Golf Course Management

JUL 2019

Golf Course Management magazine is dedicated to advancing the golf course superintendent profession and helping GCSAA members achieve career success.

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Page 45 of 139

44 GOLF COURSE MANAGEMENT 07.19 most of the water in the clay loam soil would be contained in very small pores and require much greater suction for plant uptake (water potential approaching –1,500 kilopascals). At equivalent water contents, turf on the sandy root zone may be too wet, while the turf on the clay loam root zone is wilting. Water potential •e good news is that you can use your moisture meter to estimate your water poten- tial with a simple calibration exercise. First, take several measurements shortly after a heavy rainfall or a thorough irrigation. •ese water content values will correspond to a field- capacity water potential — like having a full tank of gas. •en, during a time of year when you can let things dry down a bit, take sev - eral measurements when you begin to see "wilt footprints." •ese water content values will indicate when your greens are approach- ing wilting-point water potential — an empty gas tank. Now you have a window in which to manage the moisture content in your greens. Water content Let's take this a step further. Imagine you've completed this exercise, and the water content on your greens ranges from 5% to 20%. It is likely that you'll decide that 20% is a bit too wet and soft for playability and that you'd rather avoid approaching 5%, where the turf begins to wilt. So, you decide to maintain your greens between 7% and 17% water con- tent to maximize plant health and playability. Now, here comes the big payoff. When measuring trouble spots during the morning, you and your staff will — with a little prac- tice — become very good at estimating how many percentage points of water will be lost that day, based on the weather forecast. You can then quickly determine whether hand- watering is required and, if so, precisely how much water to add to restore the trouble spot to 17% water content. •is strategy has been a game-changer in greens management over the past decade, resulting in less time spent chas- ing hot spots on summer afternoons, healthier turf, better playing conditions and, presum- ably, better nights of sleep for the golf course management team. Rod length Another frequently asked question about using moisture meters is, "What rod length should I use?" Measurement rods vary be- tween 1.5 and 8.0 inches for the predominant moisture meters currently used in the golf industry. We think that a 2- to 4-inch rod is cause negative pressure (suction) is required to move water from soil pores into turf roots. •is suction force is created by transpiration of water from turf leaves, and turf roots can "suck" water from soil pores with a force of up to –1,500 kilopascals. •at is a suction greater than 200 PSI, which is quite impressive. •e relationship between water content and water potential is affected by soil texture and organic matter content. Imagine sandy and clay loam root zones that are both at 20% water content. Turf growing in the sand would need very little suction to move water into its roots (water potential near zero), whereas Participants in the Gadgets and Gizmos seminar at the 2019 Golf Industry Show in San Diego had the op- portunity to play with several high-tech toys — including moisture meters. Photo by Scott Hollister

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