °N, coast). Seeded PR plots could be opened to play one month after sodded KB plots. KB survived well at all sites, but complete winterkill of PR occurred in two out of three years at Kvithamar and one out of three years at Apelsvoll. At Landvik one of two main plots with PR died during the last winter. The fact that winterkill was not caused by snow mold but long-lasting ice covers or low freezing temperatures combined with little or no snow cover, shows that a milder but more unstable winter climate will not allow for pure PR pitches in the future. Pitches still ought to have KB in the base, but PR is recommended for overseeding, preferably in spring, to reduce AB ingress and improve turf quality. Overseeding of PR into KB did not outcompete KB, but overseeding of KB into PR or KB was mostly not successful.

Registration of ‘Intercross’ Ryegrass

‘Intercross’ (Reg. No. CV‐258, PI 658507) intermediate ryegrass (Lolium multiflorum × L. perenne Lam.) was developed by the Texas Agricultural Experiment Station—now Texas AgriLife Research—at what is now the Texas AgriLife Research and Extension Center at Overton, Texas. Intercross was approved for release in 2010 by Texas AgriLife Research. The objective for the development of Intercross was to improve turf quality while retaining the early transition from the annual parent. The annual parent, ‘Axcella’ does not have good turf quality, whereas the intermediate parent, experimental 01‐ARG, has good turf quality but transitioned as a perennial under Texas conditions. Therefore the cross was made in an attempt to widen the genetic base not present in the annual and then to select for improved turf characteristics in segregating populations. Intercross was tested under the experimental designation TXR2007‐TF‐PR‐A and is a turf‐type, intermediate, transition‐type ryegrass. Intercross is a diploid ryegrass where 2n = 2x = 14 chromosomes. Intercross should be labeled as an intermediate ryegrass, indicating that it has some characteristics of an annual and some characteristics of a perennial ryegrass. The main attributes of Intercross are a darker‐green leaf color compared with Axcella, ‘Axcella 2’, ‘Panterra’, and ‘Gulf’. Darker leaf color is more evident late in spring in Texas (April). Turf‐quality ratings are good from November until early May and then decline. The transition of Intercross is similar to that of Panterra and Axcella 2 and is much earlier than most intermediate or perennial ryegrass cultivars. Intercross has been evaluated in turf‐overseeding trials at Overton for the past 2 yr. Seed production of Intercross will be in Oregon.

Establishment and Maintenance During Establishment of Hybrid Bluegrass (P. arachnifera Torr. × P. pratensis L.) in the Transition Zone

The transition zone is one of the hardest places to maintain high-quality turfgrasses, and the overall research objective was to determine best management practices to establish new turf cultivars in this zone. Hybrid bluegrasses (P. arachnifera Torr. × P. pratensis L.) have been bred for heat and drought tolerance and may offer a new alternative to other turfgrasses. The specific cultivars examined in this research were ‘Thermal Blue®’ and ‘Dura Blue®’. Experiments were conducted during 2003, 2004, and 2005 in Knoxville, TN. ‘Thermal Blue’ was seeded at 50, 100, 150, 200, and 250 kg·ha−1 of seed. ‘Thermal Blue's’ ideal seeding rate was between 100 and 150 kg·ha−1 of seed in 2003 and 50 kg·ha−1 in 2004. ‘Thermal Blue’ was also seeded in January, April, July, and September of each year with 100 kg·ha−1 of seed. All seeding dates took ≈11 months to become well established. However, July seeding produced poor turf quality (less than 6) and was the only seeding date deemed unacceptable. ‘Thermal Blue’ and ‘Dura Blue’ were fertilized with ammonium nitrate at 100, 200, and 300 kg N/ha/year and urea formaldehyde at 200 and 300 kg N/ha/year starting in March of each year. These treatments were maintained at 2-, 3.5-, and 5-cm mowing heights. ‘Thermal Blue’ had higher quality evaluations and produced more clippings than ‘Dura Blue’ throughout the year. Higher fertility regimens increased quality evaluations in April but decreased quality evaluations in October. Increasing the mowing height improved turf quality and decreased biomass production for both grasses. A proposed optimum method for establishment included seeding ‘Thermal Blue’ in April at 150 kg·ha−1 and fertilizing with 300 kg·ha−1 of nitrogen and them mowing at 5-cm height. ‘Thermal Blue’ and ‘Dura Blue’ are adapted for the transition zone, but summer heat stress may cause turf quality decrease in the fall.

Protein Changes during Heat Stress in Three Kentucky Bluegrass Cultivars Differing in Heat Tolerance

Supraoptimal temperature limits growth and metabolic activities of cool‐season turfgrasses. Understanding genetic variations and mechanisms in turfgrass heat tolerance would facilitate breeding and management programs to improve turf quality under summer stress. The objective of this study was to investigate protein changes associated with heat tolerance in three Kentucky bluegrass (Poa pratensisL.) cultivars. Plants of ‘Brilliant’, ‘Midnight’, and ‘Eagleton’ were subjected to 20°C (day/night, control) or 40°C (day/night, heat stress) in growth chambers. Eagleton maintained higher chlorophyll content and fewer yellow leaves than Brilliant, while Midnight was intermediate for both parameters at 28 d of heat stress. The content of cytoplasmic and membrane proteins declined during heat stress, to a greater extent in Brilliant than in Midnight and Eagleton. The content of both types of proteins in Brilliant were significantly lower than in Eagleton, but not different from that in Midnight. The sodium dodecyl sulfate‐polyacrylamide gel electrophoresis (SDS‐PAGE) analysis revealed that Brilliant exhibited more severe protein degradation than other two cultivars. Heat stress induced expression of several heat shock proteins (HSPs) in the cytoplasm (64, 78, and 85 kDa) and membranes (39, 45, and 66 kDa) in all three cultivars, but the induction occurred 7 to 14 d earlier in Eagleton or Midnight than in Brilliant. An additional membrane protein of 68 kDa was induced in Midnight under heat stress. The results suggested that better heat tolerance in the Kentucky bluegrass was associated with induction of HSPs during the early phase of heat stress and maintenance of higher protein content and less severe protein degradation during prolonged periods of heat stress.

Improved turf quality of transgenic bahiagrass (Paspalum notatum Flugge) constitutively expressing the ATHB16 gene, a repressor of cell expansion

Bahiagrass (Paspalum notatum Flugge) is a popular low-input turfgrass in subtropical regions. However, its turf quality and widespread use as residential turf is limited by up to 60-cm-tall seedheads and its open, sparse-looking growth habit. Plant growth retardants (PGRs) are being used in bahiagrass for the suppression of seedheads and leaf growth since a dwarf bahiagrass cultivar is not available and mowing costs are increasing. However, PGRs have to be applied frequently and may result in phytotoxicity. The improvement of turf quality by genetic engineering represents a promising alternative to the application of PGRs. The data presented here indicate that over-expression of the Arabidopsis ATHB16 transcription factor in bahiagrass significantly changes plant architecture of this important low-input turfgrass. All transgenic plants investigated produced significantly more vegetative and fewer reproductive tillers, shorter leaves and shorter tillers. Over-expression of ATHB16 resulted in a proportional reduction of leaf width and leaf length. The formation of seedheads under natural photoperiod was delayed in some transgenic lines for approximately 4 weeks. Total root or shoot biomass and seed set were not compromised in semi-dwarf bahiagrass plants over-expressing ATHB16. Our findings are consistent with the proposed function of ATHB16 as a suppressor of cell expansion and demonstrate its conserved role in grasses with direct practical implications for enhancing turf quality.

Nutrient Allocation of ‘TifEagle’ Bermudagrass as Influenced by Trinexapac-Ethyl

ABSTRACT Inhibiting shoot growth of dwarf bermudagrass [Cynodon dactylon(L.) Pers. × C. transvaalensis Burtt-Davey] with a plant-growth retardant, trinexapac-ethyl (TE), may redirect nutrients and photosynthate away from leaf tissue to promote root growth and improve nutrient-use efficiency. Two greenhouse experiments evaluated three rates of TE, 0.025, 0.05, and 0.075 kg a.i. ha−1, applied every three weeks on ‘TifEagle’ bermudagrass for 12 weeks. Lysimeters constructed to United State Golf Association specifications were arranged in a randomized complete block design with four replications. Increased TE rates quadratically reduced clipping yield 38%–75%, improved turf quality 6%–13%, and enhanced chlorophyll concentrations 30%–70% over the untreated grass. Dry-root mass increased with TE rate 11%–37% after 12 weeks. Total clipping nutrients recovered from five sampling dates were reduced by approximately 50%, 85%, and 90% for turf receiving TE at 0.025, 0.05, and 0.075 kg ha−1 3 wk−1, respectively. Thatch (stolons and rhizomes) and roots had higher nitrogen (N) concentration and retention with increased TE rate, suggesting inhibited leaf growth increased N storage in belowground plant tissue. Overall, TE may effectively enhance turf quality, root growth, and nutrient-use efficiency of dwarf-type bermudagrasses. Chemical name used: trinexapac-ethyl, [4-(cyclopropyl-[α]-hydroxymethylene)-3,5-dioxo-cyclohexane carboxylic acid ethylester].

Effects of Compost Topdressing on Turf Quality and Growth of Kentucky Bluegrass

Long-term over-application of manure to agricultural fields has increased nitrate and phosphorus contamination of groundwater and surface water along the South Platte River basin. Concerns about water quality issues have contributed to the increasing interest in composting manure and topdressing it on turfgrass. The objectives of this research were to evaluate the effects that topdressing manure compost has on: (i) turfgrass quality, (ii) turfgrass growth rates, and (iii) root mass and distribution. Compost treatments at rates ranging from 0 to 99 m³/ha were topdressed onto two cultivars (‘Nuglade’ and ‘Livingston’) of Kentucky bluegrass (Poa pratensis L.) in May and September 2003 and May 2004. A synthetic fertilizer (Urea 46-0-0) was applied to balance inorganic nitrogen rates among treatments. Topdressing compost at 66 and 99 m³/ha increased the overall quality by 10% of both cultivars during the growing season, and allowed the turfgrass to retain color in the fall and early winter and green up faster in the spring. During July and August, the 66- and 99-m³/ha compost treated plots had 48 and 56% higher clipping yield than the control, respectively. No differences in rooting mass among treatments were detected in the 0- to 50-cm depth. These results suggest that compost can improve turf quality and shoot growth via its action as a slow-release fertilizer.

Response of Creeping Bentgrass to Nitrogen and Ethephon

Ethephon is an effective growth retardant for suppressing Poa annua (L.) seedheads in creeping bentgrass putting greens; however, ethylene induction may cause bentgrass leaf chlorosis, reduced rooting, and quality decline. Two greenhouse experiments investigated the effects of nitrogen (N) fertility and ethephon applications on `L-93' creeping bentgrass over 9 weeks. Ethephon was applied at 0, 3.8, and 7.6 kg·ha–1 a.i. per 3 weeks and N was applied at 4 and 8 kg·ha–1·week–1. Ethephon applications linearly reduced bentgrass quality on every weekly observation. Increased N rate to 8 kg·ha–1·week–1 improved turf quality about 10% to 20% and 10% to 30% from ethephon applied at 3.8 and 7.6 kg·ha–1 per 3 weeks, respectively. Increased N rate to 8 kg·ha–1·week–1 enhanced shoot growth 30% but reduced root mass and length 12% and 11%, respectively. After 9 weeks, ethephon reduced root length by about 30% and root mass about 35% at both rates. From nine weekly samples, ethephon reduced dry clipping yield 10% and 16% at 3.8 and 7.6 kg·ha–1 per 3 weeks, respectively. From 2 to 9 weeks after initial treatments, ethephon linearly increased leaf water content. Increasing N fertility effectively reduced bentgrass leaf chlorosis from ethephon; however, repeat applications of ethephon and increased N may restrict bentgrass root growth. Chemical names used: [(2-chloroethyl)phosphonic acid] (ethephon).