Annual bluegrass (Poa annua L.) and ‘Penncross’ creeping bentgrass (Agrostis palustris Huds.) were grown in monostand and polystand in silica sand and supplied with solutions in which 0%, 25%, 50%, 75% or 100% of the N was NH4+ and the remainder was NO3.– In polystand, annual bluegrass was more competitive than ‘Penncross’, producing more shoot and root dry weight and more tillers. Competitive ability of annual bluegrass was decreased as the percentage of NH4+ increased in nutrient solution. The decrease in competitive ability was reflected by a decline in tiller number and root and shoot dry weight. ‘Penncross’ was less affected by N form than was annual bluegrass.
Germination responses of creeping bentgrass (Agrostis palustris Huds.) and Kentucky bluegrass (Poa pratensis L.), and annual bluegrass (Poa annua L.) to elevated temperature were evaluated by germinating seed in sustained temperature regimes or by moving imbibed seed from high to intermediate or from intermediate to high temperatures. ‘Penncross’ creeping bentgrass germinated well at 40°/30°C (day/night) temperature or when moved from 40/30° to 25°/18° or from 25°/18° to 40°/30°. ‘Baron’ Kentucky bluegrass seed germination was decreased by 34°/28° and there was no germination at 40°/30°. Moving imbibed seed from 40°/30° to 24°/18° resulted in a high germination percentage, while imbibition for 12 or 24 hours at 25° resulted in some germination at 40°/30°. Annual bluegrass seed germination was significantly less at 34°/28° than at 25°/18° and was prevented at 40°/30°. Imbibition at 40°/30° prior to 25°/18° decreased germination and there was no annual bluegrass germination at 40°/30° regardlessf of pretreatments at 25° for up to 24 hours.
Five cultivars of creeping bentgrass (Agrostis palustris Huds. ‘Emerald’, ‘Penncross’, ‘Penneagle’, ‘Prominent’, and ‘Seaside’) and annual bluegrass (Poa annua L.), a weed, were grown in pot culture in silica sand and supplied with nutrient solutions in which 0%, 25%, 50%, 75%, or 100% of the N (210 mg·liter−1) was and the remainder was . Growth rate, as measured by new leaves and tillers, and final size, as measured by leaf width, leaf number, tiller number, and cover, were significantly different among species and cultivars and among N ratios. All species/cultivars produced their best growth with some mixture of and . Annual bluegrass grew better in high- conditions, while the bentgrass cultivars grew as well or better in high conditions. There were significant differences among the bentgrass cultivars in their sensitivity to N source, with ‘Penncross’ being the most sensitive and ‘Seaside’ the least.
The effect of mefluidide, a growth regulator, on the growth of annual blue-grass (Poa annua L.) was evaluated under pot culture and field conditions. In pot culture, mefluidide caused a significant reduction in shoot and root dry weight and tiller number of single annual bluegrass plants, and of annual bluegrass planted at high densities. In the latter case, mefluidide also increased the success of ‘Penncross’ creeping bentgrass (Agrostis palustris Huds.) overseeded into the annual bluegrass. Overseeding success of ‘Fiesta’ perennial ryegrass (Lolium perenne L.) in field trials increased significantly with increasing rates of mefluidide. No increase in success was noted in overseeding with creeping bentgrass in the field. There was a minimum detrimental effect of mefluidide to turf quality of the established turf species in the golf course fairway. Chemical names used: N-[2,4-dimethyl-5[[[trifluoromethyl] sulfonyl]amino]phenyl]acetamide (mefluidide).