Wednesday, November 7, 2007
268-7

Effects of Nitrogen and Potassium on Wear Tolerance and Recovery in Perennial Ryegrass.

Lindsey Hoffman1, Jeffrey Ebdon1, Michelle DaCosta2, and William Dest3. (1) University of Massachusetts, Stockbridge Hall, Amherst, MA 01003, (2) University of Massachusetts, University of Massachusetts, Dept of Plant, Soil & Insect Sciences, 11 Stockbridge Hall, 80 Campus Center Way, Amherst, MA 01003, (3) University of Connecticut, 53 McMullen Ave., Wethersfield, CT 06109-1234

Perennial ryegrass (PRG, Lolium perenne L.) is one of the most widely used turfgrass species for sports turf. Wear tolerance in response to N and K has not been studied extensively in this species. The objective of this research is to evaluate wear tolerance and recovery of PRG in response to five rate levels of N (49, 147, 245, 343, and 441 kg/ha/yr) and three rate levels of K (49, 245, and 441 kg/ha/yr). Urea (45-0-0) was used as the source of N and potassium sulfate (0-0-41.5) was the source for K. Wear was applied in the field on Bright Star SLT PRG using a differential slip wear (DSW) and grooming brush wear (GBW) applied by a walk behind greens mower. Plots were mown at 3.125 cm and irrigated to prevent stress. Significant wear injury was imposed on all plots using both the DSW and GBW, which were applied on 18 June and 14 October 2006, respectively. A visual rating scale was used to assess wear injury (1 to 9, 9=no injury). DSW and GBW ratings were highly correlated (r=0.93, p = 0.001). Recovery from GBW was rapid. Recovery following DSW was assessed weekly until full recovery was achieved. All K combinations with 245 kg N fully recovered by 12 weeks after treatment (WAT) while all other combinations required 16 WAT to achieve 100% recovery. Potassium applied at rates greater than 49 kg N combined with 245 kg N caused greater wear injury at 4, 8 and 12 WAT. Maximum wear tolerance and recovery was achieved by applying 245 kg N with 245 kg K. GBW is an effective alternative to DSW for assessing wear tolerance. However, GBW does not impose significant wear injury to effectively assess recovery typical of actual wear events that is more closely simulated by DSW.