MANAGEMENT PRACTICES AFFECTING PUTTING GREEN SPEED. The management practices identified in the survey of golf courses

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1 MANAGEMENT PRACTICES AFFECTING PUTTING GREEN SPEED The management practices identified in the survey of golf courses that possibly affect putting green speed were further evaluated in field trials. The factors were examined individually or in pairs under controlled conditions so their effect could be accurately determined. Establishment and Maintenance Level II Area All experiments except one were conducted on the Level II creeping bentgrass area at The Joseph Valentine Turfgrass Research Center. The modified soil consisted of an approximately 7:3:1 volume ratio of sand, soil, and peat. The site was modified in the late fall of 1976 and was worked for firm settling and chemically fallowed during the spring and summer of Four separate areas were established in August 1977: (1) Seeded creeping bentgrass block - three varieties, Penncross, Pen~eagle, and Seaside, 6 x 72 feet, with three replications in a randomized block design, (2) Penncross block square feet, (3) Penneagle block square feet, and (4) Varietal creeping bentgrass block - 24 seeded and 12 vegetative entries, 6 x 24 feet, with three replications in a randomized block design. The entire site was developed into a mature putting green type turf over a two-year period with automatic irrigation, two annual topdressings, moderate fertilization, and an average of five mowings per week at 5/32 inch using a Jacobsen Greens King. In 1979 the entire Level II site received a total of 4.6 pounds nitrogen per 1000 square feet from Milorganite and urea form. In 1980 all blocks except the Penncross nitrogen fertility rate block received

2 29 two applications of 1 pound nitrogen per 1000 ft 2 using Scott's : 30 May 1980 and 3 August In 1980 all areas were topdressed on 13 June Level I Area One experiment was conducted on the Level I creeping bentgrass area at The Joseph Valentine Turfgrass Research Center. The site was an unmodified Hagerstown silt loam soil that has been partially modified through the addition of topdressing from two annual topdressings. In 1975 each of four varieties of creeping bent grass were seeded on three plots 6 x 72 feet in a randomized block design. The varieties established were Penneagle, Penncross, Emerald, and an experimental variety designated PSU-2S. The site was managed as a putting green type turf for the past 5 years with automatic irrigation, two annual topdressings, moderate

3 30 fertilization, preventive disease control, and an average of five mowings a week at 5/32 inch. The site was free of ~~ L. infestation. In 1980 the site received preventive disease control, 1 pound nitrogen per 1000 square feet from Scott's , topdressing on 13 June 1980 and 19 September 1980, and sufficient moisture to sustain a quality stand of turf. This site was used to determine the effect of mowing frequency per week on putting green speed. Seeded Creeping Bentgrass Block Materials and Methods Mowing. Until 6 July 1979 the seeded creeping bentgrass block was mowed at 5/32 inch. On 6 July 1979 the variety blocks were divided into three heights of cut blocks, 24 x 54 feet each containing three replications. The mowing height was gradually lowered on a Jacobsen hand mower until two of the blocks were being mowed at 3/32 inch. Slight modifications to the mower were necessary to achieve the 3/32 inch mowing height. The vertical holes on the side of the mower where the reel is fastened had to be filed to allow the reel to be adjusted to a lower position. The mowing height of the remaining block continued to be 5/32 inch. The area was mowed six times a week until mid-september. In 1980 the mowing height of the 5/32 inch block was raised to 6/32 inch. The mowing height of one or the two 3/32 inch blocks was gradually lowered to 2/32 inch beginning on 8 July This block was also mowed with a Jacobsen hand mower. Further modifications to this mower included grinding the bottom of the bed knife to decrease the thickness so the turf could be mowed at 2/32 inch. The remaining block mowed at 3/32 inch in 1979 was mowed at 3/32 inch in 1980 with the same mower used in 1979.

4 31 The mowing procedure followed was to first remove any dew present by either dragging a hose over the area or syringe with water. The entire area was first mowed at 6/32 inch with the Jacobsen Greens King and then the blocks mowed at 3/32 and 2/32 inch were mowed using the Jacobsen hand mowers. This schedule was followed 6 days a week during the summer. This area was used for 4 separate experiments throughout the summer. One experiment was conducted throughout the entire summer and the other 3 were short term experiments that were completed without interfering with the main experiment. Seasonal putting green speed. Beginning on 16 May 1980 and continuing until 17 September 1980 speed was measured on the three varieties at three heights of cut ~ice each week when possible. Speed was measured at approximately the same time of day each day measurements were taken. Measurements were not taken from 13 June 1980 until 24 June 1980 due to topdressing and associated mowing. On a few occasions putting green speed was measured only once a week due to time limitations. A split block experimental design was used in this test. The size and layout of the plots necessitated the use of this design (Cochran and Cox, 1957). The main effects were variety and mowing height, with mowing height stripped across the varieties. Analysis of variance was calculated for each date that putting green speed was measured. Duncan's multiple range test was used to separate variety means. Regression analysis was used to determine the response of putting green speed to different mowing heights. Multiple mowings. This site was also used to determine the effect that multiple mowings, on the same day, have on putting green speed. The effect of multiple mowings was tested on three varieties at three

5 32 mowing heights. The procedure followed was to first remove the dew, measure speed before mowing, and re-measure speed immediately following mowing. This pattern was followed for the second and third mowings. Mowing the plots required 5 to 10 minutes and measuring the putting green speed an additional 25 to 30 minutes. Because of the time required each mowing height block was tested on a different date. The 2/32 inch mowing height block was tested on 30 July 1980, the 3/32 inch block on 27 August 1980 and the 6/32 inch block on 30 August Mechanical difficulties prevented the completion of the third mowing on the 3/32 inch block. The data were analyzed as a split block in time with the number of mowings analyzed as being split in time. Duncan's multiple range test was used to separate variety means and number of mowing means. A separate analysis was conducted for plots at each mowing height. Limited moisture. This area was used to determine the effect of moisture on putting green speed. The area received 0.08 inches of water per day from 19 August to 4 September 1980 with the only rain occurring on 30 August From 5-7 September 1980 the area was again watered at a rate of 0.08 inches per day. There was no further moisture until 10 September In the evening of 10 September 1980 and the early morning of 11 September inches of water was applied to the area. During the morning of 14 September inches of rain fell before putting green speed was measured. A separate analysis of variance was calculat~d for each day putting green speed was measured. A combined analysis of variance was also calculated with dates split in time. Duncan's multiple rang~ test was used to separate the mean putting speed for each date.

6 33 Mowing direction. On 20 October 1980 the 2/32 inch mowing height block was used to determine the effect of mowing height, variety. and direction of mowing on speed. The lengthwise orientation of the plots was east west and all plots were mowed lengthwise. Half of each plot was mowed with the direction of the mower moving east and the opposite half of the plot was mowed with the direction of the mower moving west. Speed was measured on both halves of each plot with the balls being rolled west and then putting green speed was measured on both halves of.the plot with the balls being rolled east. Comparisons were then made between balls rolled with and against the direction of mowing for both east and west directions. Moss cover. Throughout the course of this experiment it was very apparent that at low mowing heights (3/32 and 2/32 inch) a reduction in the turfgrass population occurred. On 21 October 1980 all plots were visually rated for percent moss cover. A one square foot wooden frame was randomly tossed on each plot at four different locations. The area enclosed by the frame was rated for percent moss cover. The average of the four ratings was used to determine the percent moss cover for the entire plot. Mowing height and variety means were separated using Duncan's multiple range test. Results and Discussion Seasonal putting green speed. Putting green speed measured on 29 of 125 days throughout the season was averaged for each plot and the individual plot means were used to calculate an A.O.V. There was a highly significant difference among mowing heights and among varieties. The mean speed measured on Penneagle was 9 feet 2 inches, Penncross 9 feet. and Seaside 8 feet 11 inches. The means for Penneagle and Penncross were not significantly different and the means for penncross and

7 34 Seaside were not significantly different at the 0.05 level using Duncan's multiple range test. There was no significant mowing height by variety interaction. When the data from each date were analyzed individually there were significant varietal differences on 11 dates and a significant mowing height by variety interaction on 7 dates. Figures 4, 5 and 6 show the response of the three varieties at the three different mowing heights. The response of the three varieties within mowing heights is similar but varying in magnitude. A slight decrease in putting green speed was measured on the plots mowed at 6/32 inch following an application of 1 pound of nitrogen per 1000 square feet on 23 May This drop in speed was not measured on either of the other two mowing height blocks because the mowing height was lowered from 6/32 to 4/32 inch on 22 ~ay This apparently counteracted the effect of nitrogen fertilization. A decrease in putting green speed was measured on all mowing heights following the 3 August 1980 application of an additional pound or nitrogen per 1000 square feet. Between 12 June 1980 and 24 June 1980 there was a 22 inch decrease in speed on plots mowed at 3/32 inch and a 13 inch decrease in speed on plots mowed at 6/32 inch. This decrease was due to topdressing on 13 June 1980, and the associated mowing schedule for 10 days following topdressing. The seasonal variation for all three heights of cut was less than 2 feet. This variation is similar to that reported by Radko et al. (1981) that was measured on several golf courses. There was a significant difference among mowing heights on all dates, except on 16 May 1980 when all plots were mowed at 6/32 inch, when the data from each date were analyzed separately. Two regression equations were calculated to explain the response of putting green speed to mowing height. The first equation is for th~ time period until

8 - +- ~ -9 o w 5la z w wffi 7. PENNEAGlE o PENNCROSS ~ Z l- I- :J a May June II July N A August SEASIDE Sept. DATE OF OBSERVATION N- Applied lib. Nitrogen/ 1000 ft. 2 TO H - Topdressed Heavi ly Figure 4. Seasonal variation in putting green speed measured on Penneagle. Penncross. and Seaside creeping bentgrass mowed at 6/32 inch. w V\

9 - II -*ō 10 w wa. (J) Z 9 w a: (!) (!) 8 z l= ir 7 N TO H N II May June July PENNEAGLE o PENNCROSS A SEASIDE August Sept. DATE N- Applied I lb. Nitrogen/ 1000 ft. 2 OF OBSERVATION TO H - Topdressed Heavily Figure 5. Seasonal variation in putting green speed measured on Penneagle. Penncross. and Seaside creeping bentgrass mowed at 3/32 inch.

10 - -'+ō 12 I' w wa. U) z w a:: C) 9 C) Z J-.- ::> n.. TO H PENNEAGLE o PENNCROSS A SEASIDE May II June July August Sept. DATE OF OBSERVATION N- Applied I lb. Nitrogen /1000 ft. 2 TD H - Topdressed Heavily Figure 6. Seasonal variation in putting green speed measured on Penneagle, Penncross, and Seaside creeping bentgrass mowed at 3/32 inch before July a and 2/32 inch July 8 and after.

11 38 8 July 1980 when there were only two mowing heights. The second equation is from 8 July 1980 on when three mowing heights were evaluated. The first equation was calculated by taking the average for each plot from six different days from 6 June 1980 to 3 July The ~ equation calculated was Y = (-.51) H, with H being the mowing height in 32nds of an inch. This equation was highly significant, with 2 an r value of 0.88 which was highly significant. The data had a C.V. of 3.4%. The second equation was calculated from the mean for each plot representing 18 different days from 11 July 1980 to 17 September The equation calculated was Y = (-.65) H, with H being the mowing height in 32nds of an inch. This equation was highly significant with 2 a highly significant r value of The data had a coefficient of variation of 1.2%. Both equations show the inverse relationship between mowing height and putting green speed. As ~he mowing height is lowered, greater leaf removal reduces the resistance to a rolling golf ball and the golf ball rolls a greater distance. Seasonal summary of speeds at three mowing heights is shown in Figure 7. For the 10-week period beginning 11 July 1980 the 6/32 inch mowing height block averaged a speed of 7 feet 10 inches, 3/32 inch block 9 feet 11 inches and 2/32 inch block 10 feet 5 inches. The speeds measured at 6/32 inch were in the range of the majority of the speeds measured on the 24 golf courses. At 2/32 and 3/32 inch the speeds were greater than the speeds measured on any of the golf courses except Oakmont Country Club.

12 - - " :: 10 o w a.. 9 (f) z ~ 8 a:: l? C> Z 7 r- r- a.. ::> N TO H II May June July August 2/32 INCH o 3/32 INCH A 6/32 INCH Sept. DATE OF OBSERVATION N- Applied I lb. Nitrogen /1000 ft. 2 TO H - Topdressed HeaviIy Figure 7. Seasonal variation in putting green speed measured at three mowing heights averaged over varieties.

13 40 Multiple mowings. Data from the 6/32 inch mowing height block showed a highly significant difference among number of mowings but no significant difference among varieties and no significant interaction. Each mowing was significantly different from all other mowings at the 0.05 level. The analyses of putting green speed data measured on the 3/32 inch mowing height block indicated a highly significant difference among number of mowings but no significant differences among varieties and no significant interaction. There was a significant difference among all mowings at the 0.05 level. The analysis of variance of putting green speed measured on the 2/32 inch mowing height block indicated a highly significant difference among number of mowings but no significant differences among varieties and no significant interaction. The mean for three mowings was significantly different from all other mowings. The means for two mowings and one mowing were not significantly different from each other but were significantly different from all other mowings. The mean for no mowing was significantly different from all other mowings. The response of putting green speed to number of mowings at each mowing height is shown in Figure 8. An increase in speed of 8 to 10 inches due to the first mowing was measured at all mowing heights. This increase is due to a major removal of new growth from the previous day. The increase measured in speed between the first and second mowing varied by mowing height. An increase of 6 inches was measured for the 6/32 inch mowing height. This compared with 4 and 1 inch increases, respectively, for the 3/32 and 2/32 inch heights. An increase in speed of 5 to 7 inches was measured due to the third mowing. The increases

14 41 II w w a... en 9 z w 0::: 8 ~ 2/32 INCH 0 3/32 INCH r- 7 r- ~ ::::> 6/32 INCH a... ~ Z NUMBER OF MOWINGS Figure 8. Effect of multiple mowings on the same day at three mowing heights. averaged over varieties on putting green speed.

15 42 measured in speed following the second and third mowings were due to removal of leaves not mowed during the first or second mowing. Limited moisture. The average putting green speed was calculated for each plot over the 5 days speed was measured. Analysis of variance calculated using these means indicated no significant difference among varieties, a highly significant difference among mowing heights, and no variety by mowing height interaction. A regression equation was calculated to explain the response of putting green speed to mowing height. The equation is Y = (-.72) H, where H is the mowing height in 32nds of an inch. This equation had a highly significant F value and a highly significant r 2 value of The coefficient of variation for the data was 1.7%. The putting green speed measured each day was analyzed as being split in time. The analysis of variance indicated a highly significant difference among dates, among mowing heights, and a highly significant date by mowing height interaction. Since there was a highly significant date by mowing height interaction the data from each mowing height were analyzed separately as a split block in time. There was a significant difference among dates at the 2/32 inch mowing height and a highly significant difference among dates at the 3/32 inch and 6/32 inch mowing heights. There was also a significant difference among varieties at the 6/32 inch mowing height. There were no significant interactions at any mowing height. The effect of moisture on putting green speed at the three mowing heights is shown in Figure 9. The results of the mean separation procedure at each mowing height are shown in Table 10. The only significant decrease in speed following

16 I I 0 w a.. en 10 z w 2/32 INCH W a:: o 3/32 INCH C> 9 <.=> 6 6/32 INCH Ẕ t- t- 8 :J 0-7 W-Water, W W 10 II DATE September OF OBSERVATION from either irrigation or rain Figure 9. Effect of water, either irrigation or rain, on putting green speed at three mowing heights averaged over variety.

17 44 Table 10. Putting green speed measured each day, averaged over varieties, for each mowing height. Date Putting Green Speed /23 inch mowing height September 12 8' 3" a September 14 8' 3" a September 13 8' I" b September 11 7'10" c September 10 7' 9" c /32 inch mowing height September 12 September 13 10' 4" a 10' 4" a September 11 10' 2" ab September 14 10' a" bc September 10 9'10" c /32 inch mowing height September ' 4" a September 10 11' 1" a September 13 11' 1" a September 11 10'11" a September 14 10' 5" b Means within a mowing height followed by the same letter are not significantly different at the 0.05 level.

18 45 irrigation or rain was on 14 September A decrease of 8 inches in speed at the 2/32 inch, and a 4 inch decrease at 3/32 inch height were measured when compared with speed measured the previous day. There were significant increases in speed on 14 September 1980 at the 6/32 inch mowing height and on 11 September 1980 at the 3/32 inch mowing height. On both days there was rain or irrigation the previous evening. The effect of water on putting green speed varied by mowing height because the condition of the thatch is more important in determining speed at lower mowing heights. At low mowing heights the ball may come in contact with the thatch while at higher mowing heights the ball is supported above the soil surface by the turfgrass canopy. At low mowing heights when the thatch dries it becomes more firm and a golf ball will roll further increasing putting green speed. Mowing direction. Speed was averaged over varieties at a 2/32 inch mowing height on both halves of the plot for each direction of measurement. When speed was measured with balls rolled east the average speed was 10 feet 7 inches on the half of the plot that was mowed with the mower moving east and 9 feet 10 inches on the opposite half of the plot. When speed was measured with balls rolled west the average speed was 9 feet 9 inches on the half of the plot that was mowed with the mower moving west and 9 feet on the opposite half of the plot. The difference was taken between speed measured with and against the direction of mowing. The differences were used to calculate an A.O.V. There were no significant differences among varieties. The differences in putting green speed due to mowing direction were: Seaside 12 inches, Penneagle 9 inches and Penncross 7 inches. Putting green speed was consistently greater when the golf ball was rolled with the direction of mowing because mowing orients the leaves

19 46 in the same direction, a difference visually observable on putting greens, football fields, etc. When a golf ball was rolled with the orientation of the leaves the resistance was less and the golf ball rolled farther, thus increasing putting green speed. Moss cover. An analysis of variance was calculated using the percent moss cover for each plot. There was a significant difference among varieties, a highly significant difference among mowing heights and a highly significant mowing height by variety interaction. Table 11 shows the percent moss cover for each variety at each mowing height. The values are means of three replications at each mowing height. The means for variety and mowing height are the mean of nine values. As the mowing height is decreased the stress on the creeping bentgrass increases and a reduction in population occurred and the moss population increased. The varietal differences were significant but the ability of one variety to tolerate close mowing while another cannot is not known and should be researched further. Morphology or vigor of growth may be possible explanations for the varietal differences. Penncross Block Materials and Methods Mowing. Beginning 6 July 1979 the Penncross block was divided into six randomized blocks, 34 x 42.5 feet. The mowing height on three of the blocks was gradually lowered to 3/32 inch using a Jacobsen hand mower. The remaining three blocks were mowed at 5/32 inch with a Jacobsen Greens King. From 6 July 1979 until mid September this area was mowed six times a week and at lesser frequencies thereafter.

20 47 Table 11. Percent moss cover on three varieties of creeping bentgrass at three mowing heights. Mowin~ Height (inch) 6/32 3/32 2/32 Mean Penneagle b Penncross ab Seaside a Mean 2 a 29 b 46 c Means followed by the same letter are not statistically different at the 0.05 level. Comparisons should be made within a row or column only.

21 48 In 1980, the mowing height of the 5/32 inch blocks was raised to 6/32 inch and mowed with a Jacobsen Greens King and the 3/32 inch blocks were again mowed at 3/32 inch with a Jacobsen hand mower. Most of the season this area was mowed six times a week. Dew was removed, using a hose or syringe irrigation. Following dew removal the entire area was first mowed at 6/32 inch and then the three blocks mowed at 3/32 inch were mowed by hand. Nitrogen levels. In 1980, five nitrogen fertility level treatments were imposed on the height of cut blocks to ascertain the effect of nitrogen on putting green speed. The levels were: I, 2, 3, 4, and 6 pounds nitrogen per 1000 square feet per season. The nitrogen source was a Scott's fertilizer, 33% water insoluble nitrogen. The nitrogen was derived from urea and methylene urease Dates and rates of fertilizer applications are shown in Table 12. Nitrogen fertility level and mowing height test. Putting green speed was measured on these plots 14 times at approximately weekly intervals throughout the summer. Measurements were made at approximately the same time of day on each of the 14 days. The experimental design for this area was a randomized complete block. Main treatments were the two mowing heights in three replicated blocks. Subplots within each mowing block were five 6 x 42.5 feet nitrogen treatment plots, on which the five nitrogen fertility treatments were applied. Treatments were randomized within each block and each treatment was replicated six times. Multiple linear regression was used to ascertain the change in putting green speed due to the different nitrogen fertility treatments and mowing heights. An equation

22 49 Table 12. Dates and rates of nitrogen applications Nitrogen Applied in Pounds per 1000 Square -- May June June July August August September Total N Applied

23 was applied to the 5.5 pound nitrogen ploc. 50 predicting putting green speed was calculated for each date speed was measured. Repeatability. To determine the repeatability of measuring putting green speed using the Stimpmeter, speed was measured three times on six plots that varied in nitrogen level and mowing height. Each time the speed was measured on a plot it was at a slightly different location than the locations of previous measurements. The treacnents were I, 3, and 6 pounds nitrogen per 1000 square feet at the mowing heights of 6/32 and 3/32 inch. Except for these treatments the plots were maintained in the same manner. The standard error of the mean and coefficient of variation were calculated for each set of measurements on each plot. Change in speed throughout the day. Putting green speed was measured at 2-hour intervals beginning at 0900 and continuing until Dew was removed and the plots mowed before the 0900 readings. On 13 August 1980 this procedure was followed for plots mowed at 6/32 inch and with nitrogen fertility rates of 1, 2.5, and 4.5 pounds nitrogen per 1000 square feet. The most recent nitrogen application to the 1 pound plots was on 10 July 1980 when 0.5 pound of nitrogen was applied. On 1 August pound of nitrogen was applied on the 2.5 pound plot and 1 pound of nitrogen was applied on the 4.5 pound plot. On 3 September 1980 this procedure was repeated for plots mowed at 3/32 inch and I, 3. and 5.5 pounds nitrogen per 1000 square feet. The most recent nitrogen application to the 1 pound plot was on 10 July 1980 when 0.5 pound nitrogen was applied. On 22 August pound nitrogen was applied to the 3 pound nitrogen plot and 1 pound nitrogen

24 51 Single versus double daily mowing. In August the 6 x 42.5 feet nitrogen plots were divided in half to evaluace the effect of single versus double daily mowing on speed. The nitrogen levels of 1, 3, and 5.5 pounds were tested ac both 6/32 and 3/32 inch mowing heighcs. Prior to beginning the double mowing treatmenc, putting green speed was measured on all plots to determine if there were differences between the,plots. Half of the plots were then double mowed for eight consecutive days. On the ninth day all the plots were mowed once. Each day the speed was measured on all the plots at approximately the same time. The experimental design was a modification of the split plot design. A separate analysis was calculated for each day that speed was measured. Limited moisture. Moisture was limited to 0.08 inches per day from 19 August to 30 August Rain fell on 30 August The plots were not watered from 31 August 1980 unci! after putting green speed was measured on 10 September 1980 although minor amounts of rain fell during this period. Following the measurement of putting green speed on 10 September inches of water was applied. Another 0.08 inches of water was applied on the morning of 11 September 1980 before putting green speed was measured. On 13 and 14 September inches of water was applied in the early morning preceding measurement of putting green speed. In addition 0.3 inches of rain fell in the early morning af 14 September No wacer was applied and no rain fell on 15, 16, or 17 September PUCting green speed was measured on these plots on 8, 9, 10, 11, 12, 13, 14, 15, and 17 September _.-lys1s of "adtace was caj.eulace.d for caehd*ta,put:tf.tig <gl'een $peed 'WW......,.... Cblt&. for alldatea wer bf.ttedad'. ~, a ~,1t~ Ia taa. The. 41.1:& f._i' eacjl. 4" WllIP"e.. ~t '... t...

25 S2 Mowing direction. On 29 September 1980 all plots in this test were used to detennine the effect of mowing height. nitrogen fertility level, and mowing direction on speed. The orientation of the plots was north south and all plots were mowed lengthwise. Half of each plot was mowed in opposite directions. Speed was measured on both halves of the plot with the balls being rolled north. and re--measured on both halves of the plot with the balls being rolled south. Comparisons were then made be~een putting green speed measured with and against the direction of mowing for both north and south directions of ball roll. Moss cover. Observation of plots mowed at 3/32 inch revealed that the amount of moss present was more abundant when compared to the plots mowed at 6/32 inch. On 22 October 1980 all plots were visually rated for percent moss cover. The rating method used was to randomly toss a one square foot wooden frame on six locations within the plot. At each location the area within the frame was rated for percent moss cover. The six ratings within a plot were used to calculate a mean for the entire plot. An analysis of variance was calculated using the mean for each plot. Duncan's multiple range test was used to separate mowing height and nitrogen fertility level means. Results and Discussion Nitrogen fertility level and mowing height. Prior to the application of nitrogen treatments putting green speed was measured on three different dates to detennine if there were differences among plots. and none were found. There was a highly signifit:;antdifference between mowing heights due to the aowing schedule in 1979 aad.iu!tution of.. t:_l'80~j;l&.scbjci4e.

26 53 Putting green speed measured on 14 dates throughout the summer. at various nitrogen fertility levels and at 6/32 and 3/32 inch mowing heights. is shown in Figures and 14. There were highly significant differences among nitrogen treacments and betveen mowing heights for all 14 dates. Using regression procedures a prediction equation was calculated for each date. The prediction equation and 2 corresponding F-value. r value. and C.V. are in Table 13. The F-value for the model was highly significant for each date indicating that the multiple linear regression model used properly portrays the dependent 2 variable putting green speed. The high r values indicate that a large amount of the variation in putting green speed can be accounted for by the variation in the nitrogen fertility levels and mowing heights. The same response to nitrogen fertility level and mowing height was seen at all 14 dates. There was an inverse linear relationship between speed and both nitrogen fertility level and mowing height. As the nitrogen fertility level increased there was an increase in growth of the bentgrass plants. Increased growth increased resistance to a rolling golf ball causing a decrease in putting green speed. As the mowing height increased. resistance to a rolling golf ball also increased because of longer leaves. This increase in resistance reduced speed. The change in putting green speed was affected more by mowing height than changes in nitrogen fertility level despite the wide range of fertility levels tested. Repeatability. The standard error of the mean and coefficient of variation were calculated for,each set of measurements on each plot. The measurem.entsaacleiancl the analysis of the measurements are shosm in: table> ';lbw values calculated for both the sundard error

27 54 I I - - 'to- -'0 o w w Cl. en 9 z w $ 8 C> ẕ r- r- 7 ::> Cl /32 INCH MOWING HEIGHT 6/32 INCH MOWING HEIGHT JUNE 24 o JUNE JULY 9 6, 2 3 NITROGEN APPLIED PRIOR TO MEASUREMENTS ( lb./1000 ft2) Figure 10. Effect of mowing height and nitrogen fertility level on putting green speed measured on June and 9 July 1980.

28 55 NITROGEN APPLIED PRIOR TO MEASUREMENTS ( Ib./IOOO ft 2 ) Figure 11. Effect of mowing height and nitrogen fertility level on putting green speed measured on 16, 24, 28 and 30 July 1980.

29 56 - -~ II - o 10 w ~ (f) 9 z w W 0: C) C) ẕ f- f- :J a NITROGEN APPLIED fi::: ::::... -:::j--o -...~,...'", I PRIOR TO MEASUREMENTS ( Ib./ 1000 ft 2 ) 3/32 INCH MONING HEIGHT 6/32 INCH MOWINGHEIGHT - \ 0_ ',_ '"'" ~GUST 5 o AUGUST 13 Figure 12. Effect of mowing height and nitrogen fertility level on putting green speed measured on 5 and 13 August 1980.

30 57 II - - 't- -10 o w a.. en 9 z w a: c:> 8 c:> z i= f- 7 :::> a.. 6 3/32 INCH MOWING HEIGHT 6/32 INCH MOWINGHEIGHT AUGUST 27 o SEPTEMBER 3 I NITROGEN APPLIED PRIOR TO MEASUREMENTS (Ib./IOOO ft 2 ) Figure 13. Effect of mowing height and nitrogen fertility level on putting green speed measured on 27 August and 3 September 1980.

31 II - 10 o w a.. en 9 z w a: ~ 8 ~ ẓ... 3/32 INCH MOWING HEIGHT 6/32 INCH MOWING HEIGHT SEPTEMBER II o SEPTEMBER 17 Co SEPTEMBER ::> a NITROGEN APPLIED PRIOR TO MEASUREMENTS ( Ib./IOOO ft 2 ) Figure 14. Effect of mowing height and nitrogen fertility level on putting green speed measured on 11, 17 and 29 September 1980.

32 59 Table 13. Prediction equation, F-va1ue, r 2, and coefficient of variation for putting green speed measured on 14 dates throughout the summer. Date Prediction Equation F-value r 2 C.v.,.. June 24 Y OH N 47**.78** 5.4,.. June 27 Y.., H N 89**.87** 4.4,.. July 9 Y H N 82**.86** 4.5,.. July 16 Y'" H N 181**.93** 3.4,.. July 24 Y H N 571**.98** 2.6 July 28 Y" H N 505**.97** 3.0,.. July 30 Y H N 130**.91** 4.3,.. August 5 Y lH N 396**.97** 3.0,.. August 13 Y H N 406**.97** 3.1,.. August 27 Y H N 307**.96** 3.7,.. September 3 Y H N 283**.95** 3.9,.. September 11 Y H N 319**.96** 3.4 September 17 Y H N 240**.95** 3.5,.. September 29 Y H N 273**.95** 3.2 H - mowing height in 32nds of an inch N - nitrogen fertility level in pounds per M **Significant at the.01 level

33 60 Table 14. Repeatability of measuring putting green speed using a.stimpmeter. Mowing Height Nitrogen Level Mean Standard Error (inch) (lb/looo ft 2 ) Speed of Mean C.v. 3/ '0" / '3" /32 6 9'8" /32 1 8'9" /32 3 8'3" /32 6 7'3"

34 of the mean and coefficient of variation indicate that the measurement of putting green speed using a Stimpmeter is repeatable with a high 61 degree of precision. Change in speed throughout the day. Contrary to expectations there was no significant difference among the mean speed, averaged over nitrogen fertility levels, measured at 0900, 1100, 1300, 1500, 1700, and 1900 hours on plots mowed at 6/32 inch. There was no nitrogen fertility level by time interaction. There were only minor fluctuations in putting green speed at the I, 2.5 and 4.5 pound nitrogen levels (Figure 15). There was a highly significant difference among nitrogen levels. There was no significant difference among the mean putting green speed, averaged over nitrogen fertility levels, measured at 0900, 1100, 1300, 1500, 1700, and 1900 hours on plots mowed at 3/32 inch. There was no nitrogen fertility level by time interaction. There were only minor fluctuations in putting green speed measured throughout the day at the 1, 3, and 5.5 pound nitrogen fertility rates (Figure 16). There was a highly significant difference among nitrogen levels. Single versus double daily mowing. Analysis of variance calculated from putting green speed measured on 25 August 1980 when all plots were single mowed indicated there was no significant difference within a plot prior to initiation of mowing treatments. There were highly significant differences between mowing heights and among nitrogen fertility levels but no significant interactions. For each of the next 8 days when half of each plot was double mowed and half was single mowed an analysis of variance was calculated. On each of these days there were highly significant differences between

35 62 - -'t-c w we C1- en z ttj7 a: ~ ~ z i= t- a. => M I L8. NITROGEN/ 1000 FT 2 o 2.5 LB.NITROGEN/IOOO FT LB. NITROGEN/IOOO FT 2 0- ~ ",0 0 0 o~ \" ~v \~O v. 0 TIME OF DAY M- Ti me of Mowing --0 Figure 15. Change in putting green speed throughout the day (13 August 1980) for three nitrogen levels and a 6/32 inch mowing height.

36 63 - I LB. NITROGEN/ 1000 FT 2 +- o 3 La NITROGEN/ 1000 FT 'to-0 2 A 5.5 LB. NITROGEN/ 1000 FT2 w a. en e- z w a: w II.. c:> c:> <:> <> ~ ~ ~ z M i= 9 f Q :J a. oc?),,0,-1:j0 \~o v.0,oj0 TIME OF DAY M- Time of Mowing Figure 16. Change in putting green speed throughout the day (3 September 1980) for three nitrogen levels and a 3/32 inch mowing height.

37 64 mowing heights, among nitrogen fertility levels, and between the double and single mowing treatments. On 29 and 31 August and 1 and 2 September 1980 there was a highly significant mowing height by nitrogen fertility level interaction. There was no other significant interaction. On 3 September 1980 all plots were single mowed and an A.O.V. was calculated to determine if the double mowing had any lasting effect on putting green speed. There was no significant difference between plots that had been double mowed and those that had been single mowed. There were highly significant differences between mowing heights and among nitrogen fertility levels. There was also a highly significant mowing height by nitrogen fertility level interaction. The effect of mowing height on speed was greatest at the lowest nitrogen level. There was no other significant interaction. The difference between single and double mowed plots averaged over nitrogen levels for both 6/32 inch and 3/32 inch mowing heights is shown in Figure 17. At both mowing heights, regardless of nitrogen level, after 3 days of double mowing the plots showed their maximum response to double mowing. After the third day of double mowing the response to double mowing leveled off and remained the same for the next 5 days. Even after 8 days of double mowing followed by 1 day of single mowing the effect of double mowing did not last and putting green speed decreased to the level of plots single mowed the entire 9 days. Limited moisture. There were highly significant differences among nitrogen fertility levels and between mowing heights. There was a significant difference among dates when putting green speed was measured. It was difficult to cor~elate the statistical difference among dates

38 65 -en cv.s::. (,J c.:.:::12 o w a. 9 (J') ẕ w 6 u z ~ 3 w ll o 3/32 INCH ~ 6/32 INCH August Sept. DATE OF OBSERVATION Figure 17. Increase in putting green speed due to single versus double (0 standard) daily mowings averaged over three nitrogen levels at 6/32 inch and 3/32 inch mowing heights.

39 66 to the response in putting green speed that was measured. A distinctly different response in putting green speed between the 6/32 and 3/32 inch mowing heights when subjected to the same watering regime is seen in Figures 18 and 19. Within a mowing height the five nitrogen fertility treatments show the same response to moisture. The differences in response to moisture. as shown in Figures 18 and 19. are confirmed by a highly significant mowing height by date interaction. Visual observations throughout the course of the experiment also indicate a different response to the drying conditions imposed on the area. On 10 September 1980 the blocks mowed at 3/32 inc3 were wilted and blueish-gray in color while those blocks mowed at 6/32 inch were tan and only slightly wilted. Putting green speed measured at the 6/32 inc3 mowing height showed no decrease following watering (Figure 18). The trend for all nitrogen levels at this mowing height was an increase in speed throughout the duration of this experiment regardless of any wate= applied. Putting green speed measured at 3/32 inch mowing height showed a response to watering at all nitrogen fertility levels (Figure 19). Following watering on 10 September 1980 an average decrease of 4 inches in speed was measured on 11 September An average speed increase of 6 inches was measured on 12 September Following watering on 12 September 1980 an average speed decrease of 3 inches was measured on 13 September Following watering on 13 September 1980 only a very slight decrease in average speed was measured. On 15 September 1980 an average decrease of 4 inches was measured. At a 3/32 inch mowing height the rolling golf ball was influenced by the condition of the thatch more than a golf ball rolled across plots mowed at 6/32 inch. At 6/32 inch the golf ball was influenced

40 ;; 9 w a- U') 8 z w a: C) 7 I LB. NITROGEN/1000 FT 2 o 2 LB. NITROGEN/1000 FT 2 b 3 LB. NITROGEN/ 1000 FT 2 4 LB. NITROGEN/1000 FT 2 o 6 LB. NITROGEN/IOOOFT 2 C) Z I- ~ 6 a- 8 9 w 10 II w w September DATE OF OBSERVATION. w- Water t from either irrigation or rain Figure 18. Effect of water, either irrigation or rain, on putting green speed at five nitrogen fertility levels and a 6/32 inch mowing height.

41 ā 12 w ~ en II z w a::: <.:> 10 <.:> z t= ~ 9 ::> ~ II I o o 6 LB. NITROGEN FT 2 La NITROGEN FT 2 LB. NITROGEN FT 2 LB. NITROGEN11000 FT 2 LB. NITROGEN11000 FT September DATE OF OBSERVATION W- Water I from either irrigation or rain Figure 19. Effect of water, either irrigation or rain, on putting green speed at five nitrogen fertility levels and a 3/32 inch mowing height.

42 69 less by the condition of the thatch since the leaf canopy supported the ball above the thatch. At the 3/32 inch mowing height the condition of the thatch (wet or dry) influenced speed more than at 6/32 inch. As the thatch dried it became more firm and was less resistant to the rolling golf ball and putting green speed increased. Mowing direction. The difference was taken between speed measured with and against the direction of mowing. The differences were averaged over nitrogen fertility levels for each mowing height and for each direction of speed measurement. The average speed at 6/32 inch was 7 feet 10 inches and at 3/32 inch 10 feet 2 inches. When putting green speed was measured with golf balls rolled north the average speed was 9 inches greater at both mowing heights on the half of the plot that was mowed with the mower moving north. When speed was measured with golf balls rolled south the average putting green speed was 7 and 4 inches greater. respectively, at the 3132 inch and 6/32 inch mowing heights on the half of the plot that was mowed with the mower moving south. The differences at 6/32 inch were not as great as reported by Engel et ale (1980). The differences were used to calculate an A.O.V. There were no significant differences becween mowing heights or among nitrogen fertility levels. The range of differences among nitrogen fertility levels was 8 inches at the 3 pound nitrogen rate to 6 inches at both the 1 and 4 pound nitrogen rate. Putting green speed was greater when the ball was rolled with the direction of mowing because mowing oriented the leaves in the same direction. When the ball was rolled with the orientation of the leaves resistance was less and the ball rolled further.

43 70 Moss cover. The percent moss cover for each plot was used to calculate an analysis of variance. The analysis of variance showed a highly significant difference between mowing heights but no significant difference among nitrogen levels. The results are summarized in Table 15. As the mowing height is lowered the stress on the creeping bentgrass plants increased which caused a gradual reduction in population. As this population reduction occurred moss began to encroach. Penneagle Block Materials and Methods Mowing. The Penneag1e block was mowed at 5/32 inch five times a week throughout the summer of 1979 using a Jacobsen Greens King and mowed at 6/32 inch five times a week in Beginning 16 August 1980 the site was mowed six times a week. On 12 September 1980 the mowing height was lowered to 4/32 inch and the mowing frequency was increased to 7 days a week. Aerifying and topdressing. A 30 x 72 feet area was used to determine the effect of aerifying and topdressing on putting green speed. Three aerifying and three topdressing treatments were tested in all possible combinations with the replications in a split block design. The aerification treatments were: punching with l/4-inch and l/2-inch tines and a non-punched check. There were 36 aerification holes per square foot regardless of tine size, using a Ryan Greensaire. Following aerification topdressing was applied. The topdressing was an 8:1:1 sand-soil-peat mixture applied with a Ryan Spread-Rite. The topdressing treatments were: a no-topdressing check, two separate light topdressing applications, and a single heavy topdressing appli-

44 71 Table 15. Percent moss cover at five nitrogen fertility levels and two mowing heights. Nitrogen Applied Mowin~ Height (inch) (lbs/looo ft 2 ) 6/32 3/32 Mean a a a a a Mean o b 7 a Means followed by the same letter are not significantly different at the 0.05 level. Comparison should be made within row or column only.

45 72 cation. Plot sizes were: 3 feet 4 inches x 24 feet for non-aerified plots, 2 feet 8 inches x 24 feet for plots aerified with 1/4-inch tines. and 4 feet x 24 feet for plots aerified with 1/2-inch tines. On 18 September 1980 the light topdressing plots were topdressed for the first time with 0.15 cubic yards per 1000 square feet and heavy topdressing plots with 0.45 cubic yards. The topdressing was thoroughly worked into the aerification holes and around the base of the plants. Coarse particles were removed from the surface. The entire area was watered that evening, settling the topdressing in the aerification holes. The next day the heavy topdressing plots were topdressed again at a rate of 0.1 cubic yards per 1000 square feet to completely fill the aerification holes. On 7 October 1980 the second light topdressing treatment was applied at a rate of 0.15 cubic yards per 1000 square feet. Putting green speed was measured every other day for the first 20 days and at weekly intervals for two more weeks. A separate analysis of variance was conducted for each day speed was measured. Duncan's multiple range test was conducted to separate aerification and topdressing means. Verticutting. Two verticutting treatnents were compared with a check to determine their effect on speed. Treatments were a very light verticutting and a groove verticutting. Plot size was 13 x 13 feet. The light verticutting was done with a Hahn Westpoint Tournament II Triplex on 23 and 28 September 1980 and 6 October The groove verticutting was done on 6 October 1980 using a Taro Triplex. The Taro groove verticutting cut grooves lib-inch deep into the putting surface at a 1/4-inch spacing. Putting green speed was measured five times after 6 October 1980.

46 73 The experimental design was a randomized complete block design and each treatment was replicated three times. Duncan's multiple range test was used to separate treatment means. Maintenance spiking. Spiking at three rates and a check were tested on 4.25 x 13 feet plots to determine the effect on speed. Spiking was done on 2 October 1980 using a Ryan Spikeaire. Rates were one. two, and three passes of the spiker. There were 24 spike holes per square foot for each pass. Putting green speed was measured before and after spiking and on eight additional days over the next 20 days. The experimental design was a randomized complete block design with each treatment replicated three times. Duncan's multiple range test was variance used to separate treatment means. y. was conducted for each date'speed " A separate analysis of was measured. Golf shoe spike marks. The effect of spike marks, created by golf shoes, on putting green speed was determined in this test. Spike marks were made by mounting the soles of golf shoes on metal bands which were then attached to a power driven roller (Shoop. 1967). Treatments consisted of one. two. or three passes across the plot plus a check. Plot size was 4 x 18 feet. The number of spike marks per square foot was 17 for each pass. Speed was measured before and after spike marks were made and on the following day. The experimental design used was a randomized complete block and each treatment was replicated three times. The data were analyzed as a split block in time in addition to separate analyses. Duncan's multiple range test was used to separate treatment means.

47 74 Results and Discussion Aerification and topdressing. For each of the 14 days that speed was measured a separate A.O.V. was calculated. There were significant differences among topdressing treatments and among aerification treat- "'--,.r -- ments on some, but not all dates. There was no significant aerifid~tion by topdressing interaction on 13 of the 14 dates. Differences due to aerification treatments are shown in Figure 20. Throughout the course of the experiment the speed measured on aerified plots was less than that measured on the checks. Also the putting green speed measured on plots aerified with liz-inch tines was less than that measured on plots aerified with l/4-inch tines. The speed measured on aerification treatments averaged over topdressing treatments is shown in Table 16. Aerification reduced the distance the golf ball rolled across the plot because the golf ball struck the back edge of the aerification holes causing it to lose momentum thus rolling a shorter distance. A greater speed reduction occurred on plots aerified with l/2-inch tines than on those aerified with l/4-inch tines. Although the response of putting green speed to aerification treatments was the same regardless of topdressing rate the magnitude of the response varied. As the rate of topdressing increased, the difference becween aerification treatments decreased. The difference in putting green speed between topdressing treatments and a non-topdressed check averaged over aerification treatments is shown in Figure 21. A decrease in speed for 8 days was measured on both light and heavy topdressing plots following initial topdressing. This decrease was due to resistance to the rolling golf ball from topdressing present on the putting surface and was greatest on heavily