Figure 8: FG1 VCS
Thatch Layer: Stain Layer:
Original Layer: USGA Specs.:
0.9 1.6 3.9
CS MS FS
15.5 37.3 26.8 27.2 35.6
42.3 39.7
60% VFS
23.1 17.0
18.9 5.3 3.5
S + C
------------------------------------ % by weight ------------------------------------ 0.02 0.0 0.2
0.6 0.4 0.1
< 10% 20% 10%
Table 1. Particle sizes expressed as percentage by weight in the thatch, stained layer, and underlying original rootzone layer measured in October 2013 from the means of four undisturbed soil core samples per putting green, with two putting greens sampled on each of four golf courses in south- ern Florida and compared with USGA specifications for new construction of golf course putting green rootzones for each particle size classification.
Te answer is in the changing nature of the sand particle sizes over time. In Table 1, the relative differences of the sands in the original mix is compared to the sand in the built-up stain layer and surficial thatch layer. From these four courses, it can be shown that the original materials fit within the USGA specifications percent wise (Table 1). By 2013, there was a large shift from larger sand sizes with larger pores to smaller sand sizes that were higher in percentage than suggested (Table1). Tis shift was having a major impact on decreasing saturated conductivity. Tat change can have direct effects on water and disease management. Why the change was occurring is up for debate. It could be a combination of sand size selection in topdressing and segregation of sands applied that either are removed during routine mowing with coarser materials not penetrating as much into the canopy. Many managers select smaller particle sizes to get more sand into the profile as ultradwarfs provide dense canopies. Some try to overcome this bias with coarser materials during summer cultivation and introduce coarser sand into aeration holes to achieve a blending of the materials over time.
Te information we have provided here today has been used by managers to monitor their practices and to provide information to their stakeholders on why such practices are necessary in order to obtain the quality playing conditions required by golfers.
John L. Cisar, PhD, has retired as Professor of Turfgrass Management and Water, University of Florida, Ft. Lauderdale Research and Education Center. He is currently a private agronomic consultant and Turf News editorial advisor for warm-season grasses. Michael Fidanza, PhD, is Professor of Plant and Soil Sciences and Director of the Center for the Agricultural Sciences and a Sustainable Environment, Pennsylvania State University, Berks Campus, and 2018 Chair of Division C5 (Turfgrass Science) of the Crop Science Society of America (CSSA).
TPI Turf News March/April 2018 49
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