Abstract
Injury to turfgrass leaf segments was measured as percent electrolyte leakage as affected by the duration and level of imposed heat stress. Species differences in heat tolerance were most apparent when injury was monitored over time at 50°C, using leaf segments which were obtained from heat-hardened plants and immersed in distilled water during the stress treatment. Quantitative differences in heat tolerance in vitro were consistent with qualitative descriptions of drought resistance for most of the species tested.
A field study was initiated in 1981 in western North Carolina to determine the influence of eight groundcover management systems on quality of `Redchief Red Delicious' apple (Malus domestica) grafted onto rootstock of M VIIA. Management systems included: bare soil, Secale cereale mulch, minimal cultivation, Festuca arundinacea, Dactylis glomerata, Poa pratensis, Muhlenbergia schreberi and Rubus sp. Thus far, fruit quality data indicate that fruits produced in plots of cool-season grasses are smaller and less mature than those produced in vegetation-free plots or plots of warm-season grasses. A negative correlation was noted between high fruit quality and water deficit stress as measured by water potential and stomatal conductance.
A field study was initiated in 1981 in western North Carolina to determine the influence of eight groundcover management systems on quality of `Redchief Red Delicious' apple (Malus domestica) grafted onto rootstock of M VIIA. Management systems included: bare soil, Secale cereale mulch, minimal cultivation, Festuca arundinacea, Dactylis glomerata, Poa pratensis, Muhlenbergia schreberi and Rubus sp. Thus far, fruit quality data indicate that fruits produced in plots of cool-season grasses are smaller and less mature than those produced in vegetation-free plots or plots of warm-season grasses. A negative correlation was noted between high fruit quality and water deficit stress as measured by water potential and stomatal conductance.
The objectives of this study were to determine the effects of high P applications on `Baron', Kentucky bluegrass (Poa pratensis L.) turf quality, chlorophyll content, soil test levels of P and K, and foliar nutrient concentration. In this 5-year field study, P was applied at 0, 22, 43, 86, 172, or 258 kg·ha-1·year-1 using triple superphosphate (210 g P/kg) in single-applications in May. Phosphorus applications did not affect overall yearly quality, chlorophyll content, or soil pH, but increased available soil P and reduced available soil K and Cu concentration in clippings.
Organic and synthetic fertilizers were evaluated under three irrigation regimes (daily, twice weekly, and rain only) for management of necrotic ring spot (Leptosphaeria korrae Walker & Smith) of Kentucky bluegrass (Poa pratensis L.). Disease severity varied due to fertilizer and irrigation treatments. After 2 years of treatments, daily irrigation reduced disease incidence as compared to twice-weekly irrigation, while organic fertilizer, as a feathermeal-bonemeal-soybeanmeal mixture, when applied monthly at 48.8 kg N/ha, reduced disease incidence as compared to urea fertilizer. For 2 of 3 years, differences in disease incidence were attributable to irrigation treatments, and after 4 years, all N fertilizers reduced disease incidence as compared to no fertilizer.
The purpose of this study was to evaluate the effectiveness of soil-incorporated hydrogel to reduce irrigation requirements of transplanted Kentucky bluegrass (Poa pratensis) sod. The treatments included an untilled control, tilled soil, and tilled soil with incorporated hydrogel. Initial irrigation treatment were made daily, at various percentages of potential evapotraspiration (PET), to determine irrigation requirements of newly transplanted sod. Other irrigation treatments were later imposed on transplanted sod which had been established at 100% of PET, to determine irrigation requirements of established sod. Turf quality was measured weekly, and sod transplant rooting strength was also measured.
Three bio-organic materials were evaluated at four application rates, based on N contents, for their potential to degrade Kentucky bluegrass (Poa pratensis L.) thatch in a field experiment. Treated thatch was reduced in thickness and had increased earthworm (Lumbricus spp. Hoff.) populations when compared to untreated thatch. Thatch thickness was negatively correlated with level of N (r = –0.91), thatch lignin content (r = –0.94), and earthworm population in the thatch (r = –0.64), and positively correlated with thatch cellulose content (r = 0.62).
Abstract
The relative sensitivity of various organs of Poa pratensis L. ‘Merion’ (Kentucky bluegrass) to osmotically induced water stress was evaluated. Lateral bud meristems (axillary buds) were most sensitive to increases in osmotic pressure. The decrease in lateral bud development subsequently resulted in a decrease in tiller and rhizome numbers. Relative growth rates of various organs of Kentucky bluegrass further established that shoot dry-matter loss in response to water stress was due primarily to decreased tiller and rhizome growth. The effect of increasing osmotic pressure had relatively similar and less severe effects on leaf and root growth. The potential use of relative growth for characterizing growth responses to water stress is discussed.
Chlorsulfuron, diclofop, and sulfometuron were evaluated for potential use in selective control of tall fescue (Festuca arundinacea Schreb.) in Kentucky bluegrass (Poa pratensis L.). Polynomial trend analyses indicated highly significant linear and quadratic response curves for percentage of tall fescue reduction for each herbicide. Fall and spring treatments with chlorsulfuron and diclofop provided significant tall fescue control, with slight to moderate initial Kentucky bluegrass phytotoxicity. Fall and spring applications of sulfometuron resulted in excellent tall fescue control, but initial Kentucky bluegrass damage was severe and would be unacceptable for high maintenance turf. Chemical names used: 2-chloro- N -[[(4-methoxy-6-methyl-l,3,5-triazin-2-yl)amino]carbonyl]-benzenesulfonamide (chlorsulfuron); 2-[4-(2,4-dichlorophenoxy)phenoxy]proponoate (diclofop); N -[[(4,6-dimethylpyrimidin-2-yl)amino]carbonyl]-2-methoxycarbonyl-benzenesulfonamide (sulfometuron).
Kentucky bluegrass (Poa pratensis L.) cultivars are often blended to incorporate diverse characteristics. Factors that may contribute to the actual cultivar composition have not been evaluated. Through the use of DNA markers, individual plants in blended stands can be identified. This study evaluated changes in cultivar composition of `Blacksburg', `Midnight', and `Unique' Kentucky bluegrass blends. Characteristics such as seed size, seed moisture content, percent germination, and seedling development did not affect the initial composition of blends at time of seeding. DNA markers were used to demonstrate how the composition of a blended `Blacksburg', `Midnight', and `Unique' turf changed during the first growing season following establishment. The composition of blends did not significantly change from time of seeding in Sept. 1999 to Apr. 2000 or from Apr. 2000 to Oct. 2000. Two of the three blends were significantly different by Oct. 2000 relative to the percentages seeded in Sept. 1999.