Objectives: Rationale:

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1 Evaluation of Various Sand Topdressing Practices on Three Creeping Bentgrass Cultivars Maintained Under Two Fertility Levels on a Research Golf Green, 2006 Purdue University Adam C. Moeller and Cale A. Bigelow Objectives: Rationale: Determine the topdressing requirements of three widely planted bentgrasses maintained under two nitrogen levels. Monitor the long-term changes in rootzone physical properties of a sand-based putting green rootzone topdressed with varying sand sizes and application frequencies and observe the effectiveness of applying topdressing frequently in replace of aerification. Sand topdressing is applied to putting greens for thatch management and to provide a smooth and firm surface. Some thatch is desirable because it provides a cushion for traffic and absorbs the impact of a golf ball. Excessive thatch, however, is very detrimental as it predisposes the turf to pest damage and may make the turf more prone to scalping. The cultural requirements necessary to manage thatch in high shoot density bentgrasses like A-4 have not been well documented. If the sand size does not match the existing rootzone the soil physical properties could decline. How it was done: Three bentgrass [Agrostis stolonifera L. var palustris (Huds.) Farw.] cultivars; Penncross, L-93, and A-4 were seeded to a sand-based research green. Five thatch management programs: no aerification but topdressed frequently, twice annual aerification (Apr/Sept) plus back-filling the holes with either a sand that matches the underlying rootzone or a finer topdressing sand, aerification plus weekly topdressing of either a traditional sand or fine sand, are being evaluated under two nitrogen fertilization ( 112 vs. 196 kg N ha-1yr-1) regimes. Plots were rated visually for overall turfgrass quality on a 0 to 10 scale where 0 equals brown or dead turf and 10 equals optimum greenness, density and uniformity. Canopy greenness was quantified weekly using a hand-held chlorophyll meter (Spectrum Technologies CM-1000). Soil water content was collected using time domain reflectometry (POGO Soil Sensor). A Clegg Impact Soil Tester was used to measure surface hardness (0.5 kg model). A double ring Turf-Tec Infiltration Ring (model IN5-W) was used to measure infiltration rates. Tiller density was measured by three times throughout the season. Dollar spot infection centers were counted as disease outbreaks occurred. Results to date: Tiller density results were as expected, A-4 had the highest number of tillers and Penncross had the lowest number of tillers. Surface hardness was lower in A 4 and L 93 compared to Penncross. Non-aerified plots yielded the firmest surface while topdressing frequently with fine sand had the softest surface. This is correlated with the data that shows that the fine topdressing sand leads to higher soil water content. TQ was highest in non-aerified plots although they had significantly more dollar spot during disease outbreaks. The plots frequently topdressed with fine 1

2 sand produced the lowest TQ, likely because of higher percentages of moss. L-93 at the high annual N rate had the best TQ among all cultivars while Penncross at the low annual N rate had the lowest TQ, primarily because of higher amounts of moss and increased dollar spot. Among cultivars across all cultivation and N levels A 4 had the most dollar spot. These results are first year data with the exception of one dollar spot measurement. Particle size distribution within the thatch and percent organic matter has yet to be analyzed. Figure 1. Medium-coarse and medium-fine topdressing sands for five thatch management programs 2

3 70 60 Medium-coarse Medium-fine 50 % mm 1mm 0.5mm 0.25mm 0.15mm 0.1mm 0.05mm <0.05mm Figure 2. Particle size distribution of two topdressing sands. Figure 3. Aerification occurred on April and 15 September using 5/8 th inch hollow tines. Cores were back-filled with either the medium-coarse or medium-fine sand. 3

4 Figure 4. Light, frequent topdressing applications were made every 7-10 d. Main plots shown here separate thatch management programs and are comprised of three different bentgrass cultivars and two N levels. Figure 5. N response after 24 kg N ha -1 was applied on 15 October 4

5 Figure 6. Dollar infection centers were counted during periods of disease outbreak. Penn A-4 plots had the highest amounts of infection centers per cultivar and non-aerified main plots had the highest amounts per thatch management program throughout all rating dates. Figure 7. Moss incidence was observed on plots receiving frequent topdressing applications with the medium-fine sand. 5

6 Figure 8. Infiltration rates were measured twice during the summer for each plot using a doublering turf infiltrometer A-4 High N A-4 Low N L-93 High H L-93 Low N Penncross High N Penncross Low N Tillers 5cm Jun 27-Jul 24-Aug 13-Oct Figure 9. Turf density was determined for all cultivars maintained under both N levels. 6

7 Table 1. Soil particle size distribution and physical properties of the sand-based rootzone. Soil particle size distribution and physical properties of the sand-based rootzone Soil Separation (%) Sieve fraction sand particle diameter (% retained) Sand Silt Clay Gravel V. Coarse Coarse Medium Fine V. Fine V. Fine < mm Bulk density K Sat Total porosity Organic matter g cm -3 cm h -1 % % Table 2. Particle size distribution of two sands used for topdressing. Sieve fraction sand particle diameter (% retained) Gravel V. Coarse Coarse Medium Fine V. Fine V. Fine Silt / Clay Sand source > < mm Medium coarse Medium fine

8 Table 3. Turf density of three creeping bentgrass cultivars under two fertility levels, Purdue University, Turf density Cultivar Annual N rate 28 June 27 July 24 Aug 13 Oct Number of tillers / 5 cm A kg N 60.5 a 45.3 a 46.3 a 57.8 a A kg N 55.3 a 44.1 ab 39.8 b 53.1 a L kg N 42.0 bc 37.5 c 38.0 b 47.5 b L kg N 46.1 b 40.1 bc 38.5 b 47.6 b Penncross 196 kg N 33.1 d 28.9 d 29.1 c 39.6 c Penncross 112 kg N 36.5 cd 26.4 d 21.6 d 37.9 c LSD Tillers were counted by hand from 5 cm 2 plugs removed from each non-aerified plot. Fertilizer was applied in granular and liquid formulations throughout the year. *Means in the same column followed by the same letter are not significantly different according to Fisher s protected LSD Table 4. Surface hardness measurements of three creeping bentgrass cultivars under two fertility levels, Purdue University, Surface hardness Cultivar Annual N Rate 24 May 29 June 13 October Surface hardness (g max ) A kg N 101 a 115 a 114 a A kg N 104 ab 120 b 117 ab L kg N 106 abc 121 b 119 bc L kg N 108 bc 123 b 118 ab Penncross 196 kg N 109 c 129 c 122 cd Penncross 112 kg N 115 d 135 d 125 d LSD Hollow tine aerification 14 April and 14 September. Fertilizer was applied in granular and liquid formulations throughout the year. *Means in the same column followed by the same letter are not significantly different according to Fisher s protected LSD 8

9 Table 5. Surface hardness measurements of five topdressing regimes, Purdue University, Surface hardness Treatment Sand particle size 24 May 29 June 13 Oct Surface hardness (g max ) No Aerification + Frequent Topdressing Medium coarse 115 a 128 a 134 a Seasonal Aerification + Seasonal Topdressing Medium coarse 109 b 128 a 121 b Seasonal Aerification + Frequent Topdressing Medium coarse 104 c 120 c 113 cd Seasonal Aerification + Seasonal Topdressing Medium fine 106 bc 124 b 116 c Seasonal Aerification + Frequent Topdressing Medium fine 103 c 118 c 112 d LSD Hollow tine aerification on 14 April and 14 September. Sand particle size distribution content seen in Table 1. *Means in the same column followed by the same letter are not significantly different according to Fisher s protected LSD. Table 6. Volumetric water content of five topdressing regimes, Purdue University, Treatment Sand particle size 3 May 19 May 14 June 17 July 13 Aug Volumetric water content (%) No Aerification + Frequent Topdressing Medium coarse 19.2 a 19.7 bc 20.5 bc 16.9 a 16.6 a Seasonal Aerification + Seasonal Topdressing Medium coarse 17.4 b 18.5 a 19.6 ab 16.8 a 16.7 a Seasonal Aerification + Frequent Topdressing Medium coarse 17.5 b 18.4 a 19.0 a 16.4 a 16.9 a Seasonal Aerification + Seasonal Topdressing Medium fine 18.6 ab 19.2 ab 19.9 abc 17.2 a 17.3 a Seasonal Aerification + Frequent Topdressing Medium fine 19.4 a 20.4 c 21.1 c 18.5 b 18.9 b LSD Hollow tine aerification 14 April and 14 September. Sand particle size distribution content seen in Table 1. *Means in the same column followed by the same letter are not significantly different according to Fisher s protected LSD. 9

10 Table 7. Infiltration rate of five topdressing regimes, Purdue University, Infiltration rate Treatment Sand particle size 30 June 16 August Infiltration rate (cm/h -1 ) No Aerification + Frequent Topdressing Medium coarse 81.2 cd 91.4 a Seasonal Aerification + Seasonal Topdressing Medium coarse a b Seasonal Aerification + Frequent Topdressing Medium coarse 98.9 b 92.9 a Seasonal Aerification + Seasonal Topdressing Medium fine 86.9 c 89.5 a Seasonal Aerification + Frequent Topdressing Medium fine 73.0 d 70.6 c LSD Hollow tine aerification on 14 April and 14 September Sand particle size distribution content seen in Table 1. *Means in the same column followed by the same letter are not significantly different according to Fisher s protected LSD. 10

11 Table 8. Infiltration rate of three creeping bentgrass cultivars, Purdue University, Infiltration rate Cultivar Annual N rate 30 June 16 August Infiltration rate (cm/h -1 ) A kg N a 99.3 a A kg N 96.7 ab 97.0 ab L kg N 93.1 abc 93.7 abc L kg N 87.7 bc 86.0 bc Penncross 196 kg N c 85.6 bc Penncross 112 kg N 87.9 bc 82.8 c LSD Infiltration rate measured through time of water to empty from the center ring of a double-ring infiltrometer. Fertilizer was applied in granular and liquid formulations throughout the year. *Means in the same column followed by the same letter are not significantly different according to Fisher s protected LSD. 11

12 Table 9. Turf quality, percent moss, and dollar spot infection centers on five topdressing regimes and three creeping bentgrass cultivars, Purdue University, Turf quality, percent moss, and dollar spot infection centers Mean turf quality Percent moss Dollar spot infection centers 24 Jul 05 1 Aug 06 9 May 22 May 1 Aug 11 Aug Treatment Sand particle size Turf quality rating ± --- % Moss / plot Number of infection centers / plot --- No Aerification + Frequent Topdressing Coarse 8.3 a 0.11 a 0.33 a 4.33 c 10.8 c 18.9 c 32.7 a Aerification + Seasonal Topdressing Coarse 7.7 c 0.12 a 0.41 ab 0.29 a 1.92 a 3.21 a 13.1 d Aerification + Frequent Topdressing Coarse 7.9 b 0.44 ab 0.41 ab 0.67 a 4.79 ab 10.9 b 19.7 cd Aerification + Seasonal Topdressing Fine 7.8 bc 0.86 b 0.87 b 1.50 ab 9.75 bc 12.1 bc 22.1 bc Aerification + Frequent Topdressing Fine 7.6 c 1.75 c 1.95 c 3.42 bc 12.7 c 12.6 bc 29.0 ab LDS Cultivar Annual N rate A kg N 8.1 b 0.02 a 0.05 a 4.25 a 19.9 a 34.3 a 47.9 a A kg N 7.5 d 0.05 a 0.10 a 5.45 a 21.8 a 21.7 b 36.6 b L kg N 8.6 a 0.10 a 0.05 a 0.30 b 0.80 b 3.70 c 16.2 cd L kg N 7.8 c 0.32 a 0.25 a 0.80 b 2.20 b 4.05 c 12.0 cd Penncross 196 kg N 8.0 b 1.06 b 1.80 b 0.70 b 1.85 b 3.60 c 19.2 c Penncross 112 kg N 7.0 e 2.40 c 2.55 c 0.75 b 1.45 b 1.95 c 8.2 d LDS Hollow tine aerification 14 April and 14 September. ± Turf quality was visually assessed on a 0-10 scale where 10 = very dense, uniform, dark green turf. Sand particle size distribution content seen in Table 1. Fertilizer was applied in granular and liquid formulations throughout the year. *Means in the same column followed by the same letter are not significantly different according to Fisher s protected LSD. 12