Use of Medium-Fine Sands for Topdressing Velvet Bentgrass and Annual Bluegrass Putting Greens.

Sand size can impact mowing, play and the ability to incorporate topdressing on putting greens. Two field trials were initiated to determine the effect of sand size on incorporation, turf quality, and root zone hydraulic properties. The first trial was initiated in 2010 on ‘Greenwich’ velvet bentgrass (Agrostis canina L.) turf maintained at 3.2 mm. Treatments included topdressing biweekly at 0.15 and 0.3 L m^-2 with medium-coarse and medium-fine sands and included an untreated control arranged in a RCBD with three replications. A second trial was initiated in 2011 on annual bluegrass [ABG; Poa annua L. f. reptans (Hausskn) T. Koyama] turf at 3.2 mm and also evaluated the effect of sand size on anthracnose disease (caused by Colletotrichum cereale Manns). Treatments were arranged in a RCBD with four replications and included medium-coarse, medium and medium-fine sands applied at 0.15 L m^-2 biweekly and a control. Initially, there was no turf response to topdressing in either trial; however, once responses occurred, all topdressed plots had better turf quality than the control. Additionally, topdressing with finer sand produced equivalent or better turf quality than plots topdressed with medium-coarse sand. All sands suppressed anthracnose disease in the ABG trial. Volumetric water content (VWC) at 0-3.8 cm depth was greater in control plots than topdressed plots on 50% and 34% of observation dates in the velvet bentgrass and ABG trials, respectively. Very few differences in VWC were found among sand sizes or topdressing rates (velvet bentgrass trial). As expected, topdressing with medium-coarse sand was more difficult to incorporate compared to the finer sands. In 2013, all sand treatments significantly increased water infiltration at near-saturation measured with mini disk infiltrometers and saturated hydraulic conductivity of the velvet bentgrass trial, indicating that all sands were improving the surface root zone by increasing macroporosity.