Adam C. Moeller*, Cale A. Bigelow, Jared R. Nemitz, and Glenn A. Hardebeck

Putting greens are routinely topdressed with sand to manage thatch, and smooth and firm the surface.  This multi-year field study has been is designed to determine the topdressing requirements of three widely planted bentgrass cultivars; ‘Penncross’, ‘L-93’, and ‘A-4’, maintained at two nitrogen (N) levels (112 vs. 196 kg N ha^-1 yr^-1) on a sand-based rootzone.  Plots were subjected to five topdressing/thatch management programs: twice annual aerification plus heavy topdressing to back-fill the holes using either a medium-coarse sand that matches the rootzone or a medium-fine sand, each of the aforementioned programs which were supplemented by weekly topdressing throughout the growing season, no aerification but weekly topdressing throughout the growing season with the medium-coarse sand.  Plots frequently topdressed with the finer sand had slower infiltration (57 vs. 76 cm hr^-1), held more (24 vs. 21 m³ m^-3) moisture at the 0-5.7 cm depth, and produced a softer surface (123 vs. 128 gmax).  After three consecutive years of topdressing with the finer sand, 20 out of 24 (83 %) subplots no longer meet USGA rootzone specifications at the 0-5.7 cm depth.  In 2007 we also observed that spring aerification recovery time was notably shorter in plots regularly topdressed with the medium-coarse sand.  Non-aerified plots had the highest surface organic matter (SOM) and the most dollar spot incidence among topdressing programs.  ‘A-4’ and ‘L-93’ had more SOM than ‘Penncross’ but slightly softer surfaces.  Low N plots had the firmest surface, but the lowest TQ.  ‘A-4’ and ‘L-93’ had higher TQ than ‘Penncross’, especially when frequently topdressed during the summer.  This research is ongoing and will result in more meaningful recommendations for sand topdressing practices to meet varying quality expectations and desired management intensities.