The use of impermeable tarps has been adopted by golf course superintendents in North America to prevent winter injury due to direct cold temperature exposure and ice damage; however, without ventilation, anoxic conditions can develop under tarps, which can result in extensive damage to annual bluegrass (Poa annua L.) greens. Currently, no information is available to help superintendents determine when or how frequently ventilation under tarps or ice cover is needed for injury prevention. A controlled environment study was performed to determine the effects of anoxic and hypoxic conditions on cold tolerance, represented by the lowest temperature at which 50% survival occurs and nonstructural carbohydrate concentrations of annual bluegrass, and to determine at what gas concentrations managers should ventilate under impermeable tarps. In general, turf exposed to anoxic conditions had reduced cold tolerance at all sampling days, highlighting the importance of avoiding anoxic conditions under impermeable covers. Glucose, fructose, sucrose, and total sugar concentrations did not respond to atmospheric gas treatments as predicted, and no relationship between elevated carbohydrates and increased cold tolerance was observed in this study. Conflicting reports on the role of carbohydrates in winter hardiness suggest a more biologically complex relationship between the two variables, and other factors such as proteins and phytotoxic compounds should be investigated. It is recommended that superintendents who are monitoring atmospheric conditions under impermeable tarping systems should ventilate under tarps as soon as oxygen levels reach 5% to prevent winter injury.
Open-field burning of Kentucky bluegrass (Poa pratensis L.) postharvest residue, which maintains grass seed yield and stand longevity, has been eliminated in Washington and is restricted in Idaho and Oregon, USA. Our objective was to develop Kentucky bluegrass germplasm that has sustainable seed yield without field burning while maintaining acceptable turfgrass quality for use as an amenity grass. From the USDA/ARS Poa pratensis L. Plant Introduction (PI) collection, 228 accessions were evaluated in a field trial and a core collection was developed. This collection was then evaluated in seed production and turfgrass trials and those possessing both good seed yield without field burning and turfgrass quality were identified and planted in a space-plant nursery at Pullman, WA. The eight PI accessions and two commercial cultivars checks were evaluated over a 2-year period and individual plants were reselected within each accession, or check, with the highest seed weight, highest seeds panicle-1 , highest panicle number area-1 , and highest seed yield. Turfgrass plots were established in 2006, 2009, and 2010 at Pullman, WA, Auburn, AL, and Puyallup, WA, respectively. Seed production plots (irrigated and non-irrigated) were established at Pullman in 2007. Selection for seed yield components had a variable response and seed yield was more dependent on accession. PI 368241, selection panicles area-1 , and Kenblue, selection seeds panicle-1 , had the best sustainable (four
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