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Global energy production is in high demand and is expanding its development into new landscapes, including grasslands. This expansion has intensive impacts on aboveground and belowground components of grasslands which need to be addressed during reclamation to promote long‐term ecological integrity. This study was conducted to ascertain how alternative reclamation practices may improve soil structure (i.e., compaction) while aiding in the creation of conditions that are conducive to both the establishment and continued growth of native grassland plant species. The grassland was reclaimed with different combinations of seeding mixtures (grass or grass and forb), ripping techniques (subsoil ripping or topsoil ripping), and the integration of mulch into the soil profile. Year, seed mixtures, and ripping techniques and their interactions significantly affected community composition and species diversity. Topsoil‐ripping and grass‐forb treatment had a higher association with native, perennial grasses while subsoil‐ripping and grass treatment favor more short‐lived species. Similar trends persisted across penetration resistance and soil moisture readings where topsoil‐ripping and grass‐forb treatment were different from subsoil‐ripping and grass treatments (p ≤ 0.10). Additionally, Kentucky bluegrass, an invasive grass species, increased by 76% over 1 year and was more common in the topsoil‐ripping and grass‐forb treatments. While early in the reclamation process, results suggest topsoil‐ripping and grass‐forb treatment are promising combination reclamation practices that can establish a native grassland community and initiate the improvement of compacted soil conditions. [ABSTRACT FROM AUTHOR]

Kentucky bluegrass (Poa pratensis L.) has become dominant in many portions of the northern Great Plains. During hot and/or dry periods, pastures consisting of mostly cool‐season grasses will most likely lack the productivity and diversity needed to provide sufficient forage for livestock. Determining the impact of weather conditions on the variation of forage production and nutritive response of Kentucky bluegrass is becoming increasingly important to agricultural producers. Sampling occurred at the USDA Northern Great Plains Research Laboratory near Mandan, North Dakota, USA. Kentucky bluegrass samples were clipped every 2–3 weeks in mowed and unmowed unfertilized rangeland plots during the growing seasons of 2017 and 2018. Samples were dried, weighed, ground to pass a 1‐mm sieve, and analysed for nutritive value. There are differences between the modelled supply of metabolizable energy and metabolizable protein and the requirements for cow‐calf pairs for all years and most months. Early defoliation of Kentucky bluegrass decreases productivity and nutritive value as the grazing season progresses. Adjusting management to allow an adequate growth interval and plant canopy cover throughout the year can ensure a more consistent supply of Kentucky bluegrass. Our data and models provide a glimpse into future scenarios, which allow producers to be more proactive in dealing with Kentucky bluegrass and projected changes in climate. [ABSTRACT FROM AUTHOR]

The growth and functionality of turfgrasses are often challenged by high soil salinity. Previous research mainly focused on plant responses to Cl- salt-induced saline conditions (e.g., NaCl). However, in some regions, including California and North Dakota, in salt-affected soils the predominant cation is Mg2+ and the predominant anion is SO4. The responses of turfgrass species to such salinity conditions have not been well documented. In this research, the responses of Kentucky bluegrass (Poa pratensis L.) cultivars Kenblue and Moonlight at the seedling growth and the vegetative growth stages to different salt type (NaCl, Na2-. The responses of turfgrass species to such salinity conditions have not been well documented. In this research, the responses of Kentucky bluegrass (Poa pratensis L.) cultivars Kenblue and Moonlight at the seedling growth and the vegetative growth stages to different salt type (NaCl, Na2SO4, MgCl2, and MgSO4) and concentration (5-20 dS m-1) were investigated. Results showed that shoot dry weight (SDW), root dry weight (RDW), root length (RL), and visual quality of the two turf cultivars decreased with increasing salt concentration at both growth stages. Specific root length increased to 235.7% of the control at the seedling growth stage but decreased to 71.6% of the control at the same salt concentration at the vegetative growth stage. Under the saline condition, Kenblue showed higher SDW (52.1%), RDW (74.4%), and RL (20.6%) than Moonlight at the seedling growth stage; however, Moonlight performed better than Kenblue at the vegetative growth stage. The two turf cultivars were more tolerant to Na2SO4 and MgSO4 stress than to NaCl and MgCl2 stress. Our research indicates that turfgrass managers need to consider plant material (cultivar and growth stage), salt type, and salt concentration to develop a successful salinity management plan. [ABSTRACT FROM AUTHOR]

Abstract: Despite evidence that prior exposure to drought can increase subsequent plant freezing tolerance, few studies have explored such interactions over ecologically relevant time spans. We examined the combined effects of drought and subsequent freezing on tiller growth and leaf sugar concentrations in the grass, Poa pratensis. We exposed tillers to no drought (−0.04 MPa), moderate drought (−0.19 MPa) or severe drought (−0.42 MPa) for 3 weeks in summer. Tillers were then frozen in autumn or spring at −5 °C (frost damage) or at 0 °C (control) for 3 days and harvested after a re‐growth period. For shoot growth, there was a significant interaction between drought and autumn freezing, whereby the relative effect of freezing on growth was least for the plants previously exposed to severe drought; however, there was no significant interaction between drought and spring freezing. For root growth, there were no significant interactions between drought and freezing in either season. Leaf sugar concentrations increased significantly with drought intensity, but these effects dissipated within a month, prior to the onset of the autumn freezing treatment. Overall, our results suggest that interactions between prior drought and subsequent freezing in P. pratensis may be most relevant in the context of autumn freezing, and despite the important role of soluble sugars in increasing both drought and freezing tolerance in this species, the retention of these compounds after drought stress does not appear to explain the occurrence of drought–frost interactions at ecologically relevant time scales. [ABSTRACT FROM AUTHOR]

Abstract: Invasion by the rhizomatous grass Kentucky bluegrass (Poa pratensis) is a global phenomenon, including into foothills rough fescue (Festuca campestris) grasslands of southwestern Alberta, Canada. In order to better understand the competitive relationships between these species, we conducted a fallow field study where rough fescue bunchgrass tussocks were transplanted at one of three planting densities (15, 30, or 45 cm spacing), and then subject to various treatments in a factorial design, including one‐time intensive summer defoliation and seeding of bluegrass into adjacent bare soil. Rough fescue plants exhibited marked intraspecific competition, as high planting densities increased tussock mortality, while decreasing plant tiller counts and relative inflorescence production, together with plant and tiller‐specific mass. However, high densities of the bunchgrass also reduced the cover and biomass of encroaching bluegrass, coincidental with reduced resource (soil moisture and light) availability in mid‐summer. Although summer defoliation increased rough fescue tiller counts, this disturbance reduced plant and tiller mass, and also increased Kentucky bluegrass. We conclude that while high densities of nondefoliated stands of rough fescue may increase resistance to bluegrass encroachment, a reduction in either fescue plant density or vigor via defoliation can increase the risk of bluegrass invasion within northern temperate grassland. [ABSTRACT FROM AUTHOR]

Prairie reconstructions are a critical component of preservation of the imperiled tallgrass prairie ecosystem in the Midwestern United States. Sustainability of this endeavor depends on establishment of persistent cover of planted native species and resistance to noxious weeds. The goal of this study was to understand the influence of early reconstruction practices on long-term outcomes. Twelve replicates of three planting methods (dormant-season broadcast, growing-season broadcast, and growing-season drill) and three seed mix richness levels (10, 20, or 34 species), fully crossed in a completely randomized design were planted in 2005 on nine former agricultural fields located in Iowa and Minnesota. Cover by species was estimated in 2005-2007, 2010, and 2015. In 2015, cover of planted species, native nonplanted species, and exotic species were similar to those recorded in 2010. Cover of the noxious weed Cirsium arvense had also declined by an average of 49% without herbicide from a peak in 2007 to low stable levels from 2010 to 2015. Richness of planted forbs, on the other hand, were still increasing in high-richness broadcast treatments (e.g. 17-59% increase 2010-1015 in Minnesota). Two results in 2015 are reasons for concern: cover of planted species is only slightly over 50% in both Minnesota and Iowa, though with forbs still increasing, this may improve; and the cool-season exotic grasses Poa pratensis and Bromus inermis are increasing at both Minnesota and Iowa sites. Control of these invasive grasses will be necessary, but care will be needed to avoid negative impacts of control methods on natives. [ABSTRACT FROM AUTHOR]

Climatic changes and the need to reduce water consumption for irrigation have led to expanded use of warm-season turf species in transitional zones. Turf managers are often hesitant to use warm-season species because they undergo dormancy for a long period during the winter. Although this issue might be addressed by mixing cool- with warm-season species, there is a lack of information on the performance and dynamics of species succession in such turfgrass mixtures. A 2-yr investigation was conducted in Legnaro, Italy, and Fayetteville, AR, to test the turf quality and species succession in mixtures of various cultivars of bermudagrass (BG) [Cynodon dactylon (L.) Pers.] with Kentucky bluegrass (KBG) (Poa pratensis L.). Bermudagrass cultivars, Yukon and Veracruz, were seeded in June 2011 at 5 g m-2 and KBG cultivars Brooklawn, Mystere, and Nublue Plus were overseeded in September 2011 at 30 g m-2. Across both studies, the frequency of BG in the mixture was generally higher for Yukon and ranged from 40 to 95%. However, the mixtures with Veracruz had superior turf quality in Legnaro from October 2012 to March 2013. The species succession was influenced by BG cultivars, whereas KBG cultivar had little effect on the rate of plant composition change. On the basis of these results, the choice of BG cultivar appears critical for establishing functional KBG and BG mixtures in transitional zones. [ABSTRACT FROM AUTHOR]

Mowing remains one of the most energy-intensive cultural practices in maintaining a turf sward. Turfgrass systems can become a larger net C sink if mower emissions are reduced. Establishing slow-growing turfgrasses has been proposed to reduce mowing requirements. Traditional recommendations for home lawns are to mow by the "one-third rule" and return grass clippings. However, their impact on annual mowing requirements remains largely unknown. This study aimed to determine (i) the number of required mowing events when mowing weekly versus using the one-third rule; (ii) the influence of returning grass clippings on mowing requirements, dry matter yield (DMY), and leaf tissue N (LTN); and (iii) how turfgrasses with differing growth rates influence mowing requirements, DMY, and LTN. The one-third rule decreased mowing requirements by 31% (approximately eight mowing events yr-1) and returning grass clippings added approximately two additional mowing events yr-1. Tall fescue [Schedonorus arundinaceus (Schreb.) Durmort., nom. cons.; Festuca arundinacea Schreb.] required more annual mowing events than Kentucky bluegrass (Poa pratensis L.)(nine and three more in 2012 and 2013, respectively). Tall fescue had a greater 2-yr cumulative DMY than Kentucky bluegrass (875 vs. 522 g m-2). Growth rate (i.e., cultivar) also affected annual mowing requirements and yield: the faster the growth rate, the more annual mowing events. Leaf tissue N concentrations were higher when clippings were returned and with slower-growing cultivars. Mowing by the one-third rule and selecting slower-growing cultivars of turfgrass species adapted to a particular location can reduce annual mowing requirements and subsequent mower emissions. [ABSTRACT FROM AUTHOR]

PREMISE OF THE STUDY: Both freezing and drought cause cellular dehydration, and they elicit similar increases in protective compounds, which suggests that these stresses could potentially interact. We examined whether the physiological changes that occur in response to freezing in the fall and spring could affect subsequent survival and growth after summer drought. METHODS: We froze Poa pratensis tillers in the late fall, early spring, or late spring at 0, -5, or -10 °C for 3 d and then subjected them to no drought (-0.025 MPa), moderate drought (-0.140 MPa), or severe drought (-0.250 MPa) for 3 wk in the summer. We quantified survival and total biomass after a 3-wk recovery period, and we determined leaf soluble sugar concentrations before and then 0, 30, and 55 d after freezing. KEY RESULTS: For survival and biomass, there were significant interactions between freezing and drought. Spring frozen tillers had the highest biomass and survival following severe drought, whereas fall freezing did not significantly increase the biomass of tillers following the severe drought. Increased drought tolerance after spring freezing did not appear to be associated with increased soluble sugar content, given that the freezing effects on leaf glucose, fructose, and sucrose content were absent 55 d post freezing. CONCLUSIONS: Our results demonstrate that multiple stresses that occur over different seasons can interact; this interaction is highly relevant to herbaceous species in northern temperate regions that are experiencing more intense and frequent stress as a result of changes in snow cover and extreme climatic events. [ABSTRACT FROM AUTHOR]

A combination of grasses, Kentucky bluegrass and Bermuda grass, with Rhodococcus erythropolis bacteria was hypothesized for bioremediation of naturally polluted soils with hydrocarbons. A 90-day greenhouse experiment as a factorial design with twelve treatments including soil inoculation with bacteria as well as soil sterilization using both plants in three replicates was performed. Both grasses significantly decreased the concentration of soil hydrocarbons compared with the control polluted soil, with Kentucky grass being the more effective one. The bacteria enhanced the bioremediation abilities of both plants, especially of Kentucky grass. Soil sterilization substantially reduced the rate of hydrocarbons in the soil. The positive effects of bacteria on the process of bioaugmentation make this method of bioremediation strongly recommendable. [ABSTRACT FROM AUTHOR]

The recent expansion of deciduous shrubs is a common observation throughout the Arctic. However, we lack a complete understanding of how physiological differences between deciduous shrubs and coexisting species may confer competitive advantages to shrubs. We combined leaf gas exchange and stable isotope analyses of two important species, Betula nana and Poa pratensis, to elucidate the processes governing seasonal carbon (C) gain in West Greenland. We tested two competing hypotheses. On one hand, we anticipated the cooler, drier soils beneath the Betula canopy could result in greater drought sensitivity in this species. Alternatively, because Poa tends to occupy sites with wetter soils, we hypothesized that it may be more sensitive to drought. Our results revealed greater drought sensitivity in Poa, which displayed reductions in Amax and gs during periods of high atmospheric demand and dry soils. Additionally, leaf Δ13C and Δ18O were negatively correlated in Poa, suggesting strong stomatal influence on Δ13C. Conversely, there was no relationship between gs and canopy or soil microclimates and no correlation between leaf Δ13C and Δ18O in Betula, indicating that variation in Δ13C may have been driven by variation in photosynthesis. Our results suggest that Poa is more susceptible to drought than Betula, whereas Betula was able to maintain steady, yet conservative, C gain. These differences in C-H2O relations may confer a competitive advantage to Betula in a warmer, drier climate. [ABSTRACT FROM AUTHOR]

Objective approaches to guide N fertilization of turfgrass sod crops are lacking. This study was conducted to determine the relationships among normalized difference vegetative index (NDVI), frequently-measured soil NO3-N concentrations, and peak-shear force of predominately Kentucky bluegrass (Poa pratensis L.) sod, and to evaluate if those relationships could help guide N fertilization. Ramp calibration strips (RCS) with varying N rates were established within production sod fields in Rhode Island across three consecutive years. At 2-wk intervals during each growing season, soil NO3-N concentrations and NDVI readings were recorded and correlated. Biweekly relative NDVI readings plateaued when soil NO3-N concentrations ranged between 5 and 12 mg kg-1. Mean relative NDVI plateaued at 196 kg N ha-1 yr-1. Relative sod peak-shear force was negatively correlated to soil NO3-N concentrations and the total amount of N applied per year. Relative peak-shear force was maximized when mean relative NDVI readings ranged from 0.969 to 0.982, but declined as mean relative NDVI increased towards 1.0. The results suggest that frequently measured NDVI and soil NO3-N concentrations show promise as guides for N fertilization of predominately Kentucky bluegrass sod. Further research will be required to validate these approaches on larger-scale sod fields. [ABSTRACT FROM AUTHOR]

Currently, the standard germination test (SGT) is the official test for evaluating seed viability in seed testing laboratories around the world. The SGT takes 3 to 4 wk to complete for most grasses, including the dormancy breaking treatment period. The tetrazolium test (TZT), however, offers quick viability determination within 24 to 48 h, even for dormant seeds. This study was conducted to compare SGT and TZT results for tall fescue (TF), annual and perennial ryegrass (ARG and PRG), orchardgrass (OG), bentgrass (BG), Kentucky bluegrass (KBG), and fine fescues (FF). A total of 3432 samples representing the seven species were evaluated for viability by SGT and TZT during 2009 to 2013 at the Oregon State University Seed Laboratory (OSUSL). According to the germination tolerance table of the Association of Official Seed Analysts (AOSA), both SGT and TZT results were within tolerance in 94.2% of TF samples, 95.2% of ARG samples, 90.4% of PRG samples, 93.7% of OG samples, 90.8% of FF samples, 83.9% of BG samples, and 42.4% of KBG samples. Dormancy was the main reason for higher viability by TZT results than by SGT in the same sample, causing the two test results to be out-of-tolerance. Based on these results, it can be concluded that the TZT can be used as an alternative viability test to the SGT for TF, ARG, PRG, OG, FF, and possibly for BG. However, the KBG has higher levels of dormancy, which brings the SGT below the TZT results, especially for freshly harvested seeds. [ABSTRACT FROM AUTHOR]

Interspecific hybridization between Poa arachnifera Torr. (Texas bluegrass) and Poa pratensis L. (Kentucky bluegrass) has shown to be a proven method for the development of turf-type hybrid bluegrass cultivars for the southern United States. Unlike in P. pratensis, the use of DNA markers for molecular characterization and flow cytometry to determine nuclear DNA contents has not been extensively utilized in P. arachnifera. In this study, 2C nuclear DNA content of 19 different genotypes of P. arachnifera (both males and females) was determined to range from 8.02 to 13.24 pg/2C using flow cytometry. The DNA content of the hybrids between P. arachnifera and P. pratensis from two different pedigrees was found to be intermediate between their parents. Furthermore, the utility of the trx (thioredoxin-like) nuclear gene in the identification of interspecific hybrids between P. arachnifera and P. pratensis was demonstrated using sequence and phylogenetic analyses. A newly discovered 851-bp trx allele may serve as a useful marker to differentiate P. arachnifera from P. pratensis and provide insights into the evolutionary origin of P. arachnifera. [ABSTRACT FROM AUTHOR]

Few correlation or calibration studies have been conducted to determine or validate sufficiency levels of N concentrations in the clippings of turfgrass for color and growth responses. In a series of field experiments conducted across six consecutive growing seasons (2007-2012) in Connecticut, clipping samples of Kentucky bluegrass (Poa pratensis L.) and tall fescue (Festuca arundinacea Schreb.) lawns were used to estimate yields and then analyzed for N concentrations. Chlorophyll and normalized difference vegetative index (NDVI) meters were used to quantify turf color before sampling. Macy's concept of three nutritional zones of plant tissue nutrient concentration was used to identify minimum and critical concentrations of N in the clippings that define sufficiency ranges for color and growth responses, in addition to luxury consumption. Averaged across all variables and seasons (spring, summer, and fall), the sufficiency ranges of N concentration in the clippings were estimated to be 32 to 46 g kg-1 for Kentucky bluegrass, and 28 to 42 g kg-1 for tall fescue. Differences in minimum and critical concentrations among seasons and between species were thought to be due to demanddriven nutrient uptake. Luxury consumption of N was observed in both species. When used in context with local conditions, tissue analysis for N concentrations in cool-season turfgrass clippings can provide an objective basis for guiding N fertilization. [ABSTRACT FROM AUTHOR]

Under climate change, alterations to precipitation and temperature regimes are expected to impact ecosystem structure and function. These impacts may in part be determined by feedbacks between plants and associated microbes, including both endophytic fungal symbionts and viral pathogens., To test potential key components of these feedbacks in a grassland system, we conducted a field experiment that factorially manipulated temperature regime, precipitation regime and endophyte infection of a dominant species, Schedonorus arundinaceus. After one growing season, we evaluated the four most frequently occurring grass species for infection by three species of barley and cereal yellow dwarf viruses (B/ CYDVs). For S. arundinaceus, we also tracked changes in viral prevalence over an additional two growing seasons, for a total of three growing seasons., Plant species identity played a strong role in determining virus prevalence; Poa pratensis and Paspalum dilatatum were more frequently infected than either S. arundinaceus (endophyte infected or endophyte free) or Eleusine indica. Both elevated temperature and elevated precipitation impacted virus prevalence, but effects varied among years and interacted with fungal endophyte symbiosis for S. arundinaceus., In the final year of data collection, elevated precipitation increased virus prevalence in endophyte-infected, but not endophyte-free, S. arundinaceus. In the same year, but regardless of endophyte infection, elevated temperature by itself increased virus prevalence for S. arundinaceus. This effect of temperature on virus prevalence may have been driven by vector abundance because the viruses are obligately aphid-transmitted, and aphids were found more frequently in heated plots., Synthesis. Overall, our investigation experimentally demonstrates strong combined impacts of biotic and abiotic factors on disease dynamics in a grassland system. Impacts of climate change on virus prevalence in grasslands may depend on the responses of aphid vectors and the presence of endophytic fungal symbionts. [ABSTRACT FROM AUTHOR]

Mixtures of turfgrass species are commonly used throughout the world when establishing cool-season grasses from seed. However, there have been limited studies investigating how various species compete with each other as the turf matures. A study was conducted in Padova, Italy, to investigate the performance and species composition of four mixtures that contained a single cultivar of Kentucky bluegrass (KB; Poa pratensis L.) and two rhizomatous or two nonrhizomatous tall fescue (TF; Festuca arundinacea Schreb.) cultivars. The trial was seeded in September 2010. Three mowing heights (20, 32, and 62 mm) were also applied to all the mixtures. General turfgrass performance of the mixtures was monitored through the 2011 growing season, and species composition was measured regularly to determine the abundance of both species in the mixture. Throughout the study, the mixtures containing the rhizomatous TF consistently had higher turfgrass quality and turfgrass density than mixtures containing the nonrhizomatous types. Mowing height had less effect on the performance of the mixtures, but the lower mowing heights (20 and 32 mm) performed more consistently than the plots mowed at the highest (62 mm) mowing height. Species composition of the mixtures was significantly influenced by the different TF cultivars, in that KB was less abundant in mixtures containing rhizomatous TF cultivars compared to nonrhizomatous cultivars, suggesting an increased competitive ability of rhizomatous TF lines. Mowing height also influenced the species composition, in that KB was significantly more abundant at lower mowing heights. [ABSTRACT FROM AUTHOR]

The use of sod to establish turf on sand-based root zones often leads to layering of contrasting soil textures within the root zone, causing adverse effects on soil drainage and moisture. These issues may be alleviated by alternative establishment methods and post-establishment cultural practices. Objectives of this study were to test the effects of sod establishment method, aerification, and sand topdressing on water infiltration, soil moisture, root mass, and divot resistance of Kentucky bluegrass (Poa pratensis L.) on sand-capped and native soil root zones. In 2010, cultivar Midnight Kentucky bluegrass was established in Fayetteville, AR, using standard (soil-based), washed, and pre-harvest, core-aerified sod on a sand-capped and a native silt loam root zone. After establishment, core aerification treatments (non-cultivated vs. 20% surface area affected annually) and topdressing treatments (0.6-cm sand applied one vs. four times yr-1) were imposed. The washed sod resulted in lower volumetric water content (VWC) (-3 to 4%) for both the root zones in 2010 and only for the sand-capped system in 2011. Core-aerification improved water infiltration rate (13% increase) and reduced the VWC (-44% at end of study) of the sand-capped root zone. The effects ofcultural practices on root mass density and divot resistance were oflimited practical importance. Core-aerification and topdressing appeared effective for managing layered root zones and would likely improve the long-term quality of golf and sports turfs. [ABSTRACT FROM AUTHOR]

Japanese beetle, Popillia japonica Newman, and oriental beetle, Anomala orientalis (Waterhouse) (both Coleoptera: Scarabaeidae) are considered invasive species and have been reported as key pests of urban landscapes in the Northeastern USA. Tiphia vernalis Rohwer and Tiphia popilliavora Rohwer ( Hymenoptera: Tiphiidae) were introduced as biocontrol agents against these beetles. These parasitic wasps burrow into the soil and search for grubs. When a host is found, the wasp attaches an egg in a location that is specific for the wasp species. It is unknown if these wasps can detect patches of concealed hosts from a distance above ground and what role, if any, herbivore-induced plant volatiles play in their host location. This study evaluated the responses of female T. vernalis and T. popilliavora to grub-infested and healthy plants in Y-tube olfactometer bioassays. Also the effect of root herbivory on the composition of turfgrass ( Poaceae) volatile profiles was investigated by collecting volatiles from healthy and grub-infested grasses. Tiphia wasps were highly attracted to volatiles emitted by grub-infested tall fescue ( Festuca arundinacea Schreb.) and Kentucky bluegrass ( Poa pratensis L.) over healthy grasses. In contrast, wasps did not exhibit a significant preference for grub-infested perennial ryegrass ( Lolium perenne L.) as compared with the control plants. The terpene levels emitted by grub-infested Kentucky bluegrass and tall fescue were greater than that of control plants. Low levels of terpenes were observed for both test and control perennial ryegrass. The elevated levels of terpenes emitted by grub-infested Kentucky bluegrass and tall fescue coincided with the attractiveness to the tiphiid wasps. Here, we provide evidence that plant exposure to root-feeding insects P. japonica and A. orientalis resulted in an increase in terpenoid levels in turfgrasses, which strongly attracts their above-ground parasitoids. [ABSTRACT FROM AUTHOR]

Drought stress encumbers the growth of turfgrass principally by disrupting the plant-water relations and physiological functions. The present study was carried out to appraise the role of silicon (Si) in improving the drought tolerance in Kentucky bluegrass (Poa pratensis L.). Drought stress and four levels (0, 200, 400, and 800mg L-1) of Si (Na2SiO3·9H2O) were imposed after 2 months old plants cultured under glasshouse conditions. Drought stress was found to decrease the photosynthesis, transpiration rate, stomatal conductance, leaf water content, relative growth rate, water use efficiency, and turf quality, but to increase in the root/shoot and leaf carbon/nitrogen ratio. Such physiological interferences, disturbances in plant water relations, and visually noticeable growth reductions in Kentucky bluegrass were significantly alleviated by the addition of Si after drought stress. For example, Si application at 400mg L-1 significantly increased the net photosynthesis by 44%, leaf water contents by 33%, leaf green color by 42%, and turf quality by 44% after 20 days of drought stress. Si application proved beneficial in improving the performance of Kentucky bluegrass in the present study suggesting that manipulation of endogenous Si through genetic or biotechnological means may result in the development of drought resistance in grasses. [ABSTRACT FROM AUTHOR]

Waterlogging is commonly seen in salt-affected soils. Previous research focused primarily on the effect of individual salinity or waterlogging on plant growth and development. However, information on saline-waterlogging (the combined condition) is limited. This study was to determine responses of 'Stonewall' tall fescue (Festuca arundinacea Schreb.) and 'Bewitched' Kentucky bluegrass (Poa pratensis L.) to saline (water electrical conductivity [ECw] at 5.4 or 11.0 dS m-1), waterlogging, and saline-waterlogging at 5.4 or 11.0 dS m-1. Soil salinity was decreased in the following order: salinity at 11.0 dS m-1 > saline-waterlogging at 11.0 dS m-1 > salinity at 5.4 dS m-1 = saline-waterlogging at 5.4 dS m-1 > control = waterlogging. Plants showed higher shoot dry weight and water content under waterlogging than the control treatment, but no significant differences in visual quality and electrolyte leakage were observed between the two treatments. Waterlogging did not elevate salinity stress at the lower salinity level (5.4 dS m-1); however, plants subjected to waterlogging had a higher shoot dry weight. Turfgrass showed higher levels of visual quality, shoot dry weight, and water content under saline-waterlogging at 11.0 dS m-1 than under salinity alone (11.0 dS m-1) at a later stage of the experiment (week 3 or 4). Stonewall tall fescue showed higher tolerance to salinity, waterlogging, and the combined condition compared with Bewitched Kentucky bluegrass at week 4. Our results showed that turfgrasses responded differently when they were exposed to individual salinity or waterlogging or combined salinewaterlogging conditions. [ABSTRACT FROM AUTHOR]

Forage establishment on fallow fields may be reduced by re-colonization and associated competition from hard to control perennial weeds that reproduce from residual root fragments. We assessed the competitive relationships between regenerating Canada thistle (Cirsium arvense L.) (CT) root fragments and seedlings of white clover (Trifolium repens L.) (WC), and Kentucky bluegrass (Poa pratensis L.) (KBG). Two greenhouse trials were conducted, each comparing 10 combinations of all three species grown in monoculture, or together (1:1:1 ratio), or in 1:2 and 2:1 binary mixtures in all possible combinations. All treatments were additionally done at two planting densities. After establishment, plants were grown for 70 d and assessed for biomass of all three species, as well as thistle shoot densities. Results from the two trials were similar. Canada thistle consistently produced the greatest biomass, and was more susceptible to intraspecific competition than competition from adjacent forage plants. Seedlings of neighboring WC were more effective competitors than KBG in reducing final thistle biomass and shoot density. White clover was also more likely to maintain shoot and root biomass under increasing weed presence. These results highlight the importance of reducing CT populations before forage seeding, as well as incorporating species such as WC that may be more tolerant of competition from the weed during the initial establishment period. [ABSTRACT FROM AUTHOR]

ABSTRACT Grasslands of the Northern Great Plains of North America are in the midst of extensive human-driven loss and redistribution of important species. Invasive plants contribute to degradation of this ecosystem and present monumental challenges for natural resource managers. Widespread decreases in populations of grassland-dependent wildlife, particularly birds, have been documented, but relatively little research has been focused on direct responses of wildlife to invading plants relative to native vegetation. Smooth brome ( Bromus inermis) and Kentucky bluegrass ( Poa pratensis) are 2 invasive cool-season grass species found across much of the Northern Great Plains that continue to expand despite management actions intended to reduce them. With eradication unlikely, creativity, cooperation, and science-based management (e.g., Adaptive Management) are paramount to protect and restore the integrity of grassland habitats across the Northern Great Plains. Published 2013. This article is a U.S. Government work and is in the public domain in the USA. [ABSTRACT FROM AUTHOR]

There are a number of strategies to minimize NO3- leaching from turfgrass, including planting turfgrass cultivars with higher NO3- absorption abilities. This column lysimeter study was conducted to examine NO3- leaching from two Kentucky bluegrass (Poa pratensis L.) cultivars differing in NO3- uptake capacity. Subsurface soil compaction was included as a second factor. Tillers of Julia and Midnight Kentucky bluegrass, previously identified as having high and low NO3- uptake capacity, respectively, were grown in column lysimeters. Each column was filled with Wagram loamy sand with or without a subsurface compaction layer 8.5 cm below the surface. The two cultivars were established and then treated to impose moderate N deficiency. Potassium nitrate was applied in solution at 49 kg N ha-1 followed by daily heavy irrigation. Leachate was collected and analyzed for NO3--N. Cumulative N leaching loss of applied N ranged from 2.6 to 19% and 2.8 to 21% for Julia and Midnight, respectively. In two out of three trials, both cultivars absorbed NO3- very efficiently in noncompacted soil, with only trace amounts of NO3- leaching. While NO3--N loss averaged 4.7% of applied N in noncompacted soil across all trials, subsurface soil compaction increased that to 8.9%. Results indicated that despite being identified as more efficient for NO3- uptake, NO3- leaching from Julia was generally similar to that from Midnight. Soil conditions and differences in root morphology and/or architecture may played a more important role than root uptake capacity in determining NO3- leaching from these Kentucky bluegrass genotypes. [ABSTRACT FROM AUTHOR]

To predict the best management practices for Kentucky bluegrass (Poa pratensis L.) lawns in Colorado, the DAYCENT ecosystem model was parameterized and applied on a turfgrass ecosystem. In this study, field-measured data on clipping yields, leaf N content, evapotranspiration (ET), deep percolation, nitrate leaching, and soil temperature from a 3-yr lysimeter study were used for parameterization and validation. The simulation result for clipping yield was improved compared to the monthly time step CENTURY ecosystem model, with correlation coefficient (r) increased from -0.32 to 0.74. The prediction of ET and deep percolation was acceptable for the 3 yr. The long-term irrigation and fertilization effects on Kentucky bluegrass biomass and soil C and N were also examined. We predicted a 50% reduction in the annual net production as irrigation decreases from 100% potential evapotranspiration (PET) to 60% PET in this semiarid region. The simulation result suggests that the annual fertilization rates should be gradually reduced for both moderately and highly managed lawns with increasing age of the turfgrass stand. [ABSTRACT FROM AUTHOR]

Background Currently, the commercial formulations of the herbicide paraquat are highly toxic to humans, and no effective antidote is available for paraquat poisoning. The aim of the present study was to develop a safe formulation, combining paraquat and the known antidote lysine acetylsalicylate. The toxicity of a mixture of Gramoxone® (20% paraquat) and lysine acetylsalicylate in adult Wistar male rats and the herbicidal efficacy against grass lawn (50% of Poa pratensis and 50% of Festuca arundinacea) were evaluated. This new formulation was administered to Wistar rats by gavage at 125 mg kg−1 of paraquat ion and lysine acetylsalicylate at 79, 158 or 316 mg kg−1 body weight, and the survival rate was observed for 30 days. Results The survival rate of the paraquat group was only 40%, while lysine acetylsalicylate provided effective protection, with full survival observed in the groups that received 125 mg kg−1 of paraquat ion and 316 mg kg−1 of lysine acetylsalicylate. Both formulations of paraquat, either in the absence or in the presence of lysine acetylsalicylate, provided the same herbicidal activity against the tested herbal species. Conclusions The present formulation of paraquat containing lysine acetylsalicylate, significantly decreases mammalian toxicity while maintaining effective herbicidal activity. © 2012 Society of Chemical Industry [ABSTRACT FROM AUTHOR]

Many organic products have been used effectively in turfgrass management programs, but their exclusive use in athletic field maintenance and effect on playing surface characteristics and soil physical properties have not been extensively researched. The objectives were to determine the effects of management regimes and overseeding perennial ryegrass (Lolium perenne L.) into an existing Kentucky bluegrass (Poa pratensis L.) stand during simulated traffic on (i) rotational traction and surface hardness and (ii) soil physical properties. Treatments were arranged as a 2 × 6 factorial in a randomized complete block design with two overseeding levels (overseeded and not overseeded) of a perennial ryegrass blend during traffic and six management regimes (fertility and pest management): (i) conventional, (ii) organic manure (OMan), (iii) organic protein (OPro), (iv) organic manure plus compost tea (OMan+CT), (v) organic protein plus compost tea (OPro+CT), and (vi) a control. This research was conducted over 2 yr on a mature stand of 'Langara' Kentucky bluegrass on a Paxton fine sandy loam. Fall traffic was simulated with a Cady Traffic Simulator. There were no consistent effects on rotational traction or surface hardness as a result of management regimes or overseeding. Management regimes did not affect soil physical properties, but overseeding increased total porosity by 2.2% and increased aeration porosity by 12.4% in 2008. In 2009, overseeding increased capillary porosity by 2.2% but had no affect on total and aeration porosity values. Overseeding minimally decreased particle and bulk density values during both years. Overseeding also increased soil organic matter by 5.7% in 2009 when accompanied by organic fertilizers but not with compost tea applications. Using organic fertilizers or compost tea showed no enhancement or deterioration of soil physical properties over this two year study. [ABSTRACT FROM AUTHOR]

Cytokinins (CKs) influence plant adaptation to environmental stresses. The objectives of this study were to (i) examine effects of foliar application of a synthetic CK, 6-benzylaminopurine (6-BA), on postdrought recovery and (ii) determine physiological factors involved in postdrought recovery affected by CKs in a perennial grass species. Kentucky bluegrass {Poa pratensis L.) cultivars Midnight (drought tolerant) and Brilliant (drought sensitive) were subjected to drought by withholding irrigation for 15 d and were then rewatered for 10 d in growth chambers. Plants were treated with 25 uM 6-BA at the time of rewatering. Applying 6-BA significantly increased endogenous zeatin riboside and isopentenyl adenosine content and decreased abscisic acid (ABA) content in both cultivars previously exposed to drought stress. Foliar 6-BA application enhanced physiological recovery of plants from drought stress, as demonstrated by the increased leaf relative water content and visual turf quality and decreased electrolyte leakage. The 6-BA application also significantly Improved photosynthetic recovery from drought, as manifested by the increase in net photosynthetic rate, transpiration rate, and stomatal conductance. Foliar application of 6-BA promoted the production of new tillers. Postdrought recovery affected by 6-BA application was more pronounced in Midnight than Brilliant, probably because the latter experiences a more sustained leaf water deficit. Our results suggested that CK-enhanced postdrought recovery of Kentucky bluegrass, particularly in the drought-tolerant cultivar, was associated with the alteration of CK:ABA balance and promotion of stomatal reopening, resumption of photosynthesis, and new tiller formation on rewatering. [ABSTRACT FROM AUTHOR]

A critical challenge facing the turf industry is increasingly limited water supplies. Identifying cultivars that use less water while maintaining acceptable quality may mitigate irrigation demands. Our objectives were to identify Kentucky bluegrass (Poa pratensis L.) (KBG) cultivars and phenotypic groups that maintained better visual quality with less water. Thirty bluegrass selections were evaluated in a 2-yr field study under a rainout shelter near Manhattan, KS. Irrigation (2.5 cm) was applied when >50% of a plot exhibited visible wilt symptoms. Visual quality was rated daily. Average irrigation applications ranged widely from 23.3 cm (mean = 2.2 mm d-1) in Bedazzled to 44.9 cm (mean = 4.2 mm d-1) in Kenblue, and days to wilt between irrigations ranged from 6.4 d in Kenblue to 13.1 d in Cabernet. Visual quality averaged at or slightly below 6.0, defined as "minimally acceptable," but this may be adequate when water conservation is a priority and some dormancy is tolerable; irrigation at <50% wilt is recommended for improved quality. Based on statistical range tests, 15 of the 30 cultivars were grouped as both receiving the least water and having the greatest visual quality. Overall, the Compact America and Mid-Atlantic KBG groups exhibited the greatest days to wilt and received the least water. Results suggest that Compact America and Mid-Atlantic phenotypes have the greatest potential for integrating reduced water inputs with maintenance of acceptable visual quality. [ABSTRACT FROM AUTHOR]

Constraints to maize (Zea mays L.) stover biomass harvest may be mitigated by using a living mulch (LM) to offset C exports and control soil erosion. Living mulches can compete with the main crop for resources. The objective of this research was to quantify competitive effects of LM management systems grown in continuous maize with stover removal. Maize was planted into creeping red fescue (CF) (Festuca rubra L.), Kentucky bluegrass (KB) (Poapratensis L.), and a mixture of CF and white clover (Trifolium repens L.) (MX) LMs in 2008, 2009, and 2010 near Ames, lA. Management treatments were fall strip-tillage (ST) and no-tillage (NT), with either a pre-planting paraquat burn-down followed by two glyphosate bands (PQ) or glyphosate bands only (GLY). Kentucky bluegrass PQST produced similar grain yields (11,230 kg ha-1) all 3 yr as the no LM control (11,810 kg ha-1) with a harvest index (HI) of 0.55 compared to 0.52 in the control, averaged across years. The control produced greater stover dry matter (SDM) (10,110 kg ha-1) 2 of the 3 yr compared to KB PQST (8600 kg ha-1). Total groundcover averaged 80% in KB PQST compared to only 45% in the no LM control. These results indicate that a combination of herbicide suppression and ST suppresses LMs adequately to maintain competitive maize grain yields. Additional research under varying climatic conditions will further quantify the risk of LM management systems to increase the sustainable stover harvest of maize biomass feedstocks. [ABSTRACT FROM AUTHOR]

Many organic products have been used effectively in turfgrass management programs, but their exclusive use in athletic field maintenance and effect on playing surface quality has not been extensively researched. The objectives were to determine the effects of management regimes and overseeding during simulated traffic on (i) turfgrass color and quality, (ii) percent cover, and (iii) weed populations. The experimental design was a 2 × 6 factorial, with two overseeding levels (overseeded and not overseeded) of a perennial ryegrass (Lolium perenne L.) blend during traffic and six management regimes: (i) conventional, (ii) organic manure (OMan), (iii) organic protein (OPro), (iv) organic manure plus compost tea (OMan+CT), (v) organic protein plus compost tea (OPro+CT), and (vi) none or the control. This research was conducted over 2 yr on a mature stand of 'Langara' Kentucky bluegrass (Poa pratensis L.) on a Paxton sandy loam soil. Fall traffic was simulated with a Cady Traffic Simulator. The conventional treatment consistently produced higher quality turfgrass, lower weed counts, and better mid- to late-fall color. Weed populations were significantly less with the conventional regime. Overseeding increased cover at the end of the traffic periods by 32% in the first year and by 103% in the second year. Overseeding was also beneficial to turfgrass color and quality and in reducing weeds. The conventional treatment also retained significantly higher turfgrass cover than the organic regimes under trafficked conditions late into the fall in 2008. However, no difference in late fall cover between the conventional and organic management regimes was observed in late fall 2009. Compost tea applications showed no enhancement of turfgrass color, quality, or cover over the entire duration of the study. [ABSTRACT FROM AUTHOR]

Plant tolerance to drought and heat stress may be interrelated. The study was designed to examine whether improved heat tolerance through drought preconditioning is associated with changes in lipid and protein content and antioxidant enzyme activities. Kentucky bluegrass (Poa pratensis L.) (cv. Brilliant) plants were well watered (non-preconditioned control) or exposed to drought without irrigation for 12 d (drought preconditioning) and then exposed to heat stress (35°C/30°C) for 25 d in growth chambers. Compared to the non-preconditioned control, preconditioned plants had higher turf quality and chlorophyll content, and lower leaf electrolyte leakage and lipid peroxidation under heat stress. Lipid saturation level increased under heat stress due to decreases in the content of linolenic (C18:3) and increases in linoleic (C18:2) and palmitic (C16:0) acids. Total fatty acid content and the content of C18:3 were significantly higher and C16:0 content was lower in preconditioned than in non-preconditioned plants at 15 d of heat stress. The activity of superoxide dismutase increased in preconditioned plants at the initiation of heat stress, but it decreased in non-preconditioned plants under heat stress. Preconditioned plants had higher catalase and ascorbate peroxidase activities than non-preconditioned plants under heat stress. Drought preconditioning accelerated the up-regulation of chaperonin and heat shock protein 90, inhibited the down- regulation of proteins for amino acid metabolism, and induced the expression of lipoxygenase. These results imply that drought-preconditioning-enhanced heat tolerance was associated with the promotion of antioxidant activities and chaperoning protein expression, protecting plants from cellular damages from heat stress. [ABSTRACT FROM AUTHOR]

Kentucky bluegrass (Poa pratensis L.) is a widely used, high-quality, sod-producing turfgrass. To maintain an acceptable level of quality and function requires irrigation in the semiarid regions of the western United States. Landscape water use, however, is coming under increased scrutiny, and reducing water inputs is a goal of many municipalities. To identify Poa germplasm that maintains green color under deficit irrigation over summer seasons, this study was designed to evaluate the percent of green cover of 24 Kentucky bluegrass cultivars, accessions (including core collections), and other Poa species. Cultivars generally had a higher percent green cover in spring and fall, while several accessions and old U.S. cultivars showed higher green cover during summer months. Other Poa species did not have percent green cover values above any cultivars and as a group consistently performed the lowest. Core collections of Kentucky bluegrass, aimed at representing overall variability of the species with fewer accessions, had variance estimates equal to or higher than the overall group of accessions. Seven cultivars and accessions consistently had higher percent green cover than the Midnight cultivar check during the August data collection dates, highlighting the potential to improve Kentucky bluegrass green cover over summer seasons under deficit irrigation. [ABSTRACT FROM AUTHOR]

An increasing amount of reclaimed water is being used in turfgrass management; however, reclaimed water is often high in total dissolved salts and can result in salt stress injury and poor turf quality. The objective of this study was to use an overhead irrigated greenhouse screening technique to identify Kentucky bluegrass (Poa pratensis L.) cultivars with increased salinity tolerance, using growth parameters and physiological measurements. Salt treatments were applied using an overhead sprinkler system. Twenty-four Kentucky bluegrasses and Texas bluegrass (Poa arachnifera Torr.) x Kentucky bluegrass hybrids were established in 100% sand tanks and evaluated at a control (1 dS m-1) and three salinity concentrations (3, 6, and 9 dS m1) for a total of 10 wk. Plants were arranged in a split plot design with three replications. Percent green ratings and digital images were collected weekly and clipping weights were collected biweekly. Root and shoot weights were taken at the end of the study. Significant differences were observed between salinity treatments and cultivars. The cultivars Eagleton, Moonshadow, Fairfax, Cabernet, and Liberator exhibited the most salt tolerance, having the least decrease in growth parameters compared to the control plants (1 dS m-1), while cultivars Baron, A0384, and A03-TB246 were the most salt sensitive when compared to control plants. Relative water content and photochemical efficiency were useful to quantify physiological differences between tolerant and susceptible cultivars. [ABSTRACT FROM AUTHOR]

Changes in fatty acid composition and saturation levels may be involved in leaf tolerance to dehydration during drought stress and recovery on rewatering. The objective of this study was to compare changes in compositional and saturation levels of leaf fatty acids between two cultivars of Kentucky bluegrass (Poa pratensis L.) contrasting in drought tolerance in response to drought stress and rewatering. Drought-tolerant `Midnight' and sensitive `Brilliant' were maintained well-watered (control) or subjected to drought for 15 d by withholding irrigation and then rewatered in a growth chamber. Compared to Brilliant, Midnight maintained higher turf quality, leaf photochemical efficiency, relative water content, and membrane stability expressed as electrolyte leakage during drought stress. Following rewatering, Midnight recovered more rapidly in each parameter than Brilliant. The degree of fatty acid unsaturation decreased in both cultivars during drought stress, and the decrease was less pronounced and occurred later in Midnight. Fatty acid unsaturation level resumed to the control level in Midnight leaves, but did not fully recover in Brilliant after rewatering. The alteration in fatty acid unsaturation level induced by drought and rewatering were mainly due to the changes in the composition of linolenic acids (18:3), linoleic acids (18:2), palmitic acids (16:0), and stearic acids (18:0). Our results suggest that leaf dehydration tolerance and postdrought recovery in Kentucky bluegrass was associated with their ability to maintain relative higher proportion and level of unsaturated fatty acids, particularly linolenic acids and linoleic acids. [ABSTRACT FROM AUTHOR]

Reduced-growth, glyphosate-resistant Kentucky bluegrass (Poa pratensis L.) has recently been developed. There has been no comparative analysis of the newly developed transgenic Kentucky bluegrass lines to conventional cultivars or tissue culture-derived lines to determine vegetative and flower characteristic differences and similarities. This study measured the vegetative and reproductive characteristics of the transgenic lines, tissue culture-derived control lines, and reference cultivars during 2004 and 2005, in Ames, IA. The study was conducted in a noncompetitive, nonmown, spaced plant setting. Data collection of vegetative characteristics included rhizome spread and total plant area. Data collection for flower characteristics included flower phenology and morphological characteristic measurements, including panicle length, number of spikelets per panicle, and flag leaf characteristics. Transgenic lines as a group exhibited 29 and 32% less rhizome spread than the reference cultivars and tissue culturederived control lines, respectively, in 2004 and 37 and 40% less rhizome spread than reference cultivars and tissue culture-derived control lines, respectively, in 2005. Flower emergence times for all transgenic lines were comparable to their respective tissue culture-derived control lines and reference cultivars. [ABSTRACT FROM AUTHOR]

Turfgrass is a major vegetation type in the urban and suburban environment. Management practices such as species selection, irrigation, and mowing may affect C input and storage in these systems. Research was conducted to determine the rate of soil organic C (SOC) changes, soil C sequestration, and SOC decomposition of fine fescue (Festuca spp.) (rainfed and irrigated), Kentucky bluegrass (Poa pratensis L.) (irrigated), and creeping bentgrass (Agrostis palustris Huds.) (irrigated) using C isotope techniques. We found that 4 yr after establishment, about 17 to 24% of SOC at 0 to 10 cm and 1 to 13% from 10 to 20 cm was derived from turfgrass. Irrigated fine fescue added the most SOC (3.35 Mg C ha-1yr-1) to the 0- to 20-cm soil profile but also had the highest rate of SOC decomposition (2.61 Mg C ha-1 yr-1). The corresponding additions and decomposition rates for unirrigated fine rescue, Kentucky bluegrass, and creeping bentgrass in the top 20-cm soil profile were 1.39 and 0.87, 2.05 and 1.73, and 2.28 and 1.50 Mg C ha-1 yr-1, respectively. Irrigation increased both SOC input and decomposition. We found that all turfgrasses exhibited significant C sequestration (0.32-0.78 Mg ha-1 yr-1) during the first 4 yr after turf establishment. The net C sequestration rate was higher, however, for irrigated fine fescue and creeping bentgrass than for Kentucky bluegrass. To evaluate total C balance, additional work is needed to evaluate the total C budget and fluxes of the other greenhouse gases in turfgrass systems. [ABSTRACT FROM AUTHOR]

1. The ability to suppress neighbour growth and the ability to withstand growth suppression are widely viewed as two forms of competition, competitive effect and competitive response. 2. We conducted a greenhouse experiment to determine whether these two forms of competition were functionally linked, and to determine which plant traits are associated with effect and response competitive abilities among seedlings of 22 perennial North American prairie species. We further explored the trait-function relationship by growing plants under different soil fertilities and with different neighbour species. 3. To determine competitive abilities, we used a phytometer approach with two phytometer species: Poa pratensis and Achillea millefolium grown in competition with each of the 22 focal species under low and high fertility. Root and shoot morphological traits were measured and principal component analyses were used to reduce the dimensionality of the data. Three axes were extracted, which roughly corresponded to size, root and shoot architecture. 4. The hierarchy of competitive effect ability of the target species did not vary with either soil fertility or neighbour identity, while the hierarchies of competitive response abilities were highly variable among the treatments. Competitive effect ability was closely associated with size-related traits under high nutrient conditions, and with root-related traits under low nutrient conditions. In contrast, few plant traits axes were related to competitive response. 5. These findings indicate significant differences between competitive effect and response ability. We suggest competitive effect ability is a consistent trait of a species, linked to specific plant traits. In contrast, we found little evidence to support the idea that competitive response ability is itself a species trait, and instead it appears this may be simply a collection of different ways of avoiding or tolerating competition and/or low nutrient conditions. Supporting this argument was a lack of any consistency in which traits were associated with competitive response ability. 6. We recognize the limitations of a single study of seedlings under greenhouse conditions. However, we suggest these findings indicate a need to critically examine current assumptions about plant competition, how it is defined, and the traits which control a species’ competitive ability. [ABSTRACT FROM AUTHOR]

Post-harvest residue removal is critical for high seed production of Kentucky bluegrass (Poa pratensis L.). Previous work showed some accessions have little yield reduction with mechanical removal of post-harvest residue compared with the controversial practice of open-field burning. Using 10 of these accessions, our objectives were (i) to relate seed yield and yield components in spaced plants to yield in row-seeded plots, (ii) to link yield to growth and development factors, and (iii) to determine variation for seed production factors among accessions. Seed yield, seeds per panicle, panide number, weight per seed, heading, anthesis, and harvest dates showed strong accession differences on spaced plants in 2002 and 2003. Yields in row-seeded plots from 1998 and 1999 data were consistently correlated with yield per plant per area in spaced plants in 2002 (r = 0.75, P < 0.05) and 2003 (r = 0.90, P < 0.01). Turf quality was negatively correlated with yield per plant per area in 2002 and 2003 but was not consistently correlated with yield components. Days from heading to anthesis consistently correlated with yield per plant per area in 2002 (r = 0.81, P < 0.01) and 2003 (r = 0.85, P < 0.01). Variation for seed yield and yield components was observed within accessions both years and differed among accessions. The results show that seed yield per plant per area in spaced plants may be a useful predictor of yield in field stands and that a long heading to anthesis period promotes seeds per panicle and seed yield. [ABSTRACT FROM AUTHOR]

Many field studies have examined how site fertility, soil differences and site history influence the diversity of a plant community. However, only a few studies have examined how the identity of the dominant species influences the diversity in grasslands. Plant species differ widely in phenology, growth form and resource uses; thus, communities dominated by different species are also likely to strongly differ in the environment that they create and in which the subdominant species exist. We examined the correlation between the four most dominant species and community diversity in 2100 plots, located in 21 abandoned agricultural fields in central Minnesota over a 23-year period. The four most common species were two non-native C3 cool season species, Poa pratensis and Agropyron repens, and two native C4 warm season species, Schizachyrium scoparium and Andropogon gerardii. We found that the differences in the dominants explained up to 27% of the community diversity. Thus, the identity of the dominant species can have a strong influence on community diversity and studies examining factors that influence plant community diversity need to incorporate the effect of the dominants. Secondly, we found that the non-native C3 grass dominated communities had lower overall and lower native species richness relative to the native C4 grass dominated communities. Therefore, a shift in dominants from C4 to C3 may lead to a large community diversity decline. We found that Poa pratensis, the most abundant non-native C3 grass increased in abundance over the 23 years; thus, the negative influence of non-natives on the community diversity is not decreasing over time and active management is required to restore native grassland plant communities. [ABSTRACT FROM AUTHOR]

Transgenic herbicide-resistant cultivars of creeping bentgrass (Agrostis stolonifera L.) have been developed and are being considered for commercial release. Concerns regarding transgenic species include potential for outcrossing of the crop, which may produce novel genotypes with increased weediness. Persistence and multiyear growth of interspecific hybrids between creeping bentgrass and velvet bentgrass (A. canina L.), colonial bentgrass (A. capillaris L.), dryland bentgrass (A. castellana Boiss. and Reut.), and redtop bentgrass (A. gigantea Roth) and the backcross progeny of the hybrids were compared with the parental species in field experiments. The plants were evaluated over 2 yr in residential Kentucky bluegrass (Poa pratensis L.) and a low maintenance roadside turf of mixed species. With the exception of redtop bentgrass by creeping bentgrass interspecific hybrids, all interspecific hybrids between creeping bentgrass and colonial, dryland, and velvet bentgrasses were equally or less competitive relative to their parental species. Backcross progeny of interspecific hybrids, including those of redtop bentgrass by creeping bentgrass hybrids, were equally or less competitive than parental species. Bentgrasses that were highly competitive in residential turf were also competitive under roadside maintenance, suggesting bentgrasses have weediness potential regardless of management intensity. [ABSTRACT FROM AUTHOR]

New turfgrass varieties and management practices have introduced new options for transition zone athletic field managers. Our objectives were to determine the wear tolerance of four turfgrasses in the transition zone with and without crumb rubber under simulated athletic field conditions, and to determine if improved cool and warm-season turfgrass species can be used for transition zone athletic fields. Field trials evaluated the use of four turfgrass species with and without crumb rubber topdressing in Knoxville, TN, and Fayetteville, AR. Experimental design was a randomized complete block with a split-strip plot treatment arrangement. Plots containing 'Thermal Blue' hybrid Kentucky bluegrass (Poa pratensis L. × P. arachnifera Torr.) or 'Riviera' [Cynodon dactylon (L.) Pers.], 'Quickstand' (C. dactylon), or 'Tifway' (C. dactylon × C. transvaalensis Burtt-Davy) bermuda-grass were evaluated. Crumb rubber treatments were topdressed to achieve a 2-cm depth. Traffic was applied to each plot using a Cady Traffic Simulator to simulate athletic field wear. Traffic applications coincided with actual fall athletic seasons ranging from October to December 2005. Hybrid Kentucky bluegrass proved to be acceptable for use in transition zone athletic fields, Riviera and Tifway showed comparable wear tolerance, and Quickstand showed the lowest wear tolerance of the varieties tested. Crumb rubber topdressing resulted in a significant increase in turfgrass wear tolerance, and a decrease in surface hardness, soil bulk density, and shear resistance. [ABSTRACT FROM AUTHOR]

Overseeding non-endophytic turfgrass lawns with endophytic turfgrass is considered promising for the development of integrated pest management programs in urban landscapes. In this context, a better understanding of the variability in the preference–performance response of insect herbivores exposed to endophytic grasses could be useful to develop efficient practices. Specifically, while endophytic varieties that are strongly toxic and avoided could provide good control of mobile pests, varieties that are toxic but not avoided could be more suitable for the control of sedentary pests. In this laboratory study, we investigated how the infection of 10 grass varieties by Neotyphodium endophytes affected the feeding performance and preference of newly hatched nymphs of the hairy chinch bug, Blissus leucopterus hirtus Montandon (Heteroptera: Lygaeidae), a common turfgrass pest in north-eastern USA. We found that endophytes generally induced a strong relationship between feeding performance and preference in this herbivore. However, two endophytic varieties did not conform to this relationship, with one variety being highly toxic but not avoided and the other less toxic but highly avoided. These results provide a solid basis to further explore the impacts of endophytic grasses on the dispersal and survival of insect pests in mixed stands of endophytic and non-endophytic plants. [ABSTRACT FROM AUTHOR]

Lawns are the largest managed turf acreage in the USA. This large acreage of fertilized turf has generated public concern regarding nitrogen (N) fertilizer misuse. This 2-yr field study evaluated the effects of eight N programs that varied by N amount, 0 to 196 kg N ha-1 yr-1, and seasonal application timing on the aboveground plant responses of three cool-season lawn species: Kentucky bluegrass (Poa pratensis L.; KBG), perennial ryegrass (Lolium perenne L.; PRO), and turf-type tall fescue (Festuca arundinacea Schreb.; TTTF). Significant cumulative species dry matter yield differences were measured for the study, with 9426, 7750, and 7011 kg ha-1 for TTTF, KBG, and PRG, respectively. Kentucky bluegrass generally possessed the greenest canopy when averaged across all N programs, followed by TTTF and PRG. Annual turfgrass quality (TQ) was highest and most seasonally consistent for TTTF, followed by KBG and PRG. Although, KBG overall TQ was lower than TTTF, primarily due to slow spring green-up, KBG was superior to TTTF on many ratings during active growth. Perennial ryegrass produced the lowest TQ compared with TTTF and KBG. This was due to summer disease in both years and substantial turf cover losses, 24 to 81% in 2005. If the goal in lawn management is to maximize turfgrass response with the fewest N inputs, the species that met this goal was TTTF, which provided acceptable TQ and color, and had less disease at relatively low, 73 to 123 kg ha-1 yr-1, N levels. [ABSTRACT FROM AUTHOR]

Tissue N analysis a tool available for N management of turfgrass. However, peer-reviewed calibration studies to determine optimum tissue N values are lacking. A field experiment with a mixed cool-season species lawn and a greenhouse experiment with Kentucky bluegrass (Poa pratensis L.) were conducted across 2 yr, each with randomized complete block design. Treatments were N application rates between 0 and 587 kg N ha-1 yr-1. In the field experiment, clipping samples were taken monthly from May to September, dried, ground, and analyzed for total N. Clippings samples were collected one to two mowings after plots were fertilized. Linear plateau models comparing relative clipping yield, Commission Internationale de I' Eclairage hue, and CM1000 index to leaf N concentrations were developed. In the greenhouse experiment, clipping samples were taken every 2 wk from May to October and composited across sample dates for leaf N analysis. Color and clipping yields were related to leaf N concentrations using linear plateau models. These models indicated small marginal improvements in growth or color when leaf N exceeded 30 g kg-1, suggesting that a leaf N test can separate turf with optimum leaf N concentrations from turf with below optimum leaf N concentrations. Plateaus in leaf N concentrations with increasing N fertilizer rates suggest, however, that this test may be unable to identify sites with excess available soil N when turf has been mowed before tissue sampling. [ABSTRACT FROM AUTHOR]

The Brinkman Traffic Simulator (BTS) has been a useful tool to simulate sports field traffic. However, rate of traffic stress produced by the BTS, a pull-behind unit with two differentially connected studded rollers, has been questioned. The Cady Traffic Simulator (CTS), a modified walk-behind core cultivation unit, was developed and tested to potentially produce more aggressive traffic stress. A comparison study was initiated between the BTS and CTS to evaluate these simulators on a Kentucky bluegrass (Poa pratensis L.) stand. Playing surface data collected were surface hardness, traction, soil moisture, bulk density, porosity, and plant counts. Higher surface hardness, lower traction, and lower plant count values resulted when the CTS applied 10 passes per week (PPW) compared with other treatments. Surface hardness, traction, and bulk density values were statistically similar when the CTS applied 2 PPW, and BTS applied 10 PPW. [ABSTRACT FROM AUTHOR]

Trinexapac-ethyl (TE) [4-(cyclopropyl-α-hydroxy-methylene)-3,5- dioxocyclohexanecarboxylic acid ethyl ester] and paclobutrazol (PAC) [(2RS,3RS)-1-(4-chlorophenyl)-4,4-dimethyl-2-(1H-1,2,4.triazol-1-yl)pentan-3-ol] are routinely used to suppress clipping production. Single-leaf turfgrass C exchange rates (CERs) in response to plant growth regulator (PGR) treatment have not been characterized. Individual Kentucky bluegrass (KBG, Poa pratensis L.) plants received label rates of TE or PAC and were placed in growth chambers at 23/18 or 30/25°C. Photosynthetic efficiency and CER measurements were recorded every 4 d for 44 d. Total root length (TRL), root surface area (SA), and average root diameter were measured at the end of the study. Reductions in CERs of TE- or PAC-treated plants were short lived with CERs suppressed 17 to 29% of control (POC) at 4 and 12 days after treatment (DAT), respectively. Plants treated at 23/18°C with PGRs typically had short-lived increases in CERs following CER suppression. A similar pattern of CER response to PGR treatment was observed at the 30/25°C temperature regime. Quantum efficiency was unaffected, but plants treated with PGRs had reduced root growth. PAC caused the greatest reduction in TRL and SA while increasing root diameter. A decline in TRL and SA in conjunction with increased tillering indicates that PGR reduced TRL and SA on a tiller basis. Changes in single-leaf CERs do not fully explain PGR. induced changes in plant growth. [ABSTRACT FROM AUTHOR]

Negative impacts of invasive plants on natives have been well documented, but much less is known about whether invasive plants can cause population level declines. We used demographic models to investigate the effects of two invasive grasses on the demography and population growth of Anemone patens, a long-lived native perennial of North American grasslands. Demographic data of A. patens growing in patches characterized by Bromus inermis, Poa pratensis, or native grasses were used to parameterize integral projection models. Models based on both average conditions and those allowing for environmental stochasticity indicate that A. patens is slowly increasing in patches of native grass (λ = 1.02) and declining in patches of invasive grasses, particularly those dominated, by B. inermis (λ = 0.93). Extinction probabilities indicate that A. patens should persist in native grass patches, but has a much higher probability of extinction in Bromus patches compared to Poa patches. While sensitivity analyses showed that survival had the biggest effect on population growth rates in all habitats, results of a Life Table Response Experiment (LTRE) revealed that slower individual growth rates in patches of invasive grasses contributed the most to the observed reduction in population growth. These results suggest that invasive grasses may cause slow declines in A. patens, despite short-term coexistence, and that controlling B. inermis only would not be sufficient to ensure A. patens persistence. [ABSTRACT FROM AUTHOR]

Kentucky bluegrass (Poa pratensis L.), one of the most commonly grown turfgrasses in temperate regions, is being developed for possible commercial release with transgenic traits. The use of this technology raises risk assessment questions because P. pratensis is perennial, often apomictic, competitive in many habitats, and hybridizes with other Poa. To further understand the potential environmental impact of a transgenic R pratensis, we measured intra- and interspecific pollen-mediated gene flow in field conditions from P. pratensis to other Poa. We used a wagon-wheel design with a glyphosate (N-phosphono methyl-glycine) resistant R pratensis as a pollen donor and a pollen receptor plot at 0 m and plots at 13 and 53 m along six equally spaced vectors. Each receptor plot included accessions from 25 Poa species. Seedlings from the receptor plants were screened for resistance to glyphosate and potential hybrids verified by PCR and genomic fingerprinting. Hybrids were found with R arachnifera Torrey, R interior Rydb., R pratensis × R secunda J. Presl, and three other P. pratensis entries, but did not occur with P. annua L., P. palustris L., P. trivialis L., or R compressa L., among other species. Overall hybrid frequency was 0.048% and hybrid frequency at the 0-m distance was 0.53%. While apomixis in receptor plants and pollen competition likely reduced the number of hybrids, gene flow did occur but at low frequency and over short distances. [ABSTRACT FROM AUTHOR]

The article discusses the effects of sealing layers made of fly ash and sewage sludge on vegetation or resistance to root penetration. The authors focus on the ability of different plant species to grow on sealing layers made of fly ash and sewage sludge. They also tackle the impact of freshly hardened fly ash on plant growth as well as plant stress response on fly ashes. It was found out that no roots could grow into compacted layer consisting only of ash, while a 6:4 ash sludge mixture admitted roots into the upper part and a 1:9 ash sludge mixture was totally penetrated by roots of willow and Scots pine, as demonstrated during a six month greenhouse study using birch, scots pine, kentucky bluegrass and willow.