Effects of Drought on the Performance of Two Hybrid Bluegrasses, Kentucky Bluegrass and Tall Fescue

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1 TITLE: OBJECTIVE: AUTHOR: SPONSORS: Effets of Drought on the Performne of Two Hyrid Bluegrsses, Kentuky Bluegrss nd Tll Fesue Evlute the effets of drought on the visul qulity nd photosynthesis in two hyrid luegrsses ( Therml Blue nd Reveille ), one Kentuky luegrss ( Apollo ), nd one tll fesue ( Dynsty ) Kemin Su, Dle Bremer, Steve Keeley, Jk Fry The Sotts Co., GCSAA, Knss Turfgrss Foundtion INTRODUCTION: Drought stress is mjor prolem in ool-seson turfgrsses during summer months in the U.S. trnsition zone. Kentuky luegrss is fine-textured, high qulity ool-seson turfgrss ommonly used in thleti fields nd golf ourses firwys nd roughs. The performne of Kentuky luegrss is mrginl in the trnsition zone euse of its sensitivity to drought. Tll fesue, lso ool-seson grss, is sometimes used in golf ourse roughs nd is populr in lwns euse of its good drought resistne, ut some golf ourse superintendents do not like its orser texture. Hyrid luegrsses, whih re geneti rosses etween ntive Texs luegrss nd Kentuky luegrss, my hve similr visul qulity s Kentuky luegrss ut greter drought- nd het-resistne thn other ool-seson grsses. To further omplite the issue, inresing ompetition for wter mong industry, griulture, nd the puli hs resulted in restritions on turfgrss irrigtion. New ultivrs of hyrid luegrsses re eing investigted s potentil lterntives tht my perform etter under drought thn urrent ool-seson turfgrsses. Despite the potentil for using hyrid luegrsses in lwns nd golf ourse firwys nd roughs, little sientifi dt re ville out the field performnes of hyrid luegrsses in the trnsition zone, inluding under well-wtered nd drought onditions. METHODS: This study ws onduted from 3 August to 8 Otoer, 2004, nd from 27 June to 1 Septemer, 200, under n utomted rinout shelter (180 m 2 ) t the Roky Ford Turfgrss Reserh Center ner Mnhttn, KS (Fig. 1). Thirty two plots (1.36 x 1.76 m) of Kentuky luegrss ( Apollo ), tll fesue ( Dynsty ), nd two hyrid luegrsses ( Reveille nd Therml Blue ) were rrnged in rndomized omplete lok design with four replitions; plots were ordered y metl edging (10 m depth) to prevent lterl soil-wter movement etween djent plots. One wter defiit tretment, whih inluded the replement of 60% of the wter lost from plnt nd soil surfes vi evpotrnspirtion (ET), ws pplied to 16 plots, or 4 plots (reps) of eh speies/ultivr. The remining 16 plots were well wtered (100% ET replement) nd served s ontrol. To determine irrigtion requirements, evpotrnspirtion (ET) ws lulted y using the Penmn-Monteith eqution (FAO, 1998) nd limtologil dt otined t wether sttion loted t Roky Ford Turfgrss Reserh Center. Wter ws pplied twie weekly through fn spry nozzle tthed to hose; meter ws tthed to ensure proper pplition rte. Plots were mowed t 7.62 m twie week with wlkehind rotry mower. Turf visul qulity ws rted on sle of 1 to 9 (1=poorest qulity, 6=minimlly eptle, nd 9=highest qulity) ording to olor, texture, density, nd uniformity. Qulity rtings were reorded weekly y the sme individul during the 2-yer study. Photosynthesis ws mesured iweekly on ler dys etween 1000 nd 1400 CST with n LI-6400 portle gs exhnge system using ustom surfe 36

2 hmer. Permnent polyvinyl hloride ollrs (10-m dim.) were pled rndomly t one lotion in eh plot nd were driven pproximtely m into the soil. Gross photosynthesis (Pg) ws estimted s the sum of photosynthesis mesured y sunlit hmer nd respirtion mesured y shded hmer. In ll plots, the volumetri soil wter ontent (θ v ) in the 0- to 0-m profile ws mesured weekly using time domin refletometry nd in drought plots t m using dul-proe het-pulse sensors. RESULTS: In well-wtered plots, visul qulity ws highest in tll fesue nd lowest in Therml Blue mong speies nd ultivrs. Visul qulity ws generlly higher in Reveille thn Therml Blue during the seond month of the study (Fig. 2A). In the drought tretment, tll fesue lso hd the highest visul qulity mong speies nd ultivrs. The visul qulity of Reveille ws greter thn Therml Blue nd Kentuky luegrss s the plots dried, ut then eme similr to Therml Blue nd Kentuky luegrss during the most severe prt of drought (Fig. 2B). After termintion of the drought tretment nd upon re-wtering (on 70 DOT), Therml Blue nd Reveille reovered fster thn Kentuky luegrss, nd oth hyrid luegrsses hd higher visul qulity thn Kentuky luegrss lte in the study (Fig. 1B). In well-wtered onditions, Pg ws generlly gretest in TF mong speies nd ultivrs (Fig. 3A). In the drought tretment, Pg ws greter in TF thn in Therml Blue nd KBG during the first two weeks, ut Pg therefter eme similr mong ultivrs nd speies. There ws generlly no differene in Pg etween TF nd Reveille (Fig. 3B). CONCLUSIONS: In well-wtered nd drought tretments, tll fesue hd highest the visul qulity nd gretest Pg mong speies nd ultivrs. In the drought tretment, Reveille performed etter thn Therml Blue, nd oth hyrids (i.e., Therml Blue nd Reveille) reovered from drought more quikly thn Kentuky luegrss. In generl, the performnes rnked: tll fesue > Reveille >= Therml Blue=Kentuky luegrss. 37

3 Figure 1. Rinout shelter (180 m2) t Roky Ford Turfgrss Reserh Center ner Mnhttn, KS. The rinout shelter utomtilly moved over plots (on trks) when rinfll egn, then retrted one hour fter rinfll ended. 38

4 Figure 2. Visul qulity of Therml Blue (HBG1), Reveille (HBG2), Kentuky luegrss (KBG), nd tll fesue (TF) rted on sle of 1 to 9 (1=poorest nd 9=highest) under well-wtered (A) nd drought (B) onditions in 200. Mens followed with the sme letter on given dy fter tretment initition (dys of tretment) re not signifintly different (P<0.0). 9 Well-wtered A 9 Drought B HBG1 HBG2 KBG TF Dys of tretment,

5 Figure 3. Gross photosynthesis (Pg; sum of photosynthesis nd respirtion) in Therml Blue (HBG1), Reveille (HBG2), Kentuky luegrss (KBG), nd tll fesue (TF) in well-wtered (A) nd drought (B) plots in 200. Mens followed with the sme letter on given dy fter tretment initition (dys of tretment) were not signifintly different (P<0.0). 3 3 Well-wtered A Drought B HBG1 HBG2 KBG TF Dys of tretment,