Overseed Greens Performance Trials
David Kopeck, Extension Turfgrass Specialist
Jeff Gilbert, Turfgrass Research Specialist
Eleven overseed entries were evaluated for overall visual performance and ball speed on a five year old 'Tifgreen' USGA specification putting green. Perennial ryegrass (PR) turf was quicker to establish than most Poa trivialis (PT) and/or Poa trivialis/creeping bentgrass mixtures. 'Saber' (PT) at the manufacture's overseed rate of 10 lbs./M provided the fastest establishment among non-ryegrass germplasm. Perennial ryegrass had darker inherent color than (PT) or mixtures containing Poa trivialis (PT). During the winter, Stardust (PT) was slightly lighter in color than Stardust (PT) when mixed with creeping bentgrass (CB) and redtop (RT). Saber (PT) at 10 lbs./M had the highest turfgrass quality in the fall, but ranked lower in the spring. In general, quality scores were greater for (PT) entries in the fall, while perennial ryegrass (PR) entries had better spring quality scores. There were some differences in rank among perennial ryegrass overseed entries for winter and spring turf quality. Ball speed (roll distance) was significantly different between overseed entries in December, January, February and March but not for November, April, or May. Maximum differences in ball speeds between surfaces was 30% in February of 1996. (PT) entries generally had greater ball roll distances than (PR) entries. Perennial ryegrass had the greatest amount of bermudagrass in early June, compared to Poa trivialis and the other overseed mixtures.
Each fall, golf course superintendents who manage either 'Tifgreen' or 'Tifdwarf" bermudagrass greens overseed in order to maintain a year round putting surface. A suitable overseed surface must be able to (1) emerge quickly, (2) tolerate traffic, (3) withstand close repeated mowing, as well as (4) maintain adequate color, quality and density. Germplasm usually used for greens overseeding includes perennial ryegrasses, Poatrivialis (PT), and mixtures which may include creeping bentgrass (with PT). An overseed test was conducted at the University of Arizona's Karsten Turfgrass Research Facility in order to assess new germplasm for this purpose. Entries included a sample of existing available cultivars, as well as experimental accessions.
Materials and Methods
A five year old 'Tifgreen' (328) bermudagrass green constructed to USGA sand and drainage specifications was utilized for the overseeding. The Tifgreen was last fertilized on September 15, one month before overseeding on October 14, 1995. Eleven entries were seeded at overseed green rates in three directions using hand shakers. All plots (including a non-overseed bermudagrass control) were topdressed with 1/4" of dry sand. Plot size was 3.5 x 12 feet with four replications per entry in a randomized complete block ( RCB) design. Irrigation scheduling was provided from a PC computer central controller linked to an on-site weather station. The turf was irrigated to avoid stress. Plots were mowed first on November 1 at 3/16". Mowing frequency was 6 x week (for five weeks), at which time (Dec 10) it was further reduced to 11/64". Plots remained at 11/64" until February 6, when they were then lowered to 5/32". Plots were mowed four times weekly from November 1 to January 10, then mowed 6 x weekly afterwards. The test received a total of 7 lbs. -N-, 3.2 lbs. -P-, and 3.2 lbs. -K- from November 1, 1995 to June 20, 1996 from ten applications of fertilizer. Thirteen ounces of Ferromec were applied from four applications (December, January and twice in February). Plots were aerated with 1/4" solid tines on January 11 and February 15. A wetting agent was applied on April 19. The label rate of Oftanol was applied on February 6 to control a heavy infestation of rove beetles.
Plots were evaluated for agronomic quality which included initial establishment, turfgrass color, quality, density, texture, uniformity, and percent bermudagrass in early June (transition). Plots were evaluated for ball speeds on seven dates after the turf was double mowed in a 45 degree criss-cross pattern. Six rolls (three per lengthwise direction) were measured in each plot and the mean of these was used for analysis. All variables were subjected to the analysis of variance for testing the main effect of overseed entries. Mean separation was performed by calculating least significant differences, only when the F ratio for overseed entries was P = 0.05, or less.
Result and Discussion
The percent plot cover (as cool season overseed) was evaluated (0-100%) on October 23, November 3, and December 1, 1995. The minimum and maximum mean overseed plot cover ranged from 14% to 61%, 62% to 93%, and 75% to 91% on each date, respectively (Table 1). On October 23, four perennial ryegrass entries ranked highest in percent cover, followed by 'Saber' (PT) which was seeded at the manufacture's overseeding rate of 10.0 lbs./M. The 'Stardust' (PT) mixture series ranged between 20% to 22% cover, regardless if it was used alone, or with the addition of bentgrass and/or redtop. 'Darkhorse' (PT) with 'Cato' creeping bentgrass had the least ground cover on October 23. On November 3, three perennial ryegrasses had achieved 90% ground cover, including ''Sabre'' (PT) at the high seed rate (Table 1). 'Darkhorse' (PT) with 'Cato' bentgrass had a mean of 62% cool season ground cover. On December 1, 'Saber' (PT) had a mean ground cover of 91%, followed by the three remaining (PT) mixtures. The decrease in percent cover in ryegrass could have been from bias in the subjective visual ratings, or from competition failure among young seedlings under mowing stress on this particular evaluation date.
Color scores were assigned on nine dates using the NTEP scale, where larger values indicate darker color. Color selection by the user is an individual preference, and light scores are not a liability at an evaluation event. During the "winter" season, the perennial ryegrasses scored the highest numerical values for turfgrass color. 'WVPB MVF-4-1' PR was very dark immediately after germination, and ranked high during the first five evaluation dates (October 23 to February 26) (Table 2). . This period comprised the "winter" color evaluations. The mixture of 'Stardust' (PT)/'Trueline' (CB)/'Brite' (RT) had a slightly darker color than either 'Stardust' (PT) alone, or the 'Stardust' (PT)/'Trueline' CB mixture. 'Sabre' (PT) was the lightest color turf during the "winter" period (Table 2)..
"Spring" color evaluations were made during March, April, May and June of 1996. The mean of these four ratings comprised the "spring color" mean average. 'WVPB MVF-4-1' (PR) had the highest numerical mean score during the spring, followed by 'Prime' (PR), which ranked fifth for color during the "fall" (Table 2). 'Stardust' (PT) alone ranked slightly higher for spring color than its component mixtures, or that of the 'Darkhorse' (PT)/'Cato' (CB) mixture. These differences in color were subtle. 'Sabre' (PT) was the lightest in color during the spring. The non-overseed bermudagrass did green up early (by March 22) and was usually darker in color than the 'Sabre' (PT). Based on the overall performance (nine months of evaluation), the perennial ryegrasses tended to yield the darkest turfgrass color scores. 'WVPB MVF-4-1' was the darkest entry. 'Stardust' (PT) was the darkest among the (PT) component mixtures, which were darker than the 'Sabre' (PT) (Table 4)..
Turfgrass quality scores were assigned to all plots on seven dates, starting December 1, 1995 and ending June 2, 1996. Three evaluations (December, January and February) were made to assess "winter" quality, while the remaining four evaluations represent "spring" turfgrass quality. Quality scores represent an integration of density, texture, uniformity, continuity of color and general appearance. The NTEP scale was utilized, where larger numbers represent higher turfgrass quality observations.
'Sabre' (PT) produced the highest quality turf on all three "winter" evaluation dates, and likewise yielded the largest "winter" quality mean (mean score = 8.2) (Table 5). . On December 1, 'WVPB 92-4' (PR) ranked second for overall turfgrass quality (mean score = 6.8), followed by 'MVF-4-1' (PR) (mean score = 6.5). For both the January 22 and February 26 ratings, 'Sabre' (PT) and the 'Stardust' (PT)/'Trueline' (CB) mixture scored mean quality values first and second in rank, respectively. 'WVPB 92-4' (PR) was the leading ryegrass for quality during the "winter" evaluation period. The 'Darkhorse' (PT)/'Cato' (CB) mixture was lower in quality, with exception of 'Prime' (PR) among overseed entries (Table 5) . The addition of mixture components to the 'Stardust' (PT) increased overall turfgrass quality slightly in the "winter", but there was no difference between these entries in the "spring" .
Beginning in March and continuing through early June, the perennial ryegrasses produced (in general) higher quality turf than the (PT), and (PT) mixtures (Table 6). . The return of warm (to hot) weather appeared to favor the ryegrass, which was adequately dense and smooth. Interestingly, 'WPVB 92-4' (PR) ranked last among the perennial ryegrasses during the "spring". This entry ranked first (among ryegrasses) during the "winter". Overall, there was a complete reversal between perennial ryegrass and Poa trivialis cultivars and mixtures between their respective "winter" and "spring" quality performance (Table 5,6).
Turfgrass uniformity scores were assigned on six dates using the NTEP scale. Higher values indicate increased relative uniformity. Uniformity indicates the degree of likeness or consistency within a plot. Absolute color or leaf texture (coarse vs. fine) are not scored, but rather, the consistency of appearance is evaluated for uniformity. December and February evaluations were used to represent the "winter" uniformity, while the remaining four months represent "spring" uniformity.
During the "winter" period, 'Sabre' (PT) scored the highest uniformity ratings, followed closely by 'WVPB MVF-4-1' (PR) and the 'Stardust' (PT)/'Trueline' (CB) mixture. The addition of the redtop to the above mixture did not necessarily enhance overall winter uniformity.
As with turfgrass quality, a reversal occurred in rankings between the perennial ryegrass and the other (PT) materials for uniformity (Tables 7,8). The exception was the 'Stardust' (PT)/'Trueline' (CB) mixture which remained consistent in rank for both the "winter" and "spring" evaluations. The 'Sabre' (PT) displayed dark circular rings within the plots in early March, which seriously detracted from the turfs appearance. The turf was somewhat thinned out in these areas. The rings lasted for about three or four weeks, until they slowly disappeared within the plots.
Turfgrass density scores were assessed visually on seven dates using the NTEP scale, where larger numerical values indicate increased shoot densities. Density scores assigned to plots during the months of December, January and February indicate "winter" performance, while the remaining four months performance were used for "spring" density performance.
The ' winter' density scores ranged from 5.1 to 8.9 among overseed entry means (Table 9). The (PT) entries and (PT) mixtures were visually more dense than the perennial ryegrasses. Though they were generally more dense, they did not exhibit similar overall turf quality. 'Sabre' (PT) (10.0 lbs./M seed rate) was by far the most dense turf, followed by the 'Stardust' line and component mixture. Among the perennial ryegrass entries 'Prime' (PR) tended to be the least dense in "winter turf density" (Table 9). Similar performance rankings occurred during the "spring". 'Sabre' (PT) produced an above average dense turf, followed by the 'Darkhorse' (PT)/'Cato' (CB) mixture, and the 'Stardust' (PT) series (Table 10). Densities remained high and acceptable up to and including June 6, when the test was concluded.
Turfgrass texture scores were assigned on six dates during the test, and scores indicate relative leaf width composition of the plot. Higher numerical values represent finer (narrow) leaf widths. Ratings assigned during December, January and February comprised "winter" performance, while March, April and May indicate "spring" performance. A June rating is not included due to bermudagrass emergence (transition).
The 'Sabre' (PT) (10.0 lbs./M seed rate) had the finest leaf texture, throughout the test, which was immediately evident by the December rating. "Sabre (PT) continued mostly unrivaled for fine texture up to and including the February ratings (Table 11). 'Stardust' (PT)/'Trueline' CB/'Bart' (PT), 'Stardust' (PT), and 'Stardust' (PT)/(CB) had slightly finer leaf textures than the 'Darkhorse' (PT)/'Cato' (CB) mixture during December. The differences between the non-ryegrass entries were minimal when averaged over the three month period, noting the exception of 'Sabre' (PT) alone (Table 11).
Similar trend and rank performance occurred for "spring" texture performance among overseed entries. The (PT) materials maintained finer leaf texture over that of the ryegrasses (but not necessarily overall quality) (Table 12). 'WVPB MVF-4-1' (PR) was the highest ranking ryegrass for texture during the "winter", but was the lowest during the "spring" when compared to other ryegrass entries (Tables 11,12). The differences were more noticeable for texture in the spring than during the fall (among the perennial ryegrasses). The non-overseed bermudagrass was at full green-up by May 22, but was coarse from a lack of topdressing and beneficial light grooming.
Transition to Bermudagrass
The percent plot bermudagrass was visually assessed on June 6, by assigning scores (0-100%) on each half of the plot. Both values were averaged for analysis on a plot basis. The percent bermudagrass ranged from 10% to 28% (Table 13). The perennial ryegrass plots had generally more visible bermudagrass than the (PT) containing germplasm. The 'Stardust' (PT)/'Trueline' (CB) mixture had almost twice as much bermudagrass than the 'Stardust' (PT)/'Trueline' (CB)/'Bart' (RT) mixture. This is contrary to expectation, but only one evaluation was made by the close of this report. Since then, the green has been treated with a herbicide, verticut, aerified and topdressed to initiate a forced transition to 'Tifgreen' bermudagrass.
On January 22, all plots were evaluated for iron type chlorosis symptoms, which often occur during the winter season when soil temperatures are low.. Plots were evaluated using a visual scale of 1-6 (1 = no chlorosis, 4 = moderate, 6 = severe) to assess the degree of chlorosis, along with the percent plot (0-100%) exhibiting any chlorosis.
The most noticeable iron chlorosis type symptoms were evident on the perennial ryegrasses. 'WVPB MVF-4' (PR) and 'WVPB 92-4' (PR) had a mean degree of chlorosis score of 3.0 (light - moderate).
The remaining (PR) germplasm exhibited mean degree score of 1.5 - 2.0 (data not shown). All (PT) material did not show the yellow-mottling condition. Perhaps the light green color masked any potential symptoms or they never developed a visual iron-type deficiency expression.
The percent plot which showed yellowing was basically in rank with mean degree symptom responses (data not shown). 'WVPB 92-4' (PR), 'WVPB 93-7' (PR), and 'WVPB MVF -4-1' (PR) had 10% to 13% plot expression, while 'Prime' (PR), and 'WVPB 93-3' had 8% expression. 'WVPB 93-6' (PR) had the least expression (4%).Again the non-perennial ryegrass materials had no yellowing.
Ball speeds were measured on seven dates (materials and methods section). Ball speed overseed entry effects were significant during December, January, February and March and non-significant for November, April and May.
For November, ball speeds ranged from 86" to 93", with the unseeded check (dormant Tifgreen) having the highest ball speed (Table 14). There was no trend between perennial ryegrasses versus the (PT) based entries. On December 19, ball speeds ranged from 83" to 95" (14% difference) among all overseed entries. The non-overseed Tifgreen had similar ball speed performance as those of the three 'Stardust' (PT) series entries and that of the 'Darkhorse' (PT)/'Cato' (CB) entry (92" - 95") (Table 14). 'Sabre' (PT) was somewhat slower, with a mean ball speed value of 87". The perennial ryegrass entries were very similar showing a 6% difference between 'WVPB 93-7' PR and 'WVPB 93-6' PR 82" vs. 87", respectively.
On January 30, the difference between surfaces for ball speed was 22%, and the overseed main effect was significant. The un-seeded check was fastest with 102" and was much greater than the overseeded surfaces, which ranged from 79" to 90" (13% range). 'Prime' (PR) ranked first (90") followed by 'Stardust' (PT) at 84" (Table 14). The LSD value for ball speed on this date is larger, showing only a slight difference between the fastest and slowest overseed treatments.
Ball speed mean values ranged from 80" to 113" on February 23 (30% range) which was highly significant. The dormant bermudagrass was greatest with a mean value of 113". Among seeded surfaces, ball speeds ranged from 91" to 80" (13% difference) which was highly significant. Generally, the (PT) materials had greater ball speed values. 'WVPB MVF-4-1' had the greatest speed among the perennial ryegrasses.
For the "winter" average ball speed (first four months), the unseeded bermudagrass had the highest ball speed by almost one foot (Table15). This is the result of compression of a non-actively growing surface by regular mowing. A six inch difference occurred (four month average) between 'Stardust' (PT) (mean = 90") and five other ryegrasses, with a mean of 83" or 84".
March, April and May ball speeds were used to calculate "spring" ball speed performance. For March, ball speeds ranged from 78" to 89" (12% range) (Table 14) . The un-seeded Tifgreen which was now greening up, maintained the fastest ball speeds, followed by the 'Stardust' (PT) series and 'Sabre' (PT). The ryegrasses had similar ball speeds compared to 'Darkhorse' (PT)/'Cato' (CB) (Table 15).
For April, mean speed values ranged from 84" to 90" and differences between entries were non-significant. The bermudagrass was now active and was now surpassed by six overseed entries for ball speed. The perennial ryegrass 'WVPB MVF-4-1' (PR) ranked first for ball speed (mean = 90"). Note however, that there was no significant effect due to overseed entries at this time (Table 14).
At the last ball speed date in May, there were again no significant differences due to overseed entries, as the F ratio for treatment (overseed entry) means was less than 1.0 This indicates that variation within an overseed entry is greater than differences between entries. Based on means, only a 5" difference occurred between the 'fastest' and 'slowest' entries (77" to 82") (Table 14).
Based on the last three months of evaluation, no differences occurred for "spring" ball speeds. This was due to the fact that the return of green bermudagrass decreased ball speeds for the non-overseeded 'Tifgreen' bermudagrass, plus a general increase in ball speed variation within plots as temperature increased (Table 15). The overall mean ball speed of all seven dates was significant (92" to 82"), but the seasonal means are of greater importance, especially during the fall (Table 15).
Appendix Table -A-
Overseed Entries - Greens Overseed Test 1995-1996
University of Arizona
Entry Composition1 Overseed Appears
in Table As
1. 80% Darkhorse PT 3 lbs./M DRKHRSE/CATO 8/2
20% Cato CB
2. Stardust PT 3.5 lbs./M STARDUST PT
3. 50% Stardust PT 3.5 lbs./M STRDST/TRU/BRTTRT
Issued in furtherance of Cooperative Extension work, acts of May 8 and June 30, 1914, in cooperation with the U.S. Department of Agriculture, James A. Christenson, Director, Cooperative Extension, College of Agriculture & Life Sciences, The University of Arizona. The University of Arizona is an equal opportunity, affirmative action institution. The University does not discriminate on the basis of race, color, religion, sex, national origin, age, disability, veteran status, or sexual orientation in its programs and activities.
25% Trueline CB
25% Bart Redtop RT
4. 60% Stardust PT 3.5 lbs./M STRDST/TRU 6/4
40% Trueline CB
5. Prime PR 35 lbs./M PRIME PR
6. Sabre PT 10 lbs./M SABRE PT
7. 93-3 PR 35 lbs./M WVPB 93-3 PR
8. 93-7 PR 35 lbs./M WVPB 93-7 PR
9. 92-4 PR 35 lbs./M WVPB 92-4 PR
10. MVF-4-1 PR 35 lbs./M WVPB-MVF-4-1 PR
11. 93-6 PR 35 lbs./M WVPB 93-6 PR
12. Check -- - - UN-SEEDED CHECK