TURFGRASS SCIENCE. Nitrogen/Potassium Fertilization Ratios for Bermudagrass Turf. George H. Snyder* and John L. Cisar

Transcription

1 TURFGRASS SCIENCE /Potassium Fertilization Ratios for Bermudagrass Turf George H. Snyder* and John L. Cisar ABSTRACT bermudagrass turf quality and shoot density were as Turfgrass fertilizers often contain approximately one-half as much good at the 50 kg K ha 1 rate as at any higher rate. potassium (K) as nitrogen (N), on a weight basis. Since K fertilization Nevertheless, Augustin (1992) reported that some turf has been shown to be very beneficial for turfgrass appearance and managers are using relatively large amounts of K fertilgrowth, higher rates of K fertilization, relative to N, have been sug- izer; i.e., fertilizing with K in amounts equal to or even gested. The effect of K/N fertilization ratios on Tifgreen bermu- exceeding the rate of N, and the authors have observed dagrass [Cynodon dactylon (L.) Pers. C. transvaalensis Burtt- an increasing trend for turfgrass managers to subscribe Davy] growth and quality was studied over a 3-yr period in south to this practice. For this reason, the current study was Florida for three rates of N fertilization. Severe K deficiencies were conducted to evaluate the effect of N/K fertilization observed in the absence of K fertilization. However, increasing K fertilization beyond a K/N fertilization ratio of 0.5 to 1 had virtually no ratios on bermudagrass turf growth and visual quality effect on turfgrass appearance, growth, on resistance to bermudagrass at three rates of N fertilization. decline, or on root weight. Increasing K fertilization relative to N fertilization did not provide commensurate increases in tissue K. METHODS AND MATERIALS The study was established on a mature sward of Tifgreen T bermudagrass growing on Hallandale fine sand (Siliceous, hyperthermic Lithic Psammaquent) at the Ft. Lauderdale (Flor- urfgrass fertilizers generally contain more N and K than other nutrients, since N and K are required ida) Research and Education Center (FLREC). The field deby turfgrasses in greater amounts (mass basis) than sign was a split plot, with six replications. Main plots, 3 m those of other fertilizer elements. Because turfgrasses 8 m, were fertilized at 2.5, 5.0, or 10.0 g N m 2 from (NH 4 ) 2 SO 4 have been shown to take up approximately half as much beginning 13 Feb. 1990, and were similarly fertilized near the middle of each month through February Subplots, 2 by K as N, it is sometimes recommended that these ele- 3 m, were fertilized with K (KCl) on the same day as the N ments be applied in a 2/1 (N/K) ratio (Turgeon, 1985). fertilizations to provide K/N ratios of 0, 0.5, 1.0, or 2.0 (K/N Various studies have focused on the importance of fertilization ratios are stipulated instead of N/K ratios, since K for maintaining turfgrass quality. Improved disease the no K treatment would produce an undefined N/K ratio, resistance, drought, heat and wear tolerance (Turner i.e., infinity). A Turf-Tender drop-type spreader (Gandy Co., and Hummel, 1992), and enhanced root growth and cold Owatonna, MN) was used for the N fertilization and weighed hardiness (Beard, 1973, p. 417) have been attributed to amounts of KCl were applied to subplots by hand. Approxi- adequate K fertilization. Furthermore, K is subject to mately 10 mm of irrigation was applied following each N and leaching in many soils (Beard, 1982, p. 141), or to fixastudy to maintain adequate soil moisture. The area was mowed K fertilization, and irrigation was provided throughout the tion in others (Brady, 1990, p ). In a growth at 1.3-cm height, and mowing frequency was adjusted to minichamber study, Gilbert and Davis (1971) concluded that mize scalping. Clippings were removed. During April 1991, a 4N/6K ratio was superior among the ratios evaluated the cutting height was lowered gradually over several weeks for providing top growth of bermudagrass (Cynodon to 0.6 cm to increase stress on the turf. This mowing height spp.) following a cold treatment, although statistically was maintained throughout the remainder of the study. (P 0.05) the 4N/6K ratio was no better than a 4N/3K On 30 Jan. 1991, a material containing 850 g elemental S or 2N/1K ratio. They recommended applying ade- and 50 g Mn kg 1 (STM-5; Traylor Chemical Co., Orlando, quate K in the late summer for improving cold resisreceiving N fertilizer at the rate of 2.5, 5.0, and 10.0 g m 2, FL) was applied at the rate of 50, 25, and 0 g m 2 to plots tance. However, even considering cold hardiness, Razmrespectively. On 14 July 1992, the entire plot area received joo and Kaneko (1993) reported that a 2N/1K ratio was sufficient to prevent winter dormancy and provide good Mg, Fe, Mn, Zn, and Cu at the rate of 100, 10, 10, 3, and 1 kg ha 1, respectively. Herbicides and insecticides were applied winter quality of perennial ryegrass (Lolium perenne L.) according to label specifications when required. in Japan. In a field study involving annual N fertilization Two weeks after each N and K fertilization, plots were rates ranging from 100 to 300 kg ha 1 and K rates from rated visually for quality on a 1-to-10 scale with 10 best 50 to 300 kg ha 1, Johnson et al. (1987) concluded that possible turf, 6 minimally acceptable turf, and 1 dead or brown turf. In conjunction with visual ratings, clippings from G.H. Snyder, Everglades Research and Education Center, Univ. of a 1.36-m 2 area were taken from each plot with a greens mower. Florida, P. O. Box 8003, Belle Glade, FL 33430; J.L. Cisar, Ft. Lauder- The clippings were oven dried at 60 C, weighed, ground in a dale Research and Education Center, Univ. Florida, 3205 College stainless steel mill (Arthur Thomas Co., Philadelphia, PA), Ave., Ft. Lauderdale, FL Contribution from the Florida Agric. wet digested (Lowther, 1986), and analyzed for N by auto- Exp. Stn. Journal Series no. R Received 22 March *Corresponding author (ghs@gnv.ifas.ufl.edu). Abbreviations: FLREC, Ft. Lauderdale Research and Education Center; Q1, Q2, Q3, Q4, Quarter 1, Quarter 2, Quarter 3, Quarter Published in Crop Sci. 40: (2000)

2 1720 CROP SCIENCE, VOL. 40, NOVEMBER DECEMBER 2000 Table 1. Effect of nitrogen fertilization on soil ph. Table 2. Effect of potassium fertilization on soil potassium in Sample date (month/year) samples taken just prior to potassium fertilizations. N rate 5/90 1/91 3/92 1/93 Sample date (month/year) gm 2 K rate 1/91 1/ gm 2 mg Kg mated colorimetry (Technicon AutoAnalyzer II; Technicon Instr. Corp., Tarrytown, NY) and for K by atomic absorption spectrometry (Varian Techtron Pty. Ltd, Springvale, Australia). Periodically, soil samples 0 to 10 cm deep were taken from each plot, or were composited across selected treatments, matter and cation exchange capacity. Apparently this and analyzed for ph (1 soil:2 water), and Mehlich I (0.05 M goal was achieved, judging by the wide range of soil HCl in M H 2 SO 4 ) extractable P, K, Ca, and Mg by K values observed in samples taken just prior to K the Extension Soil Test Laboratory, University of Florida, fertilizations (Table 2), which extend below and above Gainesville. On 4 Oct. 1990, 25 Mar. 1992, and 24 Feb. 1993, the critical soil-test value of 60 mg kg 1 provided by root weights were determined in cores 0 to 10, 10 to 20, and Sartain et al. (1999). 20 to 30 cm deep (measured below the thatch layer) and 7.5-cm Soil-test values for P appeared adequate for turfgrass diam taken from each plot (two cores per plot on the first growth throughout the study (data not presented). date, one core on the latter two dates) with a tractor-mounted sampler (Giddings, Ft. Collins, CO). Thatch depth was recorded. The roots were washed fairly free of soil, oven dried Quality Ratings (60 C), weighed, ashed in a muffle furnace (550 C), and re- fertilization always had a significant (P weighed. Root data are presented as ash-free weight, i.e., 0.05) influence on visual quality ratings (Table 3). In all oven dry weight minus ash weight. All observations that were collected on a monthly basis quarters except one, N increased visual rating scores. (e.g., ratings, clipping weights, tissue analyses) were averaged However, in the third quarter (Q3) of 1991, there was on a plot by plot basis over 3-mo intervals beginning April, a significant decrease in visual rating with increased 1990, to condense and simplify data presentation. Statistical N. A severe outbreak of bermudagrass decline disease analyses were performed on these 3-mo averages. Data were (a.k.a. Take all, caused by Gaeumannomyces graminis analyzed as a split-plot design (N Main plot, K/N sub- (Sacc.) von Arxd D. Olivier; Elliott, 1991) was observed plot) by SAS (1988) PROC ANOVA. during this quarter. Ratings for disease severity on 18 Sept revealed that the disease was aggravated RESULTS AND DISCUSSION by high N (personal communication, M. Elliott, Turf Pathologist, FLREC). When rated on a scale of 1 to 5, Soil Analysis where 5 indicated no disease and 1 indicated 80 to 100% Soil ph decreased both with time and with the rate thinning or chlorosis of turf due to disease, the 2.5, 5.0, of N fertilization (Table 1), as might be expected since and 10.0 g N m 2 rates produced ratings of 4.7, 2.8, and (NH 4 ) 2 SO 4 was the N source. Nevertheless, in Jan. 1991, 2.3, respectively (LSD ). Outbreak of this latesoil ph was sufficiently high in plots receiving 2.5 or summer disease was not observed in the first or last 5.0gNm 2 monthly that a S and Mn mixture was year of the study. However, plot ratings at higher N applied to these plots, as was described in the Methods rates were somewhat lower after Q3 1991, than they section, in order to prevent Mn deficiency due to high were before this period. Lower ratings may have re- ph. Soil ph declined after the S and Mn application sulted from incomplete recovery from bermudagrass (Table 1). In a previous study at the FLREC (Snyder decline, although they also may have been the result of et al., 1979), Mn deficiency was observed when soil ph the lowered cutting height imposed in the first month exceeded 7.0, and was prevented when soil ph was of Q2 1991, and maintained thereafter. reduced by (NH 4 ) 2 SO 4 as the N source to counter the Potassium to N fertilization ratio (K/) significantly liming effect caused by high-ph irrigation water containing affected visual ratings in all quarters of the study. appreciable amounts of carbonates and bicar- This effect occurred mainly because of the poor performance bonates. It was for this reason that (NH 4 ) 2 SO 4 was chosen of plots receiving no K (K/ 0). There as the N source in the current study. In the previous were only minor differences in visual ratings among study, excellent bermudagrass turf quality and growth plots receiving widely differing K/N ratios, as long as were obtained even when soil ph was below 5.0, since some K was applied. There were some significant interactions the soil contains little Al or other elements that reach between N and K/N, occurring mainly in the final toxic levels of availability in acid soils. Therefore, we year of the study (Table 3). This interaction occurred do not believe that the low soil phs observed in the because, with increasing N, there were greater differ- latter part of the current study were deleterious to ber- ences in plot ratings between the K/N 0 ratio and the mudagrass growth and quality. ratios that were greater than 0. In other words, at low Potassium was applied monthly to maintain a range rates of N fertilization, the absence of K fertilization of soil K levels across the K treatments, since K is subject created less loss of visual quality than occurred when to leaching in irrigated sand soils with little organic higher N rates were used. However, the effect of K/N

3 SNYDER & CISAR: NITROGEN/POTASSIUM FERTILIZATION RATIOS FOR BERMUDAGRASS TURF 1721 Table 3. Effect of N and K/N Fertilization Ratio on visual quality ratings of bermudagrass turf, averaged by quarters (Q) of a Table 4. Effect of N and K/N Fertilization Ratio on clipping weights of bermudagrass turf, averaged by quarters (Q) of a Sig. ** ** ** ** ** ** ** ** ** * ** LSD Sig. ** ** ** ** ** ** * ** ** ** ** K/ LSD K/ Sig. ** ** ** ** ** ** ** ** ** ** ** LSD Sig. * * ** ** ** ** ** ** ** ** ** N K/ Interaction LSD N K/ Interaction Sig. NS NS * NS * NS ** ** ** ** ** LSD Sig. NS NS ** ** NS NS NS ** ** NS ** LSD remained the same at all three N rates, i.e., there was little difference in visual quality among the three K/N ratios that provided some K. A similar observation was Table 5. Effect of N and K/N Fertilization Ratio on the N content made for the relationship between bermudagrass deyear for 3 yr. of bermudagrass turf clippings, averaged by quarters (Q) of a cline ratings and K/N. There was little difference in rating among any of the three treatments providing K, although greater disease severity was observed when no K was provided. For example, for K/N ratios of 0, gkg 0.5, 1.0, and 2.0, the disease ratings (1-to-5 scale, 5 1 no disease) were 2.6, 3.5, 3.6, and 3.4 (LSD ) gm Sig. ** * NS ** ** * * ** ** ** NS LSD K/ Clipping Weights Results for clipping weights were similar to those for visual ratings. Clipping weights generally were increased by increasing N fertilization (Table 4). However, a sig nificant decrease in clipping weight was observed at the Sig. NS NS NS NS NS NS NS NS NS NS NS highest N rate in Q3, 1991, when bermudagrass decline LSD was observed. The consistently observed significant ef- N K/ Interaction fect of K/N ratio on clipping weights is mainly attribut able to the reduction in growth that occurred in the absence of any K fertilization (i.e., K/ 0) There were few differences in clipping weights among plots receiving some K, regardless of whether K was applied at half or at twice the rate of N. When interac tions occurred between N and K/N, the effect was mainly attributable to the increased response to any level of K, as opposed to no K, that occurred as N increased In this regard, the interaction was similar for visual Sig. NS NS NS NS NS * NS NS NS NS NS LSD ratings and clipping rates, and was due to the magnitude, but not the direction, of the response.

4 1722 CROP SCIENCE, VOL. 40, NOVEMBER DECEMBER 2000 Table 6. Effect of N and K/N Fertilization Ratio on the K content of bermudagrass turf clippings, averaged by quarters (Q) of a Table 7. Effect of N and K/N Fertilization Ratio on the ratio of N to K in bermudagrass turf clippings, averaged by quarters (Q) of a gkg Sig. * NS ** NS ** NS NS NS NS NS NS Sig. ** * ** ** ** NS ** ** ** ** ** LSD LSD K/ K/ Sig. ** ** ** ** ** ** ** ** ** ** ** Sig. ** ** ** ** ** ** ** ** ** ** ** LSD LSD N K/ Interaction N K/ Interaction Sig. ** ** ** ** ** ** ** ** ** ** NS Sig. ** ** ** ** ** ** ** ** ** ** ** LSD LSD and the three treatments providing some K fertilization. Tissue N and K There was, however, a small but consistent trend for increasing tissue K as the K/N fertilization ratio in- The N content of clippings generally increased with creased among the three ratios that provided some K. increasing N fertilization, but the K/N fertilization ratio Nevertheless, averaged across all 11 quarters, increasing had no effect on tissue N, and there generally was no the K/N fertilization ratio four-fold (from ) ininteraction between these treatments (Table 5). Tissue creased tissue K by only 8%. A significant interaction K was also increased by N fertilization in all quarters between the treatment factors was observed in all quarexcept for Q3, 1991 (Table 6). This probably occurred ters. As with the ratings and clipping weights, the effect because as N fertilization increased, the absolute level was one of magnitude, and not of direction. When no of K fertilization was increased to achieve the target K was applied, there was little effect of N rate on tissue K/N fertilization ratios. The K/N fertilization ratio sig- K. But when some K was applied, tissue K increased nificantly increased tissue K throughout the study. How- with increasing N fertilization, probably for the reason ever, most of the increase occurred between K/N 0 previously presented. Table 8. Effect of N and K/N Fertilization Ratio on thatch accumulation in bermudagrass turf, and on root mass in the 0- to 10- and 20- to 30-cm depths, and on total root mass in the 0- to 30-cm depth for three sampling dates. October, 1990 March, 1991 February, 1993 Factor Thatch Total Thatch Total Thatch Total cm kg m 2 cm kg m 2 cm kg m Sig. ** * NS NS NS NS NS NS NS NS NS NS LSD K/ Sig. NS NS NS NS NS NS NS NS NS ** ** * LSD Sig. of N K/ Interaction NS NS NS NS NS NS NS NS NS NS NS NS

5 SNYDER & CISAR: NITROGEN/POTASSIUM FERTILIZATION RATIOS FOR BERMUDAGRASS TURF 1723 Tissue N/K ACKNOWLEDGMENTS The authors express their appreciation to Dr. Bruce Augustin (presently The Scotts Co.), and LESCO, Inc., for agro- chemicals used in this study, and to Karen Williams for techni- cal management of the experiment. The technical assistance provided by Eva Green, Theresa Sanford, Esther Figueiras, and Norman Harrison has also been very much appreciated. fertilization had little effect on the N/K ratio in plant tissue, but this observation should be viewed in the light of the N K/N interaction described below (Table 7). The ratio of K/N fertilization significantly affected the tissue N/K ratio, but most of the effect was between the ratio providing no K, and the three ratios providing some K. In the absence of K fertilization, the tissue N/K ratio increased from approximately 3.5 to over 7.0 during the course of the study. But in the presence of K fertilization, the N/K ratio varied only slightly around 2.0. Although there was a trend for decreased tissue N/K ratio with increasing K/N fertilization ratios that provided some K, averaged across all 11 quarters, a four-fold increase in K/N fertilization ratio resulted in only a 7% decrease in the tissue N/K ratio. Significant interactions between N fertilization and K/N fertilization ratio occurred because in the absence of K fertilization, N fertilization increased the tissue N/K ratio, whereas in the presence of K fertilization, increasing N fertilization, with subsequent increases in K fertilization to maintain K/N fertilization ratios, decreased the tissue N/K ratio. less, even across this range of conditions, increasing K fertilization beyond a K/N ratio of 0.5 to 1 had virtually no effect on turfgrass appearance, growth, resistance to bermudagrass decline, thatch depth, or root weight. Perhaps this occurred because increasing K fertilization relative to N fertilization did not provide commensurate increased in tissue K. REFERENCES Augustin, B.J Surviving drought. Grounds Maintenance 27(5):65,94. Beard, J.B Turfgrass: Science and culture. Prentice-Hall, Inc. Englewood Cliffs, NJ. Beard, J.B Turf management for golf courses. Macmillan Publishing Co., New York. Brady, N.C The nature and properties of soils. 10th Ed. Macmil- lan Publishing Co., New York. Elliott, M.L Determination of an etiological agent of bermudagrass decline. Phytopathology 81: Gilbert, W.B., and D.L. Davis Influence of fertility ratios on Thatch and Roots winter hardiness of bermudagrass. Agron. J. 63: fertilization significantly increased both Johnson, B.J., R.N. Carrow, and R.E. Burns Bermudagrass turf response to mowing practices and fertilizer. Agron. J. 79: thatch accumulation and the ash-free root weight in the Lowther, J.R Use of a single H 2 SO 4 -H 2 O 2 digest for the analysis 0- to 10-cm layer in the fall of the first year of the study, of Pinus radiata needles. Commun. Soil Sci. Plant Anal. 11: but had no effect on these or on other root weights Razmjoo, K., and S. Kaneko J. Plant Nutr. 16(8): during the remainder of the study (Table 8). The K/N Sartain, J.B., G.L. Miller, G.H. Snyder, J.L. Cisar, and J.B. Unruh Fertilizer program. p In J.B. Unruh and M.C. Elliott fertilization ratio had no effect on thatch accumulation, (ed.) Best management practices for Florida golf courses. 2nd ed. and only affected root weights in the final sampling. In SP-141. University of Florida, Gainesville, FL. the Feb sampling, there were less roots in the SAS, SAS/STAT Guide for personal computers. 6th ed. SAS Inst., Cary, NC. top (0 10 cm), bottom (20 30 cm), and total (0 30 cm) Snyder, G.H., E.O. Burt, and G.J. Gascho Correcting phportions of the sampled soil profile when no K was induced manganese deficiency in bermudagrass turf. Agron. J. 71: applied (Table 8). However, when K was applied in any of the three K/N ratios studied, there were no differpany, Inc. Reston, VA. Turgeon, A.J Turfgrass management. Reston Publishing Com- ences in root weights among the ratios. Turner, T.R., and N.W. Hummel, Jr Nutritional requirements A range of soil ph, soil K, clipping height, and disease and fertilization. p In D.V. Waddington et al. (ed.) Turfgrass. Agron. Monogr. 32. ASA., Madison, pressure occurred during the 3 yr of the study. Neverthe- WI.