Virginia Tech Turfgrass Research Course at Independence Golf Club

By Jordan Booth, M.S., CGCS

Established in 2017, the VT Research Course at Independence Golf Club outside of Richmond, Virginia includes nine golf holes with a wide variety of warm-season turfgrasses. The primary focus of research is warm-season ultradwarf putting green management in Virginia. After prolonged cold-temperature exposure during the winter of 2017–2018, the VT Research Course experienced considerable damage on multiple ultradwarf bermudagrass (UDB) putting greens. Damage was variable throughout the course, but four of the nine putting greens needed complete renovation and three of the remaining greens needed partial repairs. During this time of renovation, research was initiated to compare UDB re-establishment methods. This project was arranged in a completely randomized design with three replications, repeated across two UDB putting greens with varied amounts of winter damage. The putting greens were closed to play during this study. Treatments included

1. Treatment 1: Conventional sprigging (SPRIG)

Eradication of turfgrass with 2 applications of 3% glyphosate solution followed by 0.5" ID core aeration, removal of cores, vertical mowing at 0.33" depth and planting of UDB rhizomes and stolons (conventional sprigging).

2. Treatment 2: Core aeration and dragging (CORE)

0.5" ID core aeration, removal of cores, installation of healthy UDB cores, and dragging to break up cores and fill aeration holes

3. Treatment 3: Core aeration and vertical mowing (C+VM)

0.5" ID core aeration, removal of cores, installation of healthy UDB cores, and vertical mowing at a depth of 0.33".

4. Treatment 4: Core aeration and deep vertical mowing (C+DVM)

13mm core aeration, removal of cores, installation of healthy UDB cores, and deep vertical mowing at a depth of 1.0".

Treatments were established on June 7, 2018 and received equal maintenance, fertility, and watering practices. Turfgrass quality was rated weekly on a 1-9 scale with 6 being minimally acceptable. Quality ratings for each treatment over time were transformed into area under the turfgrass quality progress curve (AUTQPC ) for analysis. AUTQPC were subjected to ANO VA and means were compared (Table 1). Percent turfgrass cover ratings were made and each plot reached at least 95% cover 45 days after planting (DAP ). Upon analysis of turfgrass cover vs. DAP , all treatments were best modeled using Gompertz predictive modeling. Inverse prediction via Gompertz modeling was used to calculate approximately how many days it would take each treatment to reach 75% and 95% cover. 75% and 95% cover were chosen as potential thresholds for when golf courses may be able to realistically re-open putting greens.

It is worth noting that treatments 2 (CO RE) and 3 (C+VM) reached 75% cover faster (Table 2) than treatment 1 (SP RIG ). This may be due to the fact that SP RIG required complete eradication of remaining turfgrass while healthy turfgrass that had survived the winter remained and aided in recovery in treatments 2, 3, and 4. Each of the treatments provided complete UDB recovery but there were treatment differences in both turfgrass quality and time to reach both 75% and 95% cover. While treatments 2, 3, and 4 were viable options for recovery, especially in isolated areas of damage, treatment 1 (SP RIG ) was the fastest to reach 95% cover and provided the greatest turfgrass quality after reaching 95% cover. This study will be repeated in the future to validate these results. Initial results indicate that if budget, time, and circumstances allow, eradication of remaining turfgrass, followed by conventional sprigging will result in the fastest recovery and highest turf quality following winter damage to UDB putting greens.