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According to National Resources Inventory data, Kentucky bluegrass (Poa pratensis L.) is now present in over 85% of the areas sampled. This invasive, perennial, cool season grass can serve to stabilize soils and increase site stability; however, it also alters nutrient flows, soil structure, and plant community composition, ultimately degrading biotic integrity. In addition, Kentucky bluegrass alters the hydrologic function of an area by changing root structure and the way in which water flow is captured and released back into the ecosystem. To clarify the effect of Kentucky bluegrass on hydrological characteristics of invaded sites, rainfall simulation experiments and hydrophobicity measurements with water drop infiltration time and molarity of ethanol droplet tests were conducted at three locations all within the same ecological site in the northern Great Plains. Rainfall simulation experiments were performed on 24 large plots (6 x 2 m) at 63.5 mm h-1 and 127 mm h-1 intensities and on 16 small plots (0.7 x 0.7 m) at 63.5 mm h-1 and 103 mm h-1. Rainfall was maintained on the large plots until 10 minutes of steady-state runoff was measured or for a maximum of 30 minutes in the absence of runoff, while on the small plots, rainfall duration was set at 25 minutes. The soil layer was divided into four strata (litter, thatch, root mat, and mineral soil), which were physically separated for their hydrophobic behavior in laboratory and field water drop penetration tests and molarity analyses. Our results indicate that on dry soil strata, water drop penetration time increased by 20 seconds on litter and 3 seconds on thatch for every percentage point increase in Kentucky bluegrass in the vegetation, confirming the close association between this grass species and the development of soil hydrophobicity. Rainfall simulation on dry soils (less than 20% volumetric water content) also revealed that the time needed to initiate runoff was shortened by 5 minutes, and the runoff ratio increased by 0.004 for every percentage point increase of Kentucky bluegrass in the vegetation cover. Hydrophobicity dramatically declined in the thatch layer by a factor of 4 and was completely absent from the litter layer after wetting. In contrast to the rainfall simulations on dry soils, wet runs (volumetric water content ≥20%) showed a beneficial effect of Kentucky bluegrass on hydrologic response with delayed runoff by 5 minutes and reduced runoff ratios by 0.003 for 1% increase in Kentucky bluegrass in the vegetation cover. Prescribed fire increased litter hydrophobicity, but this did not adversely affect hydrologic response. This study highlights the need for further research contrasting detrimental effects of Kentucky bluegrass on hydrologic response in dry soil conditions with the beneficial effect of this grass on infiltration under wet conditions to better predict the overall ecohydrological outcome of an invasion by this grass species. [ABSTRACT FROM AUTHOR]

Owing to high water requirements of turfgrass, it is essential to find suitable turfgrasses for cultivation in arid and semi-arid conditions. For this purpose, physiological responses of Agropyron desertorum and Poa pratensis cv. “Barimpala” that were subjected to outdoor with holding irrigation were evaluated. Seeds of these two genuses were cultured in polyvinyl chloride tubes and were irrigated daily until drainage occurred. After establishment, irrigation was stopped until leaf wilting occurred. P. pratensis and A. desertorum were wilted during 15 and 20 days after drought treatment, respectively. Turf quality and relative water content were decreased due to drought stress, butthe extent of decrease in A. desertorum was less than that it was in P. pratensis. Five days after stress, malondialdehyde levels increased in P. pratensis more quickly than A. desertorum, while electrolyte leakage rose immediately after with holding irrigation in these genuses. Superoxide dismutase and catalase activities in the two stressed plants increased and then decreased with stress development. In these conditions activities of AT, 3-amino-1,2,4-triazole, peroxidase and glutathione peroxidase had a similar pattern in P. pratensis, while A. desertorum showed continuous increase in these enzyme activities. [ABSTRACT FROM AUTHOR]

Typhula blight is a major problem on golf courses where snow cover persists for long periods. The disease is primarily managed by applying a mixture of fungicides in the autumn prior to winter snow cover. The fungicides chlorothalonil and fludioxonil are often included in these mixtures even though they do not completely suppress Typhula blight when applied alone. We studied whether minimal control was due to a lack of persistence of these fungicides under snow, or whether certain isolates ofTyphula ishikariensisandT. incarnataexhibited tolerance to these fungicides. The persistence of chlorothalonil and fludioxonil residues in the turf was determined during the winters of 2005–06, 2006–07 and 2007–08. Concentrations of chlorothalonil and fludioxonil in the verdure decreased or remained nearly the same at most sampling dates, indicating these fungicides did not dissipate rapidly under snow. Despite this, only marginal control of Typhula blight was observed in the fungicide-treated plots. Thein vitrosensitivity ofT. ishikariensisandT. incarnataisolates to chlorothalonil and fludioxonil was tested. Growth of most isolates (70%) on agar amended with 1 µg mL−1chlorothalonil was inhibited by more than 50% relative to growth on non-amended agar. However, almost all isolates exhibited some growth at concentrations as high as 500 µg mL−1. A high proportion of isolates (85%) were inhibited by greater than 80% at 1 µg mL−1fludioxonil. Therefore, at least some growth of these isolates at high fungicide concentrations may explain why chlorothalonil and fludioxonil are not completely effective in suppressing Typhula blight. [ABSTRACT FROM AUTHOR]

The need for salt-tolerant turfgrasses in arid and semi-arid regions has increased substantially owing to shortages of fresh water and to soil salinization. We hypothesized that salt tolerance in turfgrasses is achieved by ion regulation and the accumulation of compatible solutes. We investigated changes in ionic concentrations and compatible solutes in Kentucky bluegrass (Poa pratensisL.; a salt-sensitive species) and Tall fescue (Festuca arundinacea Schreb.; a moderately salt-tolerant species) in response to elevated sodium chloride (NaCl) concentration. Sodium (Na+) and chloride (Cl–) concentrations in shoots and roots increased with increasing salinity in both turfgrasses. Kentucky bluegrass accumulated more Na+and Cl−under NaCl stress than did Tall fescue. NaCl stress induced more significantly mineral nutrient imbalances in Kentucky bluegrass than in Tall fescue. The concentrations of potassium (K+), calcium (Ca2+), magnesium (Mg2+) and nitratein Tall fescue were much less affected than those in Kentucky bluegrass. The proline concentration increased significantly in both grasses with increasing salinity. The total soluble sugar (TSS) concentration of Tall fescue was significantly higher than that of Kentucky bluegrass under elevated NaCl concentration. Inorganic ions, especially Na+, were more important in osmoregulation for Kentucky bluegrass and Tall fescue to adapt to NaCl stress. The estimated contribution of K+to osmotic potential (Ψs) decreased with increasing salinity, and it was higher in Tall fescue than in Kentucky bluegrass. The estimated contribution of TSS to Ψswas higher in Tall fescue than in Kentucky bluegrass under NaCl stress. These results indicate that Tall fescue tolerates salt better by inhibiting the accumulation of Na+and Cl−, which helps to maintain ion balance, and by accumulating sugars, which decrease the osmotic potential of the cytoplasm. [ABSTRACT FROM PUBLISHER]

Elemental sulfur (S) impregnated with Fe (S-Fe) fertilizer was evaluated on Kentucky bluegrass (KBG; Poa pratensis L.) in three glasshouse studies: (1) with/without Fe as S-Fe, ferrous sulfate (FS), or iron-ethylenediamine-N,N’-bis(2-hydroxyphenylacetic acid) (Fe-EDDHA) to soil (49 kg Fe ha−1), or foliar Fe-EDDHA (5 kg Fe ha−1) on two cultivars; (2) 0, 49, 197, or 592 kg Fe ha−1 of S-Fe deep mixed or surface mixed on two soils; (3) 0 or 49 kg Fe ha−1 applied as S-Fe on four cultivars. A field study comparing 0 and 49 kg Fe ha−1 applied as S-Fe to KBG was also conducted. Soil applied S-Fe was assimilated in shoots as efficiently as Fe-EDDHA applied to soil or foliage. Shoot Fe increased significantly with increasing S-Fe in a curvilinear response when deep mixed with soil and in a linear response when surface applied. However, no Fe source tested impacted yield or verdure in these studies. [ABSTRACT FROM PUBLISHER]

Fertilizers and pesticides applied to home lawns can contaminate surface and groundwater making them unfit for aquatic organisms and human consumption. Application of fertilizers and pesticides can improve the aesthetics of a home lawn, improve turfgrass shoot and root density, water use, organic matter accumulation, and other factors known to be influential in urban hydrology. A field study determined the impact of applying home landscape pesticides with or without supplemental irrigation of leaching into groundwater or runoff to surface water. Free-draining lysimeters having a sandy loam soil (coarse-loamy, mixed, active, mesic Lamellic Hapludalf) were used to monitor total volume and nutrients and pesticides losses. Samples from natural precipitation events were analysed for pendimethalin [N-(1-ethylpropyl)-3,4-dimethyl-2, 6-dinitrobenzenamine] applied in spring, mecoprop [2-(4-Chloro-2-methylphenoxy) propionic acid]+2, 4-D (2,4-dichlorophenoxyacetic acid) applied both in late spring and early fall, and bifenthrin [(2-methyl-1,1-biphenyl-3-y1)-methyl-3-(2-chloro-3,3,3-trifluoro-1-propenyl)-2,2-dimethyl cyclopropanecarboxylate] applied in late summer. Pesticide concentrations fluctuated over time, but no differences in concentrations were observed from irrigated or non-irrigated turfgrass for any pesticide. Mecoprop and 2,4-D were the most mobile and values found in runoff during establishment were above maximum contaminant levels (MCL) for U.S. standards. Surface runoff of lawn pesticides were observed at concentrations several magnitudes higher than leachate. The total extent of pesticide runoff was 0.71%, 1.3%, 6.0%, and 0.003% of the amount applied for 2,4-D, mecoprop, pendimethalin and bifenthrin, respectively. With the exception of one sampling period, pendimethalin concentrations in runoff and leachate were low; however, when applied during a period of minimal turf growth and high precipitation, pendimethalin could contribute significantly to surface water pollution. [ABSTRACT FROM PUBLISHER]

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

Some Kentucky bluegrass (KBG; Poa pratensis L.) is susceptible to iron (Fe)-deficiency chlorosis. Under Fe-deficiency stress, phytosiderophore is produced and released by the roots of many grasses to solubilize soil Fe and enhance uptake. In other species, quantifying phytosiderophore screens for Fe-deficiency resistant cultivars. A hydroponic study was conducted at 1 and 10 μM solution Fe to variously stress ‘Baron’, ‘Award’, ‘Limousine’, and ‘Rugby II’ KBG cultivars. One μM Fe solution produced more Fe-deficiency stress in all cultivars compared to 10 μM, resulting in greater chlorosis and phytosiderophore release but reduced shoot and root Fe concentrations and shoot weight. Of the four cultivars, Baron was the most susceptible to Fe deficiency and exhibited severe Fe chlorosis and low shoot Fe but, surprisingly, produced the most phytosiderophore. These results imply that Fe-deficiency susceptibility in KBG may be less related to phytosiderophore release and more related to inefficient uptake or utilization mechanisms. [ABSTRACT FROM AUTHOR]

The grasslands of the Appalachian region spread over undulating terrain with high annual precipitation rate which causes a large variation in soil and nutrient factors like water potential (WP), pH, nitrogen (N) and phosphorus (P) levels. There is a need to understand these factors and their interactive effects to design precise agronomic practices for acidic grasslands to maximize production. A pot experiment was conducted with an objective to quantify the effects of WP, pH, N and P rates on herbage accumulation and nutrient recovery of Kentucky bluegrass (Poa pratensis L.) cropping system. Centrally rotatable composite design was applied to study the effects of two levels of WP and five levels each of pH, N, and P fertilizer additions in order to optimize bluegrass herbage mass (yield). WP, pH, and N were significant main effects, as were the interactions WP × pH, WP × N, and pH × N. The yield response function was derived from these four factors. The order of importance for these model parameters based on their effect on herbage accumulation was WP > N > WP × pH > pH >WP × N > pH × N. The optimum levels of WP, soil pH, N, and P rates were predicted for Kentucky bluegrass by using the response surface yield model of this pot study i.e., WP of −422 kPa to −166 kPa, 5.5–6.1 soil pH, 50–68 N mg kg−1, 36–40 P mg kg−1. Concentration (%) of nutrients like N, P, potassium (K), calcium (Ca), and magnesium (Mg) were determined to study the impact of WP, pH, N, and P factors and their interactions on plant nutrient recovery. Main effects like WP, pH, and N levels had significant influence on N and P concentration in plant tissue. K, Ca, and Mg concentrations in plant tissue were significantly affected by WP, pH and their interaction. The results of this greenhouse study imply the necessity to incorporate the information about the variation of soil and nutrient factors in designing precise agronomic practices to low productive acid reclaimed grasslands with undulating topography and high annual precipitation rate. [ABSTRACT FROM AUTHOR]

We describe a new Epichloë species found in symbiosis with Poa pratensis ssp. pratensis in Liyang, China. Stromata characteristic of Epichloë spp. were present on some of the reproductive tillers of individual host grasses. Only three of the 98 stromata observed on field plants became orange and produced perithecia. Phylogenetic analyses based on sequences of tubB and tefA indicated that this Epichloë sp. was an interspecific hybrid related to both E. yangzii and members in the E. typhina complex clade (ETC). Allele-1 of tefA and tubB grouped in the E. bromicola/E. yangzii clade; allele-2 of these two genes clustered in a distinct subclade in the ETC. This is the first report of an Epichloë species that has interspecific hybrid origins. We propose the name Epichlog liyangensis Z. Wang, Y. Kang et H. Miao, sp. nov. for this species. [ABSTRACT FROM AUTHOR]

Urea replaced ammonium nitrate (AN) as a nitrogen (N) source for dryland Kentucky bluegrass seed production in the inland Pacific Northwest in the United States. This study assessed ammonia (NH3) volatilization, N recovery, and seed yield from urea as compared to AN. Laboratory incubations indicate NH3 volatilization is greater from soil covered by fresh residue than soil alone or covered by burned residue. Although pH of the fresh and burned residues exceeded 8.0, urease activity in burned residue was <15% of that in unburned residue or soil. Ammonia volatilization from dry urea and fluid urea AN was greater than AN at burned and unburned sites after a 5 October application. Ammonia volatilization was higher and N recovery and seed yield were lower for urea after a 15 November application at an unburned site. To reduce NH3 volatilization, apply urea to fields with low urease activity or moisture content and/or immediately before a significant rain event. [ABSTRACT FROM AUTHOR]

A field experiment was conducted to determine the optimal method for turfgrass revegetation at the new Incheon International Airport, Republic of Korea. The existing soil base was reclaimed sea sand dredged from the Yellow Sea. Ten different soil media main plots were created by treating the sand with combinations of mountain soil, chemical fertilizer [15-11-14 nitrogen-phosphorus-potassium (N-P-K)], peat moss, a wetting agent, pig manure, and composted pine bark. Subplots were established with five turfgrass treatments that included Zoysia japonica (ZJ), Z. sinica (ZS), Z. koreanna (ZK), cool-season grass combination I (CSG I: Festuca arundinacea 30%, Poa pratensis 40%, and Lolium perenne 30%), and cool-season grass combination II (CSG II: Festuca arundinacea 40%, L. perenne 20%, F. rubra 20%, and Puccinellia distans 20%). The highest percentage cover rate for all grass treatments occurred in sea sand treated with 5 cm of mountain soil plus 114 g m-2 of chemical fertilizer. Zoysia japonica had the highest percentage cover rates throughout the study. On 4 July 1998, the turfgrass cover ranking was ZJ (99.5% cover)>ZK (86.7%)>ZS (39.6%)>CSG II (33.3%), CSG I (33.1%). Zoysia japonica also showed the highest drought tolerance among turfgrass species on all soil bases. The treatment that included mountain soil plus chemical fertilizer reduced the pH, EC, alkalinity, and soluble sodium (Na+) by the exchange of calcium (Ca2+) for Na+. The amendment of sea sand with mountain soil and chemical fertilizer, followed by establishment to ZJ, was determined to be the best method of reclamation for the new airport. [ABSTRACT FROM AUTHOR]

An irrigated field trial was conducted to test the effects of white clover in three turfgrass species (perennial ryegrass, Kentucky bluegrass, and creeping bentgrass) on color, clipping yield, and botanical composition and to estimate nitrogen (N)2 fixation and N transfer from white clover to associated turfgrass species under different N-fertilization conditions in 1999-2002. Nitrogen fertilizers significantly increased color ratings in all observations. Grass-white clover mixtures had better color ratings than pure grass at all sampling dates and seasonal averages in unfertilized conditions. Fertilized pure grass plots yielded significantly more than control plots in all turfgrass species. Nitrogen fertilization did not affect clipping yield greatly in turfgrass-white clover mixtures. Nitrogen application significantly decreased white clover percentage in the harvested clippings in second and third year. Nitrogen fertilization increased tissue N concentration positively in all turfgrass species grown alone. In contrast, N fertilization did not greatly affect tissue N concentration of either turfgrass species or white clover in the mixtures. Nitrogen fixation of white clover was estimated as 24.6, 30.7, and 33.8 g m-2 year-1 in perennial ryegrass, Kentucky bluegrass, and creeping bentgrass, respectively. The total estimated N2 fixation gradually decreased with increasing N fertilization. Nitrogen transfer from white clover to the associated turfgrass varied from 4.2 to 13.7% of the total N that the white clover fixed annually. [ABSTRACT FROM AUTHOR]

Expansion of turf area together with irrigation have caused concern because of the increased demand for the scarce water resources in arid and semi-arid regions. Kentucky bluegrass (KBG) (Poa pratensis) has been widely used to establish turf, and selecting varieties with good drought resistance is important in reducing irrigation requirements. Its seedling stage is the key step to successful establishment. Therefore, pot experiments in the greenhouse were carried out to assess drought resistance in 11 KBG varieties. The rate of germination, survival rate, and vertical growth rate of each variety increased as field water capacity (FWC) decreased from 70% (FWC 70) to 50% (FWC 50), and then decreased from 50% to 30% (FWC 30). Tillering rate and shoot-to-root ratio decreased as FWC decreased from FWC 70 to FWC 30. Proline content and electrolyte leakage (EL) in leaves of KBG at FWC 50 was lower than those at FWC 30 and FWC 70. Uunder FWC 30, representing drought stress, rate of germination, survival rate of seedlings, vertical growth rate, and shoot-to-root ratio were significantly different among the 11 varieties. Based on the rate of germination, 'Barlin' and 'Baron' performed best. According to the survival rate of seedlings, 'Baron' performed best. For vertical growth rate, 'Barlin' and 'Compact' were superior to others. 'Barlin' was the best variety for lower shoot-to-root ratio. 'Barlin' and 'Baron' had higher proline accumulation and greater cell membrane stability (lower EL) in leaves. Using rate of germination, survival rate, vertical growth rate, shoot-to-root ratio, proline content, and EL as analysis factors, cluster analysis indicated that 'Baron' and 'Barlin' had better resistance to drought than other varieties, and suggested that they are suitable for sowing in arid and semi-arid regions because of their strong drought resistance at the seedling stage. [ABSTRACT FROM AUTHOR]

Summer patch is caused by the ectotrophic, root-infecting fungus Magnaporthe poae Landschoot and Jackson. The disease, which often infects high maintenance turf, can be difficult to control because root infection often occurs six to eight weeks before the appearance of foliar symptoms. Disease severity is reduced when turf is fertilized with ammonium nitrogen (N) sources, compared to nitrate or urea sources of N. Thiosulfate, from (NH4)2S2O3 or K2S2O3, is a nitrification inhibitor which may enhance ammonium uptake of turf by slowing nitrification. N-SURE is a triazone-based, slow release N source that is commonly used to fertilize turfgrass. Field studies were conducted from 1995 to 1996 on Kentucky bluegrass (Poa pratensis L.) grown on a Nixon loam (fine-loamy, mixed, mesic Typic Hapludult) to evaluate the effectiveness of the several N and K sources for their ability to control summer patch disease. Nitrogen fertilizers, N-SURE, (NH4)2S2O3, and (NH4)2SO4, were applied in combination with either K2SO4 or K2S2O3. The severity of summer patch was greater when the turf was fertilized with N-SURE in 1995 and 1996 and urea in 1996 compared to (NH4)2S2O3. The N sources, (NH4)2SO4 and (NH4)2S2O3, were strongly acidifying to the upper 10 cm of soil and were very effective in controlling summer patch. The application of K2S2O3 slightly acidified the upper 5 cm of soil but did not suppress the development of summer patch. The ability of thiosulfate to act as a nitrification inhibitor did not appear to play a role in the suppression of summer patch. Since foliar burn may occur if (NH4)2SO4, (NH4)2S2O3, or K2S2O3 are applied to turf without irrigation, the application of water after their use is recommended. [ABSTRACT FROM AUTHOR]

Apomixis, as it exists in Kentucky bluegrass (Poa pratensis L.), is a nearly ideal way of maintaining superior hybrids and complex traits. It combines the genetic advantages of vegetative propagation (maintenance of the genotype) with the agronomic advantages of sexual reproduction (use of the seed). Lack of knowledge on its inheritance at present hinders attempts to manipulate and transfer the apomictic trait beyond natural sexual barriers. We analyzed the occurrence of meiotic (haploid) and aposporic (diploid) parthenogenesis in P. pratensis genotypes with contrasting degrees of apomixis using embryo rescue and in vitro culture techniques. The in vitro rescue of autonomous embryos obtained after auxin-induced parthenocarpy permitted us to investigate and establish the embryological derivation of progeny plants of certain parthenogenetic origin. All recovered plants were characterized both for chromosome number and DNA fingerprint to ascertain their genetic origin. Our experiments indicated that parthenogenetic capacity is preferentially expressed by aposporic egg cells and so the genetic determinants for apomixis seem to be closely linked and inherited together. We also documented parthenogenetic development of meiotic egg cells. In a highly sexual genotype that when auxin tested showed considerable parthenogenetic capacity, the egg cells appeared to exert this potential irrespective of their cytological origin. Thus, events of segregation of apospory from parthenogenesis are rare, but possible. Although the question remains open, apomixis seems to be the result of a few tightly clustered genes rather than the combination of two processes, apospory and parthenogenesis, determined by independent genetic factors. [ABSTRACT FROM PUBLISHER]

Examines the effects of light and temperature on seed germination of Poa pratensis. Stimulation of germination with daily fluctuations in temperature; Comparison of the effects of dark germination and light/dark cycles at constant temperature; Inhibition of germination due to continuous light exposure; Effect of seed age on the stimulating effect of daily light/dark cycles.