Sand-capping effects on bermudagrass fairways

Growing demands for limited water resources mean that golf courses increasingly are being managed with poor-quality irrigation water. Because of this and the need for improved playing conditions, sand-capping fairways has become common in new golf course construction and renovation. Sand-capping can be particularly beneficial on sites where fine-textured soils have been irrigated with poor-quality water and elevated sodium levels have degraded physical properties of the soil and led to excessive fairway wetness, slow drainage, high runoff, poor aeration or severe compaction.

Key objectives of this 3-year project are to evaluate Tifway bermudagrass (Cynodon dactylon [L.] Pers. x Cynodon transvaalensis Burtt-Davy) root development and fairway performance as influenced by four capping depths (gradual buildup to 2 inches by topdressing and initial applications of 2, 4, and 8 inches of sand) atop two subsoils (clay loam and sandy loam). In addition, we are seeking to determine how sand-capping and subsoil combinations influence irrigation frequency requirements, root-zone soil moisture dynamics and development of subsoil sodicity over time. In the final year of the study, a 60-day summer dry-down will be imposed to evaluate turf response and recovery characteristics as influenced by sand-cap and subsoil treatments.

Results to date have shown that sand-capping depth influences sprig establishment. Plots that were not initially capped with sand (topdressed only) reached nearly full establishment after only eight weeks. However, establishment times were progressively delayed with increasing depth of the sand caps. Also, sodicity of subsoils increased sharply over a relatively short period of time due to high sodium concentration (270 ppm) in the irrigation water; However, this rate of increase was delayed by sand-capping. Interestingly, once established, levels of percent green cover in plots have been largely unaffected by capping depth or by irrigation frequencies of one or two days per week (at 60 percent of reference evapotranspiration).

USGA recommendations currently do not exist for either particle size or depth of capping sand. This study may lend insight into development of recommendations for the physical properties of capping sands and how those properties should differ from those currently used for sand in USGA-design putting greens.

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