Golfdom, August 2010

M A I N T A I N I N G H E A L T H Y T U R F 60 TURFGRASS TRENDS August 2010 www turfgrasstrends com PHOTO BY EYEWIRE INC Continued from page 59 While traffic is broken down into wear and soil compaction few studies have directly compared these two confounding factors and their interactive effects on plant response Until now with nitrogen at 413 pounds 231 pounds and 148 pounds and acre and the silt loam at 283 pounds 187 pounds and 148 pounds an acre in 2005 2006 and 2007 respectively Percent turfgrass cover prior to wear treatments was taken in the fall 2004 to spring 2005 Wear ratings were taken immediately after wear treatments using a scale of 1 to 9 1 equals severe wear with 50 percent bare ground 5 equals leaf injury with loss of color and density 6 equals leaf injury with loss of color and less than 6 acceptable with progressively less injury starting in 2006 Recovery from injury was rated several days after the wear treatments using the same scale with acceptable recovery indicated when the rating was greater than 6 with 9 equaling 100 percent recovery Five cores 12 square inches were taken from all plots prior to wear treatment on June 6 2006 and after termination of the study on June 14 2008 to assess species composition Aerial shoots of Kentucky bluegrass and perennial ryegrass were separated by species and pooled to estimate species composition by count Six cores 12 square inches were taken in October 2007 to a depth of 6 inches to measure root weights The cores were divided in half to measure root biomass between 0 to 3 inches and 3 to 6 inches respectively The soil was washed from the cores and dried at 70 degrees C until a constant weight was obtained The roots were weighed and then ashed at 600 degrees C for two hours The ash weight was subtracted from the oven dry weight to obtain the weight of the roots Penetration resistance was measured using a Proving Ring Penetrometer with a cone point which was pushed slowly and at a constant rate into the top 2 inches of soil Two readings were taken per plot beginning in 2004 with the results reported in megapascals MPa Two intact cores 2 inches in diameter by 24 inches in length were obtained in the fall 2006 with a brass cylinder fitted inside a metal tube from each plot for determining bulk density and air filled porosity Thatch and soil were removed to 2 inches below the surface before inserting the metal tube with the brass cylinder Soil samples were collected from the silt loam and sand rootzone prior to setting out the experiment to determine the soils maximum dry density using the Proctor Test Modified Compaction Effort ASTM D1557 07 2008 The maximum dry density is used as a reference in which the observed bulk density is expressed as a proportion of the maximum dry density Field saturated hydraulic conductivity Kfs was determined in the fall 2007 using the Guelph Field Permeameter Reynolds 1993 Reynolds Elrick 1985 which maintains a stable depth of water in an uncased auger hole Results grass establishment Full cover on the silt loam was achieved by April 20 2005 while full cover on the sand rootzone did not achieve full cover until June 29 2005 Soil compaction also significantly reduced stand establishment over both soils up until June 7 2005 Table 1 Although most of the reduction in vegetative cover was associated with the sand rootzone the data strongly suggests that soil compaction as a result of construction activities can have a profound effect on turfgrass establishment Species composition Perennial ryegrass increases significantly in the population with a concomitant decrease in Kentucky bluegrass in the compacted plots compared to the non compacted plots