J.L. EGGENS. Can. J. Plant Sci. Downloaded from by on 01/30/18

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1 THATCH CONTROL ON CREEPING BENTGRASS TURF J.L. EGGENS Department of Horticultural Science, University of Guelph, Guelph, Ontario NIG 2WI. Received 20 Feb. 1980, accepted 3 July Eccrrqs, J.L Thatch control on creeping bentgrass turf. Can. J. Plant Sci.60: The effectiveness of thatch control practices commonly employed in Ontario on Penncross creeping bentgrass turf maintained as a putting green was evaluated from July 1976 to October The most effective treatments were coring and vertical mowing followed by top, and top alone. The least amount of winter injury occurred in plots where coring was followed by top. Coring reduced thatch accumulation more than did vertical mowing. Vertical mowing increased winter injury and annual bluegrass content in the plots more than did coring. Thatch accumulation was less at the 5-mm than at the 8-mm mowing height. Nitrogen treatments of 2 and 4 kg N. 100 m-2 did not influence thatch accumulation. L'efficacit6 des pratiques de d6feutrage couramment utilis6es en Ontario sur les gazons d'agrostide Penncross des pelouses d'arriv6e dans les terrains de golf a 6t6 observ6e de juillet 1976 ir octobre Les traitements les plus efficaces ont 6t6 le terreautage seul, ou pr6c6d6 de carottage et de tonte par lames ir axe vertical. Les d6gdts les moins graves dus ir I'hiver ont 6t6 constat6s dans les parcelles traitees par carottage suivi de terreautage. Le carottage a davantage contribu6 b r6duire la formation de feutre que la tonte par lames I axe vertical. Ce.dernier traitement a, d'autre part, plus accrue le degr6 d'endommagement par I'hiver ainsi que la proportion de piturin annuel dans le gazon, que l'a6ration par carottage. La hauteur de tonte de 5 mm a donn6 lieu i une moindre accumulation de feutre que celle de 8 mm. La dose de fumure azot6e, soit 2 ou 4 kg N '100 m-2, n'a pas eu d'effet sur la formation de feutre. Thatch may be defined as the accumulation of living and dead grass leaves, stems and organic debris between the soil surface and the green vegetation in a turf (Beard 1973). Thatch accumulation is due to a reduction in the rate of decomposition of litter and reduction in earthworms and chanses in microbial flora. Although thatch ir not considered to be a primary causal factor in turf death, it is a major indirect contributor to poor turf quality, localized dry spots, scalping, increased disease and insect problems, increased winter injury (Beard 1973) and poor stands ofoverseeded grasses (Schmidt and Shoulders 1972). Annual bluegrass (Poa annua L.) is an aggressive weed grass capable of invading Can. J. Plant Sci. ffiz 170/ (October 19t0) injured turfgrass swards growing under conditions deleterious to the growth of the desirable grasses (Youngner 1959). While thatch control by cultural methods, which do not disrupt the turf surface, is preferred (Ledeboer and Skogley 1967), mechanical thatch removal by vertical mowing and 'coring on putting greens is often necessary (Beard 1973). Schrnidt and Shoulders (1972) showed that Bermudagrass putting green plots that did not receive cultivation had significantly less annual bluegrass than plots that had received cultivation treatments during periods of optimum annual bluegrass germination and establishment. This study evaluated the relative effectiveness of common thatch control practices utilized in Ontario and assessed the influence of these practices on the ingress of annual t209

2 l2to CANADIAN JOURNAL OF PLANT SCIENCE bluegrass into turf maintained as a putting green. MATERIALS AND METHODS This study was conducted from July 1976 to October 1979 on a 7-yr-old Penncross creeping bentgrass (Agrostis paluslris Huds.) sward grown on a sandy loam soil. When the thatch control treatments were begun, the thatch thickness was approximately 22 mm and relatively uniform throughout the research area. The soil ph was approximately neutral and remained so throughout the study. Earthworm castings were observed on all research plots throughout the study. The sward contained approximately 5Vo annual bluegrass uniformly distributed throughout the research area. Phosphorus and potassium were supplied on the basis of soil tests. Irrigation was supplied to prevent any limitation of water on plant growth. Fungicides fortyphula gray snow mold and diazinon for cutworms were applied as required. No wear treatments or herbicides were applied to the plots. Plots for the main treatment were 2.6 x 6.0 m arranged in a randomized complete block design with four replications. Main treatments included (1) vertical mowing alone or (2) followed by top, (3) coring alone or (4) followed by top and (5) top alone. With the exception of vertical mowing once per week, all main treatments were applied once per month from May to October. The vertical mower was adjusted for each treatment to remove the maximum amount of thatch possible without ripping out pieces of creeping bentgrass turf. The coring treatments were applied with a Ryan Greensaire turf aerator. The l3-mm diameter steel tines were reduced in length so that only the minimum amount of soil necessary for the extraction of the core of thatch was removed during each coring operation. The cores ofthatch and soil were removed from the plots. Top consisted of a Fox sandy loam soil with a gradation index D90/Dl0 of 47.5 and mid-particle diameter size of 240 microns. It was applied at the rate of 0.1 ms.l00 m-2 and thoroughly worked into the turf in four directions with an aluminum rake. The four subplot (1.3 x 3.0 m) treatments consisted of two mowing heights of 5 and 8 mm and two nitrogen application rates of 2 and 4 kg N.100 m-2 per growing season. The mowing frequency was five times per week during most of the growing season but was increased to six times per week during peak growth periods. The 8-mm mowing treatment was started mid-july 1976 and the 5-mm mowing treatment was started late August The mowing height was reduced from 8 to 5 mm over a 5-day period. The nitrogen treatments were applied as ammonium nitrate at the rate of 0.5 kg N. 100 m-'per application every three (4 kg) or six (2 kg) weeks over the growing season starting mid-april and ending late September. The content of thatch (including mat) in each plot was determined by removing a lo-cm plug of sod and measuring the thatch content in millimeters on three sides of the plug. For those treatments that received top, it was necessary to adjust the thatch measurement obtained by subtracting the thickness of thc top intermingled in the thatch layer. A minimum of two independent thatch measurements were made each time and the mean of the six values used as the thatch thickness for that treatment. Winter injury as affected by treatment was visually evaluated in late April (after shoot growth had started) using a scale of I - 10, with l 0 representing green turf and 1 representing dead turf. Annual bluegrass was visually estimated on a scale of 0- I 0; with I 0 representing I 007o of the plot occupied by annual bluegrass. The mean of the independent visual evaluations (minimum of three) was used as the measure of the annual bluegrass content in each plot. As the plots were treated with glyphosate atzkg (active) /ha in mid-july, the l8 Sept 1979 evaluation recorded the amount of annual bluegrass that had subsequently germinated and developed in the treated plots in the absence ofcreeping bentgrass competition. RESULTS On 3 May 1978, after l0 treatment applications, the amount of thatch in plots receiving monthly vertical mowing or coring followed by top, and top alone was significantly less than that for the control and other thatch control treatments (Table l). Increasing the vertical mowing frequency from monthly to weekly did not result in reduced thatch. Vertical mowing was effective in reducing thatch content only when followed by top. Vertical mowing alone did not provide a satisfactory

3 EGGENS THATCH CONTROL ON TURF lzt - I Table 1. Accumulated thatch (mm) on 3 May 1978 after fourtreatments during 1976 and six treatments during 1977 Vertical mow Control Weekly plus top. plus top Top I l.) ab 9.4ab 4.O c 8.t b 4.9 c 4-ZC tvalues are the mean of two mowing heights and two nitrogen levels replicated four times (16 observations). a-c Means followed by the same letter are not significantly different (Duncan's multiple range test, P : 0.05) playing surface. Results indicate that top without vertical mowing or coring would be effective in controlling thatch. coring without top provided better thatch control, was less destructive to the turf and provided a better putting surface than monthly vertical mowing without top. Mowing height was significant in thatch control. The thatch thickness at 5- and 8-mm mowing heights was 4.5 and 10.2 mm, respectively. Nitrogen treatments were not significant. Winter injury was less on plots cored and topdressed monthly. The most severe winter injury occwred on plots vertical-mowed weekly during the previous growing season (Table 2). Plots topdressed only or cored or vertical-mowed followed by top had significantly less winter injury than the control plots. Plots in which the creeping bentgrass was injured by thatch control treatments had more annual bluegrass than plots that were injured by treatment (Table 3). Top monthly vertical-mowed plots increased the density of the creeping bentgrass and resulted in less annual bluegrass on 3l May and 26 July than on plots vertical-mowed monthly without top. Control Annual bluegrass in plots topdressed only was not significantly greater than the control until 18 Sept After three growing seasons and 2O treatment applications, the plots with similar annual bluegrass content as the control plots were those cored monthly. DISCUSSION Top was found to be an effective thatch control treatment alone or in combination with vertical mowing and coring. The results of this study agree with those of Thompson and Ward (1966) and Ledeboer and Skogley (1967) who observed that top decreased thatch accumulation by improving the microenvironment for thatch decomposition. As found by Smith (19'79), top improved turf quality by significantly reducing the severity of scalping injury at the 5-mm mowing height during the first 5 mo of the study. By incorporating top into the intact thatch, a firm smooth surface was provided for the mowing operation. The influence of top on the content of annual ' bluegrass in the plots was not clear but tended to agree with results of a study by Engel and Alderfer (1967) in which the Table 2. Influence ofthatch control treatments on winter injury ( ) recorded 2l Apr Weekly Vertical mow plus top MonthlY Plus top Top 5.'1 cl 3.8 d 4.9 c 7.sb '7.2b 9.7 a 7.9b tvisual evaluation using a rating system of l-10, with I representing dead turfand l0 green growing turf. a-d Means followed byihe same letter are not significantly different (Duncan's multiple range test, P = 0.05).

4 1212 CANADTANJoURNAL of plant science Table 3. Influence of 2l thatch control treatments over a 3-yr period on the ingress of annual bluegrass Treatment Control Vertical mow weekly Vertical mow monthly Vertical mow monthly plus top Core monthly Core monthly plus top Top 1977 t978 r9'79 3l Aug. 31 May 26 July 3l Oct. 18 Sept l.)bc 1.9 b 2.6b 1.6b 1.6b 2.9a 4.7 a 4.6a 5.O a 5.4 a 2.7 a 3.9 a 4.1 a 4.8a 5-2a 2.4ab t.7 b 2.5 b 3.9a 6.9a l.lc 2.5 b 2.7 b 2.4 b 2.9 b l.3c 2.5 b 2.6 b 4.9 a 6.1 a.2c t.8 b 2.3 b l.8b 5.4a tvisual evaluation using a rating system of 0-10 with l0 representing IOOVo of the plot populated with annual bluegrass. a-c Means within columns followed by the same letter are not significantly different (Duncan's multiple range test, P : 0.0s). annual bluegrass composition appeared less on plots that received top. The suppression of annual bluegrass germination in the topdressed vertical-mowed plots on 3l May and 26 July 1978 (Table 3) may have been the result of light exclusion by the top as suggested by Madison (197l) but was more likely due to the strong competition provided by the tight Penncross turf developed by the top treatment. The significant increase in annual bluegrass content in the top-only treatment l8 Sept cannot be readily explained. Coring was a more effective thatch control practice when combined with top than when used alone (Table 1). Coring in this study differed from the aerification (coring) treatment described by Murray and Juska (1977), where a 5-cm core of thatch and soil was extracted and the soil worked into the turf after the core had been broken up with a vertical mower. Since coring without top promoted significantly less annual bluegrass than vertical mowing without top (Table 3), the use of coring with shortened tines should be considered as a thatch control measure on areas that are not compacted, and the disruptive process of aerification by coring can be avoided. Winter injury was more severe on plots where the creeping bentgrass was injured by thatch control treatments (Table 2). All treatments receiving top had significantly less winter injury than the control plots; this was probably related to the reduced thatch level, the moderation of temperature extremes and reduced desiccation from the presence of topsoil around the crowns during the winter months (Beard 1973t. The nitrogen treatment did not influence thatch accumulation. Meinhold etal. (1973) found that the high level of nitrogen increased thatch accumulation 3OVo as compared to the low level of nitrogen. However, their high nitrogen level was 7.5 kg.l00 m-2 over the growing season. The low and high nitrogen treatments of 2 and 4 kg N.100 m-2 in this study were within the noffnal range utilized for the culture of creeping bentgrass turf in Ontario. ACKNOWLEDGMENTS The financial support provided by the Ontario Ministry of Agriculture and Food and the technical assistance of N. E. McCollum are greatly appreciated. BEARD, J.B Turfgrass: Science and culture. Prentice-Hall, Inc., Englewood Cliffs, N.J. ENGLE, R.E. andalderfer, R.B The effect of cultivation, top, lime, nitrogen and wetting agents on thatch development on l/4-inch bentgrass turf over a ten-year period.

5 EGGENS - THATCH CONTROL ON TI]RF t2t3 New Jersey Agric. Exp. Sta. Bull pp. 32-4s. LEDEBOER, F.B. and SKOGLEY, C.R Investigations into the nature of thatch and methods for its decomposition. Agron. J. 59: MADISON, J.H. 197 l. Practical turfgrass management. Van Nostrand Reinhold Company, New York, N.Y. MEINHOLD, V.H., DUBLE, R.L.,. WEAVER, R.W. and HOLT, E.C Thatch accumulation in Bermudagrass turf in relation to management. Agron. J. 65: MURRAY, J.J. and JUSKA, F.V Effects of management practices on thatch accumulation, turf quality, and leaf spot damage in common Kentucky bluegrass. Agron. J. 69: SCHMIDT, R.E. and SHOULDERS,I.F Winter turf development on dormant Bermudagrass as influenced by summer cultivation and winter N fertilization. Agron. J. 64: SMITH, G.S Nitrogen and aerification influence on putting green thatch and soil. Agron. J. 7l: THOMPSON, W.R. and WARD, C.Y Prevent thatch accumulation on Tifgreen Bermudagrass greens. Golf Superintendent 34: YOUNGNER, V.B Ecological studies on Poa annua in turfgrasses. J. Br. Grassl. Soc. 14:

6 This article has been cited by: 1. K. Dickson, J. Sorochan, G. Munshaw, A. Thoms Comparison of Cultivation Methods Impact on Playability of Agrostis stolonifera Greens. Journal of Testing and Evaluation 46:3, [Crossref]