Percent Green Cover Research Articles

QTL mapping of morphological characteristics that correlated to drought tolerance in St. Augustinegrass.

St. Augustinegrass is a warm-season grass species widely utilized as turf in the southeastern U.S. It shows significant variation in plant growth and morphological characteristics, some of which are potentially associated with drought tolerance. However, the genetic basis of these variations is not well understood. Detecting quantitative trait loci (QTL) associated with morphological traits will provide a foundation for the application of genetic and molecular breeding in St. Augustinegrass. In this study, we report QTL associated with morphological traits, including leaf blade width (LW), leaf blade length (LL), canopy density (CD), and shoot growth orientation (SGO) in a St. Augustinegrass ‘Raleigh’ x ‘Seville’ mapping population containing 115 F1 hybrids. Phenotypic data were collected from one greenhouse and two field trials. Single and joint trial analyses were performed, finding significant phenotypic variance among the hybrids for all traits. Interval mapping (IM) and multiple QTL method (MQM) analysis detected seven QTL for CD, four for LL, five for LW, and two for SGO, which were distributed on linkage groups RLG1, RLG9, SLG3, SLG7, SLG8 and SLG9. In addition, three genomic regions where QTL colocalized were identified on Raleigh LG1 and Seville LG3. One genomic region on Seville LG3 overlapped with two previously reported drought-related QTL for leaf relative water content (RWC) and percent green cover (GC). Several candidate genes related to plant development and drought stress response were identified within QTL intervals. The QTL identified in this study represent a first step in identifying genes controlling morphological traits that might accelerate progress in selection of St. Augustinegrass lines with lower water usage.

Evaluation of Compost and Soil Mix Ratios for Perennial Ryegrass Establishment on Topsoil and Subsoil

Soil degradation during construction often results in soil loss through erosion and reduced vegetation establishment. Composted organic materials are used to restore soil health of compromised urban soils when planting trees and shrubs; however, less is known about compost amendments for turfgrass establishment. The objective of this trial was to determine the effects of differing compost incorporation rates in two soil types on perennial ryegrass [PR (Lolium perenne)] establishment. The hypothesis was that as compost incorporation rates increase, turfgrass germination would increase until the compost rate becomes detrimental to turfgrass germination because of increased nitrate content and electrical conductivity (EC) levels. A salt-sensitive PR cultivar and a salt-tolerant PR cultivar were seeded into a loam topsoil and a clay subsoil at soil:compost volume ratios of 100:0, 80:20, 70:30, 60:40, 50:50, 40:60, and 0:100 using a mixed-source mature compost. Percent green cover (PGC) and leachate pH, EC, and nitrate content were measured during the 5-week establishment period. This trial showed that with a suitable topsoil, compost incorporation may be unnecessary to obtain acceptable PGC, but that compost additions (30% to 40%) to a clay subsoil achieve faster establishment while limiting the potential for reduced establishment because of increased nitrate content or EC associated with greater levels of compost incorporation. The EC or pH of soil:compost leachate was not found to predict turfgrass establishment. This trial suggests that soil type should be considered when making compost use rate recommendations; however, further research is needed to link compost physiochemical properties to compost use rates.

UAV remote sensing based estimation of green cover during turfgrass establishment

Turfgrass is an important urban crop in the United States. Determining the percent green cover (PGC) to assess turfgrass quality/health and the rate of establishment is a crucial parameter for evaluating different species and experimental lines within species. However, evaluating the PGC of individual plots within large breeding nurseries in a conventional way, either visually or through digital image analysis is a time-consuming and laborious process. In the present study, we used the unmanned aerial vehicle (UAV) with multispectral and RGB sensors to estimate PGC during turfgrass establishment. We evaluated thirty approaches with different levels of complexity based on vegetation indices, supervised and unsupervised machine learning classification methods, and image processing methods for high-throughput turfgrass PGC estimation. An HSV (Hue-Saturation-Value) color space-based green pixel identification (GPI) method was introduced for the first time for estimating UAV derived PGC (UAVPGC). The results indicate that the GPI achieved the highest coefficient of determination, 0.86–0.96, with lowest mean absolute error when compared to ground percent green cover (GroundPGC). Overall, UAV-derived RGB image-based support vector machine methods were in agreement with GroundPGC (R2 = 0.88–0.95). This suggests that UAV-derived RGB images are adequate in accurately determining percent green cover (green vegetation within an experimental plot); however, multispectral images might offer a solution to determine turfgrass coverage (green and non-green vegetation within an experimental plot) during turfgrass establishment to account for non-green vegetation which is not captured by RGB (visible light spectrum) based estimation of PGC.

Effects of mowing height and Cynodon spp. cultivar on traffic tolerance

AbstractAthletic field managers often adjust agronomic practices according to the desires of coaches and athletes. One such agronomic practice often adjusted is mowing height. In an attempt to have athletes run faster, field managers are persuaded to reduce mowing height, thereby reducing potential friction from the surface on an athlete. With newer bermudagrass [Cynodon datylon (L.) Pers.] and hybrid bermudagrass [Cynodon dactylon (L.) Pers. × C. transvaalensis Burtt Davy] cultivars, maintaining a field at reduced mowing heights is much easier to achieve without apparent negative effects on surface performance. However, these expected effects have not been verified through rigorous research and are solely dependent on anecdotal data. The objectives of this study were to compare traffic tolerance of four hybrid bermudagrass cultivars ‐ ‘Latitude 36 Turf Bermudagrass’ (Latitude 36) and ‘Northbridge Turf Bermudagrass’ (Northbridge), ‘Tifway’, and ‘Patriot’ ‐ and two bermudagrass cultivars ‐ ‘Riviera’, and ‘Hollywood’ ‐ and determine the effect of mowing height on traffic tolerance. Treatments were arranged in a randomized complete block design with eight replications. Measurements of percent green cover, surface hardness, and peak rotational traction were collected before, during, and after simulated traffic. Latitude 36 and Northbridge were more traffic tolerant than any of the other cultivars tested. While there was not an interaction between cultivars and mowing height, the higher mowing height had greater traffic tolerance.

Performance of diploid and interploid hybrids of St. Augustinegrass under moderate shade

AbstractShadetolerance is an important factor for cultivar selection in urban areas. Diploid (2n = 2x = 18) cultivars of St. Augustinegrass [Stenotaphrum secundatum (Walt.) Kuntze] with moderate to high shade tolerance have been popular choices for residential and commercial landscapes in the southern United States. This study evaluated 26 elite drought resistant diploid and interploid (polyploid × diploid) hybrids and four commercial cultivars under 75% continuous shade from 20 June 2017 through 30 Oct. 2018. Biweekly data were collected during the growing season for percent green cover, visual turfgrass quality, canopy color, shoot density, and daily leaf elongation rates (DER; mm d–1). Spring greenup was rated annually, and to gray leaf spot incidence was rated when naturally occurring. All genotypes lost green cover through 2017, and greenup was delayed transitioning into the summer of 2018 when most diploids struggled to recover from disease, shade, and winter injury whereas, on an average, interploid hybrids reached up to 84.0% green cover. Daily leaf elongation rates were lower for diploids than polyploids in both years. Turfgrass quality, color, and density generally declined under shade as expected. Overall, three interploid hybrids (DALSA 1329, 1404, and 1406) were the top performers demonstrating good retention of turfgrass performance traits and reduced DER under shade.

Response of Retail Lawn Seed Products during Acute Drought and Recovery

Consumers often have multiple choices when purchasing retail lawn products in stores. In this study, we evaluated the acute drought performance of locally available retail lawn seed products (mixtures or blends) at two mowing heights of 2.5 and 3 inches. We hypothesized that the species present in the products and the height-of-cut differentially influence the drought resistance and recovery of the mixtures and blends. In Fall 2016 and 2017, 28 different products consisting of 25 mixtures and 3 blends of turfgrass seeds were established under a fully automated rainout shelter at the St. Paul campus of the University of Minnesota. The drought treatments lasted for 67 days in 2017, and 52 days in 2018; both the 2017 and 2018 treatments were followed by a recovery period. Data were obtained during acute drought treatments and recovery periods for visual turfgrass quality and green turfgrass cover using digital images of the plots. During the first year, several products displayed higher green stability (or the ability to remain green) at the 3-inch height-of-cut compared with the 2.5-inch height-of-cut. Products with tall fescue (Schedonorus arundinaceus) and fine fescue (Festuca sp.) as dominant species generally performed better during the drought treatments, whereas an increasing presence of perennial ryegrass (Lolium perenne) and kentucky bluegrass (Poa pratensis) decreased the visual drought performance of the products. During the recovery period, an effect of the interaction between mowing height and the date of data collection on the percentage of green cover was observed: the lower mowing height improved the early recovery of green cover after acute drought. These findings suggest that consumers in the upper midwestern United States and areas with a climate similar climate to that of St. Paul, MN, who are challenged with multiple choices of lawn seed products should choose products containing a higher tall fescue content and adjust their mowing heights to optimize recovery.

Evaluation of Algae-Based Fertilizers Produced from Revolving Algal Biofilms on Kentucky Bluegrass

The revolving algal biofilm (RAB) system is a wastewater treatment method that is effective at removing nutrients from wastewater, and as a result produces algae that could be used as a sustainable fertilizer source. A two-year greenhouse study was conducted to investigate if algae-based fertilizers produced from the RAB wastewater treatment system could be used as an effective and sustainable turfgrass fertilizer. Fertilizer treatments included pure algae (PA), algae + cellulosic filler (Blended), Milorganite, urea, and a nontreated control. Overall, in terms of percent green cover (PGC), Blended and PA performed similar to Milorganite and outperformed urea and the nontreated control. At the conclusion of the study, Blended was the only treatment to have an increased PGC relative to urea, which was a 29% increase. On average throughout the duration of the study, Blended and PA resulted in similar dark green color index (DGCI) relative to Milorganite and urea, and outperformed the nontreated control. Blended, PA, and Milorganite resulted in 50% and 111% greater total root length compared to urea and the nontreated control, respectively. Furthermore, Blended and Milorganite resulted in 107% and 136% greater root surface area and root volume, respectively, compared to urea and the nontreated control. Pure algae resulted in 58% greater root surface area relative to urea and the nontreated control. Blended and Milorganite increased the longest root by 22% compared to urea. Additionally, Blended and Milorganite resulted in 114% and 110% greater root and shoot biomass relative to the nontreated control, respectively. Blended and PA had a similar longest shoot length to Milorganite and urea. Overall, Blended and PA performed similar or better compared to Milorganite and urea in terms of turfgrass shoot growth, cover, color, and rooting. Thus, algae-based fertilizers (PA and Blended) produced from the RAB system should be considered an effective, sustainable turfgrass fertilizer.

Drought Resistance and Recovery of Kentucky Bluegrass (Poa pratensis L.) Cultivars under Different Nitrogen Fertilisation Rates

Kentucky bluegrass (Poa pratensis L.) is one of the most popular cool-season turfgrass species. However, little is known about the effects of N supply on its resistance to drought stress. The objective of this study was to assess the effects of acute drought followed by a recovery period on four Kentucky bluegrass cultivars (‘Barduke’, ‘Brooklawn’, ‘NuBlue Plus’ and ‘Marauder’) and one tall fescue (‘Rhambler SRP’) under two different nitrogen fertilisation rates (100 or 200 kg N ha−1 yr−1). The study was conducted over two years in a rain-out structure to control water input in spring and summer. The cultivars were subjected to a drought stress phase (absence of irrigation) followed by a recovery phase (weekly irrigation with an intake of 80% of ET). The green cover percentage, visual quality, NDVI, and soil moisture were measured weekly. We found that Kentucky bluegrass maintains sufficient turf quality for 2 weeks without irrigation. During the first year of the experiment, slight differences were observed among the Kentucky bluegrass cultivars, with ‘Marauder’ showing a 15% of green turf cover less than ‘Brooklawn’ after 6 weeks of acute drought, while in the second year, ‘NuBlue Plus’ displayed higher green turf cover and NDVI than the other cultivars. Nitrogen treatment had limited influence on the performances of the cultivars, ‘Marauder’ being the only one benefitting from the higher rate of applications.

Daily light integral requirements for bermudagrass and zoysiagrass cultivars: Effects of season and trinexapac‐ethyl

AbstractShade is a major problem facing turf managers worldwide. Availability of low‐cost devices and methods for quantifying daily light integral (DLI) offer the turf manager the ability to more precisely determine DLI levels in shade, yet minimal DLI requirements for acceptable turf quality (DLIm) for many commonly used warm‐season turf cultivars grown under longer‐term chronic shade stress have not been extensively tested. The objectives of this 2‐yr field shade study were to (a) determine effects of growth regulator trinexapac‐ethyl (TE) and season (summer or fall) on DLIm of nine commercially available bermudagrass (Cynodon spp.) and zoysiagrass (Zoysia spp.) cultivars; (b) determine effects of shade level and TE on summer percent green cover and root growth; and (c) determine effects of shade treatments on soil temperatures across the growing season. Significantly higher DLIm were noted during summer compared to fall for all cultivars in the study. The DLIm were generally higher for bermudagrass than zoysiagrass cultivars. ‘Tifway’ required the highest DLIm (ranging from 23.5 to 27.2 mol m−2 d−1) of the bermudagrasses. ‘TifGrand’, ‘Celebration’, and ‘Latitude 36’ showed comparable DLIm during summer and fall. Fewer consistent differences were detected between zoysiagrasses, with ‘Zorro’ and ‘Zeon’ showing the lowest summer DLIm (18.1 and 19.1 mol m−2 d−1, respectively) and ‘Geo’ showing the lowest fall DLIm (11.7 mol m−2 d−1). Trinexapac‐ethyl reduced DLIm only in Zorro, ‘Palisades’, and ‘JaMur’ zoysiagrass, but had no effect on bermudagrass DLIm. The DLIm for a number of cultivars were higher than those previously reported in the literature, which may be attributed to lower mowing heights and/or use of permanent shade structures that were not removed for the duration of the 27‐mo study. The findings should benefit turf managers by guiding data‐driven, seasonal‐based, warm‐season turfgrass cultivar selection for shaded environments.

Response of Twenty Tall Fescue (Schedonorus arundinaceus (Schreb.) Dumort.) Cultivars to Low Mowing Height

Tall fescue (Schedonorus arundinaceus (Schreb.) Dumort.) is the most widely used species in the European transition zone, however, despite its good wear tolerance, its use is still limited to lawns and landscape areas due to concerns about its ability to withstand low mowing regimes. A two years field study was conducted to access performance of twenty tall fescue cultivars (‘Ares’, ‘Armani’, ‘Dynamites LS’, ‘Firecracker SLS’, ‘Firewall’, ‘Foxhound’ ‘Granditte’, ‘JT-LT2′, ‘JT-338′, ‘Karakum’, ‘Lexington’, ‘Olympic Gold’, ‘Rebounder’, ‘Rhambler SRP’, ‘Starlett’, ‘Supersonic’, ‘Talladega’, ‘Thunderstruck’, ‘Titanium 2LS’, ‘Turfway’) mowed weekly at 18 mm. Turfgrass was evaluated every two weeks for visual quality, color, density, texture and uniformity, as well as percent green cover (PGC) and dark green color index (DGCI), and normalized difference vegetation index (NDVI), and traction twice per year. Although no cultivars showed sufficient quality throughout the year, ‘Turfway’, ‘Titanium 2LS’ and ‘JT-338’ achieved high quality rating during spring and fall, the two seasons with the highest frequency of games played on sports field in northern Italy. Traction ratings collected in these study fell within acceptable range for football fields. Our results suggest that improved dwarf-type tall fescue cultivars can be used in sport fields in Northern Italy.

An evaluation of mat hybrid turfgrass systems under simulated traffic

AbstractThe addition of synthetic fibers to natural grass athletic fields forms a hybrid turf system, and this system claims to increase traffic tolerance and playability. The objectives of this research were to evaluate the physical effects of simulated traffic on two hybrid, carpet‐based mat systems (Eclipse and Hero) with Kentucky bluegrass (Poa pratensis L.), compared to a non‐hybrid control (100% Kentucky bluegrass). Field research was conducted in 2018 at Michigan State University (MSU), Iowa State University (ISU) and the University of Tennessee (UT) to evaluate the percent green cover, surface hardness, and shear resistance under 25 simulated traffic events (STE). Percent green cover across all treatments was reduced after 25 STE. After 25 STE the hybrid systems had greater percent green cover (Eclipse 49% and Hero 48%) than the non‐hybrid control (33%) at the ISU location. Surface hardness values differed between treatments on many rating dates. The hybrid systems reported higher surface hardness values, but these values were never above 100 Gmax. These results indicate that the Eclipse and Hero systems can offer a safe and stable surface even if turfgrass cover is reduced.

Impact of stitched hybrid systems in hybrid bermudagrass athletic fields

AbstractThe use of hybrid turf systems is very common in Europe and is increasing in popularity in the United States. Little research was found on the impact of stitched hybrid systems on hybrid bermudagrass ‘NorthBridge’ (Cynodon dactylon (L.) Pers. × C. Transvaalensis Burtt Davy) athletic fields. A study was conducted to determine the impact of stitched hybrid systems on hybrid bermudagrass performance at the University of Tennessee Center for Athletic Field Safety in Knoxville, TN USA in the fall of 2018 and 2019. A randomized complete block design with four replications was utilized. The study treatments consisted of synthetic fibers spacing stitched in 2 cm by 2 cm, 2 cm by 4 cm treatments, and an untreated control. Each plot received 30 games of simulated traffic events with 12 test variables collected including: percent green cover, surface hardness, head impact criteria, ball rebound, ball roll, angled ball rebound, vertical deformation, energy restitution, force reduction, surface temperature, and rotational and horizontal traction. Results indicated that the only differences among stitched treatments were in rotational traction with the 2 cm by 2 cm treatment having the highest values, increasing the traction for athletic movements. Traffic had a significant effect on green cover, surface hardness, head injury criterion, ball rebound, force reduction, energy restitution, and vertical deformation, regardless of treatment. These findings suggest that the stitched fiber system did not significantly impact hybrid bermudagrass athletic field performance.

Suppression of Microdochium patch using rotations of mineral oil, sulfur, and phosphorous acid

AbstractMicrodochium patch is a turfgrass disease caused by the fungal pathogen Microdochium nivale (Fr.) Samuels and I.C. Hallett that occurs in cool, humid conditions, which are commonplace in the U.S. Pacific Northwest and northern Europe. Pesticide restrictions in certain areas make suppressing Microdochium patch challenging, and alternative control methods are desired. Previous research has shown that mineral oil, S, and phosphorous acid (H3PO3) suppress Microdochium patch, but abiotic damage was associated with repeated mineral oil applications. Two field experiments in western Oregon focusing on the suppression of Microdochium patch and turfgrass quality on annual bluegrass (Poa annua L.) greens are presented. The first experiment compared tank mixtures of mineral oil and S or mineral oil and H3PO3 in rotation with a tank mixture of S and H3PO3. The second experiment focused on seasonal rotations that excluded mineral oil in certain months and compared 2‐ and 3‐wk application frequencies. All rotations, in both experiments, suppressed Microdochium patch compared to the non‐treated control, although differences in turfgrass quality were observed. In the first experiment, green cover percentage was used to assess abiotic damage. A mineral oil and H3PO3 tank mixture rotated every 2 wk with S and H3PO3 resulted in the highest green cover percentage. In the second experiment, most of the applications made every 2 wk completely suppressed Microdochium patch. Two treatments applied every 2 wk that withheld mineral oil in the winter months resulted in turfgrass quality ratings considered acceptable for putting greens on all rating dates.

Geomatics and epidemiology: Associating oxidative stress and greenness in urban areas

Green spaces may benefit human health mainly by mitigating noise and air pollution, promoting physical or social activities and improving mental health. Based on the influence that green space exposure seems to exert on Public Health and using a multidisciplinary approach, we investigated, the association between oxidative stress (OS) and green exposure in children. Overall, 207 subjects (10–13 yrs) living in Torino (NW- Italy) were involved in this study. Each participant provided a urinary sample, used to quantify a reliable OS biomarker (15-F2t-IsoP), and their residence addresses, used for geocoding. Green exposure was characterised by calculating i) the Soil Adjusted Vegetation Index (SAVI) within fixed buffers around each participant's home, using remotely-sensed data; ii) Tree Map accounting for evergreen/broadleaf species; iii) The percentage of green cover (PGC). Significant negative correlation (Pearson's r = −0.758, p < 0.001) between PGC and 15-F2t-IsoP was found. Greater SAVI was associated with lower OS (Pearson's r = −0.717, p < 0.001). Noticeably, evergreens seemed to determine a significant OS reduction compared to broadleaves (slope = −0.12 and −0.02, respectively; Warton-test F = 12.48, p = 0.0011). Finally, a spatial distribution of 15-F2t-IsoP estimates map, overlying with 2011 Census Data on same-aged dwellers of Torino, was generated. Predictive models accounting for green spaces influence on OS can be useful tool derived from geomatic employ in the Public Health field. Future developments of such a multidisciplinary approach should be considered in urban planning and policy-makers decisions to better define priority zones to requalify in urban settings.

Comparison of mechanical removal of perennial ryegrass overseeding out of bermudagrass to chemical transitions

AbstractIn the fall, bermudagrass athletic fields are overseeded with perennial ryegrass [Lolium perenne L.] to provide a uniform playing surface to slowed or dormant bermudagrass. Chemical techniques have been utilized for quick and efficient spring transition of perennial ryegrass. Fraise mowing has been identified as a tool that can aid in ryegrass transition in the spring. These studies were to determine the effectiveness of spring transition comparing mechanical removal of perennial ryegrass overseeding to traditional techniques on ‘Riviera’ bermudagrass [Cynodon dactylon (L.) Pers.]. In 2017, field studies were conducted at the University of Tennessee Center for Athletic Field Safety (Knoxville, TN) and the Oklahoma State University Turfgrass Research Center (Stillwater, OK). The seven treatments for the study were: fraise mow at 6.4 mm from the grass surface, fraise mow at 12.7 mm from the grass surface, fraise mow at 19.1 mm from the grass surface, spray application of trifloxysulfuron at the 27.8 g ha−1 with non‐ionic surfactant at 0.25% v/v, spray application of foramsulfuron at the 28.9 g ha−1, scalping (19.1 mm) with a rotatory mower, and an untreated control. Treatments were initiated on 11 May 2017 in Stillwater, OK USA and 17 May 2017 in Knoxville, TN USA. Plots were monitored for six weeks following treatment application. Fraise mowing at 12.7 mm was identified as the optimum depth for perennial ryegrass transitioning in this study compared to chemical transitions. This study found that the fraise mowing at 12.7 mm removed more perennial ryegrass and maintained percent green turfgrass cover throughout the study. However, if time of use for the turfgrass area is not a primary concern then depths greater than 12.7 mm are effective at perennial ryegrass removal but delay spring green‐up.

Tall Fescue (Schedonorus arundinaceus (Schreb.) Dumort.) Turfgrass Cultivars Performance under Reduced N Fertilization

The identification of minimal N requirements for sustaining turfgrass quality and functionality became necessary to reduce N fertilization inputs and avoid potential environmental impacts in the European Union. A two year study was conducted at Padova University in Legnaro, northeastern Italy to investigate the performance of four tall fescue (Schedonorus arundinaceus (Schreb.) Dumort.) cultivars (‘Lexington’, ‘Rhambler SRP’, ‘Rhizing star’, and ‘Thunderstruck’) fertilized twice per year at either 75 or 150 kg N ha−1 year−1. Turfgrass was evaluated every two weeks for turfgrass visual quality, percent green cover (PGR) as well as dark green color index (DGCI) through digital image analysis and normalized difference vegetation index (NDVI). ‘Rhizing star’ was the only cultivar that showed poor adaptation to the environment, achieving acceptable turfgrass quality (6.0 or higher) only during June and July 2019. Turf fertilized at 150 kg N ha−1 year−1 generally showed higher performance than 75 kg N ha−1 year−1, however, the increase in turfgrass quality was mostly negligible and detected only during the winter months. Results suggest that well adapted tall fescue cultivars could be fertilized at 75 kg N ha−1 year−1 in Northern Italy.

Drought Stress Response of Turf-Type Perennial Ryegrass Genotypes in a Mediterranean Environment

Perennial ryegrass is generally known as exhibiting poor drought tolerance with poor recuperative capacity. The objective of this study was to evaluate the effects of acute drought followed by a recovery period, on 11 perennial ryegrass varieties (Apple SGL, Azimuth, Barrage, Caddieshack, Double, Double Time, Ecologic, New Orleans, Pizzaz 2, Rainwater, Turfgold) and one tall fescue (Olympic Gold). The study was conducted in a rain-out structure to control water inputs. Green cover percentage, visual quality, color, normalized difference vegetation index (NDVI), and soil moisture were measured weekly. Eighty percent coverage was considered optimal and was reached only during the first two weeks of the drought period. Starting from the fourth week, a significant decrease in green cover was observed for most of the perennial ryegrass cultivars. However, 5 cultivars displayed a visual quality rate greater than 6, which is considered acceptable during this period, while color ratings were recorded greater than 6 for 7 cultivars. At the end of the drought phase, the cultivar ’New Orleans’ exhibited significantly greater green cover compared to most other perennial ryegrasses. The recovery of the grasses was slow and at the end of the experiment the variability in green cover between cultivars was greater than during the first week.

Identification of wetting agents for water conservation on deficit‐irrigated hybrid bermudagrass fairways

AbstractWetting agents have been reported to alleviate localized dry spot and save water while maintaining turf quality at an acceptable level. However, limited research has been conducted on comparing the effects of different wetting agent products. A study was conducted from May to October in 2018 and 2019 in Riverside, CA to evaluate 10 wetting agent treatments on performance of ‘Tifway II’ hybrid bermudagrass [Cynodon dactylon (L.) Pers. × C. transvaalensis Burtt Davy] under deficit irrigation at three reference evapotranspiration (ETo) levels: 45, 55, and 65% ETo. Ten wetting agent treatments were selected based on manufacturer recommendations. Plots were evaluated for visual turf quality, percent green cover (PGC), dark green color index, normalized difference vegetation index (NDVI), soil volumetric water content, soil moisture variability, and proline content in dry‐leaf samples. Wetting agent treatments improved turf quality and PGC, and decreased soil moisture variability. Moreover, up to 16% increase in soil moisture levels was observed on treated vs. untreated control. No differences were observed for NDVI, proline content in leaves, or fall color retention. Overall, soil moisture variability declined in 2019, and turf quality improved in both years when any wetting agent treatment was applied, and only minor differences were observed among wetting agent treatments evaluated in this study. Other physiological indicators and soil rootzone characteristics are needed to gauge the effects of wetting agents under deficit‐irrigated turfgrass.

Sand‐capping depth and subsoil influences on ‘Tifway’ bermudagrass response to irrigation frequency and drought

AbstractGolf courses and sports fields with turfgrass surfaces have been moving toward sand‐based root zone construction to enhance playability. Sand‐capped systems are ideally suited for situations where poor water quality and/or clayey soils necessitate rapid drainage and the need to flush salts. This study evaluated sand‐capping depth and subsoil texture on dynamics and availability of water as well as subsequent turf canopy and rooting characteristics. Objectives of this study were (a) to assess season‐long turf performance and root distribution of ‘Tifway’ hybrid bermudagrass (Cynodon dactylon × C. transvaalensis Burt. Davy) turf established on various sand‐cap depths (0–5 cm topdressed over 2 yr or 5, 10, or 20 cm) atop two subsoils (fine sandy loam or clay loam) and (b) to determine how sand‐capping × subsoil combinations influence required irrigation frequency (1 vs. 2 d wk−1 at 0.6 × reference evapotranspiration) and soil moisture dynamics. Irrigation frequency had minimal effect on percent green cover during the entire study period. Root mass detected within the underlying 30‐cm subsoil was inversely proportional to sand‐cap depth. Turf performance during the study was primarily affected by capping depth and subsoil, suggesting that playing surfaces can be negatively affected if the wrong capping depth is chosen in the construction of sand‐capped turfgrass systems.

Effect of Wetting Agent on Nutrient and Water Retention and Runoff from Simulated Urban Lawns

Wetting agents have been widely used in the turf industry for ameliorating hydrophobic soil conditions and improving water use efficiency. However, limited information is available regarding potential benefits of wetting agents on fine textured soil lawns where wettable soils are commonly found, because most prior studies have been conducted in sand-based turf systems. This 2-year field study evaluated the potential for wetting agents to improve turf quality, as well as to reduce runoff losses of water and nutrients from st. augustinegrass [Stenotaphrum secundatum (Walt.) Kuntze] lawns. Over two seasons, turfgrass quality, percent green cover, and soil moisture in plots were evaluated in response to wetting agent and fertilizer treatments. During precipitation events, total runoff volumes were measured, as well as total export of nutrients including NO3-N, NH4-N, total dissolved N, dissolved organic N, dissolved organic C, and PO4-P. No runoff was detected from any treatments when precipitation was less than 13 mm. St. augustinegrass turfgrass quality and soil moisture were slightly improved by wetting agent and fertilizer treatments during the study, but no significant effects of either of the treatments were found on runoff volumes or nutrient exports. Although turf was managed under deficit irrigation levels of 0.3 × reference evapotranspiration, irrigation events were not withheld due to rainfall, and thus, little to no drought stress was observed during the study.