1998 Iowa Turfgrass Research Report
Managing Bentgrass Stress on Putting Green Slopes
David D. Minner, Nick E. Christians, Iowa State University
Tom Verrips, Otter Creek Golf Course, Ankeny, IA
Meaningful research is necessary if superintendents are to make confident changes in their golf management program. A recent GCSAA survey showed that 82% of the respondents felt that "research trials conducted on golf courses yield more accurate and usable information for the golf industry than the same trials conducted on university field plots". The actual research location may not be so important but the take-home message here is that researchers must begin to manage field plot facilities under the same level of stress that actually occurs under golfing conditions. For example, intense traffic, extremely low mowing height, and excessive ball marks are seldom found in research plots. Further more, research greens are usually perfectly flat, often deep rooted, and seldom require a regiment of hand watering even during hot and dry summers.
Difficult summer growing conditions, such as high temperature and moisture extremes, can dictate the fate of problem greens even when the best turf management practices are used. Excessive rain followed by high humidity and heat leads to a shallow dysfunctional root system. Dry spots develop and greens require more frequent watering. Summer diseases begin to show up and fungicide application is increased. Some turf loss occurs and algae begins to invade the moist surface where grass is thin. The amount of turf loss in any given year is unfortunately dependent upon the weather and how long the adverse conditions persist. Turf management practices are usually applied uniformly across a putting surface, however problem areas on a green are anything but uniform. Severe turf loss occurs in high stress areas of putting greens, and therefore, it is important to evaluate management practices and products under realistic conditions of high stress.
A sloped research green (SRG) was constructed at the Horticulture Research Station, Ames, IA, in 1997 to evaluate bentgrass management under difficult and variable growing conditions. The green was seeded with Crenshaw creeping bentgrass in September 1997 and currently has 70% turf cover. Treatments are scheduled to begin September 1998. Construction of the green was funded by Iowa State University, Iowa Golf Course Superintendents Association, and the Golf Course Superintendents Association of America. The SRG was erected to simulate the undulating topography that occurs on many putting greens - as opposed to a typical flat research green. The sand-based portion of the SRG is 100 ft by 40 ft by 1 ft. The subgrade, gravel blanket, and sand rootzone all follow the same contour. The 12-inch sand rootzone contains no amendment and is positioned over a 4-inch gravel blanket with 4-inch drain lines. The SRG has four distinct microenvironments that will be simultaneously evaluated for nine different treatments. The microenvironments are:
To our knowledge, the type of sloped green project that we are proposing has never been used for putting green research.
No amendments, organic or inorganic, were used to construct the 12-inch rootzone. The sand has a pH of 8.2 and is calcareous. Topdressing treatments will begin in 1998 and will be routinely applied to 40 ft. by 3.5 ft plots. The long and narrow plots are situated so that each treatment covers all four distinct micro-environments on the green. This plot arrangement allows for three replications of nine topdressing treatments. The nine topdressing treatments include combinations of organic (Dakota Peat or hypnum peat) and inorganic amendments (porous ceramic clay, diatomaceous earth, and zeolite).
To evaluate treatments and simulate actual growing conditions, greens will receive routine traffic and mowing at 0.135 inches (3.4 mm). Simulated traffic (18,000 rounds per year) will be applied with a Brouwer TR224 cleated roller that was converted to apply differential slip type traffic (design by Dr. Bob Carrow). Heavy spring rains will be simulated by excessive irrigation in May. Dry conditions will be simulated by restricting irrigation on a temporary basis from June through August. A "spoon feeding" fertility program will be applied based on soil and tissue testing results from the non-amended control plots.
We are not seeking subtle differences in turf quality, but instead seek the difference between survival and complete loss of turf that may be related to stresses that accumulate on sloped areas of greens.
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ISU Horticulture:Publications:1998 Turfgrass Report | College of Agriculture |