Effects of Combined Kikuyugrass Management Practices On Turfgrass Quality.

Kikuyugrass (Pennisetum clandestinum Hochst. ex Chiov.) is considered either an invasive weed or the desired species on many golf courses and other turf areas along coastal and inland California. As part of a comprehensive project aimed at kikuyugrass improvement and management, a field study was initiated in August 2011 to identify cultural and chemical practices that are most important for producing quality turf and optimal playing conditions on golf course fairways. The cultivar ‘Whittet’ was established from sod on a Hanford fine sandy loam.  A two-level, five-factor factorial design was used to evaluate mowing frequency (three vs. six times/wk), cultivation (grooming three times/wk vs. verticutting twice/yr), trinexapac-ethyl (none vs. 0.95 L/ha bi-weekly), nitrogen (98 vs. 244 kg/ha/yr), and fungicide treatment (none vs. monthly preventative applications according to disease activity).  Turf quality and color were assessed visually and by normalized difference vegetation index (NDVI).  Turf firmness and ball roll were measured with a Clegg Soil Impact Tester (2.5 kg hammer Gmax) and Pelzmeter, respectively.  Trinexapac-ethyl, verticutting, and more frequent mowing produced the highest kikuyugrass quality and playing conditions in 2012, especially in July and August 2012 when turf growth was most vigorous and prone to scalping.  Firmer turf resulted from verticutting without trinexapac-ethyl. Darker turf color was observed in the spring and fall with the higher nitrogen treatment.  Ball roll increased with the grooming treatment when compared to verticutting.  In 2013, higher nitrogen and trinexapac-ethyl produced higher turf quality in July and August of 2013.  Ball roll was best with the grooming treatment and higher nitrogen.  Scalping was decreased with verticutting and trinexapac-ethyl. Thus far in 2013, all five factors produced significant positive results in part due to cooler spring weather and disease pressure during the winter months. Overall, it appears that optimal kikuyugrass quality and playing conditions are contingent upon higher cultural and chemical inputs that may be alleviated by improvements through breeding and genetics.