Surface Runoff Assessment from Creeping Bentgrass and Perennial Ryegrass Turf

The potential for offsite movement of nutrients and pesticides in surface 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 perennial ryegrass ( Lolium perenne L.) had on the surface movement of water 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 hydragraphs. As the grasses matured, runoff from ryegrass occurred earlier and at greater volumes than from bentgrass. Four additional experiments were conducted to provide some explanation of these runoff differences. In one experiment, average infiltration rates for the bentgrass (64 mm h −1 ) and ryegrass (35 mm h −1 ) plots were not significantly different, because of high sampling variation. In an experiment that used 0.25‐m 2 sloped trays of turf, bentgrass retarded the flow of surface runoff through its vegetation significantly longer than ryegrass. It was also found that bentgrass (1410 tillers dm −2 ) intercepted 113% more water than ryegrass (260 tillers dm −2 ), and that bentgrass thatch slowed runoff initiation because of its high water‐holding capacity and increased hydraulic resistance. The high‐density, thatch‐forming bentgrass provided a more tortuous pathway for water movement, which increased resistance and in turn increased residence time and allowed for greater infiltration. For golf courses that have potential runoff concerns, the selection of creeping bentgrass rather than perennial ryegrass could reduce surface runoff from golf fairways.