SURFACE RUNOFF ASSESSMENT FROM CREEPING BENTGRASS AND PERENNIAL RYEGRASS TURF

The potential for offsite movement of nutrients and pesticides in surf ace runoff from golf courses has generated a need to better understand the movement of water from intensely maintained turfgrass. This study assessed the influence that creeping bentgrass [Agrostis stolonifera L. var. palustris (Huds.) Farw.; syn. Agrostis palustris Huds.] and pe rennial ryegrass (Lolium perenne L.) had on the surface movement of wa ter when maintained similarly to golf fairways. On eight dates, 123.5- m(2) sloped plots of bentgrass and ryegrass were irrigated at 152 mm h (-1) to force runoff for the generation of hydrographs. As the grasses matured, runoff from ryegrass occurred earlier and at greater volumes than from bentgrass. Four additional experiments were conducted to pr ovide some explanation of these runoff differences. Tn one experiment, average infiltration rates for the bentgrass (64 mm h(-1)) and ryegra ss (35 mm h(-1)) plots were not significantly different, because of hi gh sampling variation. In an experiment that used 0.25-m(2) sloped tra ys of turf, bentgrass retarded the Bow of surface runoff through its v egetation significantly longer than ryegrass. It was also found that b entgrass (1410 tillers dm(-2)) intercepted 113% more water than ryegra ss (260 tillers dm(-2)), and that bentgrass thatch slowed runoff initi ation because of its high water-holding capacity and increased hydraul ic resistance. The high-density, thatch-forming bentgrass provided a m ore tortuous pathway for water movement, which increased resistance an d in turn increased residence time and allowed for greater infiltratio n. For golf courses that have potential runoff concerns, the selection of creeping bentgrass rather than perennial ryegrass could reduce sur face runoff from golf fairways.