CUTTING HEIGHT AND FREQUENCY-EFFECTS ON COMPOSITION, YIELD, AND QUALITY OF A BERMUDAGRASS CRABGRASS MIXTURE

'Coastal' bermudagrass [Cynodon dactylon (L.) Pers.] is the most abund ant warm-season perennial grass in the lower South. Large crabgrass [D igitaria sanguinalis (L.) Scop.] will often invade stands of Coastal b ermudagrass but little is known about the response of this species mix ture to defoliation management. A study was conducted in 1990 and 1991 to determine the effects that cutting height and interval have on spe cies composition, dry matter (DM) yield and quality of a bermudagrass- crabgrass mixture. Percentage crabgrass, DM yield, crude protein (CP) and in vitro organic matter digestibility (IVOMD) were measured on sma ll plots of coastal bermudagrass that were cut at three cutting height s (1, 4, and 7 in.) and five cutting intervals (1, 2, 3, 4, and 6 wk). Percentage crabgrass was low in 1990 and did not show a response to c utting height. Higher crabgrass percentages in 1991 showed a positive linear response to cutting height and a negative linear response to cu tting interval at both the middle and end of the experiment. There was a linear decrease in DM yield as cutting height increased, but yield increased linearly with increased cutting interval. Crude protein perc entage declined linearly with increased cutting interval, but a linear response to cutting height in both years changed from negative to pos itive as interval increased. There was a curvilinear increase of IVOMD as cutting height increased in both years. In 1990, there was a linea r decrease of IVOMD as interval increased with the rate of decrease be ing higher as cutting height increased; however, in 1991, there was a curvilinear decrease of IVOMD with increasing interval. Results of thi s study indicate that cutting height and frequency interact to affect the productivity, quality, and composition of bermudagrass-crabgrass m ixtures.