The culture of creeping bentgrass (Agrostis palustris Huds.) at low mowing heights on putting greens in the hot humid region of the USA presents numerous water management problems. Frequent irrigation of greens to prevent water stress has been credited with producing shallow rooted turf with reduced tolerance to environmental stress. The present study was conducted to determine the relationship between irrigation frequency and turf quality, shoot density, and root length density for five cultivars of creeping bentgrass grown on a sand‐based root zone and maintained to putting green standards. A total of 81 plots, 1.5 by 1.5 m each, were established on a USGA‐type root zone mixture and organized into nine irrigation cells of nine plots each. Each irrigation cell could be irrigated individually. One plot in each irrigation cell was planted to the following bentgrass cultivars: A‐4, Crenshaw, Mariner, L‐93, and Penncross. The remaining four plots in each irrigation cell were also planted with bentgrass but were not a part of this study. Irrigation frequency treatments of 1‐, 2‐, and 4‐d were imposed on three irrigation cells each. After establishment, measurements of turf quality, shoot density and root length density were made over a 2‐yr period. In both years, Crenshaw and L‐93 had the best turf quality. At the end of the study, shoot densities for Crenshaw, L‐93, and A‐4 were 37 to 42% greater than Mariner and Penncross. Because of frequent rainfall events in 1997, there were no significant (P ≤ 0.05) effects of irrigation frequency on shoot density or root length density. However, in 1998, turf was more dependent on irrigation and bentgrass irrigated every 4 d had significantly greater turf quality, shoot density, and root length density than that watered every 1 or 2 d. The data show that even under putting green management conditions, reduced irrigation frequency of bentgrass produces a larger and deeper root system resulting in greater overall plant health, turf quality, and shoot density.

Ultradwarf bermudagrass cultivars are widely used for putting greens due to their high shoot density, low mowing heights, and high‐quality putting surface. However, successful management may require cultivar‐specific annual N application rates and thatch control measures as compared to those used for the cultivar ‘Tifdwarf.’ This study evaluated the effects of N fertility, topdressing and vertical mowing on thatch development, shoot density and turf quality of five dwarf bermudagrass cultivars: Tifdwarf, ‘Champion,’ ‘Floradwarf,’ ‘Miniverde,’ and ‘Tifeagle.’ The study was conducted using a strip‐split plot design and extended over a 63‐month period. All treatments were replicated three times. Suggested optimum N fertilization rates for all five grasses in the study are 10 lbs of N per 1,000 ft2/year. This N rate should provide good‐quality turf ‐‐ a high shoot density without excessive thatch accumulation. Floradwarf was most susceptible to high soil pH, followed by Champion. Careful soil pH management is needed when growing these cultivars. Frequent light vertical mowing was advantageous during the first year, but was detrimental to mature stands of ultradwarf cultivars when bermudagrass decline was active. Topdressing treatments used in this study were not sufficient to control thatch accumulation. When averaged across all treatments, thatch depth equal to or greater than 0.5 inch occurred by 42, 30, 42, 38, and 38 months after planting for Tifdwarf, Champion, Floradwarf, Miniverde, and Tifeagle, respectively.

ation (Huang et al., 1998) decrease root growth and increase root mortality. In addition, a synergistic effect The culture of creeping bentgrass (Agrostis palustris Huds.) at between high soil temperature and low soil aeration furlow mowing heights on putting greens in the hot humid region of the USA presents numerous water management problems. Frequent ther contributes to bentgrass decline (Huang et al., 1998).irrigation of greens to prevent water stress has been credited with Very short mowing heights also reduce root growth of producing shallow rooted turf with reduced tolerance to environmen-

A formal approach for integrating Computer-Aided Design (CAD), Computer-Aided Process Planning (CAPP), and shop floor control for rotational components is presented in this paper. It is assumed that this approach will be implemented within the framework of a three level hierarchical CIM architecture that consists of the following levels in the hierarchy: shop floor, workstation and equipment (Joshi et al., 1991). Our approach to CAPP consists of machining feature identification, definition, classification, representation, and reasoning, provided through a CAD model of a product. Geometric entities are identified from a Drawing Exchange Format (DXF) file. The identified entities form the basis for the construction of primitive manufacturing features. The primitive features are assembled together based upon the precedence among features, into a graph, called a feature graph. However, the primitive features may or may not be manufacturable in terms of depth of cut, tool geometry, surface finish, and material handling required. Hence it is necessary to convert the feature graph into a manufacturing task graph, which consists of specifications of alternative functional tasks that are manufacturable. The task graph may be converted into a hierarchical set of process plans, based on the planning criteria at each level in the control hierachy, to reflect the processing requirements at each level. The shop planning function decomposes the task graph into a set of workstation level plans. Each workstation level plan is aggregated into a set of equipment level process plans by the workstation planning function. The equipment level plan is converted into a unique task sequence by the equipment planning function. This sequence is then executed according to specifications by the equipment level execution function. Provision of alternative routes in process plans provides for flexible means of on-line planning and control.

Disease is a major problem in creeping bentgrass (Agrostis stolonifera L.) on golf course putting greens. Genetic composition and uniformity of host populations can affect disease development. This study was conducted to determine the effects of blending creeping bentgrass cultivars on dollar spot (caused by Sclerotinia homoeocarpa F. T. Bennett) severity. ‘Penn A‐4’, ‘Crenshaw’, ‘L‐93’, ‘Mariner’, and ‘Penncross’ were planted in monostands or as two‐way or three‐way blends in a completely random design with three replications on a sand‐based putting green in the field at College Station, TX. Disease severity was determined by the number of infection centers and by total blighted area. Crenshaw was most susceptible, L‐93 most resistant, and all other cultivars were moderately resistant to dollar spot in monostands. Cultivar susceptibility in monostands to S. homoeocarpa was representative of each cultivars contribution to dollar spot severity in blends. In blends, L‐93 suppressed, whereas Crenshaw increased dollar spot. Penncross, Penn A‐4, and Mariner did not affect dollar spot severity across all blend combinations. Number of infection centers and infected area pooled across all monostands were similar when compared to all two‐ and three‐way blends indicating that dollar spot activity in blends was a compromise between resistance levels of individual cultivars. Two‐way blends of Penn A‐4, L‐93, Mariner, or Penncross with Crenshaw, however, resulted in 46 to 67% fewer infection centers and 71 to 98% less blighted area, when compared to the Crenshaw monostand. These data indicated that blending a resistant cultivar with a susceptible cultivar reduced dollar spot severity in the blended population.