Golf Green Research Articles

Long‐term influence of nitrogen, plant growth regulators, and iron sulfate on annual bluegrass populations and turfgrass quality on a golf green

AbstractAnnual bluegrass (ABG, Poa annua L.) is often considered an undesirable species on golf courses in many regions of the United States. However, the long‐term effect of the cultural and chemical management practices of ABG control is not sufficiently investigated. The objective of this study was to determine the long‐term effect of N, Fe sulfate, and plant growth regulators (PGRs) on ABG populations in a creeping bentgrass (CBG, Agrostis stolonifera L.) golf green. The study was established on a mixed stand of ‘L‐93′ CBG (∼75%) and ABG (∼25%) and managed as a putting green in University Park, PA, from 2012 to 2018. Treatments included ammonium sulfate (24 and 147 kg ha−1 yr−1), Fe sulfate (0, 12, or 49 kg FeSO4 ha−1 application−1), and the PGRs trinexapac‐ethyl (TE, 0.043 kg a.i. ha−1 application−1), flurprimidol (FL, 0.28 kg a.i. ha−1 application−1) and a nontreated control. Treatments were initiated in late April or early May each year and reapplied where required every 3 wk for nine applications annually. In general, ABG populations were lowest under lower N rates and with applications of FL. The long‐term effect of FeSO4 was minimal. In the first year of this study (2012), turfgrass quality was reduced, but quality levels generally increased in subsequent years. Although low N and FL may reduce ABG and high N and TE may increase ABG, seasonal variations in environmental conditions may reduce the efficacy of these treatments.

Effects of rolling and N-fertilization on dollar spot and Microdochium patch on golf greens in Scandinavia

Dollar spot was officially documented in Scandinavia in 2013 and the spread and damage from this disease has increased during last years. In summer 2017, on the golf greens with red fescue (Vallda GC, Sweden) and with the mixture of red fescue, colonial bentgrass and annual bluegrass (Roskilde GC, Denmark) rolling 2 times per week reduced dollar spot 61% and 37% and rolling 4 times per week reduced dollar spot 95% and 54%, respectively. Thus, rolling 3-4 times per week can be recommended on golf greens with dollar spot pressure. In the experiment 2018 dollar spot was reduced 24% with increase in nitrogen from 150 to 240 kg ha-1 yr-1 on creeping bentgrass/annual bluegrass golf green (Kävlinge GK, Sweden). However, the increased N-rate lead to a higher degree Microdochium patch from 14% to 30%.

Influence of Nitrogen, Plant Growth Regulators, and Iron Sulfate on Annual Bluegrass Populations on a Golf Green

Annual bluegrass (ABG, Poa annua L.) is often considered a weed on golf greens. Although numerous sustainable and low‐input management practices have gained popularity, no research‐based information is available on their ability to reduce ABG while promoting more desirable species, such as creeping bentgrass (CBG, Agrostis stolonifera L.). The objective of this 2‐yr field study was to elucidate the interaction of nitrogen (N) rates, plant growth regulators (PGRs), and iron sulfate (Fe) rates as they relate to reducing ABG populations in a golf green. Turf consisted of a mature stand of ‘L‐93’ CBG (∼75%) and ABG (∼25%). Factors included N from ammonium sulfate (21 N‐0 P‐0 K) (24 or 108–147 kg N ha−1 yr−1),the PGRs trinexapac‐ethyl (TE, 0.043 kg a.i. ha−1 application−1) and flurprimidol (FL, 0.28 kg a.i. ha−1 application−1), and Fe from iron sulfate (0, 12, or 49 kg Fe ha−1 application−1). Treatments were initiated in May and applied approximately every 3 wk in 2010 and 2011. Plots receiving 24 kg N ha−1 yr−1 received only four applications during the season. The effect of N and PGR was greatest on ABG populations. Few differences in ABG populations existed among plots treated with TE or no PGR. Turf within plots treated with FL had a seasonal average of 4 and 14% ABG in 2010 and 2011, respectively. Plots treated with 24 kg N ha−1 yr−1 generally had lower ABG populations. In 2011, ABG populations were negatively correlated with Fe rate in turf receiving 24 kg N ha−1 yr−1, but not in plots treated with 147 kg N ha−1 yr−1. Flurprimidol had the greatest effect on ABG populations in the N × PGR × Fe programs. Few differences in soil pH or organic matter levels, mostly agronomically insignificant, were observed among treatments. While ABG populations varied among select treatment combinations, the long‐term impact on species composition and overall turfgrass quality remains unknown.

Influence of Dissolved Organic Carbon from Natural and Synthetic Fertilizers on Phosphate Leaching from a Sand‐Based Golf Green

For intensively managed golf greens, organic fertilizers are recommended as an alternative to synthetic fertilizer to reduce nutrient contamination. Dissolved organic C (DOC) strongly enhances solute mobility. Golf greens were established as ‘Penncross’ creeping bentgrass (Agrostis stolonifera L.) sod to examine two commercial organic fertilizers, Milorganite and Nature Safe, compared with synthetic fertilizer and their influence on DOC and phosphate (PO43−) leachate concentrations. Greens were constructed according to the recommendations of the US Golf Association (USGA). Leachates from fertilizer were analyzed for DOC and PO43−. Fertilizers were applied as three applications at 50 kg N ha−1 in July, September, and October of 2006. Total P applied was 24.2, 21.5, and 11.2 kg ha−1 for Nature Safe, Milorganite, and synthetic fertilizer, respectively. Dissolved organic C from Milorganite in the fertilizer was 2.4 vs. 0.9% for Nature Safe, with the DOC extract from Milorganite containing 2.7‐fold greater C content than Nature Safe. Greater DOC from Milorganite more strongly influenced PO43− transport than Nature Safe DOC. Concentrations of PO43− were correlated with DOC in leachate (r = 0.68, P ≤ 0.001). Milorganite promoted 15 to 18% greater PO43− in leachate than synthetic fertilizer and Nature Safe, with Milorganite PO43− as high as 2.49 mg L−1. Greater PO43− in leachate, with Milorganite having 13% lower total P than Nature Safe, can be attributed to Milorganite's 2.7‐fold greater DOC content. The results suggest that DOC from organic fertilizer and their chemical properties may increase PO43− leaching especially on soils with low P sorption capacities.

Dollar Spot Control in a Creeping Bentgrass Golf Green with Two Commercial Products Based on Microbial Fermentation and Micronutrients

Dollar spot (caused by Sclerotinia homoeocarpa F.T. Bennett) is one of the most important diseases affecting creeping bentgrass (Agrostis stolonifera L.) golf course greens. The objective of this research was to test two commercial products for dollar spot control, one based on microbial fermentation and the other a micronutrient, comparing their control level with a synthetic fungicide (iprodione). The test was made over two dollar spot‐infected creeping bentgrass greens in autumn 2014 and summer 2015. In both experiments, the products inhibited the normal development of the disease at some point, although iprodione achieved a better control.

Managing golf greens: Aligning golf green quality with resource inputs

Golf course managers need to manage their facilities efficiently for both economic and qualitative reasons. Golf greens are the most significant area on the golf course for play, intensity of maintenance practice, and player judgement of quality. The gap in knowledge lies between measurement of golf green performance and operations efficiency. Performance measurement is the process of controlling management operations to achieve optimum resource input efficacy but in considering existing performance management systems it was found that none provided a definitive tool that could be used to monitor operations for golf green management. This research aims to determine whether a performance management system can be developed for golf green management. Four golf courses were selected to collect management data for operations practices and qualitative tests of golf green performance. Interviews provided operations data for the core practices, identified from literature, including material inputs. The comparison of maintenance inputs and their costs against playing quality allow objective comparison and determination of management efficacy. A survey of golf course managers and review of industry operations practice also informed the key parameters in the development of a performance management framework. Research data for maintenance intensity, cost, and quality have been plotted onto analysis framework graphs which indicate the quality golf course managers are achieving within golf green culture with known levels of resource input. This research proposes a performance management framework for golf course managers to enable them to better manage their golf greens. The adopted research methodology and methods have produced a performance based management framework for golf green management. Mapping key parameters of quality, costs, and inputs in a benchmarking radar chart reflects the efficacy of golf green management in a way that allows stakeholders to identify and adjust operation variables. In a survey of Golf Course Managers in the UK, 73% of respondents stated that they would find a performance management framework beneficial for their work.

Topdressing Sand Color, Cultivation Timing, and Cultivation Method Effects on Disruption of a Creeping Bentgrass Golf Green in the Intermountain Pacific Northwest

Topdressing Sand Color, Cultivation Timing, and Cultivation Method Effects on Disruption of a Creeping Bentgrass Golf Green in the Intermountain Pacific Northwest

Diamond Zoysiagrass Golf Green Response to Reduced Light Environments with the Use of Trinexapac‐Ethyl

A 2‐yr study was conducted to determine the tolerance of a mature Diamond zoysiagrass [Zoysia matrella (L.) Merr.] golf green to reduced light environments (RLE) treated with trinexapac‐ethyl (TE) at 0 and 0.013 kg ha−1 wk−1. Three levels of RLE, 0, 60, and 90%, were imposed to coincide with maximum seasonal growth of zoysiagrass. Plant growth measurements included turf quality (TQ), chlorophyll concentration, clipping yield, and total nonstructural carbohydrates. Zoysiagrass grown in full sunlight and 60% RLE maintained commercially acceptable TQ (≥7) with and without TE throughout Year 1 while 90% RLE treatments fell below an acceptable level 2 mo after study initiation. Sixty percent RLE treatments without TE demonstrated unacceptable TQ during Year 2. Application of TE sustained turf viability in 90% RLE through Year 2. Clipping yield increased in 60% RLE without TE compared to full sunlight treatments. Application of TE to 60% RLE treatments reduced clipping yield 30 to 76% in Year 1. Chlorophyll concentration in 60% RLE treatments was similar 10 wk after RLE implementation compared to full sunlight treatments in Year 1 and higher in Year 2. Total nonstructural carbohydrate concentration of roots, rhizomes, and stolons was similar in full sun and 60% RLE treatments at the end of both years and between 47 and 100% lower in 90% RLE treatments compared to full sun treatments. These results support the use of Diamond zoysiagrass in up to 60% reduced light putting green environments with concurrent use of a gibberellin biosynthesis inhibiting product such as TE.

Study on optimization of moisture retention for golf green rootzone soil mixtures

Most golf course green have been constructed with pure sand or sand-based rootzone mixes. As we know, high sand content provides rapid drainage despite sand’s inefficiency in retaining moisture. However, drainage capability and water retention are both essential elements to the golf course green, and the addition of peat could increase the soil moisture retention, therefore, the research on the drainage capability and water retention of the sandy golf green has become more and more important these years. In this study, extreme vertex design was applied which is one of the mixture experiment designs widely used in mixture experiments, the study investigated the effects of the thirteen different rootzone soil mixtures using middle-coarse, fine sand, very fine sand plus silt and clay as well as peat as the materials under three kinds of golf green profile (1-layer profile, 2-layer profile, 3-layer profile) conditions on the water retention of green rootzone. Through the qualitative, quantitative and optimization analysis of water retention capability of the sandy golf green, evidence a basis for choice of green profiles and rootzone matrix could be provided. And the significantly correlative regression model was established between the moisture retention and components of rootzone soil mixture. In addition, the order of factor contribution ratio, effect of single and double factor and optimization of the model were analyzed in detail. The results were as follows: both green profile and soil mixture, which had interaction of each other, had significant effects on soil moisture retention. Additional attributes include high porosity and greater water holding capacity than sand, and the higher content of peat, fine sand plus silt and clay, the better water retention. The mixtures had much higher water content in 1-layer profile than that in the other two profiles. There was significantly higher water content in 2-layer profile for pure sand mixtures (A–E) and low peat mixture (F) than that in 3-layer profile, while there was no higher water content for other 7 high peat mixtures (G–M) (>5%) in 2-layer than that in 3-layer profiles. The significance of key factors in rootzone soil mixture on moisture retention were: very fine sand plus silt and clay > peat > middle-coarse > fine sand. According to the moisture retention 15–25% specification of USGA (United States Golf Association), the optimal soil mixture in 1-layer profile was: middle-coarse 71.4–73.5%; fine sand 17.8–21.5%; very fine sand plus silt and clay 6.8–8.4%; peat 0–1%. The optimal soil mixture in 2-layer profile was: middle-coarse 65.0–73.4%; fine sand 17.8–20.5%; very fine sand plus silt and clay 7.5–8.9%; peat 0.2–6.3%. The optimal soil mixture in 3-layer profile was: middle-coarse 62.3–73.9%; fine sand 17.7–21.4%; very fine sand plus silt and clay 7.3–10.7%; peat 0–6.3%. These optimal recipes took through the limitation of previous research, which were practically important to golf green soil selection and profile design. Thus, both proportion and interaction should be considered when we choose the soil mixture.

Nitrogen remote diagnosis in a creeping bentgrass golf green

Nitrogen fertilization is a key factor of the aesthetics and playability for golf greens. Nitrogen fertilization management is based on predetermined scheduled applications, set rates, or expected improvement in visual quality and green speed. As a consequence, the objective of this study was to obtain seasonal N application models (algorithms) based on remote sensing, optimizing playability and aesthetic quality. A 3-yr field study under Mediterranean conditions was conducted on an experimental ‘L-93’ creeping bentgrass ( Agrostis stolonifera L.) USGA green, to examine effects of seasonal N fertilizer rates on color, clipping yields, and ball roll (green speed). The remote sensors used were a digital camera and reflectance meter (FieldScout CM1000 Chlorophyll Meter). From digital photographs, a dark green color index (DGCI) was calculated. All data were normalized (relative). For all seasons, a third-order polynomial response model was the best when using a CM1000 and a digital camera. Clipping yields and ball roll regressions were linear, increasing and decreasing when the N fertilizer rate increased, respectively. Ball roll and clipping relative values were correlated with both sensors. To fit a seasonal optimum N fertilizer rate model as a function of remote sensors and the other measured parameters, the intersection of models obtained from relative values of CM1000 and digital camera with ball roll and clipping was calculated, but ball roll was considered the most suitable. The model of the digital camera with automatic settings was less accurate and underestimated the optimum N rate. However, because the actual values of digital camera and CM1000 were correlated, converting DGCI values and applying CM1000 models enabled the obtaining of practically the same N fertilizer applications. A practical application procedure of these seasonal models for an entire golf course was also shown. Actual N recommendation applications with a quick remote diagnosis (CM1000) for creeping bentgrass golf green are feasible under similar management practices in Mediterranean environments. A digital camera can also be used successfully, but it should be better when its analysis is based on CM1000 models.

Use of Industrial Byproducts to Filter Phosphorus and Pesticides in Golf Green Drainage Water

Golf courses are vulnerable to phosphate (PO) and pesticide loss by infiltration of the sandy, porous grass rooting media used and through subsurface tile drainage. In this study, an effort was made to remove PO, chlorothalonil, mefenoxam, and propiconazole in a golf green's drainage water with a filter blend comprised of industrial byproducts, including granulated blast furnace slag, cement kiln dust, silica sand, coconut shell-activated carbon, and zeolite. To test this filter media, two 6-h storm events were simulated by repeat irrigation of the golf green after PO and pesticide application. Drainage flows ranged from 0.0034 to 0.6433 L s throughout the course of the simulations. A significant decrease in the chlorothalonil load for the experimental run (with filter media) was observed compared with the control (without filter media) ( < 0.05). In general, percent reductions in chlorothalonil were very high (>80%) near peak flows. In contrast, filter media was not effective in removing PO, mefenoxam, or propiconazole ( > 0.05). Instead, it appears that the filter blend added PO to the effluent above flow rates of 0.037 L s. Overall, flow rate, the amount of filter media used, and contaminant properties may have influenced the filter media's ability to remove contaminants. More research is needed to determine the optimal blend and configuration for the filter media to remove significant amounts of all contaminants investigated.

The potential of a surfactant to restore turfgrass quality on a severely water-repellent golf green

Soil water repellency (SWR) is a common phenomenon on sand-based golf greens. Soils are considered severely water repellent if water droplets remain on the surface of undisturbed, air-dried soil samples for more than 600 seconds before penetrating. The objective of this research was to evaluate the potential of a surfactant to overcome SWR and restore turfgrass quality on a green with severe drought symptoms. The surfactant Aqueduct® was applied at a rate of 25 L ha−1 at weekly intervals from 4 June through 25 June 2008, either alone or after aeration with solid tines to 5 cm depth before each application. The experiment was irrigated uniformly corresponding to 1.65 times pan evaporation values from 4 June till 12 June, after which irrigation was not necessary due to natural rainfall. Conspicuous and statistically significant improvements in turfgrass quality occurred 10–12 days after the first application of surfactant, and the difference from untreated control plots continued to increase for about two and a half months after the completion of treatments. The improvement was accompanied by a significant increase in the SWC of the 0–20 cm soil layer and a deeper root system. The difference in WDPT between treated and untreated plots was significant at 1 cm, but not at 2, 3, 5 or 10 cm soil depths which were always far more water repellent than the thatch layer. Repeated aeration had no significant effect on turfgrass quality, and there was no significant interaction between surfactant and aeration treatments.

Thatch and Mat Management in an Established Creeping Bentgrass Golf Green

Thatch is a layer of partially decomposed organic matter between green shoot tissue and the soil surface, and mat is thatch partially intermixed with topsoil. Excessive thatch–mat layering (&gt;2.54 cm) is generally detrimental to turfgrass management, and numerous techniques including various mechanical and topdressing regimes, have been attempted to reduce its severity. This factorial experiment investigated the effectiveness of combining mechanical–biological and topdressing treatments for controlling thatch–mat levels in an established USGA‐specified golf green planted with ‘A‐1’ creeping bentgrass [Agrostis stoloniferous L. var. palustris (Huds.)]. Two levels of topdressing were used, and the mechanical–biological treatments included vertical mowing at two different depths and timings, core cultivation, grooming, a biological granular supplement (Thatch‐X), and combinations of core cultivation with grooming and/or vertical mowing. Differences among the mechanical–biological treatments were detected following 2 consecutive yearly applications. Thatch–mat depth (mm) was 12 to 15% greater for Thatch‐X and topdressing alone compared with other treatments. Organic matter content (g kg−1) increased 32% for the untreated and decreased 19% for core cultivation combined with vertical mowing and grooming, whereas all other treatments maintained pre‐study levels. Compared with the untreated, surface hardness was reduced ∼9% for all treatments using core cultivation, while water infiltration rates increased 127 to 168%. Vertical mowing treatments improved water infiltration rates by 40 to 65%. Turfgrass quality was not greatly impacted by the mechanical–biological treatments as ratings ranged from 8.4 to 10.0. However, mower scalping and dry spots contributed to unacceptable or only marginally acceptable turfgrass quality (6.4–7.2) for the untreated by the end of the study. Compared with topdressing alone, ball roll distance was decreased 6% by vertical mowing 7 days after treatment (DAT) and 5 to 8% by core cultivation up to 14 DAT. Sand topdressing alone was insufficient for managing thatch–mat levels in an established creeping bentgrass golf green.

Atmospheric Composition under Impermeable Winter Golf Green Protections

The utilization of impermeable winter covers on annual bluegrass [Poa annua var. reptans (Hauskn.) Timm.] golf greens as a protection against excess water and ice is increasing rapidly in Canada and elsewhere in northern climates. A study was conducted to examine the impact of these covers on the atmospheric composition over golf green turfgrass during the 1997–1998 and 1998–1999 winters in Québec City and in Montréal, Canada. Winter protective covers tested included a commercial impermeable cover on top of either curled wood shavings mat (CW‐CC), 15 cm of straw mulch (SM‐CC) or a felt material (FM‐CC), a clear polyethylene cover on top of a curled wood shavings mat (CW‐PC), and an unprotected control. Oxygen was consumed at variable rates under impermeable winter protective covers. As a result, anoxic conditions were not reached during winter at the Québec City site but high respiration rates at the Montréal site resulted in anoxic conditions that lasted for periods as long as 50 d, without apparent damage to the annual bluegrass plants. Further tests were conducted on greens experiencing recurrent damages that could not be explained by freezing temperatures, snow mold pathogens, excess water, or ice. We showed that these problem greens had higher soil respiration rates than nonproblem greens indicating that the differences in O2 consumption amongst golf greens are likely due to differences in soil biological activity rather than in plant respiration. We also established that the higher activity in soils of recurrently damaged greens was related to higher levels of soil organic C. Accordingly, sand‐based golf greens built according to the USGA specifications had lower soil organic matter and lower respiration rates than greens built on native soils. We conclude that high rates of O2 consumption by golf greens with high soil organic matter content results in potentially harmful anoxic conditions under impermeable covers during winter.

Normal and Flush Irrigation Effects on Nitrogen Leaching from Simulated Golf Greens in the Greenhouse

Nitrogen (N) can leach in porous golf greens, especially when they are flushed with high rates of irrigation. Drain water often discharges to the surface, possibly endangering surface waters with eutrophic concentrations of nitrogen. A greenhouse study was initiated to study the effects of fertilizer source and rate and irrigation schemes on leaching of nitrate and ammonium nitrogen. Simulated golf green columns were sodded with bermudagrass. Treatments were 3 fertilizer sources (20‐20‐20, ammonium nitrate, and a sulfur‐coated urea), 3 rates (zero control, 12, and 24 kg ha−1), and 2 irrigation schemes. The first was a daily rate of 0.6 mm (N.I.), and the second was the same daily rate with several flushes of 11.5 cm each (FL). Essentially no nitrogen leached for the N.I. scheme, whereas the FL treatment resulted in significant leaching of nitrate‐N. Ammonium‐N leached to a much less extent than nitrate‐N. The nitrate‐N concentration “break through” occurred earlier, the peaks were higher, and the flushes were more prominent for 20‐20‐20 and ammonium nitrate than for the sulfur‐coated urea. The sulfur‐coated urea had a gradual nitrate‐N concentration peak that tapered off slowly. The percent N leached of that applied was higher for the flushes, and all sources were the same for flushes and the high N rate (about 20%). At the low N rate and flushes, the percent leached was highest for ammonium nitrate (10.2%), 20‐20‐20 was intermediate (4.3%), and sulfur‐coated urea was the lowest (0.14%). These data show that fertilizer sources and rates can make a difference in nitrate‐nitrogen leaching but only when significant leaching is taking place as with flushing.

Sorption, degradation and leaching of the fungicide iprodione in a golf green under Scandinavian conditions: measurements, modelling and risk assessment

In cold climates, fungicides are used on golf greens to prevent snow mould causing serious damage to the turf. However, fungicide residues have been detected in runoff from golf courses, which may lead to restrictions on use. There is therefore an urgent need to improve understanding of the processes affecting leaching of fungicides from turfgrass systems to allow identification of green construction and management practices that minimize environmental impacts. In this study we monitored the leaching of the fungicide iprodione in a putting green. Sorption and degradation of iprodione was measured in batch and incubation experiments, and the simulation model MACRO was used as a risk assessment tool. Degradation of iprodione was bi-phasic, with a rapid initial phase (half-life 17 h) caused by enhanced biodegradation. Degradation rates slowed considerably after 5 days, with half-lives of up to 38 days. Sorption of iprodione was linear, with a K(oc) value of ca 400 cm(3) g(-1). MACRO reasonably accurately matched measured drainflows and concentrations of iprodione in soil and drainflow. However, peak concentrations in drainage were underestimated, which was attributed to preferential finger flow due to water repellency. The results also showed the importance of the organic matter content in the green root zone in reducing leaching. It was concluded that, with 'reasonable worst-case' use, losses of iprodione from greens can occur at concentrations exceeding water quality limits for aquatic ecosystems. Snow mould problems should be tackled by adopting green root zone mixes that minimize leaching and 'best management practices' that would avoid the need for intensive prophylactic use of fungicides.

Minimizing Thatch and Mat Development in a Newly Seeded Creeping Bentgrass Golf Green

Excessive (&gt;1.3 cm) thatch and mat layering of turfgrass is considered undesirable because it reduces hydraulic conductivity, water infiltration, increases localized dry spots and pest problems, and reduces pesticide effectiveness and turf tolerance to temperature extremes. The objective of this 2‐yr study was to determine the efficacy of topdressing alone and in combination with several mechanical and biological methods to control thatch–mat accumulation in a newly established ‘L‐93’ creeping bentgrass [Agrostis stolonifera L. var palustris (Huds.) Farw.] sand‐based golf green. Mechanical and biological methods included vertical mowing at various depths and timings, core cultivation, grooming, a biological thatch control agent (Thatch‐X), and combinations of core cultivation with grooming, core cultivation with vertical mowing, and core cultivation combined with grooming and vertical mowing. No treatment prevented thatch–mat accumulation, and thatch–mat depth for all treatments were similar to, or greater than, the untreated at the end of the study. Increases in percent organic matter content during the study ranged from 53% for core cultivation combined with grooming and vertical mowing to 123% for the untreated. Combinations of core cultivation plus vertical mowing with or without grooming were the most effective at minimizing thatch–mat accumulation. These treatments decreased percent organic matter 38 and 45%, respectively, compared with the untreated. Surface hardness was reduced an average of 19% by treatments that included core cultivation, and the cultivation treatments increased water infiltration rates an average of 58% in 2001 and 188% in 2002 compared with the untreated. Turf quality was not adversely affected by any management practice and remained acceptable (≥7.0) throughout the study.

Quantifying a Daily Light Integral Requirement of a ‘TifEagle’ Bermudagrass Golf Green

‘TifEagle’ bermudagrass [Cynodon dactylon (L.) Pers. × C. transvaalensis Burtt‐Davy] is a fine textured hybrid bermudagrass used for golf course putting greens in the subtropical and tropical regions of the world. The growth and performance of TifEagle and other bermudagrass often decline in reduced light environments (RLEs). This study quantified a daily light integral (DLI; mol m−2 d−1) required to maintain commercially acceptable TifEagle bermudagrass maintained under golf green conditions. Three levels of shade, none, low, and high (0, 41, and 92%), were applied to mature TifEagle bermudagrass during morning (sunrise to 1100 h) and afternoon (1500 h to sunset) hours, allowing full irradiance from 1100 to 1500 h to mimic a golf green situation where trees or structures are adjacent to, but rarely directly overhead. The study was performed for 8 wk in June to August 2001 and 2002. An average minimal DLI of 32.6 mol m−2 d−1 was needed to maintain commercially acceptable TifEagle turf quality (TQ ≥ 7). Other plant responses measured included percentage lateral regrowth (RG), total shoot chlorophyll, and total nonstructural carbohydrates (TNC). These responses declined significantly when the DLI ≤ 32.6 mol m−2 d−1 Differences in diurnal shade exposure occurred. High afternoon shade reduced TifEagle bermudagrass TQ, percentage lateral RG, shoot chlorophyll, and TNC by 3.0 rating units and 17, 39, and 27%, respectively, compared with no afternoon shade (NSA). High morning shade reduced TQ, percentage lateral RG, and shoot chlorophyll by 1.5 rating units and 11 and 16%, respectively, compared with no morning shade (NSM). Overall, afternoon shade applications were more detrimental to TifEagle bermudagrass growth and performance compared with morning shade.

Plant Responses and Characteristics Associated with Dollar Spot Resistance in Creeping Bentgrass

Dollar spot, incited by Sclerotinia homoeocarpa F.T. Bennett, is one of the most important diseases affecting creeping bentgrass (Agrostis stolonifera L.) golf greens, fairways, and tees. Genetic resistance to dollar spot is a promising control strategy. A study was initiated to: (i) evaluate dollar spot resistance of 265 collections of creeping bentgrass in two locations; (ii) determine bentgrass clone stability of dollar spot resistance; and (iii) evaluate 10 resistant and susceptible clones for disease, turf, and leaf traits. The field experiments were arranged in randomized complete blocks with six and five clonally propagated replicates in each of two locations evaluated across 2 yr in North Brunswick, NJ. Five isolates of S. homoeocarpa were used to inoculate the field experiments. New Jersey fairway collections had the highest percentage of stable dollar spot resistant clones compared with Illinois fairway and New Jersey and New York golf green collections in this particular study. Resistant clones maintained a significantly higher turf density and percentage green turf cover and smaller dollar spot diameter sizes compared with susceptible clones.

Carbon Dioxide Content in Golf Green Rhizosphere

Anaerobic soils limit the amount of free oxygen available in the rhizosphere, and therefore will impede grass root development and restrain nutrient availability for turf growth. An in situ study was conducted on existing greens to investigate the relationship between CO2 content in the rhizosphere and turf quality. Nine greens were selected in the study. On each green, five 1‐m‐diam. circular plots were randomly selected for conducting the experiment. The greens were sampled seven times from August 1998 to August 1999. Data collected from each plot included turf quality index (TQI), CO2 content, and physical properties of the rooting mixtures. Turf quality declined drastically when CO2 content in the rhizosphere increased to 5 to 6 μL L−1 during the late summer season. The CO2 content increased as water content in the root zone increased, but was inversely related to infiltration rate. Cultivation of a golf green may reduce CO2 content in the rhizosphere, but the benefit of cultivation decreased with time.