( Table 1 ); these cultivars had been developed for salt tolerance, adaptation to low-input environments, or both. The cultivars represented seven species: red fescue, alkaligrass, kentucky bluegrass ( Poa pratensis L.), tufted hairgrass [ Deschampsia
Abstract
Seedlings of Kentucky bluegrass (Poa pratensis L.), perennial ryegrass (Lolium perenne L.), red fescue (Festuca rubra L.), and weeping alkaligrass [Puccinellia distans (L.) Parl.] were exposed to water stress prior to measuring heat tolerance of leaf blade segments. Heat tolerance was determined using an electrolyte leakage assay. Water stress pretreatments did not increase in vitro heat tolerance of turfgrass leaves.
Abstract
Three preemergence herbicides [S-(0, 0-Diisopropyl phosphorodithioate) ester of N-(2-mercaptoethyl) benzenesulfonamide (bensulide) at 8.4 and 15.7 kg/ha, Dimethyl tetrachloroterephthalate (DCPA) at 11.8 and 16.8 kg/ha, and 2-tert-butyl-4-(2,4 dichloro-5-isopropoxyphenyl)-Δ2l,3,4-oxadiazolin-5-one (oxadiazon) at 2.2, 4.5, and 9 kg/ha] were applied to plugs of Kentucky bluegrass (Poa pratensis L. cvs. Baron, Enmundi, Newport, and Park) in the greenhouse. Bensulide and oxadiazon reduced root weight, but there were no cultivar differences. Cultivar differences in response to oxadiazon were observed for rhizome weight, rhizome length, and turfgrass quality, with ‘Newport’ and ‘Baron’ damaged more by oxadiazon than ‘Park’ and ‘Enmundi’. There were no cultivar differences in rhizome weight, rhizome length, and quality in response to bensulide or DCPA.
Abstract
Sixty Kentucky bluegrass (Poa pratensis L.) cultivars and experimental lines and 24 bluegrass blends were investigated for thatching tendency. Cultivars and experimental lines differed in thatch accumulation during the course of this 5-year study. Increasing N level from 10 to 20 g N m-2 season -1 had no effect on thatch accumulation. Thatch accumulation in cultivars and experimental lines was correlated (r = 0.87) to verdure, indicating vigorous cultivars had greater thatching tendency. Thatching tendency of cultivars was correlated (r = 0.74) to their total cell-wall content expressed on a mg dm-2 basis. Accumulation of thatch in blends approximated the mean accumulation for cultivars growing in pure stands. These results indicate a potential for reducing thatch accumulation in Kentucky bluegrass lawns through blending of appropriate cultivars.
Abstract
Ammonia volatilization from urea-N applied to Kentucky bluegrass ( Poa pratensis L. ‘Bensun’) was investigated using a chamber trapping procedure. Urea was spray-applied in a 0.2 cm depth at N of 5 g·m−2 with and without additional irrigation of 0.5, 1, 2, or 4 cm. Losses up to 36% of the applied N occurred when urea was applied without irrigation. Supplemental irrigation of as little as 1.0 cm reduced the loss to 3-8%, while a 4.0-cm irrigation further reduced losses to about 1%. Of the ammonia volatilized, most was lost in the first 24 hr. Maximum N loss was associated with the thatch layer, a zone having high urease activity.
Abstract
Four categories of billbug (Sphenophorus parvulus Gyllenhal) resistance were identified and contrasted in terms of anatomical, morphological, and physiological characteristics of 12 Kentucky bluegrass (Poa pratensis L.) cultivars. Discriminant analysis was used as a separatory procedure to determine the relative importance of these plant characteristics to observed billbug resistance and to construct a prediction procedure for potential billbug resistance classes. Variables measured from field-, controlled environment-, and greenhouse-grown plants were analyzed for the most biologically revealing characteristics of potential billbug resistance. Separatory discrimination indicated that cultivars exhibiting moderate and high billbug resistance had tougher tissue than tolerant or susceptible cultivars. Tolerant and highly resistant cultivars differed from those susceptible and moderately resistant by concealing billbug injury. Development of a predictive classification procedure was promising, with percent correct classification ranging from 67% to 94%, depending on number and type of discriminating variables analyzed.
Abstract
Ammonia (NH3) volatilization was determined from 15N-labeled urea applied foliarly in 35 ml·m−2 water at 1.7 and 3.4 g N/m2 to a ’Park’ Kentucky bluegrass (Poa pratensis L.) turf that was grown on Sharpsburg silty clay loam (Typic Argiudoll). Field measurements of NH3 volatilization were made 1, 5, 9, 13, and 25 hr after treatment (HAT). Additional volatilization measurements were made at 2, 3, and 4 days after treatment (DAT). Maximum NH3 losses of 9.7 and 23.0 mg N/m2 per hr at 5 and 25 HAT occurred with the 3.4 g N/m2 treatment. Maximum volatilization during 25 HAT coincided with periods of high leaf surface moisture followed by rapid drying. On the second day after treatment, the maximum NH3 loss of 14.0 mg N/m2 per hr occurred from the 3.4 g N/m2 treatment. Cumulative 4-day NH3 volatilization losses for foliar-applied urea at 1.7 and 3.4 g N/m2 were 35% and 31%.
Abstract
A modular assimilation chamber (MAC) was developed for rapid examination of CO2 exchange rate (CER) of multiple turfgrass replicates. Kentucky bluegrass (Poa pratensis L. ‘Enoble’) and tall fescue (Festuca arundinacea Schreb. ‘Houndog’) were grown in Cone-tainers with attached base plates under greenhouse conditions. A chamber top was sealed to the base plate to complete the MAC. It then was used under laboratory conditions to measure CER by an open, differential CO2 method or by closed chamber-syringe sampling method. The two-module concept provided a relatively simple tool for making rapid, multiple measurements of CER when used as part of a closed system. However, a larger chamber volume is needed for closed system measurements because: 1) CER values were significantly larger with the open system, rapid drops in CO2 concentration occurred during closed-system measurements, and CER measurements after 2 min of closure were significantly lower than those made after 1 min of closure.
Abstract
Fenoxaprop-ethyl at rates of 0.09 to 0.28 kg·ha−1 provided effective smooth crabgrass [Digitaria ischaemum (Schreb.) Muhl.] control with minor injury to ‘Baron’ Kentucky bluegrass (Poa pratensis L.). Optimum timing for application was the 4-leaf to 5-tiller stage of crabgrass growth. At this stage of growth, fenoxaprop-ethyl applied at 0.20, 0.28, or 0.38 kg·ha−1 provided excellent (90% or better) season-long crabgrass control. Fenoxaprop-ethyl at 0.09 kg·ha−1 was an effective crabgrass control treatment at 2 to 4 leaf stage when combined with DCPA at 11.76 kg·ha−1. Split applications of fenoxaprop-ethyl in June and July at both 0.14 + 0.14 and 0.28 + 0.28 kg·ha−1 also provided season-long crabgrass control. Chemical names used: (±)-ethyl 2-[4-[(6-chloro-2-benzoxazolyl)oxy]phenoxy]propanoate (fenoxaprop-ethyl); and dimethyl tetrachlo-roterephthalate (DCPA).
Abstract
The effectiveness of ethephon for reducing the growth of annual bluegrass (Poa annua L.), when grown as single plants in pot culture in the greenhouse or outdoors, and within a Kentucky bluegrass (Poa pratensis L.) sod, was evaluated. Ethephon reduced the growth of annual bluegrass more than that of Kentucky bluegrass. Concentration was more important in reducing plant spread than the number of applications. Ethephon applied to field grown turf reduced the leaf area per tiller of annual bluegrass but not Kentucky bluegrass. Leaves per tiller and the shoot dry weight of field grown Kentucky bluegrass increased with increasing ethephon rates compared to nontreated plots. Although significant growth retardation occurred for both species in pot culture, only Kentucky bluegrass canopy height decreased in the field with increasing ethephon rates. Decreased Kentucky bluegrass canopy height resulted from reduced sheath length. Chemical names used: (2-chloroethyl) phosphonic acid (ethephon).