Golf Course Management

JUN 2018

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 71 of 105

64 GOLF COURSE MANAGEMENT 06.18 layer) at the sand/gravel interface. • e plastic barrier (the wicking barrier) that is sometimes installed vertically at the green perimeter is considered optional in a USGA green. Additional information on the use of this plastic liner is available in the docu - ment "Building the USGA Putting Green: Tips for Success." • e laboratory professionals identified the Micro-Deval abrasion test (ASTM D6928) as the preferred method for evaluating the mechanical stability of gravel. is test is more accurate and repeatable when com - pared to the formerly used sulfate soundness and L.A. Abrasion test. e Micro-Deval method tests the stability of material when immersed in water, which more closely rep - licates the conditions the gravel will endure in a putting green environment. • Finally, the review committee unani - mously agreed it was important to educate courses on the potential hazard of placing low-pH root-zone mixtures over high-pH gravel materials. is scenario may con - tribute to the formation of iron oxide lay- ers at the root-zone and gravel interface. e USGA is continuing to fund research on this topic to discover preventive and cu - rative solutions. Step 5. e root-zone mixture e section on selecting a root-zone mix - ture was a focus of the 2018 revisions and re- ceived much of the attention during the revi- sion process. e 2018 revision better educates the reader on the intricacies of selecting a root- zone material and allows courses to customize root-zone mixes to fit the local environmental conditions and golfer expectations at their fa - cility. For example, because of golfer feedback, some courses have expressed interest in pro - viding very firm putting surfaces. is docu- ment explains how to select sand root-zone materials that are more likely to provide such conditions. e primary revisions in Step 5 are listed below. • Expanded explanation of root-zone materials. e 2018 revision delivers better guidance on how to customize the root-zone mixture for your site conditions and golfer expecta - tions. • Calcareous sands. Highly calcareous sands such as coral should be avoided for root- zone material. • Root-zone stability and putting green firm - ness. A CU range (coefficient of unifor- mity) has been included. e CU should range from 1.8 to 3.5 for mixtures con - taining peat and from 2 to 3.5 for mixes with sand only or with sand amended with inorganic materials. • Sand shape. In addition to influencing the coefficient of uniformity, sand shape also affects stability and putting green firmness. • Organic matter selection. ere is expanded information on using various organic amendments, including composts, along with the recommended chemical and physical characteristics when using such materials. • Value-added products. Other organic prod - ucts such as biochar, humates, seaweed products and vermiculture byproducts are described as "value-added" and not a re - placement for peat or inorganics. Dr. Hum- mel stressed that, if these products are used, courses must include the product(s) at the intended rate in the performance testing evaluation. • Physical properties of the root-zone mixture. e recommended infiltration rate (Ksat) remains unchanged at a minimum of 6 inches per hour. However, the review com - mittee commented that historically too much emphasis has been placed on this one characteristic without much thought given to moisture retention. erefore, the section on the physical properties of the root-zone mixture has been enhanced to better ex - plain the moisture-retention characteristics of a root-zone mix. is document empha - sizes moisture retention — that is, capillary porosity — while retaining air porosity. In the recommendations, Dr. Hummel wrote "if the capillary porosity of a root-zone mix is within the recommended range, the mix should not be excessively droughty even if the Ksat is high." erefore, courses can have their cake and eat it too! ey can have ample water-infiltration rates and still have adequate moisture retention with the right mixture. • Quality-control testing. ere is expanded discussion and explanation on using the provided confidence intervals to evalu - ate the quality of the root-zone materials through the green construction process. A few of the confidence intervals were ex - panded based on feedback from the labo- ratory personnel, the sand-blending com- panies and the soil experts on the review committee. For example, the infiltration rate confidence interval increased to 25% (from 20%) to account for the variability of this laboratory test. For more informa - tion on how to accurately sample sand and root-zone piles, read the article, "Quality Control Sampling of Sand and Root-zone Mixture Stockpiles." Samples of root-zone mixtures destined for laboratory testing should be collected on-site at the production facility.

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