Golfdom, January 2017

CART PUSHING FOR SCIENCE Winter traffic stress on a Transition Zone bentgrass green By Winston Nickles Mirmow Haibo Liu Ph D Bert McCarty Ph D and James Rieck Ph D M any factors affect the durability of turfgrass under traf fic stress including the turfgrass species and cultivar timing and type of traffic root zone composition and construction type soil moisture levels recovery time and maintenance regiments A 2008 study noted that both mower and foot traffic at 7 a m had a negative effect on turfgrass quality when creeping bentgrass Agrostis stolonifera L had a canopy temperature lower than 32 degrees F Vehicular or human foot traffic can be extremely damaging to turfgrass when temperatures are below freezing resulting in injury or even death to the crowns Traffic inevitably causes turfgrass stands to lose quality It can negatively affect the turfgrass by compacting soil compaction or causing wear damage Sand based root zone mixes for putting greens have minimized the effects of compaction but wear from traffic still causes problems especially in extreme temperatures with low mowing heights Wear injury on turfgrass shoots is characterized by crushing tearing stripping or abrasion of leaf tissue followed by a degradation of chlorophyll and subsequent photosynthesis reduction The prevai ling theory among researchers is that wear is the primary form of traffic related injury on sandy soils or soils with water contents below field capacity Conversely soil compaction may be the primary form of traffic injury on finer textured soils with higher water contents when greens see heavy loads Because traffic stress most often occurs on closely mowed turfgrass stands on sand based root zones its reasonable to conclude that wear rather than compaction is the primary stress In addition a 2009 study identified wear stress as the most important influence on turfgrass quality and that compaction is less important on sand based or silt loam root zones The cushioning effect of surface organic matter likely is a reason for the low importance of compaction in various studies POTASSIUM EFFECTS ON TOLERANCE Potassium K is a required nutrient often applied to turfgrasses especially creeping bentgrass to help plants tolerate stresses Fall K fertilization is thought to aid in creeping bentgrass winter traffic tolerance but research on the subject is limited and inconsistent Research done in 1975 found that creeping bentgrass wear tolerance increased with higher K fertilization levels The greatest increases were at 55 to 74 lbs K per 1000 sq ft per year 27 to 36 g K m2 The study also indicated a low relationship between K fertilization and total cell wall content but 38 Golfdom January 2017 Golfdom com PHOTOS COURTESY WINSTON NICKLES MIRMOW Super Science Research provided and funded by USGA FIGURE 1 A modified water filled push turfgrass roller that weighed 165 lbs and applied a force of 027 lbs per sq ft was used to apply traffic treatments on the Crenshaw creeping bentgrass research putting green