Effects of Sand Size for Topdressing Putting Green Turf.

Topdressing sand is applied to smooth the surface of putting greens and maintain desirable rootzone characteristics.  Sand size can impact the ease of incorporation and interference to mowing and play.  A field trial was initiated in July 2010 on ‘Greenwich’ velvet bentgrass (Agrostis canina L.) to determine the effects of sand particle size distribution and application rate on the ease of incorporation, turf quality, surface hardness (Clegg Impact Soil Tester) and water retention.  Treatments were arranged in a 2 x 2 factorial and included an untreated control in an RCBD with three replications.  Topdressing was applied biweekly at 0.15 and 0.3 L m^-2 with medium-coarse and medium-fine size sands.  Differences in hardness and turf quality were not apparent during 2010; however, all topdressing treatments had better turfgrass quality than the non-topdressed check during 2011, 2012 and 2013.  Additionally, plots topdressed at 0.3 L m^-2 had better turfgrass quality than plots topdressed at 0.15 L m^-2.  Topdressing with medium-fine sand produced equivalent or better turf quality than plots todpressed with medium-coarse sand.  Surprisingly, surface hardness decreased for 17% and 70% of the 0.5- and 2.25-kg Clegg measurements, respectively, compared to the non-topdressed control during 2012 and 2013.  Volumetric water content (VWC) at 0- to 3.8-cm depth zone was greater in non-topdressed plots than topdressed plots on 50% of observation dates.  No substantial differences in VWC were found among sand sizes and topdressing rates.  Topdressing at 0.3 L m^-2 or with medium-coarse sand increased the time for sand to incorporate or be removed from the turf surface with mowing compared to 0.15 L m^-2 and the medium-fine sand, respectively.  The amount of medium-coarse sand removed by mowing increased as the topdressing rate increased from 0.15 to 0.3 L m^-2; whereas there was no increase in medium-fine sand removal between these topdressing rates during 2012.