Characterization of the growth of annual bluegrass (Poa annuaL.) and creeping bentgrass (Agrostis palustrisHuds.) over a broad range of pH and phosphate levels was needed to better investigate potential effects of soil acidity and P on annual blue-grass infestation in creeping bentgrass stands. Two acid soils were treated with varying rates of lime and P fertilizer. Clipping yields and P uptake of both grasses, as well as the levels of soil NaHCO3-extractable P and exchangeable Al, were all significantly related to lime and P treatments. High lime and high P treatments benefited annual bluegrass more than creeping bentgrass as revealed by clipping yields and P uptake. Lime invariably reduced the exchangeable soil Al with a small effect on NaHCO3-P levels in the lime rates used. The increased responses of clipping yields and P uptake to NaHCO3-P by liming could be attributed to the reduction of phytotoxic Al. The molar ratio of NaHCO3-P to exchangeable Al was a suitable parameter to describe the overall lime and P effects on the growth of either grass. High lime and high P applications which lead to high molar ratios of NaHCO3-P to exchangeable Al should be avoided in order to reduce the competition of annual blue-grass, particularly for soils that contain high organic matter and organic N. Further study is needed to elucidate the contribution of organic N mineralization to the differential growth behavior between the two grasses in the turf system.