Late-season bermudagrass nutrition and cold tolerance ... - GCSAA

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081-092 Sept04Techwell 8/17/04 5:21 PM Page 84RESEARCHSept. 15. Both winters of the study (1998-1999 and 1999-2000) were mild for theregion, and no winter injury was observed inany of the plots. Thus, controlled freezing testswere used to determine the low temperaturesurvival of field-harvested rhizomes. Additionallate-summer nitrogen enhanced fall colorretention and spring green-up without affectingcold hardiness, as determined by rhizomesurvival after controlled freezing (11) (Table 3).Study 4: Munshaw and ErvinThis study used two-year-old Tifwaybermudagrass managed at 0.63 inch (16.0millimeters) on a silt loam (pH 6.8 andmedium-low soil-test levels of potassium of120 pounds/acre [134.5 kilograms/hectare])at the Virginia Tech Turfgrass ResearchCenter in Blacksburg. All plots received 1.0pound nitrogen/1,000 square feet (48.8kilograms/hectare) monthly from Maythrough July in 2001 and 2002. BeginningAug. 15 of each year, the nitrogen treatmentreceived additional nitrogen from ammoniumnitrate at 1.0 pound nitrogen/1,000square feet (48.8 kilograms/hectare) everythree weeks, with the last application aboutOct. 17. Therefore, annual nitrogen rates forthe control were 4.0 pounds/1,000 squarefeet (195.3 kilograms/hectare), and the nitrogentreatments received 7.0 pounds/1,000square feet (341.8 kilograms/hectare).The data show that the extra nitrogen didnot provide a large late-season color benefit.We may have applied the nitrogen, seen aquick greening response (although data werenot collected) and then had a frost before ourscheduled visual rating date, thereby losingthe data that showed the benefit. However,the most important point is that additionallate-season nitrogen enhanced Novembercolor retention without affecting cold hardiness,as determined by rhizome survival aftercontrolled freezing (Table 4) (11).The 2001-2002 winter was normal, andno field winterkill was noted. The 2002-2003winter was colder than normal, and Tifwaywinterkill of approximately 30% was noted.However, winterkill percentage was the sameregardless of late-season nitrogen rate.Study 5: Miller and DickensThe second standard practice of the lateseasonbermudagrass management scenario isto apply potassium liberally with the intentionof promoting plants that are more coldhardy.Researchers at Auburn Universityconducted a study to answer this question:How much potassium is enough?Mature Tifway bermudagrass, managed at0.5 inch (12.7 millimeters) on a loamy sand(pH 6.0) at the Auburn University TurfgrassResearch Center in Auburn, Ala., was used inthis 1992-1994 study. The objective was toevaluate the effects of high annual potassiumapplication rates on cold resistance inbermudagrass (10). Initial soil-available potassiumwas very low at 36.0 pounds/acre (40.4kilograms/hectare).Potassium was applied from April throughOctober to cover a low to very high range ofmonthly rates: 0, 0.25, 0.5, 1.0, 2.0 and 4.0pounds potassium/1,000 square feet (0,12.2, 24.4, 48.8, 97.6 and 195.3 kilograms/hectare).Only the three highest potassiumrates were chosen for determination ofcold resistance. The most significant resultsare outlined below.• At the end of the study (September1994), soil-test potassium levels wereapproximately 80 (low), 115 (low) and160 (moderate) pounds/acre (89.7, 128.9and 179.3 kilograms/hectare) for the 1.0,2.0 and 4.0 pounds potassium/1,000square feet/month (0, 48.8, 97.6 and195.3 kilograms/hectare/month) treatments,respectively.• The amount of potassium in bermudagrassleaf tissue increased until the 1.0 poundpotassium/1,000 square feet/month (97.6kilograms/hectare) level was reached. Atthis monthly potassium level and above,leaf-tissue potassium flat-lined at approx-COLOR AND FREEZING TOLERANCE, 2001-2002Nitrogen applicationTurf color (9 = darkest)August September October NovemberControl 8.2 8.0 7.0 3.6Late-season 8.2 7.9 7.2 4.3*% rhizome survival following freezing †39 F (3.9 C) 27 F (-2.8 C) 23 F (-5 C) 19 F (-7.2 C)Control 57.5 23.3 8.6 0.0Late-season 50.7 23.2 6.9 0.7*Significantly different from the control.†The percenages for rhizome survival following freezing are the averages of the data from Jan. 2 and Feb. 3, 2002.Table 4. Color ratings of Tifway bermudagrass and rhizome freezing tolerance as affected by late-summer and fall nitrogen applications averaged over 2001 and 2002.84 GCMSeptember 2004
081-092 Sept04Techwell 8/17/04 5:21 PM Page 85RESEARCHimately 1.1%. This indicates that plantuptake of potassium was saturatedat monthly application rates of 1.0 poundor above.• Greenhouse, lab and field observationsindicated that applied potassium had noeffect on cold resistance.ConclusionsA 1971 trial (6) demonstrated that adequate,balanced ratios of nitrogen and potassiumwere more effective in promotingwinter survival of two bermudagrass cultivarsthan either high-nitrogen or high-potassiumfertilization programs. All of the studies summarizedin this paper, in which potassiumwas maintained at approximately moderatesoil-test sufficiency levels throughout theexperiments, support these earlier reports andsuggest that continuing nitrogen fertilizationinto the later months of the growing seasondoes not significantly affect freeze toleranceof bermudagrass, as long as other macronutrientssuch as potassium are not limiting.The last 15 years of research in the uppersoutheast and the transition zone of theUnited States indicate the possibility of aparadigm shift in our late-season nutrientmanagement of bermudagrass. Keepingbermudagrass green later in the fall has notresulted in a loss of cold-hardiness.We have two recommendations, withthree added precautions.If soil tests indicate potassium levels are inthe moderate to high range (121-400pounds/acre [135.6-448.3 kilograms/hectare), high rates of potassium do not needto be applied late in the season to improvebermudagrass cold hardiness.Applications of soluble nitrogen at 0.5 to1 pound nitrogen/1,000 square feet (24.4-48.8 kilograms/hectare) at two- to four-weekintervals, until hard frosts have resulted incomplete dormancy, will prolong fall colorretention and may enhance spring green-up(Figure 2).• Precaution 1. Apply lower rates of nitrogenon sandy soils where the risk of nitrateleaching is greater.• Precaution 2. Prove the benefits of late-seasonnitrogen to yourself and your constituentson a small scale beforeimplementing on the whole course.Experiment with rates and timings foryour location on one fairway or nurseryarea for at least one year.• Precaution 3. Be especially skeptical whenFigure 2. Late-October color resonses of Tifway bermudagrass three weeks after treatments were applied. From top tobottom, the treatments were: no nitrogen treatment, ammonium nitrate, IBDU (Isobutylidene Diurea, a slow-release nitrogensource) and methylene urea.considering the implementation of lateseasonnitrogen on areas of the course historicallyprone to spring dead spot, as someresearch and experience has indicatedhigher late-season nitrogen causes greaterincidence of spring dead spot (9).Literature cited1. Adams, W.E., and M. Twersky. 1959. Effect of soilfertility on winter killing of Coastal bermudagrass.Agronomy Journal 52:325-326.2. Beard, J.B. 1973. Turfgrass: Science and culture.Prentice-Hall, Englewood Cliffs, N.J.3. Beard, J.B., and P.K. Rieke. 1966. The influence ofnitrogen, potassium and cutting height on the lowtemperature survival of grasses. AgronomyAbstracts 58:34.4. Carroll, J.C., and F.A. Welton. 1939. Effect of heavyand late applications of nitrogenous fertilizer on thecold resistance of Kentucky bluegrass. PlantPhysiology 14:297-308.5. Carrow, R.N., D.V. Waddington and P.E. Rieke. 2001.Turfgrass soil fertility and chemical problems. AnnArbor Press, Chelsea, Mich.6. Gilbert, W.B., and D.L. Davis. 1971. Influence of fertilityratios on winter hardiness of bermudagrass.Agronomy Journal 63:591-593.7. Goatley, J.M. Jr., V. Maddox, D.J. Lang and K.K.Crouse. 1994. ‘Tifgreen’ bermudagrass response tolate-season application of nitrogen and potassium.Agronomy Journal 86:7-10.8. McCarty, L.B. 2001. Best golf course managementpractices. Prentice-Hall, Upper Saddle River, N.J.9. McCarty, L.B., L.T. Lucas and J.M. DiPaola. 1992.Spring dead spot occurrence in bermudagrass followingfungicide and nutrient applications.HortScience 27(10):1092-1093.10. Miller, G.L., and R. Dickens. 1996. Potassium fertilizationrelated to cold resistance in bermudagrass.Crop Science 36:1290-1295.11. Munshaw, G., and E.H. Ervin. 2004. Nutritional andPGR effects on lipid unsaturation, osmoregulantcontent, and relation to bermudagrass cold hardiness.Ph.D. dissertation, Virginia PolytechnicInstitute and State University: ETD-01162004-171301.12. Richardson, M.D. 2002.Turf quality and freezing toleranceof ‘Tifway’ bermudagrass as affected bylate-season nitrogen and trinexapac-ethyl. CropScience 42:1621-1626.13. Schmidt, R.E., and D.R. Chalmers. 1993. Late summerto early fall application of fertilizer and biostimulantson bermudagrass. International TurfgrassSociety Research Journal 7:715-721.14. Turgeon, A.J. 2002. Turfgrass management, 6th ed.Prentice-Hall, Upper Saddle River, N.J.E.H. Ervin, Ph.D. (ervin@vt.edu), is an assistant professorand J.M. Goatley Jr., Ph.D., is a turfgrass specialistin the department of crop and environmental scienceat Virginia Polytechnic Institute and State University,Blacksburg; M.D. Richardson, Ph.D., is an associateprofessor in the department of horticulture, Universityof Arkansas, Fayetteville; and G. Munshaw, Ph.D., is anassistant professor in the department of plant and soilsciences, Mississippi State University, Starksville.September 2004GCM 85
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