ESTABLISHMENT, DROUGHT TOLERANCE AND RECOVERY, AND CANOPY ANALYSIS OF TURFGRASSES IN THE TRANSITION ZONE ANTHONY LEE GOLDSBY

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1 ESTABLISHMENT, DROUGHT TOLERANCE AND RECOVERY, AND CANOPY ANALYSIS OF TURFGRASSES IN THE TRANSITION ZONE y ANTHONY LEE GOLDSBY B.S., Knss Stte University, 2005 M.S., Knss Stte University, 2008 AN ABSTRACT OF A DISSERTATION sumitted in prtil fulfillment of the requirements for the degree DOCTOR OF PHILOSOPHY Deprtment of Horticulture, Forestry, nd Recretion Resources College of Agriculture KANSAS STATE UNIVERSITY Mnhttn, Knss 2013

2 Astrct Incresing wter scrcity my result in greter irrigtion restrictions for turfgrss. Drought tolernce nd recovery of Kentucky luegrsses (Po. prtensis L.) (KBG) were evluted during nd fter 88 nd 60 dy dry downs in 2010 nd 2011, respectively, under rinout shelter. Chnges in green coverge were evluted with digitl imges. Green coverge declined slowest during dry downs nd incresed fstest during recoveries in the cultivr Apollo, indicting it hd superior drought tolernce. Electrolyte lekge, photosynthesis, nd lef wter potentil were evluted in 7 KBG cultivrs during nd fter the dry downs. Soil moisture t 5 nd 20 cm ws mesured. There were generlly no differences in physiologicl prmeters mong cultivrs during or fter dry down. The highest reduction in soil moisture t 5 nd 20 cm ws in Apollo, suggesting it hd etter developed root system for mining wter from the profile during drought. Weed prevention nd turfgrss estlishment of Legcy ufflogrss (Buchloe dctyloides [Nutt.] Engelm.) nd Chisholm zoysigrss (Zoysi jponic Steud.) grown on turf reinforcement mts (TRM) ws evluted. Chisholm zoysigrss stolons grew under the TRM; s such, use of TRM for this cultivr is not prcticl. Bufflogrss hd 90% or greter coverge when estlished on TRM in 2010 nd 65% or greter coverge in 2011; coverge ws similr to tht in oxdizon-treted plots t the end of ech yer. Legcy ufflogrss plugs were estlished on TRM over plstic for 3 weeks, stored in TRM under tree shde for 7, 14, or 21 dys, nd evluted for estlishment fter storge. In 2010, plugs on mts stored for 7 dys hd similr coverge to the control, ut in 2011 displyed similr coverge to plugs stored on TRM for 14 or 21 dy tretments. Green lef re index (LAI) is n importnt indictor of turfgrss performnce, ut its mesurement is time consuming nd destructive. Mesurements using hyperspectrl rdiometry were compred with destructive mesurements of LAI. Results suggest spectrl rdiometry hs potentil to ccurtely predict LAI. The roustness of prediction models vried over the growing seson. Finding one model to predict LAI cross nd entire growing seson still seems unrelistic.

3 ESTABLISHMENT, DROUGHT TOLERANCE AND RECOVERY, AND CANOPY ANALYSIS OF TURFGRASSES IN THE TRANSITION ZONE y ANTHONY LEE GOLDSBY B.S., Knss Stte University, 2005 M.S., Knss Stte University, 2008 A DISSERTATION sumitted in prtil fulfillment of the requirements for the degree DOCTOR OF PHILOSOPHY Deprtment of Horticulture, Forestry, nd Recretion Resources College of Agriculture KANSAS STATE UNIVERSITY Mnhttn, Knss 2013 Approved y: Co-Mjor Professor Dle J. Bremer Approved y: Co-Mjor Professor Jck Fry

4 Astrct Incresing wter scrcity my result in greter irrigtion restrictions for turfgrss. Drought tolernce nd recovery of Kentucky luegrsses (Po. prtensis L.) (KBG) were evluted during nd fter 88 nd 60 dy dry downs in 2010 nd 2011, respectively, under rinout shelter. Chnges in green coverge were evluted with digitl imges. Green coverge declined slowest during dry downs nd incresed fstest during recoveries in the cultivr Apollo, indicting it hd superior drought tolernce. Electrolyte lekge, photosynthesis, nd lef wter potentil were evluted in 7 KBG cultivrs during nd fter the dry downs. Soil moisture t 5 nd 20 cm ws mesured. There were generlly no differences in physiologicl prmeters mong cultivrs during or fter dry down. The highest reduction in soil moisture t 5 nd 20 cm ws in Apollo, suggesting it hd etter developed root system for mining wter from the profile during drought. Weed prevention nd turfgrss estlishment of Legcy ufflogrss (Buchloe dctyloides [Nutt.] Engelm.) nd Chisholm zoysigrss (Zoysi jponic Steud.) grown on turf reinforcement mts (TRM) ws evluted. Chisholm zoysigrss stolons grew under the TRM; s such, use of TRM for this cultivr is not prcticl. Bufflogrss hd 90% or greter coverge when estlished on TRM in 2010 nd 65% or greter coverge in 2011; coverge ws similr to tht in oxdizon-treted plots t the end of ech yer. Legcy ufflogrss plugs were estlished on TRM over plstic for 3 weeks, stored in TRM under tree shde for 7, 14, or 21 dys, nd evluted for estlishment fter storge. In 2010, plugs on mts stored for 7 dys hd similr coverge to the control, ut in 2011 displyed similr coverge to plugs stored on TRM for 14 or 21 dy tretments. Green lef re index (LAI) is n importnt indictor of turfgrss performnce, ut its mesurement is time consuming nd destructive. Mesurements using hyperspectrl rdiometry were compred with destructive mesurements of LAI. Results suggest spectrl rdiometry hs potentil to ccurtely predict LAI. The roustness of prediction models vried over the growing seson. Finding one model to predict LAI cross nd entire growing seson still seems unrelistic.

5 Tle of Contents List of Figures... viii List of Tles... xiv Acknowledgements... xv Dediction... xvi Chpter 1 - Response of Kentucky Bluegrss Cultivrs to Prolonged Drought Stress in the Trnsition Zone... 1 Astrct... 2 Introduction... 3 Mterils nd Methods... 5 Study site nd experimentl design... 5 Plot Mintennce... 7 Mesurements... 7 Sttisticl nlysis... 8 Results nd Discussion Conclusions Figures nd Tles References Chpter 2 - Physiologicl responses of Kentucky Bluegrss Cultivrs to Prolonged Drought Stress in the Trnsition Zone Astrct Introduction Mterils nd Methods Study site nd experimentl design Mesurements Sttisticl nlysis Results nd Discussion Percent green coverge nd visul color nd qulity rtings Soil Wter Content v

6 Lef Wter Potentil Electrolyte Lekge Gross Photosynthesis Conclusions Figures nd Tles References Chpter 3 - Evlution of Turf Reinforcement Mts nd Their Effect on Estlishment of Bufflogrss nd Zoysigrss Astrct Introduction Mterils nd Methods Study site nd experimentl design Turf Reinforcement Mts Plot Mintennce Mesurements Results nd Discussion Turfgrss Estlishment nd Weed Suppression Zoysigrss Bufflogrss Economic Considertions Conclusions Figures nd Tles References Chpter 4 - Estlishment of Bufflogrss from Vegettive Plugs fter Short-term Storge on Turf Reinforcement Mts Astrct Introduction Mterils nd Methods Study sites nd experimentl design Turf Reinforcement Mt Mesurements vi

7 Sttisticl Anlysis Results nd Discussion Conclusion Figures nd Tles References Chpter 5 - Utilizing hyperspectrl rdiometry to predict green lef re index of Kentucky luegrss Astrct Introduction Mterils nd Methods Study Site nd experimentl design Plot Mintennce Mesurements Sttisticl Anlysis Results nd Discussion Conclusions Figures nd Tles References vii

8 List of Figures Figure 1.1- Averge ir temperture during the dry downs in 2010 nd Solid lck lines signify the strt nd cesstion of the 2010 dry down. Dshed lck lines signify the strt nd cesstion of the 2011 dry down. Mrkers represent 5 dy verges Figure 1.2- Originl imge (left) followed y the color composite imge fter eing processed with imge nlysis softwre (right). The softwre identifies pixels tht fll under preset green hue settings nd then highlights them in red Figure 1.3- Plots on Septemer 4, 2010, fter receiving no irrigtion for 88 dys Figure 1.4- Plots on August 1, 2011, fter receiving no irrigtion for 60 dys Figure 1.5- Digitl imges of ll three replictes of the KBG cultivr Cernet in 2010, t the eginning (26 June) nd end (2 Sept.) of the dry down nd fter 60 dys of recovery (5 Nov.) Figure 1.6- Predicted dry-down curves for the 30 luegrsses in Figure 1.7- Predicted dry-down curves for 30 luegrsses in Figure 1.8- The 95% confidence intervls for the numer of dys fter irrigtion ws withheld until luegrss cultivrs reched 75% nd 25% green cover in Green rs represent dys until cultivrs reched 75% nd lue represent 25% green cover. Cultivrs with overlpping rs were not significntly different Figure 1.9- The 95% confidence intervls for the numer of dys fter irrigtion ws withheld until luegrss cultivrs reched 75% nd 25% green cover in Green rs represent dys until cultivrs reched 75% nd lue represent 25% green cover. Cultivrs with overlpping rs were not significntly different Figure Predicted recovery curves for 30 luegrsses in Figure Predicted recovery curves for 30 luegrsses in Figure The 95% confidence intervls for the numer of dys fter irrigtion until luegrss cultivrs reched 75% green cover in Cultivrs with overlpping rs were not significntly different Figure The 95% confidence intervls for the numer of dys fter irrigtion until luegrss cultivrs recovered in Cultivrs with overlpping rs were not significntly different viii

9 Figure 2.1- Averge ir temperture during the dry downs in 2010 nd Solid lck lines signify the strt nd cesstion of the 2010 dry down. Dshed lck lines signify the strt nd cesstion of the 2011 dry down. Mrkers represent 5 dy verges Figure 2.2- Predicted dry-down curves of 7 cultivrs of KBG during 60-dy dry down in Tretments included Apollo; Bedzzled; Moonlight; Cernet; Blue Velvet; Aey nd Wellington. Dshed line indictes DAI Figure 2.3- Predicted dry-down curves of 7 cultivrs of KBG during 60-dy dry down in Tretments included Apollo; Bedzzled; Moonlight; Cernet; Blue Velvet; Aey nd Wellington. Dshed line indictes DAI Figure 2.4- Predicted recovery curves of 7 cultivrs of KBG following 60-dy dry down in Tretments included Apollo; Bedzzled; Moonlight; Cernet; Blue Velvet; Aey nd Wellington. Dshed line indictes DAI Figure 2.5- Predicted recovery curves of 7 cultivrs of KBG following 60-dy dry down in Tretments included Apollo; Bedzzled; Moonlight; Cernet; Blue Velvet; Aey nd Wellington. Dshed line indictes DAI Figure 2.6- Visul qulity rting of 7 cultivrs of KBG during 60-dy dry down in 2010 nd Tretments included Apollo; Bedzzled; Moonlight; Cernet; Blue Velvet; Aey nd Wellington. Verticl solid lck lines in the ove grphs indicte the completion of the dry down. Verticl dotted lines in oth yers indicte rin shelter mlfunctions. Mens followed y the sme letter on dte re not significntly different ccording to the F-LSD (P < 0.05) Figure 2.7- Volumetric Wter Content (5cm) of 7 cultivrs of KBG during 60-dy dry down in 2010 nd Tretments included Apollo; Bedzzled; Moonlight; Cernet; Blue Velvet; Aey nd Wellington. Verticl solid lck lines in the ove grphs indicte the completion of the dry down. Verticl dotted lines in oth yers indicte rin shelter mlfunctions. Mrkers represent 5 dy verges. In 2011, dt were not ville in Bedzzled ecuse of sensor filure Figure 2.8- Volumetric Wter Content (20cm) of 7 cultivrs of KBG during 60-dy dry down in 2010 nd Tretments included Apollo; Bedzzled; Moonlight; Cernet; Blue Velvet; Aey nd Wellington. Verticl solid lck lines in the ove grphs indicte the ix

10 completion of the dry down. Verticl dotted lines in oth yers indicte rin shelter mlfunctions. Mrkers represent 5 dy verges Figure 2.9- Volumetric Wter Content (0-50cm) of 6 cultivrs of KBG during 60-dy dry down in Tretments included Bedzzled; Moonlight; Cernet; Blue Velvet; Aey nd Wellington. Verticl solid lck line in the ove grph indictes the completion of the dry down Figure Electrolyte Lekge of 6 cultivrs of KBG during 60-dy dry down in 2010 nd Tretments included Bedzzled; Moonlight; Cernet; Blue Velvet; Aey nd Wellington. Apollo ws not included in the dt collection for Red horizontl dshed line indictes level of 50% electrolyte lekge. Mens followed y the sme letter on dte re not significntly different ccording to the F-LSD (P < 0.05) Figure Gross Photosynthesis of 7 cultivrs of KBG during 60-dy dry down in 2010 nd Tretments included Bedzzled; Moonlight; Cernet; Blue Velvet; Aey nd Wellington. Apollo ws not included in the dt collection for Figure 3.1- Coverge of Chisholm zoysigrss from vegettive plugs s ffected y estlishment method t Mnhttn, KS in 2010 nd Tretments included plnting in turf reinforcement mts (TRM); ppliction of oxdizon t 3.9 kg.i. h -1 just fter plnting; nd untreted. Plnting ws done on 1 July 2010 nd 23 June 2011 nd susequent rting dtes re referred to s dys fter plnting (DAP). Coverge ws rted visully on 0 to 100% Scle. Mens followed y the sme letter on dte re not significntly different ccording to the Fisher s Protected LSD (P < 0.05) Figure 3.2- Weed coverge in Chisholm plots plnted s vegettive plugs s ffected y estlishment tretment t Mnhttn, KS in 2010 nd Tretments included plnting in turf reinforcement mts (TRM); ppliction of oxdizon t 3.9 kg.i. h -1 just fter plnting; nd untreted. Plnting ws done on 1 July 2010 nd 23 June 2011 nd susequent rting dtes re referred to s dys fter plnting (DAP). Coverge ws rted visully on 0 to 100% Scle. Mens followed y the sme letter on dte re not significntly different ccording to the Fisher s Protected LSD (P < 0.05) Figure 3.3- Coverge of Legcy ufflogrss from vegettive plugs s ffected y estlishment method t Mnhttn, KS in 2010 nd Tretments included plnting in turf reinforcement mts (TRM); ppliction of oxdizon t 3.91 kg.i. h -1 just fter x

11 plnting; nd untreted. Plnting ws done on 1 July 2010 nd 23 June 2011 nd susequent rting dtes re referred to s dys fter plnting (DAP). Coverge ws rted visully on 0 to 100% Scle. Mens followed y the sme letter on dte re not significntly different ccording to the Fisher s Protected LSD (P < 0.05) Figure 3.4- Weed coverge in Legcy ufflogrss plots plnted s vegettive plugs s ffected y estlishment tretment t Mnhttn, KS in 2010 nd Tretments included plnting in turf reinforcement mts (TRM); ppliction of oxdizon t 3.91 kg.i. h -1 just fter plnting; nd untreted. Plnting ws done on 1 July 2010 nd 23 June 2011 nd susequent rting dtes re referred to s dys fter plnting (DAP). Coverge ws rted visully on 0 to 100% Scle. Mens followed y the sme letter on dte re not significntly different ccording to the Fisher s Protected LSD (P < 0.05) Figure 4.1- Temperture inside TRM contining Legcy ufflogrss plugs during storge in Mnhttn, KS in 2011nd Dt were collected using Hoo dtloggers plced in the 21 dy storge tretment Figure 4.2- Coverge of Legcy ufflogrss from vegettive plugs s ffected y storge time t Olthe (left) nd Mnhttn (right), KS in 2010 nd Bufflogrss ws plnted on TRM nd estlished on plstic in full sun for three weeks. Mts were then lifted, rolled, nd stored for 7, 14, or 21 dys in dense shde efore plnting. Plnting ws done following the lpse of the respective storge time nd susequent dtes re referred to s dys fter plnting(dap). Coverge ws rted visully on 0 to 100% Scle. Mens followed y the sme letter on dte re not significntly different ccording to the F-LSD (P < 0.05) Figure 4.3- Legcy ufflogrss stored on turf reinforcement mt for 0 dys prior to plnting on 23 June 2011 in Olthe, KS. Photo tken 22 Sept Figure 4.4- Legcy ufflogrss stored on turf reinforcement mt for 7 dys prior to plnting on 1 July 2011 in Olthe, KS. Photo tken 22 Sept Figure 4.5- Legcy ufflogrss stored on turf reinforcement mt for 14 dys prior to plnting on 7 July 2011 in Olthe, KS. Photo tken 22 Sept Figure 4.6- Legcy ufflogrss stored on turf reinforcement mt for 21 dys prior to plnting on 13 July 2011 in Olthe, KS. Photo tken 22 Sept xi

12 Figure 4.7- Legcy ufflogrss stored on turf reinforcement mt for 0 dys prior to plnting on 22 June 2012 in Mnhttn, KS. Photo tken 19 Sept Figure 4.8- Legcy ufflogrss tretment on turf reinforcement for 7 dys prior to plnting on 29 June 2012in Mnhttn, KS. Photo tken 19 Sept Figure 4.9- Legcy ufflogrss stored on turf reinforcement mt for 14 dys prior to plnting on 6 July 2012 in Mnhttn, KS. Photo tken 19 Sept Figure Legcy ufflogrss stored on turf reinforcement mt for 21 dys prior to plnting on 13 July 2012 in Mnhttn, KS. Photo tken 19 Sept Figure 5.1- Tretments for the study included plots mowed t 5, 8.9, nd 12.7 centimeters Figure 5.2- Reserchers set up nd clirte the spectrordiometers prior to mesurements eing cquired Figure 5.3- Reserchers otining rdiometer redings from the vrious mowing heights Figure 5.4- Imge nlysis system (WinRHIZO) ws used to clculte totl lef re index Figure 5.5- Prtil Lest Squre regression models for predicting LAI Model A includes ll 2400 wvelengths mesured y the rdiometer. Model B includes regions ±10 nm centered round 600, 690, 761, 960, 1330, 1420 nm. These regions were selected from the fctor weights from the first itertion models Figure 5.6- Fctor weights for 24 June 2010 first model itertion. The grph on the left shows the fctor weights of the first fctor. The grph on the right shows fctor weights of the second fctor Figure 5.7- Prtil Lest Squre regression models for predicting LAI on 17 My Model A includes ll 2400 wvelengths of mesured spectrum. Model B includes regions ±10 nm centered round 600, 690, 761, 960, 1330, 1420 nm. These regions were selected from the fctor weight nd lodings from the first model Figure 5.8- Fctor weights for 17 My 2011 first model itertion. The grph on the left shows the fctor weights of the first fctor. The grph on the right shows fctor weights of the second fctor Figure 5.9- Prtil Lest Squre regression models for predicting LAI on June, Model A includes ll 2400 wvelengths of mesured spectrum. Model B includes regions regions ±10 nm centered round 600, 690, 761, 960, 1330, 1420 nm. These regions were selected from the fctor weight nd lodings from the first model xii

13 Figure Fctor weights for 30 June 2011 first model itertion. This grph shows the fctor weights of the single fctor for this model Figure Prtil Lest Squre regression models for predicting LAI on 18 July Model A includes ll 2400 wvelengths of mesured spectrum. Model B includes regions ±10 nm centered round 600, 690, 761, 960, 1330, 1420 nm. These regions were selected from the fctor weight nd lodings from the first model Figure Fctor weights for 18 July 2011 first model itertion. This grph shows the fctor weights of the single fctor for this model Figure Prtil Lest Squre regression models for predicting LAI on August, Model A includes ll 2400 wvelengths of mesured spectrum. Model B includes regions ±10 nm centered round 600, 690, 761, 960, 1330, 1420 nm. These regions were selected from the fctor weight nd lodings from the first model Figure Fctor weights for 18 July 2011 first model itertion. This grph shows the fctor weights of the single fctor for this model xiii

14 List of Tles Tle 1.1- Phenotypic types nd cultivrs of Kentucky luegrss nd hyrid luegrsses Tle 1.2- Hypothesis test summries for luegrss entry effects on green turf coverge during dry-down nd susequent recovery in 2010 nd Tle 1.3- Sttisticl prmeters for predicting dry-down chrcteristics of Kentucky luegrss cultivrs. Smller (more negtive) slope vlues trnslte to more rpid chnges in green cover over time. Dys 25 is the predicted numer of dys from irrigtion withheld for the selected cultivr to rech 25% turfgrss coverge Tle 1.4- Sttisticl prmeters for predicting recovery chrcteristics of Kentucky luegrss cultivrs. Lrger (more positive) slope vlues trnslte to more rpid chnges in green cover over time. Dys 75 is the predicted numer of dys from irrigtion initition for the selected cultivr to recover to 75% turfgrss coverge Tle 2.1- Hypothesis test summries for luegrss entry effects on green turf coverge during dry-down nd susequent recovery in 2010 nd xiv

15 Acknowledgements I would like to express my pprecition to my wonderful wife, Cndce Ruth Goldsy for her endless love nd support. Without her support nd dediction towrds rising our children this disserttion would not hve een possile. To Drs. Dle Bremer, Jck Fry, Steve Keeley, nd Kevin Price for ll their time nd ssistnce in developing nd completing these projects. Their guidnce nd support ws the min reson for the success of these projects. To the rest of the turfgrss tem: Drs. Megn Kennelly, nd Rodney St. John for their ssistnce nd guidnce with my studies. To my fellow grdute students: Cole Thompson, Zne Rudenush, Kenton Peterson, Josh Chon, Cody Domengini, nd Kir Arnold Shonkwiler for ll their ssistnce nd friendship on the vrious ventures we hve experienced. Finlly, I would like to thnk my prents for rising me with vlues tht tught me the mening of hrd work nd discipline. Your love nd guidnce re the mjor reson I m the mn I m tody. xv

16 Dediction I dedicte this to my wonderful children Emm nd Hrper. Keep dreming nd reching for the strs throughout your lives s ll things re possile through Jesus Christ. xvi

17 Chpter 1 - Response of Kentucky Bluegrss Cultivrs to Prolonged Drought Stress in the Trnsition Zone 1

18 Astrct Wter restrictions for irrigtion my e imposed during drought with little or no regrd for effects on the lndscpe. My ojectives were to evlute responses of Kentucky luegrss (Po prtensis L.) (KBG) to prolonged drought in the trnsition zone ner Mnhttn, KS, USA. Irrigtion ws withheld from 30 luegrsses for 88 dys in 2010 nd 60 dys in Plots were sheltered from rinfll y n utomted rinout shelter. Digitl imges were collected weekly during dry down nd recovery to otin percent green turfgrss coverge. In 2010, plots were completely rown (0% green coverge) y the end of the 88 dy dry down. Among cultivrs, green coverge declined to 25% y 44.3 to 54.1 dys fter irrigtion (DAI) ws withheld. In 2011, plots were less rown (15-30% green cover) y the end of the 60 dy dry down ecuse ll plots received 39 mm of precipittion fter the rinout shelter mlfunctioned, green coverge declined to 25% y 39.0 to 57.1 DAI withheld. In oth yers, green coverge declined slowest in Apollo, Bedzzled, Blue Velvet, Envict, Midnight II, nd Therml Blue Blze nd fstest in Blue Knight, Cernet, Kenlue, Limousine, nd Touchdown. Recovery of green coverge fter dry downs in oth yers ws fstest in Apollo, Awrd, Bron, Unique, nd Moonlight nd slowest in Aey, Brtiti, Nu Destiny, Prk, nd Touchdown. Given its slower decline in green coverge during dry downs in oth yers nd fster recovery therefter, Apollo displyed superior drought tolernce. The recupertive ility of ll 30 luegrsses ws noteworthy ecuse ll entries eventully recovered fter prolonged drought. 2

19 Introduction Wter scrcity is n incresing chllenge to the turfgrss industry nd my result in irrigtion restrictions eing imposed without regrd for dmge to turfgrss (Berd nd Kenn, 2008). For turf mngers, thriving in n industry where turf qulity is of utmost importnce is difficult when wter is limiting. Therefore, reserch investigting turfgrss resistnce to drought stress hs ecome incresingly importnt. Kentucky luegrss is the most widely used cool-seson turfgrss for lwns, golf courses, thletic fields, nd other res where dense grss cover is desired (Christins, 2004; Brooks Gould, 2004; Lymn et l., 2007). In the continentl U.S., KBG is grown predominntly in the cool-rid/humid regions. However, KBG hs rod rnge of dptility tht lso mkes it suitle for use s fr south s the trnsition zone of the U.S. Wide rnges in drought tolernce nd wter use mong KBG cultivrs undoutedly contriute to its dptility (Shermn, 1986; Edon nd Petrovic, 1998; Richrdson et. l., 2009; Merewitz et l., 2010; Lewis et l., 2012). Drought resistnce in turfgrsses hs two primry components: dehydrtion voidnce nd dehydrtion tolernce (Berd, 1989). For exmple, cool-seson grss such s tll fescue (Festuc rundince Schre.) hs the ility to void dehydrtion y mining soil moisture from deeper in the profile with n extensive rooting system. Even in KBG, cultivrs with greter root mss deeper in the profile (15-45 cm) voided drought stress etter thn cultivrs with less root mss t those depths (Bonos nd Murphy, 1999). In the ltter study, soil moisture ws depleted more t cm in drought-tolernt cultivrs thn in intolernt cultivrs. Nevertheless, the root system in KBG is reltively shllow compred with tll fescue (Christins, 2004). Therefore, in order to survive extended periods of drought, KBG my undergo dormncy (Christins, 2004). Dormncy is ssocited with dehydrtion tolernce, not voidnce, nd is ccompnied y loss of green color in folige (Berd, 1989). Crowns nd rhizomes of KBG cn live for severl 3

20 months under drought conditions, which llow for regrowth when wter ecomes ville (Christins, 2004). A numer of studies hve screened cool-seson grsses for drought tolernce under controlled conditions in greenhouses or growth chmers (Arhm et. l., 2004; Edon nd Kopp, 2004; Wng et l., 2008). In such studies, lysimeters re typiclly used, which my restrict soil volumes for root growth, result in higher root tempertures thn would e found in mient soils in the field, nd lter physiologicl properties of turfgrsses (e.g., lef re, ovend elow ground iomss density) (Bremer, 2003), ll of which my impct drought resistnce. Furthermore, while growth chmers nd greenhouses hve the dvntge of more controlled environments, they my not ccurtely predict responses of cultivrs to the more dynmic, stressful conditions typicl in the field. In other reserch, drought tolernce mong KBG cultivrs hs een successfully evluted in the field using rod screening techniques including visul qulity, digitl imge nlysis, nd physiologicl mesurements (Keeley nd Koski, 2001; Richrdson et. l., 2008, 2009; Merewitz et. l., 2010). In those studies, irrigtion ws withheld for pproximtely 35 dys or less, which typiclly resulted in severe drought stress ut with frction of the cnopies remining green. In Texs, seven cultivrs of St. Augustinegrss survived 60 dys with no irrigtion or precipittion, nd in one yer most of the cultivrs were nerly completely dormnt y the end of the study (Steinke et l., 2010). Tht reserch ws in response to locl wter municiplity requiring list of turfgrsses with the ility to survive without wter for 60 dys during summer months. Presumly, similr irrigtion restrictions my occur where KBG is grown, ut the ility of KBG to survive 60 dys without irrigtion or precipittion hs not een evluted. 4

21 Due to considerle diversity in growth nd performnce mong KBG cultivrs, reserchers hve clssified them into phenotypic groups (Murphy et l., 1997; Bonos et l., 2000; Brooks Gould, 2004). Becuse of reltively quick turnover of commercilly-ville KBG cultivrs, determining the drought tolernce of phenotypic groups my provide vile lterntive for estimting drought tolernce of cultivrs not included in ny specific study. Keeley nd Koski (2001) investigted visul qulity nd lef firing during field dry downs of 22 to 33 dys in 15 cultivrs of KBG representing vrious KBG phenotypic groups. Those uthors reported dehydrtion voidnce rnkings from high to low were Mid-Atlntic > Bellevue > Bron, BVMG, Vict, Merit, nd Gnome > Common. Conversely, Richrdson et l. (2008) did not find trends in drought tolernce mong KBG phenotypic groups, s mesured y dys to 50% green cover. Beyond the ltter studies, few hve investigted reltive drought tolernce mong phenotypic groups of KBG in field setting. A fully utomted rinout shelter locted in the trnsition zone in northestern Knss, USA, offered the ility to compre growth nd performnce of multiple KBG cultivrs in the field while restricting wter. The ojective of this study ws to evlute percent green coverge, using digitl imge nlysis, of 28 cultivrs of KBG nd two hyrid luegrsses (KBG Texs luegrss [Po rchnifer Torr.]) during exposure to prolonged drought nd during the recovery period fter rewtering. Mterils nd Methods Study site nd experimentl design This study ws conducted from 15 June to 4 Sept (88 d), nd 1 June to 1 Aug (60 d). Turfgrss plots were mintined under n utomted rinout shelter (12 y 12 m) t the Rocky Ford Turfgrss Reserch Center ner Mnhttn, Knss, USA (39 o N, 96 o

22 W). The rinout shelter rests north of the plot re ut utomticlly covered the plots s precipittion egn nd retrcted 1 h fter cesstion of rinfll. The rinout shelter mlfunctioned three times, once in the first yer of the experiment, nd twice during the second yer. The first mlfunction occurred on 5 July 2010 nd llowed pproximtely 25 mm of precipittion to fll on the study plots. The susequent mlfunctions occurred on 15 July 2011 nd 21 July 2011, llowing pproximtely 7 mm of precipittion nd 32 mm, respectively. The soil t the site ws Chse silt lom (fine, smectitic, mesic, Aquertic Argiudoll) with ph of 6.9. A soil test prior to the study indicted P nd K levels were dequte. Wether dt for Mnhttn, KS during the study were otined from Knss Stte University wether dt lirry ( Air tempertures during the study were generlly greter thn the 30-yer norml in oth yers (Figure 1.1). Furthermore, 2011 ws generlly wrmer thn For exmple, ir temperture during the dry down verged 0.8 o C greter thn norml in 2010 nd 2.7 o C greter thn norml in Dily mximum ir tempertures exceeded 35 o C on 21 dys during the 88-dy study in 2010 nd on 29 dys during the 60-dy study in 2011 (dt not shown). Ninety plots, consisting of 28 cultivrs of Kentucky luegrss (Po prtensis L.) nd two hyrid luegrsses (Tle 1.1), were rrnged in rndomized complete lock design with three replictions. The plots, estlished in Sept. 2006, mesured 1.13 y 1.22 m nd were ordered with metl edging (10 cm depth). Commercilly ville cultivrs of KBG were selected to include representtives from mjor phenotypic groups (Murphy et l., 1997; Bonos et l., 2000). Becuse visul color nd qulity were of interest in this study, cultivr performnce in previous NTEP trils ws evluted to guide in the cultivr selection (Ntionl Turfgrss Evlution 6

23 Progrm, 2001). Additionl detils out plot estlishment nd cultivr selection cn e found in Lewis et l. (2012). Plot Mintennce Plots were mintined t 7.6 cm mowing height nd fertilized with ure (46-0-0), to provide N t 49 kg N h -1 in April, Septemer, nd Octoer of ech yer. Imidcloprid (1-[(6- chloro-3-4 pyridinyl) methyl 3 (2-chloro-3,3,3-trifluoro-1-propenyl)-2,2- dimethylcyclopropnecroxylte) ws pplied t 0.12 kg.i. h -1 to control illug grus nd white grus (Cyclocephl lurid Blnd) on 1 My 2010 nd 3 My Azoxystroin ((methyl(e)-2-{2-[6-(2-cynpphenoxy) pyrimidin-40yloxy]phenyl}-3 methoxycrylte)) ws pplied t 0.61 kg.i. h -1 on 15 April 2010 nd 9 April 2011 for summer ptch (Mgnoporthe poe Lndschoot & Jckson) prevention. The hericides crfentrzone-ethyl (Ethyl α,2-dichloro- 5-[4(difluoromethyl)-4,5-dihydro-3-methyl-5-oxo-1H-1,2,4-trizol-1-yl]-4- fluoroenzenepropnote) (0.03 kg.i. h -1 ) + 2,4-D [2-ethylhexyl ester (2,4 dichlorophenoxycetic cid] (1.29 kg.i. h -1 ) + Mecoprop-p cid [(+)-R-2-(2-methyl-4 chlorophenoxy)propionic cid] (0.27 kg.i. h -1 ) + dicm cid (3,6-dichloro-o-nisic cid)(0.08 kg.i. h -1 ) were pplied on 6 April 2010, 23 Oct. 2010, nd 9 April 2011 for rodlef weed control. Applictions of dithiopyr [S,S -dimethyl 2-(difluoro-methyl)-4-(2- methylpropyl)-6-(trifluoromethyl)-3,5-pyridin-edicrothiote] were mde t 0.58 kg.i. h -1 on 6 April 2010 nd 9 April 2011 to control nnul grssy weeds. Wter ws pplied three times weekly for totl of 25 mm of precipittion per week. Mesurements The plots were well wtered until 15 June 2010 nd 1 June Therefter, plots were llowed to dry-down for 88 dys in 2010 nd 60 dys in 2011 with no precipittion or irrigtion. 7

24 Overhed photos of ll pots were tken weekly nd imges were used to clculte percent green turfgrss cover ccording to the method of Richrdson et. l., (2001) nd Krcher nd Richrdson (2005). Imges were otined with Nikon D3000 (Nikon Co., Tokyo, Jpn) digitl cmer. In 2010, the cmer ws mounted on tripod 3.0 m in height with horizontl rm tht ws mounted t 90 o from verticl nd extended 1.0 m wy from the tripod center. All imges were collected under cler skies t (~1200 CST) to minimize chnges in solr zenith ngle. In 2011, construction of cmer light ox llowed for more flexiility in the time of dt collection (Peterson et l., 2011). The light ox ( cm) ws fricted from cm. thick luminum. Four compct fluorescent light uls (model CF13EL/MICRO/C/865/BL2; color temperture = 6,500K; Sylvni, Dnvers, MA) mimicking nturl sunlight color temperture (5,500 to 6,500 K) were instlled inside the ox. The light uls re powered y portle power pck (Durcell Power Pck 600, Durcell, Bethel, CT). The cmer ws mounted in the center of the ox nd sponge surrounding the lens prevented sunlight from entering the light ox nd provided support for the cmer. The imges were sved in JPEG formt with color depth of 16.7 million colors, nd n imge size of 1280 y 960 pixels. Cmer settings included shutter speed of 1/400 s, perture of F4.0, nd focl length of 26 mm. The imges were nlyzed with SigmScn Pro (v. 5.0, SPSS, Chicgo, IL). The progrm selectively identified green pixels (leves) in the imge with the hue rnge set from 47 to 110 nd the sturtion set from 0 to 100 (Figure 1.2). Sttisticl nlysis Digitl imge dt were nlyzed on dte-y-dte sis with the MIXED procedure of SAS (SAS Institute, Cry, NC). In cses where the F-test for tretment differences were 8

25 significnt (P=0.05) on given dte, 95% confidence intervls were used for comprison mong individul tretment mens. Sctter plots of percent green turf cover versus dys fter irrigtion ws withheld (DAIW) during drought stress, nd dys fter irrigtion (DAI) ws pplied during recovery from drought, indicted nonliner reltionships. Furthermore, the dt fit very well to sigmoid vrile slope model similr to tht descried y Krcher et l., (2008). The slope prmeter of oth models defines how rpidly turf cover chnges over time. For the dry-down, more negtive vlues represent steeper slopes of the sigmoid curve. For the recovery, more positive vlues indicte quicker chnge in green cover over time. Briefly, for the dry-down in oth yers sum of squres reduction F-test ws used to determine if KBG cultivrs significntly ffected green turf cover during drought stress nd the susequent recovery. The F-test compred the sum of squres from glol model (verge of ll cultivrs for Dy 25 or Dy 75 nd slope vlues) ginst the cumultive sum of squres from seprte models of ech cultivr for Dy 25, Dy 75, nd the slopes. For the dry down periods, Dy 75 nd Dy 25 vlue ws clculted to estimte DAIW until ech plot reched 75 % nd 25% green cover. For the recovery periods Dy 75 ws clculted to estimte DAI ws initited efore ech plot rech 75% green cover. After the 2010 dry down, mesurements of cnopy green cover during the recovery were only otined for 60 DAI ws repplied. However, most cnopy regrowth in the luegrss entries with the slowest recoveries occurred therefter, primrily during the next spring prior to the 2011 dry down. Therefore, Dys 75 during the 2010 recovery ws extrpolted using the sigmoid models in most cultivrs. For 2011, ll plots hd reched 75% green cover y 45 dys fter irrigtion ws returned. Nonliner regression nlysis of the turf percent cover dt ws performed using GrphPd Prism version 4.0 for Windows (Grphpd Softwre, Sn Diego, CA). 9

26 Results nd Discussion In 2010, ll plots were completely rown (0% green cover) y end of the 88-dy dry down (Figure 1.3). At the end of the dry down in 2011 the plots were less rown thn in 2010, rnging from 15 to 30% green cover (Figure 1.4). Greter percent green coverge t the end of the 60-dy dry down in 2011 ws likely result of 39 mm of totl precipittion tht indvertently fell on the plots fter the rinout shelter mlfunctioned on two occsions, t 44 nd 51 DAI withheld. Bluegrss cultivr significntly ffected green turf coverge during oth the dry down nd susequent recovery periods in oth yers of the study (Tle 1.2). The sigmoid models used to predict percent green cover provided good fit of the green cover dt, resulting in verge coefficient of determintion (R 2 ) vlues of 0.93 nd 0.88 during drought stress in 2010 nd 2011, respectively, nd 0.57 nd 0.86 during recovery fter drought in 2010 nd 2011, respectively (Tles 1.3 nd 1.4). The weker goodness of fit of the sigmoid models during recovery from drought stress in (R =0.57) ws the result of slow recovery period tht lsted into the spring of 2011, with green turf cover vrying considerly mong replictions of ech cultivr (Fig. 1.5). Slower recovery in 2010 ws proly cused y the longer dry down period (88 dys), which resulted in greter drought stress thn during the 60-dy dry down in In 2010, green coverge ws etween % mong cultivrs t the eginning of the dry down (Fig. 1.6). In contrst, green coverge ws lower t the eginning of the dry down in 2011, rnging from 79-98% mong cultivrs (Fig. 1.7). This ws likely n rtifct of the slow recovery in 2010, in which some plots hd not yet reched full green coverge y the eginning of the dry down in

27 In oth yers, green coverge egn to decline quickly in some cultivrs fter irrigtion ws withheld (Figure 1.6 nd 1.7). Bsed on predictions from the sigmoid models, the Dys 25 verged 50.7 in 2010, which ws lmost two dys greter thn the verge of 48.9 in However, the rnge of Dys 25 mong cultivrs ws 44.3 to 54.1 in 2010 ( 9.8-dy spn), which ws nrrower thn the rnge of 39.0 to 57.1 dys in 2011 (n 18.1-dy spn) (Tle 1.3). The nrrower rnge in Dys 25 in 2010 resulted in fewer differences in Dys 25 mong cultivrs thn in 2011 (Figs. 1.8 nd 1.9). The cuse of these differences in Dys 25 etween yers is uncertin. The verge ir temperture during the first dys of the dry down ws similr etween yers (Figure 1.1). Thus, it is unlikely tht differences in het stress cused the differences in Dys 25 etween yers. It is more likely tht ecuse some cultivrs strted with less green coverge in 2011, they declined to 25% fster thn in 2010 when they were closer to full coverge. The cultivrs tht demonstrted the gretest numer of dys to rech 25% green cover in oth yers of the study were: Apollo, Bedzzled, Blue Velvet, Envict, Midnight II, nd Therml Blue Blze (Figure 1.7 nd 1.8). Apollo consistently rnked in the top ten cultivrs, s mesured y slowest decline in green coverge, mong the cultivrs during oth yers of the study. Previous reserch hs shown good tolernce of cultivrs in Compct types (Moonlight nd Div) nd Compct Americ types (Mllrd, SR 2284, nd Brillint) for drought tolernce, since those cultivrs in their respective groups performed well (Richrdson et l., 2008). In our study, Compct Americ types (Apollo nd Bedzzled) showed superior drought tolernce in drydowns of oth yers. Furthermore, in our study Compct types (Moonlight nd Div) showed contrsting drought tolernce with ech cultivr flling into the top ten in one yer nd then in the middle/ottom of the cultivrs in the other yer. The cultivrs exhiiting the lest drought 11

28 tolernce in oth yers of the study were: Blue Knight, Cernet, Kenlue, Kingfisher, Limousine, nd Touchdown (Figure 1.8 nd 1.9). Previous reserch hs indicted tht KBG hyrids re similr to KBG cultivrs in their susceptiility to drought stress (Su et l., 2007, 2008, 2009; Richrdson et l., 2008, 2009). In our study, drought tolernce ws reltively good in Therml Blue Blze ut ws less consistent in the other hyrid Longhorn. These results support the oservtions of Richrdson et l. (2008), who suggested tht hyrids hve wide rnges in drought tolernce ut no inherent superiority to KBG cultivrs. Predictions from the sigmoid models illustrte the slower post-drought recovery in 2010 (men Dys 75 = 86.9 dys) thn in 2011 (men Dys 75 = 30.5 dys) (Tle 1.4), which ws discussed erlier. Among cultivrs, the Dys 75 during recovery verged lmost two months (56 dys) more in 2010 thn in The rnge in Dys 75 during recovery ws from 57.8 to 148 dys in 2010 nd from 20 to 43.7 dys in 2011 (Tle 1.4). The cultivrs with the fstest recovery (i.e., the fewest Dys 75 ) during oth yers were Apollo, Awrd, Bron, Unique, nd Moonlight (Figure 1.10 nd 1.11). These results from Apollo nd Moonlight support oservtions y others tht indicted cultivrs with the est drought tolernce during drought re typiclly the quickest to recover fter drought (Richrdson et l., 2008). The cultivrs demonstrting the slowest recovery in oth yers of the study were: Aey, Brtiti, Nu Destiny, Prk, nd Touchdown (Figure 1.12 nd 1.13). The cultivr Touchdown required the fewest dys to rech 25% green coverge in For 2011, Touchdown ws in the top four cultivrs which required the fewest dys to rech 25% green coverge. 12

29 Conclusions Results from this study illustrte the importnce of proper cultivr selection where the possiility exists for long-term drought nd susequent irrigtion restrictions. In some cses, there were differences of 18 dys mong cultivrs in the Dys 25 during drought. Furthermore, there were differences of 90 dys mong cultivrs in the Dys 75 fter the 2010 dry down. These differences could e significnt if KBG cultivrs re locted in municiplity which during drought my fce intermittent or extended periods of irrigtion restriction. Overll, the mzing recupertive ility of KBG from prolonged drought is noteworthy for ll cultivrs. Apollo demonstrted gret drought tolernce nd susequent recovery for oth the 2010 nd 2011 dry down. Furthermore, it ws one of the fstest to recover from drought stress fter the return of irrigtion. Informtion from this study could ssist cultivr selection for turfgrss mngers locted in municiplity which my fce extended periods of irrigtion restriction. 13

30 Figures nd Tles Figure 1.1- Averge ir temperture during the dry downs in 2010 nd Solid lck lines signify the strt nd cesstion of the 2010 dry down. Dshed lck lines signify the strt nd cesstion of the 2011 dry down. Mrkers represent 5 dy verges. 14

31 Figure 1.2- Originl imge (left) followed y the color composite imge fter eing processed with imge nlysis softwre (right). The softwre identifies pixels tht fll under preset green hue settings nd then highlights them in red. 15

32 Figure 1.3- Plots on Septemer 4, 2010, fter receiving no irrigtion for 88 dys. 16

33 Figure 1.4- Plots on August 1, 2011, fter receiving no irrigtion for 60 dys. 17

34 Figure 1.5- Digitl imges of ll three replictes of the KBG cultivr Cernet in 2010, t the eginning (26 June) nd end (2 Sept.) of the dry down nd fter 60 dys of recovery (5 Nov.). 18

35 Figure 1.6- Predicted dry-down curves for the 30 luegrsses in

36 Figure 1.7- Predicted dry-down curves for 30 luegrsses in

37 Blue Knight Nu Destiny Awrd Kingfisher Cernet Touchdown Nu Destiny Awrd Shmrock Blue Knight Juli Skye Aey Midnight Prk Lngr Midnight Cernet Midnight 2 Limousine Skye Kenlue Wellington Longhorn Kingfisher Prk Limousine Unique Moonlight Moonlight Lngr Brtiti Prekness Shmrock Unique Wellington Touchdown Prekness Bron Egleton Div Div Blue Velvet Aey Kenlue Blue Velvet Egleton Midnight 2 Therml Blue Blze Therml Blue Blze Longhorn Juli Envict Bron Brtiti Bedzzled Bedzzled Envict Apollo Apollo Dys fter irrigtion withheld Figure 1.8- The 95% confidence intervls for the numer of dys fter irrigtion ws withheld until luegrss cultivrs reched 75% nd 25% green cover in Green rs represent dys until cultivrs reched 75% nd lue represent 25% green cover. Cultivrs with overlpping rs were not significntly different. 21

38 Brtiti Prk Nu Destiny Envict Kenlue Shmrock Cernet Aey Blue Knight Wellington Touchdown Bron Kingfisher Skye Lngr Juli Therml Blue Blze Unique Longhorn Limousine Div Awrd Midnight Apollo Egleton Blue Velvet Moonlight Bedzzled Prekness Midnight 2 Brtiti Cernet Limousine Touchdown Kenlue Blue Knight Shmrock Unique Kingfisher Div Lngr Prk Bron Skye Wellington Nu Destiny Juli Aey Egleton Bedzzled Envict Longhorn Apollo Prekness Moonlight Midnight Awrd Therml Blue Blze Blue Velvet Midnight Dys fter irrigtion withheld Figure 1.9- The 95% confidence intervls for the numer of dys fter irrigtion ws withheld until luegrss cultivrs reched 75% nd 25% green cover in Green rs represent dys until cultivrs reched 75% nd lue represent 25% green cover. Cultivrs with overlpping rs were not significntly different. 22

39 Figure Predicted recovery curves for 30 luegrsses in

40 Figure Predicted recovery curves for 30 luegrsses in

41 Brtiti Touchdown Nu Destiny Lngr Skye Midnight2 Prk Div Blue Knight Aey Bedzzled Blue Velvet Longhorn Wellington Midnight Therml Blue Blze Prekness Limousine Moonlight Awrd Bron Envict Unique Juli Kenlue Cernet Shmrock Apollo Kingfisher Egleton Dys fter irrigtion Figure The 95% confidence intervls for the numer of dys fter irrigtion until luegrss cultivrs reched 75% green cover in Cultivrs with overlpping rs were not significntly different. 25

42 Prk Aey Brtiti Envict Shmrock Prekness Touchdown Cernet Juli Nu Destiny Therml Blue Blze Limousine Skye Midnight Blue Knight Div Longhorn Kenlue Moonlight Blue Velvet Egleton Bedzzled Midnight 2 Wellington Unique Bron Apollo Awrd Lngr Kingfisher Dys fter irrigtion Figure The 95% confidence intervls for the numer of dys fter irrigtion until luegrss cultivrs recovered in Cultivrs with overlpping rs were not significntly different. 26

43 Tle 1.1- Phenotypic types nd cultivrs of Kentucky luegrss nd hyrid luegrsses. Group Common Compct Compct Americ Juli Mid-Atlntic Compct Midnight Shmrock BVMG Aggressive Europen Texs luegrss hyrids Kentucky luegrss clssifiction types s descried in Bonos et l., Blue Knight nd Brtiti hve since een reclssified s Other Type (Brooks Gould, 2004). Cultivr Kenlue Wellington Prk Div Skye Moonlight Lngr Bedzzled Apollo Juli Egleton Prekness Cernet Midnight Midnight II Blue Velvet Nu Destiny Awrd Shmrock Bron Envict Aey Limousine Touchdown Blue Knight Brtiti Therml Blue Blze Longhorn 27

44 Tle 1.2- Hypothesis test summries for luegrss entry effects on green turf coverge during dry-down nd susequent recovery in 2010 nd Sums of squres reduction test Dry-down 2010 Dry-down 2011 Recovery 2010 Recovery 2011 Null hypothesis Shred regression prmeters (slope nd dys 25//75 ) for ll vrieties Alterntive hypothesis Different regression prmeters for ech vriety Numertor df Denomintor df F vlue P vlue < < < < Slope nd dys 25/75 vlues determine percent green turf cover ccording to the sigmoid vrile slope model. 28

45 Tle 1.3- Sttisticl prmeters for predicting dry-down chrcteristics of Kentucky luegrss cultivrs. Smller (more negtive) slope vlues trnslte to more rpid chnges in green cover over time. Dys 25 is the predicted numer of dys from irrigtion withheld for the selected cultivr to rech 25% turfgrss coverge. Dry down 2010 Dry down 2011 Cultivr Slope SE Dys25 SE 2 R Cultivr Slope SE Dys25 SE R 2 Apollo Midnight Envict Blue Velvet Bedzzled Therml B Bron Awrd Juli Midnight Therml BB Moonlight Midnight Prekness Blue Velvet Apollo Aey Longhorn Div Envict Egleton Bedzzled Prekness Egleton Wellington Aey Shmrock Juli Brtiti Nu Destiny Moonlight Wellington Unique Skye Prk Bron Longhorn Prk Kenlue Lngr Limousine Div Cernet Kingfisher Lngr Unique Midnight Shmrock Skye Blue Knight Blue Knight Kenlue Awrd Touchdown Touchdown Limousine Kingfisher Cernet Nu Destiny Brtiti

46 Tle 1.4- Sttisticl prmeters for predicting recovery chrcteristics of Kentucky luegrss cultivrs. Lrger (more positive) slope vlues trnslte to more rpid chnges in green cover over time. Dys 75 is the predicted numer of dys from irrigtion initition for the selected cultivr to recover to 75% turfgrss coverge. Recovery 2010 Recovery 2011 Cultivr Slope SE Dys75 SE 2 R Cultivr Slope SE Dys75 SE R 2 Apollo Kingfisher Shmrock Lngr Cernet Awrd Kenlue Apollo Juli Bron Unique Unique Envict Wellington Bron Midnight Awrd Bedzzled Moonlight Egleton Limousine Blue Velvet Prekness Moonlight Therml BB Kenlue Midnight Longhorn Wellington Div Longhorn Blue Knight Blue Velvet Midnight Bedzzled Skye Aey Limousine Blue Knight Therml BB Div Nu Destiny Prk Juli Midnight Cernet Skye Touchdown Lngr Prekness Nu Destiny Shmrock Touchdown Envict Brtiti Brtiti Egleton Aey Kingfisher Prk

47 References Arhm, E.M., B. Hung, S.A. Bonos, nd W.A. Meyer Evlution of drought resistnce for Texs luegrss, Kentucky luegrss, nd their hyrids. Crop Sci. 44: Berd, J.B Turfgrss wter stress: Drought resistnce components, physiologicl mechnisms, nd species-genotype diversity. p In H. Tktoh (ed.) Proc. 6 th Int. Turf. Res. Conf., Tokyo, Jpn. 31 July-5 Aug Jpnese soc. Turfgrss Sci., Tokyo. Berd, J.B. nd M.P. Kenn (eds) Wter qulity nd quntity issues for turfgrsses in urn lndscpes. Council for Agriculture Science nd Technology, Ames, IA, USA. Bonos, S.A., R.f. Br, W.K. Dickson, D.A. Smith, M.M. Mohr, E., Wtkins, J.A. Murphy, W.A. Meyer, nd C.R. Funk Performnce of Kentucky luegrss cultivrs nd selections in NJ turf trils, Rutgers Turfgrss Proc. 31: Bremer, D.J Evlution of microlysimeters used in turfgrss evpotrnspirtion studies using the dul-proe het-pulse technique. Agron. J. 95: doi: /gronj Brooks Gould, A., editor Rutgers Turfgrss Proceedings. New Jersey Turfgrss Expo, Atlntic City, NJ. 7 9 Dec New Jersey Turfgrss Assoc., Atlntic City, NJ. Christins, N Fundmentls of Turfgrss Mngement, 2 nd Sons, Hooken, NJ Ed. John Wiley & Edon, J.S., nd K.L. Kopp Reltionship etween wter use efficiency, cron isotope discrimintion, nd turf performnce in genotypes of Kentucky luegrss during drought.crop Sci. 44: Edon, J.S., nd A.M. Petrovic Morphologicl nd growth chrcteristics of lownd high-wter use Kentucky luegrss cultivrs. Crop Sci. 38: Knss Stte Reserch nd Extension Wether Dt Lirry [Online]. Aville t (ccessed 11 Nov. 2012). Krcher, D.E., M.D. Richrdson, K. Hignight, nd D. Rush Drought tolernce of tll fescue vrieties selected for high root:shoot rtios. Crop Sci. 48: Krcher, D.E., M.D. Richrdson, Btch nlysis of digitl imges to evlute turfgrss chrcterstics. Crop Sci. 45:

48 Keely, S.J., nd A.J. Koski Dehydrtion voidnce of diverse Po prtensis cultivrs nd cultivr groups in semi-rid climte. Int. Turfgrss Soc. Res. J. 9: Lewis, J., D.J. Bremer, S.J. Keeley, nd J.D. Fry Wilt-sed irrigtion in Kentucky luegrss: Effects on visul qulity nd irrigtion mounts mong cultivrs. Crop Sci. 52: Lymn, G.T., C.S. Throssell, M.E. Johnson, G.A. Stcey, nd C.D. Brown Golf course profile descries turfgrss, lndscpe nd environmentl stewrdship fetures. Online. Applied Turfgrss Science doi: /ats rs. Merewitz, E., W. Meyer, Stcy Bonos, nd Bingru Hung Drought stress responses nd recovery of Texs x Kentucky Hyrids nd Kentucky Bluegrss genotypes in temperte climte conditions. Agron. Journ. 102: Murphy, J.A., S. Bonos, nd P. Perdomo Clssifiction of Po prtensis genotypes. Int. Turf Soc. 8: Ntionl Turfgrss Evlution Progrm ntionl Ky. luegrss test. Rep Dt Finl report. NTEP, Beltsville, Mrylnd. Peterson, K., K. Shonkwiler, nd D. Bremer Custom light ox for digitl imge turfgrss nlysis. Turfgrss Reserch. Knss Agriculturl Experiment Sttion Puliction SRP p Richrdson, M.D., D.E. Krcher, nd L.C. Purcell Quntifying turfgrss cover using digitl imge nlysis. Crop Sci. 41: Richrdson, M.D, D. Krcher, K. Highnight, nd D. Rush Drought tolernce nd rooting cpcity of Kentucky Bluegrss Cultivrs. Crop Sci. 48: Richrdson, M.D., D.E. Krcher, K. Highnight, nd D. Rush Drought tolernce of Kentucky Bluegrss nd hyrid luegrss culitvrs. Applied Turfgrss Science. 10: SAS Institute Inc User instlltion guide for the SAS system, version 9 for microsoft windows. SAS Institute, Cry, NC. Shermn, R.C Kentucky luegrss cultivr evpotrnspirtion rtes. HortScience 21: Steinke, K., D. Chlmers, J. Thoms, R. White, nd G. Fipps Drought response nd recovery chrcteristics of St. Augustinegrss cultivrs. Crop Sci. 50:

49 Su, K., D.J. Bremer, S.J. Keeley, nd J.D. Fry Mowing nd drought effects on hyrid luegrss compred with Kentucky luegrss. Int. Turf. Soc. Res. J. 11: Su, K., D.J. Bremer, S.J. Keeley, nd J.D. Fry Rooting chrcteristics nd cnopy responses to drought of turfgrsses including hyrid luegrsses. Agron. J. 100: Su, K., D.J. Bremer, S.J. Keeley, nd J.D. Fry Effects of high temperture nd drought on hyrid luegrss compred with Kentucky luegrss nd tll fescue. Crop Sci. 47: Wng, J.P., nd S.S. Bughrr Morpho-physiologicl responses of severl Fescue grsses to drought stress. Hort. Sci. 43(3):

50 Chpter 2 - Physiologicl responses of Kentucky Bluegrss Cultivrs to Prolonged Drought Stress in the Trnsition Zone 34

51 Astrct Incresing wter scrcity my result in irrigtion restrictions eing imposed with no regrd for dmge to turfgrss. My ojectives were to evlute visul performnce nd physiologicl prmeters during prolonged drought of Kentucky luegrss (Po prtensis L.) (KBG) cultivrs. Irrigtion ws withheld from six luegrsses for 88 dys in 2010 nd seven luegrsses for 60 dys in 2011; cultivrs were selected due to their rod rnge of dys to wilt etween wtering in n erlier study. Plots were protected from rinfll y n utomted rinout shelter ner Mnhttn, KS, in the trnsition zone of the USA. Visul color nd qulity, nd digitl imges were collected weekly during the dry downs. Physiologicl mesurements included electrolyte lekge (EL), lef wter potentil (Ψ lef ), nd photosynthesis. In generl, there were no differences in EL, Ψ lef, nd photosynthesis mong cultivrs during or fter ech dry down. Apollo consistently demonstrted the gretest drought tolernce s mesured y slowest decline to 25% green cover during oth yers (54.1 nd 53.4 dys in 2010 nd 2011, respectively), perhps from Apollo s greter ility to mine soil moisture from the profile thn the other cultivrs. The men time to decline to 25% green cover for ll cultivrs ws 52.1 dys in 2010 nd 51.7 dys in All plots recovered from prolonged drought ut Apollo reounded the fstest to75% green cover (57.7 nd 23.8 dys in 2010 nd 2011, respectively; men of ll cultivrs=78.9 nd 29.7 dys in 2010 nd 2011, respectively). Overll, ll luegrsses displyed remrkle recovery fter prolonged drought stress incurred during oth dry downs. 35

52 Introduction Drought tolernce vries widely mong Kentucky luegrss (KBG) cultivrs (Edon nd Petrovic, 1998; Richrdson et. l., 2009; Lewis et l., 2012). There re likely numer of underlying physiologicl mechnisms ffecting drought tolernce. Such mechnisms my include plnt wter potentil, cellulr memrne stility, nd photosynthesis. The mintennce of fvorle sttus in these mechnisms during drought stress my improve the performnce of some cultivrs reltive to others. In greenhouse study, reltive wter content, electrolyte lekge (EL) (n indictor of cellulr memrne stility), nd photochemicl efficiency were mesured in severl KBG cultivrs nd hyrid luegrsses (KBG Texs luegrss [Po rchnifer Torr. P. prtensis]) under drought stress (Arhm et. l., 2004). Interestingly, mong ll the physiologicl prmeters exmined in tht study, EL ws the most sensitive indictor of drought stress. Originlly, EL ws used for screening new genotypes to predict whole-plnt het tolernce (Mrcum, 1998). However, this technique hs een used in more recent studies to evlute turfgrss drought tolernce, s well s the comintion of het nd drought stresses (Du et l., 2009; Liu et l., 2007; Su et l., 2007, 2009; Merewitz et. l., 2010; Domenghini et l., 2013). Lef wter potentil hs strong effects on cellulr growth, which is highly sensitive to drought nd responds efore stomtl conductnce or photosynthesis (Hsio, 1973). During periods of drought, when wter potentils re low, cell expnsion ecomes limited nd growth is reduced (Fry nd Hung, 2004). Lef wter potentil hs successfully een used to evlute drought tolernce in severl cool-seson turfgrsses (Hung et l., 1998; Wng nd Bughrr, 2008; Domenghini et l., 2013). Photosynthesis is fundmentl indictor of plnt stress nd growth (Slisury nd Ross, 1978) nd my e used to evlute reltive drought tolernce mong turfgrsses (Hung et l., 36

53 1997; DCost et l., 2004; Hung nd Go 1999; Su et. l., 2007). Reserchers evluting KBG undergoing nine dys of soil drying, reported reductions in photosynthesis of pproximtely 35-45% (DCost et l., 2004). Similr reductions in photosynthesis of (~33%) were lso reported in KBG undergoing deficit irrigtion (Su et. l., 2007). Although the physiologicl mechnisms of Ψ lef, cellulr memrne stility (EL), nd photosynthesis hve een used to evlute drought tolernce in cool-seson turfgrsses, their responses in KBG cultivrs exposed to prolonged drought, s descried in Chpter 1, hve not een evluted. Therefore, the ojectives of this study were to evlute the responses Ψ lef, EL, nd photosynthesis in KBG cultivrs exposed to the 88 nd 60 dy dry down in 2010 nd 2011, respectively. Visul rtings of qulity nd color s well s mesurements of percent green coverge nd soil moisture were lso collected. Mterils nd Methods Study site nd experimentl design This study ws conducted from 15 June to 4 Sept (88 d), nd 1 June to 1 Aug (60 d). Turfgrss plots were mintined under n utomted rinout shelter (12 y 12 m) t the Rocky Ford Turfgrss Reserch Center ner Mnhttn, Knss, USA (39 o N, 96 o W). The rinout shelter rests north of the plot re ut utomticlly covered the plots s precipittion egn nd retrcted 1 h fter cesstion of rinfll. The rinout shelter mlfunctioned three times, once in the first yer of the experiment, nd twice during the second yer. The first mlfunction occurred on 5 July 2010 nd llowed pproximtely 25 mm of precipittion to fll on the study plots. The susequent mlfunctions occurred on 15 July 2011 nd 21 July 2011, llowing pproximtely 7 mm nd 32 mm of precipittion, respectively, to fll on the plots. The soil t the site ws Chse silt lom (fine, smectitic, mesic, Aquertic 37

54 Argiudoll) with ph of 6.9. A soil test prior to the study indicted P nd K levels were dequte. Wether dt for Mnhttn, KS during the study were otined from Knss Stte University wether dt lirry ( Air tempertures during the study were generlly greter thn the 30-yer norml in oth yers (Figure 2.1). Furthermore, 2011 ws generlly wrmer thn For exmple, ir temperture during the dry down verged 0.8 o C greter thn norml in 2010 nd 2.7 o C greter thn norml in Dily mximum ir tempertures exceeded 35 o C on 21 dys during the 88-dy study in 2010 nd on 29 dys during the 60-dy study in 2011 (Dt not shown). Becuse it ws not prcticl in this study to evlute physiologicl mechnisms in ll 30 of the luegrsses descried in Chpter 1, suset of six KBG cultivrs ws selected; n dditionl cultivr ws dded in the second yer ecuse of its notly superior performnce in the first yer. The cultivrs were selected sed on results from study conducted on these sme plots y Lewis et. l. (2012), in which cultivrs were rnked y the mount of wter pplied over the growing seson using wilt-sed irrigtion. Specificlly, we selected six cultivrs from cross rod rnge of wter requirements in the previous study in order to evlute physiologicl mechnisms tht my ffect drought resistnce in KBG cultivrs. In oth yers, cultivrs included Wellington, Aey, Bedzzled, Blue Velvet, Moonlight, nd Cernet. The cultivr Apollo ws dded in the second yer (2011) fter recovering the quickest mong cultivrs fter the 2010 dry down. Additionl detils out overll cultivr selection, plot estlishment nd mintennce, nd experimentl design cn e found in Chpter 1 nd Lewis et l. (2012). Mesurements 38

55 The plots were well wtered until 15 June 2010 nd 1 June Therefter, plots were llowed to dry-down for 88 dys in 2010 nd 60 dys in 2011, with no precipittion or irrigtion. Turfgrss color nd qulity were recorded on weekly sis, during the growing seson, y the sme resercher throughout the study. The rting scle for color ws 1 to 9, where 1= rown nd 9= drk green. The rting scle for visul qulity ws lso 1 to 9, where 1= rown, ded turfgrss, 6=minimlly cceptle for home lwns, nd 9= highest qulity sed on color, density, texture nd uniformity (Emmons, 2000). Digitl imges of ll cultivrs were cquired on weekly sis nd were used for clculting percent green turfgrss cover, ccording to the methods of Richrdson et l (2001) nd Krcher nd Richrdson (2005). In 2010, ll imges were collected under cler sky conditions t (~1200 CST) to minimize chnges in solr zenith ngle. In 2011, construction of cmer light ox llowed for more flexiility in the time of dt collection. The imges were nlyzed with SigmScn Pro (v. 5.0, SPSS, Chicgo, IL). Further detils out collection nd nlysis of digitl imges cn e found in Chpter 1. Visul qulity nd color rtings, s well s digitl imges, were collected from ll seven cultivrs in oth yers. Physiologicl mesurements included Ψ lef, which ws collected iweekly, nd EL nd photosynthesis, which were collected weekly; these mesurements were not tken for Apollo in Lef wter potentil nd EL were mesured t pproximtely 1100 CST. Mesurements of EL nd Ψ lef were otined from five leves rndomly smpled from ech turfgrss plot. Leves were plced in Ziploc g nd quickly trnsported to the l, where Ψ lef nd EL smples were prepred within one hour of eing hrvested from the plots. The Ψ lef ws mesured with wter potentil meter (WP4-T PotentiMeter, Decgon Devices, Pullmn, WA). 39

56 The technique used to mesure EL ws similr to the method of Blum nd Eercon (1981) nd Mrcum (1998) with modifictions. Lef smples were tken from ech plot nd plced in test tue filled with 50 ml of deionized wter. Lef smples were prepred in the following mnner: one 2-cm segment ws cut out of three leves tken from the luegrss smples, exposing six cut ends of equl size within ech turfgrss species. Test tues were shken on Titer Plte Shker (L Line Instruments, Melrose Prk, IL) for 24 hours to dissolve electrolytes tht hd dhered to the lef lde or leked from cells. An initil mesurement of conductivity (C 1 ) ws then mesured with n Okton Conductivity Meter (Model CON510 Series, OAKTON Instruments, Vernon Hills, IL). Therefter, the test tues were plced in C wter th for 1 h (Model MSB-1122A-1 Mgni-Whirl Temp Wter Bth, Blue M Electric, Blue Islnd, IL) to destroy ll cell memrnes. Test tues were shken for 24 h to extrct the remining electrolytes from the cells nd second conductivity mesurement ws tken (C 2 ). The clcultion (C 1 /C 2 )*100 ws used to determine the percentge of electrolytes tht leked. Photosynthesis ws mesured with custom chmer descried y Murphy (2007) nd modified for turfgrss y Lewis (2010). Gross photosynthesis (Pg) ws clculted from chmer mesurements using the method of Bremer nd Hm (2005). Briefly, this method involves consecutive mesurements with sunlit nd shded portle photosynthesis chmer, respectively, t ech loction; shded mesurements were otined y covering the chmer with n opque shell tht locked solr rdition from the chmer. Using Eq. [5] nd [6] from Bremer nd Hm (2005), sunlit mesurements were used to determine Pg - (Rc+Rs) nd the shded chmer mesurements to determine Rc + Rs, where Rc is cnopy respirtion nd Rs is 40

57 soil respirtion; ll vlues re defined s positive. Gross photosynthesis ws clculted using their Eq. [8]: Pg=sunlit chmer + shded chmer. Volumetric soil wter content (θ v ) ws monitored dily t 5 nd 20 cm utilizing the dulproe het-pulse technique (Cmpell et l., 1991; Trr nd Hm, 1997; Song et l., 1998). Sensors were fricted in the lortory s descried y Bsinger et l. (2003) nd Bremer (2003). Mesurements of θ v were logged twice dily with micrologger nd ccessories (CR10x nd three AM16/32 multiplexors, Cmpell Scientific, Logn, UT). In 2011, sensors in ll plots of Bedzzled t 5 cm mlfunctioned. In ddition, Time Domin Reflectometry (TDR) (Model 6050X1, Soilmoisture, Snt Brr, CA) rods 50 cm in length were instlled in ech of the 6 selected cultivrs nd mesurements were collected weekly in Due to mlfunction of the TDR unit, dt (0-50 cm) were not collected during the 2011 dry down. Sttisticl nlysis Sctter plots of percent green turf cover versus dys fter irrigtion ws withheld (DAIW) during drought stress, nd dys fter irrigtion pplied (DAI) during recovery from drought, indicted the dt fit very well to sigmoid vrile slope model similr to tht descried y Krcher et l. (2008). Further detils out these nlyses cn e found in Chpter 1. Briefly, for the dry down periods, Dy 75 nd Dy 25 vlue ws clculted to estimte DAI withheld until ech plot reched 75 % nd 25% green cover, respectively. For the recovery periods Dy 75 ws clculted to estimte DAI ws initited efore ech plot reched 75% green cover. Nonliner regression nlysis of the turf percent cover dt ws performed using GrphPd Prism softwre (v. 4.0, Grphpd, Sn Diego, CA). Physiologicl dt were nlyzed with the MIXED procedure of SAS (SAS Institute Inc., Cry, NC). In cses where the F-test for 41

58 tretment differences ws significnt (P=0.05), 95% confidence intervls were used for comprison of individul tretment mens. Results nd Discussion Percent green coverge nd visul color nd qulity rtings. In 2010, ll plots were completely rown (0% green cover) y end of the 88-dy dry down (Fig. 2.2). At the end of the dry down in 2011 the plots were less rown thn in 2010, rnging from 15 to 30% green cover (Fig. 2.3). Greter percent green coverge t the end of the 60-dy dry down in 2011 ws likely result of 39 mm of totl precipittion tht indvertently fell on the plots fter the rinout shelter mlfunctions tht occurred 44 nd 51 dys fter irrigtion (DAI) ws withheld. Bluegrss cultivr significntly ffected green turf coverge during oth the dry down nd susequent recovery periods in oth yers of the study (Tle 2.1). The sigmoid models used to predict percent green cover provided good fit of the green cover dt, resulting in verge coefficient of determintion (R 2 ) vlues of 0.90 nd 0.81 during dry downs in 2010 nd 2011, respectively, nd 0.42 nd 0.81 during the recovery periods in 2010 nd 2011, respectively. The weker goodness of fit of the sigmoid models during recovery from drought stress in 2010 (R 2 =0.42) ws the result of slow recovery period tht lsted into the spring of 2011, with green turf cover vrying considerly mong replictions of ech cultivr. Slower recovery in 2010 ws proly cused y the longer dry down period (88 dys), which resulted in greter drought stress thn during the 60-dy dry down in 2011 (Figs. 2.2 nd 2.3.). In 2010, green coverge ws etween % mong the seven cultivrs t the eginning of the dry down (Fig. 2.2). In contrst, green coverge ws lower t the eginning of 42

59 the dry down in 2011, rnging from 85-98% mong the seven cultivrs (Fig 2.3). This difference ws likely the result of the slow recovery in 2010, in which some plots hd not yet reched full green coverge y the eginning of the dry down In oth yers, green coverge egn to decline quickly in some of the cultivrs fter irrigtion ws withheld (Figs. 2.2 nd 2.3). Bsed on predictions from the sigmoid models, the Dys 25 verged 52.1 in 2010, which ws just slightly longer thn the verge of 51.7 dys in However, the rnge of Dys 25 mong the seven cultivrs in 2010 ws 49.6 to 54.1dys ( 4.5-dy spn), which ws nrrower thn the rnge of 43.2 to 55.7 dys in 2011 ( 12.5-dy spn). The nrrower rnge in 2010 resulted in fewer differences Dys 25 mong the seven cultivrs thn in The verge ir temperture during the first dys of the dry down ws similr etween yers (Figure 2.1). Thus, it is unlikely tht differences in het stress cused the differences in Dys 25 etween yers. It is more likely tht ecuse some cultivrs strted with less green coverge in 2011, they declined to 25% fster thn in 2010 when they were closer to full coverge. All seven cultivrs recovered to ~85-100% green turfgrss cover fter the dry downs in 2010 nd However, complete recovery from the dry down in 2010 ws not chieved until the following spring (Mrch 2011) (dt not shown). In 2011, ll plots hd completely recovered y pproximtely 2 months (~Octoer) fter irrigtion ws returned. The cultivrs tht demonstrted the gretest Dys 25 in oth yers were Apollo nd Bedzzled, ut the gretest drought tolernce mong ll cultivrs ws consistently in Apollo (See Chpter 1). The cultivr exhiiting the lest drought tolernce in oth yers ws Cernet. By contrst, in study evluting minimum wter requirements of KBG cultivrs using wilt-sed irrigtion in these sme plots, Cernet ws low wter user while mintining high visul qulity (Lewis et l., 2012). Although, the methodology of tht study differed from the current 43

60 one, the results suggest Cernet my tolerte intermittent drought conditions etter thn prolonged drought experienced in this study. Bsed on recovery predictions from the sigmoid models, the Dys 75 verged 78.9 in 2010, which ws longer thn the verge of 29.7 dys in The verge numer of dys to rech 75% coverge ws 49 dys longer in 2010 thn in The cultivr tht required the fewest dys to rech 75% green cover during oth yers of the study ws Apollo (Figs. 2.4 nd 2.5). This result is similr to previous reserch which suggested tht cultivrs with good drought tolernce during dry down re typiclly the quickest to recover following drought (Richrdson et l., 2008). The cultivr tht demonstrted the slowest recovery in oth yers of the study ws Aey. Visul color declined during the dry downs in oth 2010 nd Anlysis of vrince indicted significnt differences (P = 0.05) mong the selected cultivrs on 3 of 29 smpling dtes in 2010 (dt not shown). In 2010, visul color rtings were lower in Cernet t the strt of the 60 dy dry-down, which suggests genetic color difference. By 12 nd 18 August, or pproximtely 8 weeks into the dry-down, color rtings in Apollo were highest mong cultivrs, indicting greter resiliency in Apollo to mintin color during drought. However, in 2011 there were no differences in color rtings mong cultivrs on ny mesurement dte. Visul qulity declined sustntilly during the dry downs of oth yers. In generl, visul qulity ws similr mong cultivrs s drought effects intensified. In fct, differences in visul qulity mong cultivrs occurred only on three mesurement dtes in 2010 nd never in 2011 (Fig. 2.6). In 2010, reductions in visul qulity were evident y five DAI withheld. Overll, the verge qulity mong cultivrs decresed from 7.0 on 17 June to 6.1 y 30 June On 30 June 2010, the visul qulity of Apollo nd Bedzzled (oth re Compct 44

61 Americs) were greter thn Cernet, Blue Velvet, nd Aey. One week lter (7 July 2010), visul qulity ws greter in Bedzzled, Apollo nd Aey thn in Wellington nd Cernet. On 12 August 2010, visul qulity ws gretest in Apollo mong cultivrs. Visul qulity dt from 2010 re similr to the dt previously discussed tht ws collected y digitl imge nlysis. For oth rting methods, cultivrs representing the phenotypic group Compct Americ (i.e. Apollo nd Bedzzled) displyed the highest visul qulity or percent green turfgrss cover mong cultivrs. Previous studies hve recommended selecting cultivrs from this phenotypic group ecuse of their greter drought tolernce (Richrdson et l., 2008; Lewis et l., 2012). Prior to the 2011 dry down visul qulity ws elow cceptle levels. Following the dry down initition, visul qulity egn to decline y 22 DAI withheld. On verge, visul qulity mong cultivrs decresed from 5.5 on 15 June to 4.8 y 29 June 2011 (Fig. 2.6). Overll, the decrese in visul qulity during the dry down ws much less severe in 2011 thn in 2010, proly ecuse the plots received 39 mm of precipittion when the rinout shelter mlfunctioned in However, dt collected y the digitl imge method showed steeper decline when compred to visul qulity dt. The differences etween the two methods re possily relted to the more sujective nture of visul rtings. Plots were rted y the sme resercher throughout the study, ut visul qulity ws lower when compred with percent green turfgrss coverge dt otined through digitl imge nlysis in 2011 s in Soil Wter Content Volumetric soil wter content t 5 cm, 20 cm, nd in the 0 to 50 cm profile decresed during oth dry downs in oth yers (Figs. 2.7, 2.8, nd 2.9). In 2010, θ v content t 5 cm ws similr mong cultivrs t the eginning of the dry down (33-34%) (Fig. 2.7). During the next 45

62 21 dys, θ v declined rpidly ut then ruptly incresed on 5 July fter the plots received 25 mm of precipittion when the rinout shelter mlfunctioned. During the next 25 dys, θ v gin declined mong cultivrs efore generlly leveling off in the finl 35 dys of the dry down. In 2011, θ v t 5 cm ws lso similr mong cultivrs t the eginning of the dry down (24-26%). Therefter, θ v declined rpidly for the first 15 dys nd egn to level off in four cultivrs y 15 June; θ v continued to decline in Blue Velvet nd Wellington for n dditionl 10 dys. Volumetric soil wter content incresed sustntilly fter ll plots received 25 mm of precipittion on 21 July, 2011 when the rinout shelter mlfunctioned second time in the study. In oth yers, the gretest depletion of soil moisture t 5 cm ws in Cernet nd Apollo. By the end of the period of soil moisture depletion in ech yer, when θv t 5 cm leveled off, θ v hd declined in Cernet y 29% in 2010 nd 17% in 2011, nd in Apollo y 22% in 2010 nd 16% in Cernet elongs to the KBG phenotypic group Mid-Atlntic, whose cultivrs re known for hving extensive root nd rhizome systems nd good tolernce nd recovery from summer stress (Bonos et l., 2000; Brooks Gould, 2004). Greter depletion of soil moisture t 5 cm y Cernet in this study supports these reports. Apollo elongs to the KBG phenotypic group Compct Americ, whose cultivrs hve een reported s hving moderte ility to recover from summer stress (Brooks Gould, 2004). Both Cernet nd Apollo were mong the top performing cultivrs in study tht rnked minimum wter requirements of 28 KBG nd two hyrid luegrsses (Lewis et l., 2012). In 2010, θv t 20 cm ws similr mong cultivrs t the eginning of the experiment (36-38%) (Fig. 2.8). Soil moisture declined rpidly during the first 15 dys of the dry down nd then ruptly incresed fter plots indvertently received 25 mm of precipittion on 5 July. Therefter, θ v declined for the next 30 dys efore generlly leveling off. By the end of the 46

63 entire 88 dy dry down, the gretest decline in θ v mong cultivrs ws in Apollo (23%). In 2011, θ v t 20 cm ws lso similr in ll cultivrs t the eginning of the dry down (30-31%). The θ v generlly declined from 1 June to 2 July. During this 30 dy period the gretest reduction in θ v ws in Bedzzled (19%). In oth yers the soil ws much drier y the end of the dry down t 5 cm thn t 20 cm (Figs. 2.7 nd 2.8). Presumly, greter root density nerer the surfce resulted in greter depletion of soil moisture t 5 cm (Su et l., 2008). At 20 cm, the gretest decline in θv ws in cultivrs from the phenotypic group Compct Americ (i.e., Apollo nd Bedzzled), which indictes tht cultivrs from tht group hd greter ility to mine wter from deeper in the profile (20 cm). In study conducted y (Bonos nd Murphy, 1999) soil moisture of drought tolernt cultivrs ws significntly lower t the cm depth compred with intolernt cultivrs. These results suggest tht Apollo nd Bedzzled my e more drought tolernt thn the other cultivrs. However, cultivr Wellington from the Common type phenotypic group lso hd lrge declines in θ v t the 20 cm profile for oth yers, ut did not disply superior drought tolernce. In 2010, θv in the 0-50 cm profile ws similr t the eginning of the experiment (38-43%) (Figure 2.9). The fstest decline in θ v occurred from 6 July to 9 August. During this 33 dy period, the gretest reduction in θ v ws in the Common phenotype Wellington (~21%). Interestingly, decreses in θ v in Wellington were less t 5 cm nd greter t 20 cm thn most of the other cultivrs. This suggests tht Wellington my hve depleted even greter soil moisture from deeper in the profile, perhps ecuse of deeper root system (21-50 cm). 47

64 Lef Wter Potentil Lef wter potentil egn to decline in the first week of the dry down in oth yers (dt not shown). There were differences in Ψ lef mong cultivrs on only 8 out of 55 mesurement dtes during the two-yer study (P=0.05), ut there were no conclusive trends. In 2010, verge Ψ lef mong the six cultivrs declined y 52%, from MP to MP, during the first 21 DAI withheld. Overll, the decline in Ψ lef during this period ws the most rpid of the entire dry down in At the end of this 21-dy period, on 5 July, the plots received 25 mm of precipittion fter the rinout shelter mlfunctioned. After receiving precipittion, Ψ lef reounded to n verge of MP mong the six cultivrs on 7 July. However, fter the remining 67 dys of the 88 dy dry down, Ψ lef hd gin declined to MP mong the six cultivrs, decrese of nerly two times. For the first 16 dys of recovery, verge Ψ lef rnged from MP to MP mong the six cultivrs. On 27 Septemer 2010 or pproximtely 23 dys into recovery Ψ lef finlly reched n verge level of MP which ws similr to the cultivrs t the eginning of the dry down. In 2011, verge Ψlef mong cultivrs decresed y 1.47 times, from MP to MP, during the first 44 dys of the dry down (dt not shown). At the end of those 44 dys, on 15 July, the plots received 7 mm of precipittion fter the rinout shelter mlfunctioned. However, Ψ lef mong the cultivrs still continued to decline reching the lowest point of MP on 21 July On this dte 51 DAI, second rin shelter mlfunction occurred nd the plots received 32 mm of precipittion. By 26 July 2011 Ψ lef hd reounded to MP when verge cross the six cultivrs. Overll, in this two-yer study Ψ lef did little towrds discerning differences in drought tolernce mong KBG cultivrs. Vlues of Ψlef in this study were low t the eginning of the dry down, prticulrly in 2010 (men = MP), s well s t the end of the dry down (e.g., rnge of Ψ lef from -6 to 48

65 -10.8 MP in 2010). Other studies hve reported Ψ lef from -0.5 to -1.8 under well-wtered conditions down to <-4 MP under conditions of severe drought (Qin nd Fry, 1997; Wng et l., 2008; Domenghini et l., 2013). The low vlues of Ψ lef in the present study were likely cused y comintion of the severity of the drought nd the fct tht Ψ lef ws mesured t middy rther thn under pre-dwn conditions. Electrolyte Lekge Electrolyte lekge (EL) ws generlly similr mong the six cultivrs during the dry down nd recovery periods in oth yers (Fig.2.10). In ddition, there were no sustntil increses in EL s the dry down progressed in oth yers, indicting the effects of drought stress on cellulr memrne stility were negligile. Cell memrne lekge of greter thn 50% will typiclly result in tissue deth (Dr. C.B. Rjshekr, personl communiction). In this study, EL exceeded 50% on only few occsions in 2010, ut typiclly dropped elow the 50% threshold the following smpling period. For 2011, EL never exceed the 50% threshold. Interestingly, EL incresed sustntilly in Bedzzled, Aey, nd Wellington on 7 Sept. 2010, which ws three dys into the recovery (i.e, three DAI ws repplied). During this period, the cnopy ws mixture of newly emerging leves nd older leves. In pepper plnts (Cpsicum nnuum L.), EL ws reportedly greter in mture leves thn in immture leves on the sme plnt (Anderson et l., 1990). Therefore, it is possile tht erly in the recovery period of the present study, differences in EL resulted from the rndom selection of older leves in Bedzzled, Blue Velvet, nd Cernet thn in the other cultivrs. In support of this, EL decresed in Bedzzled, Blue Velvet, nd Cernet y the next mesurement dte, with no differences in EL mong ny of the cultivrs. This indictes limittion in using EL to ssess 49

66 drought stress effects in KBG, which typiclly goes dormnt during severe drought. The difficulty is in selecting leves tht re representtive of the entire cnopy, which consists of mny immture nd mture leves. The results of this study contrdict those from growth chmer study conducted y Arhm et l., (2004), in which EL ws sensitive indictor of drought stress in turfgrss. However, numer of other studies hve reported negligile effects of drought stress on EL mong turfgrss species (Su et. l., 2007; Merewitz et l., 2010; Domenghini et l., 2013), which is similr to the results from the present study. Gross Photosynthesis Photosynthesis decresed sustntilly in ll six KBG cultivrs over the course of the 2010 dry down nd in ll seven cultivrs in 2011 (Fig. 2.11). In 2010, differences in Pg mong cultivrs were only oserved on the initil mesurement dte of 18 June, which ws three dys fter the dry down egn. On tht dy, Pg rnged widely mong cultivrs from 10.2 to 27.4 μmol m -2 s -1 nd ws greter in Bedzzled thn in Cernet, Aey, nd Wellington. Within 12 dys, Pg hd declined y 50 to 73% mong cultivrs. By 23 July, which ws out 5 weeks into the dry down, Pg ws less thn 5 μmol m -2 s -1 in ll cultivrs nd remined so through the end of the 12.6-week dry down. Interestingly, fter re-wtering plots on 4 Sept. Pg continued to decline nd y 20 Sept. ws less thn 1 μmol m -2 s -1 in ll cultivrs; this ws pproximtely 2 weeks fter the plots were re-wtered, lthough most of the cnopy either remined dormnt or ws decesed. Overll, Pg declined y >95% in ll cultivrs from the study initition through 20 Sept

67 By 26 Oct.2010, Pg hd incresed ut remined 43 to 75% less thn t the eginning of the dry down. Previous reserch hs indicted prolonged drought my dmge the photosynthetic pprtus of cool-seson turfgrss, which my inhiit Pg even fter lef wter sttus returns to norml (Hung et l., 1998). Therefore, the severity of dmge to the KBGs during the 88-dy drought likely resulted in slow recovery. On 3 Nov., it ws visully evident tht most plots hd not fully recovered due to ptchy green cover in most plots tht resulted in low percent green coverge (Figs. 2.2 nd 2.3). Lower solr elevtion ngles in Nov. thn in June lso reduced photosyntheticlly ctive rdition (dt not shown), which proly further depressed Pg in Nov. In 2011, Pg verged 18 μmol m -2 s -1 mong the seven cultivrs t the eginning of the dry down 6 June (Fig. 2.11). By 8 July, Pg hd decresed y 24 to 77% mong cultivrs nd ws 75 to 133% greter in Apollo thn in Wellington, Cernet, Aey, nd Bedzzled; 8 July ws the only dy in 2011 where differences in Pg were oserved mong cultivrs. Greter Pg in Apollo, Compct Americ phenotype, is similr to the results from two seprte 30-dy dry downs in n erlier study on these sme plots, which lso indicted greter Pg in Apollo thn in other KBG cultivrs (Lewis, 2010); unfortuntely, Pg in Apollo ws not mesured in 2010 in the present study. By 20 July 2011, Pg in ll seven cultivrs hd declined y out 85% from the eginning of the dry down, verging 2.69 μmol m -2 s -1 mong cultivrs. Optiml temperture rnge for photosynthesis nd plnt growth in cool-seson grsses is o C (Fry nd Hung, 2004). Tempertures exceeded 30 o C on dys during oth dry downs in 2010 nd Greter reductions in Pg during the 88-dy dry down in 2010, which resulted in slower recovery, indicted greter severity in drought stress thn during the shorter (60-dy) dry down in 2011 nd susequent fster recovery. In fct, the recovery period fter the 2010 dry 51

68 down extended into nd through the spring of 2011 (dt not shown). Nevertheless, plots hd recovered to (85-98%) turfgrss coverge y the eginning of the dry down in 2011 (Figs 2.5), indicting remrkle cpcity for recovery y KBG fter extended drought. Conclusions In summry, ll cultivrs of KBG recovered from prolonged drought stress which ws incurred during oth dry downs. One of the most significnt fctors in distinguishing mong the seven cultivrs exmined cme from their ility to extrct soil moisture while undergoing irrigtion deficit. The KBG cultivrs Cernet nd Apollo showed the highest reduction in volumetric wter content from the 5-cm soil profile for oth yers of the study. However, those two cultivrs hd contrsting drought tolernce s mesured y the mount of dys to rech 25% green turfgrss coverge. At 20 cm, the gretest decline in θ v ws in cultivrs from the phenotypic group Compct Americ (i.e., Apollo nd Bedzzled), which indictes tht cultivrs from tht group hd greter ility to mine wter from deeper in the profile (20 cm). Apollo consistently demonstrted the gretest drought tolernce mong the cultivrs while Cernet ws the lest drought tolernt. The cultivr tht required the fewest dys to rech 75% green cover during the recovery in oth yers ws Apollo. With the exception of greter Pg in Apollo lte in the dry down of the second yer, there were generlly no differences in the physiologicl fctors of EL, Ψlef, nd Pg mong cultivrs in this study 52

69 Figures nd Tles Figure 2.1- Averge ir temperture during the dry downs in 2010 nd Solid lck lines signify the strt nd cesstion of the 2010 dry down. Dshed lck lines signify the strt nd cesstion of the 2011 dry down. Mrkers represent 5 dy verges. 53

70 Figure 2.2- Predicted dry-down curves of 7 cultivrs of KBG during 60-dy dry down in Tretments included Apollo; Bedzzled; Moonlight; Cernet; Blue Velvet; Aey nd Wellington. Dshed line indictes DAI

71 Figure 2.3- Predicted dry-down curves of 7 cultivrs of KBG during 60-dy dry down in Tretments included Apollo; Bedzzled; Moonlight; Cernet; Blue Velvet; Aey nd Wellington. Dshed line indictes DAI

72 Figure 2.4- Predicted recovery curves of 7 cultivrs of KBG following 60-dy dry down in Tretments included Apollo; Bedzzled; Moonlight; Cernet; Blue Velvet; Aey nd Wellington. Dshed line indictes DAI

73 Figure 2.5- Predicted recovery curves of 7 cultivrs of KBG following 60-dy dry down in Tretments included Apollo; Bedzzled; Moonlight; Cernet; Blue Velvet; Aey nd Wellington. Dshed line indictes DAI

74 Visul Qulity Rting (1-9) c c c Tretments Apollo Bedzzled Moonlight Cernet Blue Velvet Aey Wellington 0 6/16 6/30 7/14 7/28 8/11 8/25 9/8 9/22 10/6 10/20 6/8 6/15 6/22 6/29 7/6 7/13 7/20 7/27 8/3 8/10 8/17 Figure 2.6- Visul qulity rting of 7 cultivrs of KBG during 60-dy dry down in 2010 nd Tretments included Apollo; Bedzzled; Moonlight; Cernet; Blue Velvet; Aey nd Wellington. Verticl solid lck lines in the ove grphs indicte the completion of the dry down. Verticl dotted lines in oth yers indicte rin shelter mlfunctions. Mens followed y the sme letter on dte re not significntly different ccording to the F-LSD (P < 0.05). 58

75 (5 cm) 2011 (5 cm) Soil Volumetric Wter Content (%) Tretments Apollo Bedzzled Moonlight Cernet Blue Velvet Aey Wellington 0 6/21 7/5 7/19 8/2 8/16 8/30 6/6 6/20 7/4 7/18 8/1 Figure 2.7- Volumetric Wter Content (5cm) of 7 cultivrs of KBG during 60-dy dry down in 2010 nd Tretments included Apollo; Bedzzled; Moonlight; Cernet; Blue Velvet; Aey nd Wellington. Verticl solid lck lines in the ove grphs indicte the completion of the dry down. Verticl dotted lines in oth yers indicte rin shelter mlfunctions. Mrkers represent 5 dy verges. In 2011, dt were not ville in Bedzzled ecuse of sensor filure. 59

76 Soil Volumetric Wter Content (%) (20 cm) Tretments Apollo Bedzzled Moonlight Cernet Blue Velvet Aey Wellington 2011 (20 cm) 0 6/21 7/5 7/19 8/2 8/16 8/30 9/13 9/27 6/6 6/20 7/4 7/18 8/1 8/15 Figure 2.8- Volumetric Wter Content (20cm) of 7 cultivrs of KBG during 60-dy dry down in 2010 nd Tretments included Apollo; Bedzzled; Moonlight; Cernet; Blue Velvet; Aey nd Wellington. Verticl solid lck lines in the ove grphs indicte the completion of the dry down. Verticl dotted lines in oth yers indicte rin shelter mlfunctions. Mrkers represent 5 dy verges. 60

77 50 Soil Volumetric Wter Content (0-50 cm) (%) Cernet Blue Velvet Bedzzled Wellington Moonlight Aey 0 7/7/10 7/21/10 8/4/10 8/18/10 9/1/10 Month Figure 2.9- Volumetric Wter Content (0-50cm) of 6 cultivrs of KBG during 60-dy dry down in Tretments included Bedzzled; Moonlight; Cernet; Blue Velvet; Aey nd Wellington. Verticl solid lck line in the ove grph indictes the completion of the dry down. 61

78 Aey Cernet Wellington Bedzzled Blue Velvet Moonlight 2011 Electrolyte Lekge (%) /01 8/01 9/01 10/01 6/1 7/1 8/1 Figure Electrolyte Lekge of 6 cultivrs of KBG during 60-dy dry down in 2010 nd Tretments included Bedzzled; Moonlight; Cernet; Blue Velvet; Aey nd Wellington. Apollo ws not included in the dt collection for Red horizontl dshed line indictes level of 50% electrolyte lekge. Mens followed y the sme letter on dte re not significntly different ccording to the F-LSD (P < 0.05). 62

79 Pg (µmol m -2 s -1 ) Tretments Blue Velvet Wellington Cernet Moonlight Aey Bedzzled Apollo 5 0 Jul Aug Sep Oct Jun Jun Jul Jul Aug Aug Figure Gross Photosynthesis of 7 cultivrs of KBG during 60-dy dry down in 2010 nd Tretments included Bedzzled; Moonlight; Cernet; Blue Velvet; Aey nd Wellington. Apollo ws not included in the dt collection for Verticl solid lck lines in the ove grphs indicte the completion of the dry down. Verticl dotted lines in oth yers indicte rin shelter mlfunctions. Mens followed y the sme letter on dte re not significntly different ccording to the F-LSD (P < 0.05). 63

80 Tle 2.1- Hypothesis test summries for luegrss entry effects on green turf coverge during dry-down nd susequent recovery in 2010 nd Sums of squres reduction test Dry-down 2010 Dry-down 2011 Recovery 2010 Recovery 2011 Null hypothesis Shred regression prmeters (slope nd dys 25//75 ) for ll vrieties Alterntive hypothesis Different regression prmeters for ech vriety Numertor df Denomintor df F vlue P vlue < Slope nd dys 25/75 vlues determine percent green turf cover ccording to the sigmoid vrile slope model. 64

81 References Arhm, E.M., B. Hung, S.A. Bonos, nd W.A. Meyer Evlution of drought resistnce for Texs luegrss, Kentucky luegrss, nd their hyrids. Crop Sci. 44: Anderson, J., G. McCollum, nd W. Roerts High temperture cclimtion in pepper leves. Hortscience 25: Bsinger, J.M., G.J. Kluitenerg, J.M. Hm. J.M. Frnk, P.L. Brnes, nd M.B. Kirkhm Lortory evlution of the dul-proe het-pulse method for mesuring soil wter content [Online]. Aville t Vdose Zone J. 2: Blum A. nd Eercon, A Cell memrne stility s mesure of drought nd het tolernce in whet. Crop Science 21: Bonos, S.A., R.f. Br, W.K. Dickson, D.A. Smith, M.M. Mohr, E., Wtkins, J.A. Murphy, W.A. Meyer, nd C.R. Funk Performnce of Kentucky luegrss cultivrs nd selections in NJ turf trils, Rutgers Turfgrss Proc. 31: Bremer, D.J., nd J.M. Hm Mesurement nd prtitioning of in situ cron dioxide fluxes in turfgrsses using pressurized chmer. Agron. J 97: Brooks Gould, A., editor Rutgers Turfgrss Proceedings. New Jersey Turfgrss Expo, Atlntic City, NJ. 7 9 Dec New Jersey Turfgrss Assoc., Atlntic City, NJ. Cmpell, G.S., C. Clissendorff, nd J.H. Willims Proe for mesuring soilspecific het using the het pulse method. Soil Sci. Soc. Am. J. 62: DCost, M. Z. Wng, nd B. Hung Physiologicl dpttion of Kentucky luegrss to loclized soil drying. Crop Sci. 44: Domenghini, J.C., D.J. Bremer, J.D. Fry, nd G.L. Dvis Evpotrnspirtion nd performnce mong turfgrss nd ornmentl lndscpe species in response to irrigtion deficit. In press t ITSRJ. Du, H., Z. Wng, nd B. Hung Differentil responses of wrm-seson nd coolseson turfgrss species to het stress ssocited with ntioxidnt enzyme ctivity. Journl of the Americn Society for Horticulture Science 134: Edon, J.S., nd A.M. Petrovic Morphologicl nd growth chrcteristics of lownd high-wter use Kentucky luegrss cultivrs. Crop Sci. 38: Emmons, R.D Turfgrss Science nd Mngement. 3rd ed. Delmr, Alny, NY. 65

82 Fry, J. nd B. Hung Applied Turfgrss Science nd Physiology. John Wiley & Sons, Hooken, NJ. Hsio, T.C Plnt responses to wter stress. Ann. Rev. Plt Phyiol. 24: Hung, B., R.R. Duncn nd R.N. Crrow Drought-resistnce mechnisms of seven wrm-seson turfgrsses under surfce soil drying: I shoot response. Crop Sci. 37: Hung, B., J. Fry, nd B. Wng Wter reltions nd cnopy chrcteristics of tll fescue cultivrs during nd fter drought stress. Hort. Sci. 33(5): Hung, B. nd H. Go Physiologicl responses of diverse tll fescue cultivrs to drought stress. Hort. Sci. 34: Krcher, D.E., M.D. Richrdson, K. Hignight, nd D. Rush Drought tolernce of tll fescue vrieties selected for high root:shoot rtios. Crop Sci. 48: Krcher, D.E., M.D. Richrdson, Btch nlysis of digitl imges to evlute turfgrss chrcterstics. Crop Sci. 45: Lewis, J Cron, nitrogen, nd wter fluxes from turfgrss ecosystems. Ph.D. disserttion, Knss Stte University. Lewis, J., D.J. Bremer, S.J. Keeley, nd J.D. Fry Wilt-sed irrigtion in Kentucky luegrss: Effects on visul qulity nd irrigtion mounts mong cultivrs. Crop Sci. 52: Liu, J., Xie, X., Du, J., Sun, J. nd Bi, X Effects of simultneous drought nd het stress on Kentucky luegrss. Scienti Horticulture 115: Mrcum, K.B Cell memrne thermostility nd whole-plnt het tolernce of Kentucky luegrss. Crop Science 38: Merewitz, E., W. Meyer, Stcy Bonos, nd Bingru Hung Drought stress responses nd recovery of Texs x Kentucky Hyrids nd Kentucky Bluegrss genotypes in temperte climte conditions. Agron. Journ. 102: Murphy, J.T Ptterns of cron dioxide nd wter vpor flux following hrvest of tllgrss prire t different times throughout the growing seson. Ph.D. Knss Stte University, Mnhttn, KS. Qin, Y. nd Fry, J.D Wter reltions nd drought tolernce of four turfgrsses. Journl of Americn Society for Horticulture Science 122:

83 Richrdson, M.D., D.E. Krcher, nd L.C. Purcell Quntifying turfgrss cover using digitl imge nlysis. Crop Sci. 41: Richrdson, M.D, D. Krcher, K. Highnight, nd D. Rush Drought tolernce nd rooting cpcity of Kentucky Bluegrss Cultivrs. Crop Sci. 48: Richrdson, M.D., D.E. Krcher, K. Highnight, nd D. Rush Drought tolernce of Kentucky Bluegrss nd hyrid luegrss culitvrs. Applied Turfgrss Science. 10: Slisury, F.B. nd C.W. Ross (eds.) Plnt physiology. 4th ed. Wdsworth Pulishing Compny, Belmont, CA. SAS Institute Inc User instlltion guide for the SAS system, version 9 for microsoft windows. SAS Institute, Cry, NC. Song, Y., J.M. Hm, M.B. Kirkhm, nd G.J. Kluitenerg Mesuring soil wter content under turfgrss using the dul-proe het-pulse technique. J. Am. Soc. Hortic. Sci. 123: Su, K., D.J. Bremer, S.J. Keeley, nd J.D. Fry Effects of high temperture nd drought on hyrid luegrss compred with Kentucky luegrss nd tll fescue. Crop Sci. 47: Su, K., D.J. Bremer, S.J. Keeley, nd J.D. Fry Mowing nd drought effects on hyrid luegrss compred with Kentucky luegrss. Int. Turf. Soc. Res. J. 11: Trr, J.M., nd J.M. Hm Evlution of dul-proe het-cpcity sensors for mesuring soil wter content in the lortory nd in the field. Agron. J. 89: Wng, J.P., nd S.S. Bughrr Morpho-physiologicl responses of severl Fescue grsses to drought stress. Hort. Sci. 43(3): Wng, Z., nd B. Hung Physiologicl recovery of Kentucky luegrss from simultneous drought nd het stress. Crop Sci. 44:

84 Chpter 3 - Evlution of Turf Reinforcement Mts nd Their Effect on Estlishment of Bufflogrss nd Zoysigrss *This pper ws ccepted for puliction in the Interntionl Turfgrss Society Reserch Journl 8/21/2012 (ITSRJ ) 68

85 Astrct Turf reinforcement mts (TRM) cn reduce erosion nd prevent weed encrochment during turfgrss estlishment. Legcy ufflogrss (Buchloe dctyloides [Nutt.] Engelm.) nd Chisholm zoysigrss (Zoysi jponic Steud.) were evluted in seprte field studies for estlishment when vegettive plugs were 1) plnted in TRM; 2) plnted in plots which were susequently treted with oxdizon; or 3) untreted. Plugs were estlished on TRM over plstic prior to trnsplnting to study res. Chisholm zoysigrss stolons grew under the TRM; s such, use of TRM for this cultivr is not prcticl. Bufflogrss hd > 90% coverge when estlished on TRM in 2010 nd > 65% coverge in 2011; coverge ws similr to tht in oxdizon-treted plots in ech yer. Weed levels in plots where TRM (up to 8% weed coverge) were used were generlly lower thn those where oxdizon ws pplied (up to 43% weed coverge); untreted plots (up to 63% weed coverge) generlly hd higher weed levels thn the other tretments. Turf reinforcement mts offer potentil for estlishment of Legcy ufflogrss where lor involved in plnting individul plugs on site is not ville, use of hericides is not desired, or soil erosion concerns exist. 69

86 Introduction Estlishment of wrm-seson turfgrsses in the trnsition zone cn e n rduous tsk. Rinfll events cn cuse significnt erosion on new seededs or res estlished with vegettive plugs. Such erosion increses the trnsport of sediments into surfce wters (U.S. Environmentl Protection Agency, 1999). Trditionlly, erosion control mterils tht utilize concrete locks, rock riprp, nd reinforced pving systems hve een used in highly erosive res. While these mterils cn withstnd significnt hydrulic forces, they do not provide sediment removl cpilities (U.S. Environmentl Protection Agency, 1999). In ddition to erosion, nnul weed competition fter plnting wrm-seson grsses cn impede successful estlishment (Fry et l., 1986; Hrivndi et l., 1993). Weeds compete with desirle turfgrss species for light, wter, nd nutrients (Berd, 1973). Pre- nd postemergence hericides hve een commonly used to control weeds during estlishment, ut erosion could still e concern. Turf reinforcement mts my provide the lndscpe mnger with mens to prevent erosion nd suppress weeds during estlishment of wrm-seson turfgrsses. Turf reinforcement mts re typiclly mnufctured using tightly compressed plnt fier. An exmple of this is jute, which is extrcted from the stems of plnts elonging to the genus Cochorus. The mt my, or my not, e reinforced with plstic netting nd provides high-strength mteril tht prevents soil erosion (U.S. Environmentl Protection Agency, 1999) nd germintion of weed seeds, or weed seedling survivl fter germintion (Lowe et l., 1999). Severl wrm-seson turfgrsses hve een successfully estlished for soilless sod using orgnic fier mediums composed of kenf, fier-sed plnt product comprle to the mteril used in TRM (Rowell nd Stout, 1998). Specificlly, kenf-sed orgnic fier mts provided suitle medium for sprigging of MS Express ermudgrss (Cynodon X mgenissii 70

87 Hurc.), common centipedegrss (Eremochlo ophiuroides Munro Hck.), nd Meyer zoysigrss (Z. jponic Steud.) (Hensler et l, 1998). One dvntge to TRM is tht vegettive plntings cn e estlished on the mts t the grower s loction prior to instlltion t the jo site. In fct, this hs een done commercilly with ntive lndscpe plnts nd turfgrss sod (Mtt Cmpell, personl communiction). This is idel for the lndscpe mnger who my not hve the lor to plnt individul plugs on site, or for customers who my prefer non-hericide pproch to weed control nd erosion prevention enefits fforded y TRM. Our ojective ws to evlute the estlishment of Legcy ufflogrss nd Chisholm zoysigrss from vegettive plugs on TRM. Mterils nd Methods Study site nd experimentl design Seprte experiments were conducted to evlute estlishment of Chisholm zoysigrss nd Legcy ufflogrss from vegettive plugs in 2010 nd Chisholm ws most recently evluted s DALZ 0102 zoysigrss in the 2002 Ntionl Turfgrss Evlution Progrm Zoysigrss Test (Ntionl Turfgrss Evlution Progrm, 2006). Experiments were conducted t the Rocky Ford Turfgrss Reserch Center ner Mnhttn, Knss, USA (39 o N, 96 o W). Soil ws Chse silt lom (fine, smectitic, mesic, Aquertic Argiudoll) with ph of 6.9. Tretments for the two experiments were: 1) plugs estlished in TRM; 2) plugs plnted in plots which were susequently treted with oxdizon; nd 3) untreted. In ech experiment, plots mesured 3 y 3 m, nd were rrnged in rndomized complete lock design with three replictions. 71

88 Chisholm zoysigrss plugs were initilly estlished from sprigs t the KSU greenhouse; plnting ws done in Mrch 2010 nd Legcy ufflogrss plugs were purchsed from Todd Vlley Frms (Med, NE) prior to experiments in ech yer. Turf Reinforcement Mts The TRM used in this study were designed nd mnufctured y StyTurf (Jimoom Turf Compny, Acci Ridge, Austrli). The originl StyTurf TRM re composed of felted jute fier mnufctured t 650 g m -2 with UV resistnt plstic netting inserted. Testing conducted t the Texs Deprtment of Trnsporttion Erosion Control Lortory found StyTurf cceptle for protection up to 194,013 L min -1, 58 kg m -2 sher force, nd velocity of m s -1 (Mtt Cmpell, personl communiction). The compny lso offers similr product without the plstic netting (StyTurf Soil Sver.), which ws the product used herein. For the TRM tretment, plugs were plnted into the mts in n re djcent to the experiment loctions on 10 June 2010 nd 1 June 2011, three weeks prior to plugs in other tretments eing plnted. This ws done to mimic the pproch grower would use to estlish plugs on the TRM prior to delivery to the jo site. A single turfgrss plug ws inserted into 2.5- cm dimeter slits on 30.5 cm centers on ech 3 m x 3 m section of TRM. The TRM rested directly on lyer of 7-mil. lck plstic. Irrigtion ws pplied three times dily to deliver up to 2 mm of wter in order to ensure mts styed moist nd to prevent turfgrss stress. On 1 July 2010 nd 23 June 2011, three weeks fter inserting plugs into mts, TRM contining plugs of the respective species were lifted from the plstic nd plnted in djcent, seprte, zoysigrss nd ufflogrss study res. These were considered the dtes plnting occurred in field. At the dte of plnting ech experiment, 5-cm dim. zoysigrss nd ufflogrss plugs were lso plnted on 30.5 cm centers (16 plugs per plot) in untreted plots nd plots to e treted 72

89 with oxdizon. Oxdizon ws pplied t 3.9 kg.i. h -1 using hnd-held shker ottle to plots receiving tht tretment. All plots were topdressed with 49 kg P h -1 from dimmonium phosphte ( ) t the time of plnting. Plot Mintennce Irrigtion ws pplied s necessry to keep soil t field cpcity (~33% volumetric wter content) sed upon twice weekly mesurements t 0 to 20 cm depth with time domin reflectometer (Soil Moisture Equipment Corportion, Snt Brr, CA). Ech study re ws fertilized with N from ure t 49 kg h-1 on 24 July 2010 nd 13 July Mesurements Plots were rted visully for percentge turfgrss coverge nd weed coverge periodiclly during ech study. Rtings were done visully on 0 to 100% scle, where 0 = no turf or weed coverge, nd 100% = complete turf or weed coverge. Weed species present in the study res included nnul luegrss (Po nnu L.), goosegrss [Eleusine indic (L.) Gertn.], spotted spurge (Euphori mculte L.), nd dndelion (Trxcum officinle Weer ex F.H. Wigg.). Sttisticl nlysis Dt were suject to nlysis of vrince using the GLM procedure of SAS (SAS Institute Inc., Cry, NC). Mens were seprted using Fisher s Protected LSD (P < 0.05). Levene s test ws used to ssess the homogeneity of vrinces in order to determine if dt on turfgrss or weed coverge in ech experiment could e pooled for over yers (P < 0.05) (Levene, 1960). Results nd Discussion 73

90 Turfgrss Estlishment nd Weed Suppression Zoysigrss Chisholm zoysigrss estlished on TRM exhiited lower levels of coverge compred to oxdizon-treted or untreted plots in 2010 nd 2011 (Fig. 3.1). Chisholm produced stolons tht grew elow the TRM. These plugs did not receive photosyntheticlly ctive rdition nd ppered to e etiolted. This reduced zoysigrss coverge rtings ecuse stolons were not visile. The use of TRM for estlishment of Chisholm zoysigrss from plugs ws not prcticl due to its growth hit. Perhps there re other zoysigrss cultivrs whose stolons would develop on the surfce of the TRM nd would e more fvorle cndidtes for estlishment on TRM; more investigtion is necessry. Between 17 nd 78 DAP 2010, zoysigrss in the oxdizon-treted plots exhiited weed coverge (up to 18%), which ws lower thn untreted (up to 57%), nd similr to the TRM tretment (0%) (Fig 3.2). Between 55 DAP nd 99 DAP 2011, weed suppression provided y the TRM tretment (0 %) ws superior to tht provided y oxdizon (up to 43%), nd oth were superior to untreted plots during this period (up to 68%). Despite weed suppression in the oxdizon tretment which ws superior to untreted turf on 7 dtes in 2010 nd 4 dtes in 2011, zoysigrss coverge t the end of the growing seson in the oxdizon tretment ws superior to untreted only in 2011 (Fig. 3.1). Oxdizon (3.4 kg.i. h -1 ) lso incresed coverge of Meyer zoysigrss estlished from sprigs in Mrylnd (Crroll et l., 1996). This ws due, in prt, to 66% reduction in crgrss cover where oxdizon ws pplied compred to untreted plot. Oxdizon (3.4 kg.i. h -1 ) reduced coverge of nnul grsses y 78% to 97% in Mrylnd, which contriuted to 74

91 incresed coverge of Meyer zoysigrss from vegettive plugs nd sprigs compred to untreted plots (Fry et l., 1986). Bufflogrss There ws significnt (P < 0.05) tretment effect on ufflogrss coverge on 6 of 24 evlution dtes (Fig. 3.3). Bufflogrss treted with oxdizon or estlished on TRM hd greter coverge thn untreted plots t 63 nd 111 DAP in On the other 2 dtes in 2010 when differences occurred, ufflogrss coverge ws greter in oxdizon treted plots thn untreted plots, ut coverge in the TRM tretment ws similr to tht in untreted plots. Bufflogrss coverge ws higher in oxdizon-treted plots nd TRM-treted plots thn untreted plots t 19 DAP 2011; no differences occurred on other dtes. On severl occsions in 2011, wind lifted the TRM in one replicte, which dislodged few of the ufflogrss plugs. This ultimtely ffected the level of coverge oserved, nd reduced the overll coverge men oserved in the TRM tretment. Weed coverge in ufflogrss plnted in TRM (0%) or oxdizon-treted plots (up to 18%) ws lower thn tht in untreted plots (up to 58%) on most rting dtes in 2010 (Fig 3.4). Likewise, weed coverge in ufflogrss plnted in the TRM tretment (up to 8%) ws lower thn tht in oxdizon-treted plots (up to 40%) on four dtes in Weed coverge in the oxdizon tretment did not differ from untreted (up to 63%) t 14, 21, 43, 48 nd 100, nd 116 DAP Annul weedy grsses nd rodleves cn e controlled in ufflogrss using severl pre-nd postemergence hericides (McCrty nd Colvin, 1992; Fry et l., 1997; Shermn et l., 2004; Goss et l., 2006). Oxdizon (2.2 kg.i. h -1 ) ws lso shown to reduce weed competition nd enhnce ufflogrss estlishment from plugs in Cliforni (Hrivndi et l., 1993). 75

92 Economic Considertions Totl cost for Legcy ufflogrss plugs is pproximtely $ 463 USD h -1 if plnted on 30.5 cm centers. Purchsing TRM to cover the sme one hectre re would cost pproximtely $ 220 USD. In contrst, cost of oxdizon for weed control t the rte used herein would e pproximtely $8.61 USD h -1. Therefore, high costs ssocited with TRM my mke its use prcticl only those situtions which pose high risks for erosion. One prticulr re where ufflogrss estlished in TRM could e useful is on rodside chnnels long highwys where vegettion is desired. Rodside chnnels ply n importnt role in the highwy dringe system s the initil conveynce for runoff (U.S. Deprtment of Trnsporttion nd Federl Highwy Administrtion, 2005). Bufflogrss hs een recognized s n importnt species for soil stiliztion long rodwys (Christins, 2007). Conclusions Turf reinforcement mts were effective in encourging successful estlishment of Legcy ufflogrss from vegettive plugs. However, estlishment of Chisholm zoysigrss with TRM ws not successful due to stolon growth eneth the mt. Turfgrss reinforcement mts effectively eliminted ll weed competition. Despite higher weed levels in oxdizontreted ufflogrss, coverge ws comprle to plots estlished using TRM y the end of the seson. Turf reinforcement mts my e suitle technique for vegettive ufflogrss plugs where lor involved in plnting individul plugs is not ville, use of hericides is not desired, or soil erosion concerns exist. 76

93 Figures nd Tles Zoysigrss Coverge (%) TRM Oxdizon Untreted c c c DAP Figure 3.1- Coverge of Chisholm zoysigrss from vegettive plugs s ffected y estlishment method t Mnhttn, KS in 2010 nd Tretments included plnting in turf reinforcement mts (TRM); ppliction of oxdizon t 3.9 kg.i. h -1 just fter plnting; nd untreted. Plnting ws done on 1 July 2010 nd 23 June 2011 nd susequent rting dtes re referred to s dys fter plnting (DAP). Coverge ws rted visully on 0 to 100% Scle. Mens followed y the sme letter on dte re not significntly different ccording to the Fisher s Protected LSD (P < 0.05). 77

94 TRM Oxdizon Untreted Weed Coverge (%) c c c c DAP Figure 3.2- Weed coverge in Chisholm plots plnted s vegettive plugs s ffected y estlishment tretment t Mnhttn, KS in 2010 nd Tretments included plnting in turf reinforcement mts (TRM); ppliction of oxdizon t 3.9 kg.i. h -1 just fter plnting; nd untreted. Plnting ws done on 1 July 2010 nd 23 June 2011 nd susequent rting dtes re referred to s dys fter plnting (DAP). Coverge ws rted visully on 0 to 100% Scle. Mens followed y the sme letter on dte re not significntly different ccording to the Fisher s Protected LSD (P < 0.05). 78

95 TRM Oxdizon Untreted Bufflogrss Coverge (%) DAP Figure 3.3- Coverge of Legcy ufflogrss from vegettive plugs s ffected y estlishment method t Mnhttn, KS in 2010 nd Tretments included plnting in turf reinforcement mts (TRM); ppliction of oxdizon t 3.91 kg.i. h -1 just fter plnting; nd untreted. Plnting ws done on 1 July 2010 nd 23 June 2011 nd susequent rting dtes re referred to s dys fter plnting (DAP). Coverge ws rted visully on 0 to 100% Scle. Mens followed y the sme letter on dte re not significntly different ccording to the Fisher s Protected LSD (P < 0.05). 79

96 TRM Oxdizon Untreted Weed Coverge (%) c 0 c DAP Figure 3.4- Weed coverge in Legcy ufflogrss plots plnted s vegettive plugs s ffected y estlishment tretment t Mnhttn, KS in 2010 nd Tretments included plnting in turf reinforcement mts (TRM); ppliction of oxdizon t 3.91 kg.i. h -1 just fter plnting; nd untreted. Plnting ws done on 1 July 2010 nd 23 June 2011 nd susequent rting dtes re referred to s dys fter plnting (DAP). Coverge ws rted visully on 0 to 100% Scle. Mens followed y the sme letter on dte re not significntly different ccording to the Fisher s Protected LSD (P < 0.05). 80

97 References Berd, J.B Turfgrss pests. p In Turfgrss: Science nd Culture, Prentice-Hll, Inc., Englewood Cliffs, NJ. Crroll, M.J., P.H. Dernoeden nd J.M Krouse Zoysigrss estlishment from sprigs following ppliction of hericides, nitrogen, nd iostimultor. HortScience. 31: Christins, N Wrm-Seson grsses. p In Fundmentls of Turfgrss Mngement, 3 rd Ed. John Wiley & Sons, Hooken, NJ. Fry, J.D., P.H. Dernoeden, nd J.J. Murry Estlishment nd rooting of zoysigrss (Zoysi jponic) s ffected y preemergence hericides. Weed Sci. 34: Fry, J.D., R.E. Gussoin, D.D. Bern, nd R.A. Msters Bufflogrss estlishment with preemergence hericides. HortScience 32: Goss, R.M., McCll J.H., Gussoin, R.E. nd M.D. Richrdson Hericide tolernce of ufflogrss. Applied Turfgrss Science doi:: ?ats rs. Hrivndi M.A., C.L. Elmore, nd L. Wu Preemergence hericide use during ufflogrss estlishment. Int. Turfgrss Soc. Res. J. 7: Hensler, K.L., B.S. Bldwin, nd J.M. Gotlley, Jr Kenf-sed fier mt s sustrte for estlishing soilless sod. HortTechnology. 8: Levene, H Roust tests for the equlity of vrinces. p In Contriutions to Proility nd Sttistics. 1 st ed. Stnford University Press, Olkin, Plo Alto, CA. Lowe, D.B., T. Whitwell, L.B. McCrty, nd W.C. Bridges Kylling revifoli, K. squmult, nd K. pumil seed germintion s influenced y temperture, light nd nitrte. Weed Sci. 17: McCrty, L.B. nd D.L. Colvin Bufflogrss tolernce to postemergence hericides. HortScience 27: Ntionl Turfgrss Evlution Progrm ntionl zoysigrss test Finl report. NTEP, Beltsville, Mrylnd. 81

98 Rowell, R.M., nd H.P. Stout Jute nd kenf. p In M. Lewin (ed.) Hndook of Fier Chemistry: 2 nd ed. Mrcel Dekker, Inc., New York. Shermn, B.C., T.P. Riordn, nd P.G. Johnson Bufflogrss. p In L.E. Moser et l. (ed.) Wrm-seson (C 4 ) Grsses. Agron. Monogr. no. 45. ASA,CSSA,SSSA, Mdison, WI. U.S. Deprtment of Trnsporttion, nd Federl Highwy Administrtion Design of rodside chnnels with flexile linings. Hydrulic Engineering Circulr No.l5, 3 rd ed. U. S. Evironmentl Protection Agency Storm wter technology fct sheet Office of Wter. EPA-832-F U.S. Gov. Print. Office, Wshington, DC. 82

99 Chpter 4 - Estlishment of Bufflogrss from Vegettive Plugs fter Short-term Storge on Turf Reinforcement Mts 83

100 Astrct Turf reinforcement mt (TRM) cn reduce erosion nd prevent weed encrochment during turfgrss estlishment. Legcy ufflogrss plugs were estlished on TRM over plstic for 3 weeks, stored in TRM under tree shde for 7, 14, or 21 dys, nd evluted for estlishment fter storge. Averge dily temperture inside the rolls during storge in rnged from 19 to 28 o C. In 2011, ufflogrss coverge ws lower for the 14 nd 21 dy storge tretments thn the control or 7 dy tretments on 7 of 9 evlution dtes. Bufflogrss stored on TRM for 0 or 7 dys hd similr coverge (75%) y the end of the growing seson. Coverge of ufflogrss y seson s end when stored on TRM for 14 dys ws 26%. Coverge of ufflogrss fter 21 dys of storge ws (<5 %) y the end of the growing seson. In 2012, ufflogrss coverge ws lower for the ufflogrss stored on TRM for 7, 14 nd 21 dys thn tht stored for 0 dys t 35 nd 42 DAP. In comprison to 2011, ufflogrss stored for 0 dys exhiited significntly higher estlishment (81%) y the end of the 2012 growing seson in comprison to the 7 dy storge tretment (48%). Mximum coverge of ufflogrss stored on TRM for 7 dys ws 27%, wheres tht stored for 14 dys ws (36%) in Bufflogrss plnted s vegettive plugs in TRM my e stored for seven dys in shded conditions efore plnting with miniml impct on coverge y the end of the growing seson. 84

101 Introduction Estlishing wrm-seson turfgrsses provides unique set of chllenges to homeowners. Rinfll events cn cuse significnt erosion on new seededs or res estlished with vegettive plugs. Furthermore, nnul weed competition during estlishment of wrm-seson grsses cn lso impede growth (Fry et l., 1986; Hrivndi et l., 1993). Weeds compete with desirle turfgrss species for light, wter, nd nutrients (Berd, 1973). Annul weedy grsses nd rodleves cn e controlled in ufflogrss using severl pre-nd postemergence hericides (McCrty nd Colvin, 1992; Fry et l., 1997; Shermn et l., 2004; Goss et l., 2006). However, these hericides do not offer ny protection from erosion. Turf reinforcement mt (TRM) comines vegettive growth nd synthetic mterils to form high-strength mt nd helps prevent soil erosion (U.S. EPA, 1999). Furthermore, TRM hs the potentil to suppress weeds during ufflogrss estlishment (Chpter 3). Turf reinforcement mts re typiclly mnufctured using tightly compressed plnt fier such s Jute. Jute is the common nme given to the plnt fier which is extrcted from the stems of plnts elonging to the genus Cochorus, fmily Tilice (Rowell nd Stout, 1998). The mt my, or my not, e reinforced with plstic netting nd provides high-strength mteril tht prevents soil erosion (U.S. EPA, 1999) nd germintion of weed seeds, or weed seedling survivl fter germintion (Lowe et l., 1999). Severl wrm-seson grss species hve een successfully estlished for soilless sod using orgnic fier mediums composed of kenf, fier-sed plnt product comprle to the mteril used in TRM (Hensler et l, 1998; Rowell nd Stout, 1998). Specificlly, jute-sed TRM ws effective for estlishment of Legcy ufflogrss from vegettive plugs (Goldsy nd Fry, 2012). In tht experiment, ufflogrss estlished in TRM hd coverge similr to 85

102 oxdizon-treted plots throughout the study. However, weed suppression ws superior in plots estlished with TRM (~8% weed coverge) when compred to those where only oxdizon ws pplied (~43% weed coverge). The use of TRM with ufflogrss is idelly suited for res where lor involved in plnting individul plugs is not ville, use of hericides is not desired, or soil erosion concerns exist. Another dvntge provided y using TRM is tht vegettive plntings cn e estlished on the mts t the grower s loction prior to instlltion t the jo site. In fct, this hs een previously done with ntive lndscpe plnts nd turfgrss sod (Mtt Cmpell, personl communiction). Similr to trditionlly cut sod, the TRM cn e divided into sections nd rolled up nd plced in storge for future instlltion. When turfgrss sod is hrvested, it is commonly rolled up nd stored. However, het ccumultion inside of rolls cn cuse sod qulity to decline nd my eventully result in turfgrss deth (King, 1970). Reserch hs een conducted evluting storge effects on common ermudgrss (Cynodon dctylon (L.) during summer months in Alny, GA (Mw et l., 1998). The rolls were stored for three weeks in full sun, nd tempertures inside the rolls reched 35 o C, which ws 12 o C ove mient temperture. Four weeks fter plnting the rolls, 75% of the ermudgrss hd fully recovered (Mw et l., 1998). High tempertures cn increse the turfgrss crohydrte reserves expended for respirtion, nd such crohydrtes re criticl for growth nd development fter the sod is lid (Wtschke et l., 1970). After instlltion, the comined effects of oth het stress coupled with expended crohydrte reserves my hve detrimentl effect on turfgrss estlishment. Although trditionl sod nd vegettive plugs on TRM cn oth e hrvested nd stored prior to plnting, there is little informtion ville regrding wht impct temporry storge of 86

103 TRM my hve on estlishment. Our ojective ws to evlute the estlishment of Legcy ufflogrss from vegettive plugs on TRM fter temporry storge. Mterils nd Methods Study sites nd experimentl design Experiments were conducted t the Olthe Horticulturl Reserch Center, Olthe, KS USA ( N ltitude, W longitude) in 2011 nd the Rocky Ford Turfgrss Reserch Center in Mnhttn, KS USA (39.128N ltitude, W longitude) in The soil t Olthe, KS site ws Kenneec silt lom with ph of 7.0. The soil t Mnhttn ws Chse silt lom (fine, smectitic, mesic, Aquertic Argiudoll) with ph of 6.9. Wether dt for Olthe nd Mnhttn during the study period were otined from Knss Stte University wether dt lirry ( The men monthly ir temperture during the study period in Olthe in 2011 ws: 28.8 o C in June; 30.7 o C in July; 28.4 o C in August nd 19.5 o C in Septemer. The men monthly ir temperture during the study period in Mnhttn 2012 ws: 25.7 o C in June; 29.9 o C in July; 24.6 o C in August nd 20.3 o C in Septemer. Legcy ufflogrss plugs were purchsed from Todd Vlley Frms (Med, NE) five weeks prior to plnting on TRM in 2011 nd Grsses were estlished s 5-cm dim. vegettive plugs in TRM in Mnhttn, KS on 2 June 2011 nd 1 June 2012, three weeks prior to eing plced in storge. This ws done in order to mimic the pproch sod grower would use to estlish plugs on the TRM prior storge or immedite delivery t the jo site. A single turfgrss plug ws inserted into 2.5-cm dimeter slits on 25.5 cm centers on ech 1 m x 1 m section of TRM. Ech 1 y 1 meter mt contined 9 evenly spced plugs of Legcy ufflogrss. The mts rested directly on lyer of 7-mil. lck plstic. Irrigtion ws pplied 87

104 three times dily to deliver 1 to 2 mm of wter in order to ensure mts styed moist nd to prevent turfgrss stress. After the three weeks of estlishment on the plstic, the 0 dys of storge tretment TRM (control) ws removed from the plstic nd lid with plugs intct into the study re in Olthe, Knss on 23 June 2011, nd Mnhttn, Knss on 22 June Mts representing tretments for other storge times were lifted from the full-sun plot in the field, rolled up, nd plced under dense shde (~160 µmol m -2 s -1 or ~80% reduction from full sun PAR) t Mnhttn, KS. Mts remined in storge for 7, 14, or 21 dys efore plnting in the field. In Olthe in 2011, plnting dtes for respective tretments were: 1 July for 7 dys of storge; 7 July for 14 dys of storge; nd 14 July for 21 dys of storge. In 2012 t Mnhttn, plnting dtes for respective tretments were: 29 June for 7 dys of storge; 6 July for 14 dys of storge; nd 13 July for 21 dys of storge. These were considered the dtes plnting occurred in field. The four storge times (0, 7, 14, nd 21 dys) were rrnged in rndomized complete lock design t ech site with four replictes. In 2011, mts in storge were unrolled every other dy nd wetted with fn spry nozzle ttched to grden hose. In 2012, mts in storge were unrolled dily nd wetted. -1 Dimmonium phosphte ( ) ws pplied t 49 kg P h to ll tretments t their respective time of plnting. All plots received n dditionl 49 kg N h -1 from ure on 23 August 2011 nd 19 August Irrigtion ws pplied s needed in order to prevent ufflogrss stress during estlishment. Turf Reinforcement Mt The TRM utilized in this study ws product designed nd mnufctured y StyTurf (Jimoom Turf Compny, Acci Ridge, Austrli). The originl StyTurf TRM is 88

105 composed of felted Jute fier mnufctured t 650 g m -2 with UV resistnt plstic netting inserted. Testing conducted t the Texs Deprtment of Trnsporttion Erosion Control Lortory found StyTurf cceptle for protection up to 194,013 L min -1, 58 kg m -2 sher force, nd velocity of m s -1 (Mtt Cmpell, personl communiction). The compny lso offers other products similr to the TRM tht excludes the plstic netting (StyTurf Soil Sver). StyTurf Soil Sver ws the product used in this evlution. Mesurements Turfgrss coverge ws rted visully on weekly sis on 0 to 100% scle, where 0 = no turf, nd 100% = complete turf coverge. Dily verge temperture inside the stored rolls ws recorded y using Hoo Dtloggers (HOBO Pro v2, Onset Computer Corp., Bourne, MA). Hoo Dtloggers were initilly inserted into three rndomly selected TRM s. However, the mts contining these dtloggers were designted s the 21-dy storge tretments in order to llow for temperture monitoring throughout the entire storge period. Sttisticl Anlysis Dt were sujected to nlysis of vrince using the GLM procedure of SAS (SAS Institute Inc., Cry, NC). Mens were seprted using Fisher s Protected LSD (P < 0.05). Results nd Discussion Averge dily tempertures inside the rolls during shde storge in Mnhttn, KS rnged from (19-28 o C) (Fig. 4.1). In Olthe in 2011, ufflogrss coverge ws lower for 14 nd 21 dy storge tretments thn the control or 7 dy storge tretments eginning t 14 DAP (Fig. 4.2). Bufflogrss stored on TRM for 7 dys hd similr level of coverge (74%) t the end of the growing seson s the control (75%) (Fig. 4.3 nd 4.4). Mximum coverge for 89

106 ufflogrss stored on TRM for 14 dys efore plnting ws 26% t the end of the growing seson (Fig. 4.5). In plots estlished to ufflogrss stored on TRM for 21 dys, only one replicte survived nd coverge ws <5% t the end of the growing seson (Fig. 4.6). Lower coverge oserved in ufflogrss stored on TRM for 14 or 21 dys storge tretment my e prtilly ttriuted to lck of photosyntheticlly ctive rdition ville during storge. During this time ufflogrss likely expended non-structurl crohydrtes during respirtion. Non-structurl crohydrtes would e criticl for root development nd folir growth fter plnting (Hull, 1992). Furthermore, ufflogrss stored on TRM ws t disdvntge ecuse dylength declined s time progressed, which would fvor tretments tht were plnted in the field erlier. The men dily solr rdition during the study period in Olthe in 2011 ws: 28.3 MJ/m 2 in June; 27.4 MJ/m 2 in July; 24.0 MJ/m 2 in August; 20.6 MJ/m 2 in Septemer nd 15.9 MJ/m 2 in Octoer. The men monthly solr rdition during the study period in Mnhttn 2012 ws: 24.9 MJ/m 2 in June; 26.6 MJ/m 2 in July; 24.7 MJ/m 2 in August; 20.3 MJ/m 2 in Septemer nd 17.5 MJ/m 2 in Octoer. The higher men monthly solr rdition in June nd July would fvor tretments tht were plnted in the field erlier. Another disdvntge for TRM stored for 14 nd 21 dys cme during the rrivl of shorter dys nd cooler nighttime tempertures during August, Septemer nd Octoer. The men monthly ir temperture during the study period in Olthe in 2011 ws: 28.8 o C in June; 30.7 o C in July; 28.4 o C in August; 19.5 o C in Septemer nd 14.5 o C in Octoer. The men monthly ir temperture during the study period in Mnhttn 2012 ws: 25.7 o C in June; 29.9 o C in July; 24.6 o C in August; 20.3 o C in Septemer nd o C in Octoer. The wrmer verge ir tempertures during June, July nd August would fvor the tretments tht were plnted erlier in the summer. 90

107 In Mnhttn in 2012, ufflogrss coverge ws lower for the 7, 14 nd 21 dy storge tretments thn the control tretments t 35 nd 42 DAP, nd lso t 70 DAP for the 21 dy storge tretment (Fig. 4.2). In comprison to 2011, ufflogrss plnted in the control tretment exhiited significntly higher coverge (81%) y the end of the growing seson in comprison to the 7 dy storge tretment (48%) (Fig. 4.7 nd 4.8). Turfgrss coverge for the control tretment nd 7 dy storge tretment differed etween In 2011, 7 nd 14 dy storge tretments egn to seprte from the remining tretments t pproximtely 20 DAP. In 2012, the control tretment egn to seprte from the remining tretments t pproximtely 28 DAP. Mximum coverge for ufflogrss stored on TRM for 14 dys efore plnting ws (36%) (Fig. 4.9), wheres coverge for the 21 dy storge tretment ws (27%) y the end of the growing seson (Fig.4.10). Coverge of ufflogrss stored for 14 or 21 dys ws higher t the end of the seson in 2012 thn As previously discussed, wtering frequency of stored rolls ws incresed from every other dy in 2011 to dily in 2012, in order to reduce intermittent drying. This ws done in n ttempt to decrese ufflogrss stress during storge, nd possily increse susequent estlishment following plnting. Additionlly, following TRM plnting in Olthe 2011, wter ws pplied y overhed irrigtion s needed to prevent visile stress. During estlishment in Mnhttn 2012, wter ws pplied lmost every dy y overhed irrigtion controlled y n utomtic timer. These differences in wtering frequency during oth storge nd susequent estlishment my hve encourged survivl of turf stored for 14 nd 21 dys. Averge dily tempertures inside the rolls during shde storge in Mnhttn, KS rnged from (19-27 o C) (Figure 4.1), which were comprle to mient temperture verges ( o C). Reserch done on common ermudgrss sod stored on pllets for three 91

108 weeks during summer in full sun, found tempertures inside the rolls reched 35 o C, which ws 12 o C ove mient temperture (Mw et l., 1998). This ws not mjor concern in our study due to TRM rolls eing stored under shde conditions. However, if rolls re going to e stored or trnsported under full sun conditions, high internl temperture of sod rolls my e concern. Conclusion In summry, estlishing Legcy ufflogrss on TRM over plstic for three weeks, nd then lifting nd storing in shde for up to seven dys ppers fesile. However, further reserch investigting storge in n rtificilly cooled environment should e investigted. 92

109 Figures nd Tles Tretments Dt Logger 1 Dt Logger 2 Dt Logger 3 26 Degrees (C) Jul Jul Figure 4.1- Temperture inside TRM contining Legcy ufflogrss plugs during storge in Mnhttn, KS in 2011nd Dt were collected using Hoo dtloggers plced in the 21 dy storge tretment. 93

110 Bufflogrss Coverge (%) Tretments Control 7 Dy Storge 14 Dy Storge 21 Dy Storge 20 c 0 c c c c c 10 d DAP Figure 4.2- Coverge of Legcy ufflogrss from vegettive plugs s ffected y storge time t Olthe (left) nd Mnhttn (right), KS in 2010 nd Bufflogrss ws plnted on TRM nd estlished on plstic in full sun for three weeks. Mts were then lifted, rolled, nd stored for 7, 14, or 21 dys in dense shde efore plnting. Plnting ws done following the lpse of the respective storge time nd susequent dtes re referred to s dys fter plnting(dap). Coverge ws rted visully on 0 to 100% Scle. Mens followed y the sme letter on dte re not significntly different ccording to the F-LSD (P < 0.05). 94

111 Figure 4.3- Legcy ufflogrss stored on turf reinforcement mt for 0 dys prior to plnting on 23 June 2011 in Olthe, KS. Photo tken 22 Sept Figure 4.4- Legcy ufflogrss stored on turf reinforcement mt for 7 dys prior to plnting on 1 July 2011 in Olthe, KS. Photo tken 22 Sept

112 Figure 4.5- Legcy ufflogrss stored on turf reinforcement mt for 14 dys prior to plnting on 7 July 2011 in Olthe, KS. Photo tken 22 Sept Figure 4.6- Legcy ufflogrss stored on turf reinforcement mt for 21 dys prior to plnting on 13 July 2011 in Olthe, KS. Photo tken 22 Sept

113 Figure 4.7- Legcy ufflogrss stored on turf reinforcement mt for 0 dys prior to plnting on 22 June 2012 in Mnhttn, KS. Photo tken 19 Sept Figure 4.8- Legcy ufflogrss tretment on turf reinforcement for 7 dys prior to plnting on 29 June 2012in Mnhttn, KS. Photo tken 19 Sept

114 Figure 4.9- Legcy ufflogrss stored on turf reinforcement mt for 14 dys prior to plnting on 6 July 2012 in Mnhttn, KS. Photo tken 19 Sept Figure Legcy ufflogrss stored on turf reinforcement mt for 21 dys prior to plnting on 13 July 2012 in Mnhttn, KS. Photo tken 19 Sept

115 References Berd, J.B Turfgrss: Science nd culture, Prentice-Hll, Inc., Englewood Cliffs, NJ. Fry, J.D., P.H. Dernoeden, nd J.J. Murry Estlishment nd rooting of zoysigrss (Zoysi jponic) s ffected y preemergence hericides. Weed Sci. 34: Fry, J.D., R.E. Gussoin, D.D. Bern, nd R.A. Msters Bufflogrss estlishment with preemergence hericides. HortScience 32: Goldsy, A.L. nd J.D. Fry Evlution of turf reinforcement mts for estlishment of ufflogrss nd zoysigrss from vegettive plugs. Intntl. Turgrss Soc.Res. J:(Accepted for Puliction 8/21/2012). Goss, R.M., McCll J.H., Gussoin, R.E. nd M.D. Richrdson Hericide tolernce of ufflogrss. Applied Turfgrss Science doi:: ?ats rs. Hrivndi M.A., C.L. Elmore, nd L. Wu Preemergence hericide use during ufflogrss estlishment. Int. Turfgrss Soc. Res. J. 7: Hensler, K.L., B.S. Bldwin, nd J.M. Gotlley, Jr Kenf-sed fier mt s sustrte for estlishing soilless sod. HortTechnology. 8: King, K.W Fctors ffecting the heting nd dmge of merion Kentucky luegrss (Po prtensis L.) sod under simulted shipping conditions. Ph.D. disserttion, Michign Stte Univ., Est Lnsing. Lowe, D.B., T. Whitwell, L.B. McCrty, nd W.C. Bridges Kylling revifoli, K. squmult, nd K. pumil seed germintion s influenced y temperture, light nd nitrte. Weed Sci. 17: Mw, B.W., S. Gison, nd B.G. Mullinix Het tolernce of ermudgrss sod in trnsit. J.Turfgrss Mgt. 2: McCrty, L.B. nd D.L. Colvin Bufflogrss tolernce to postemergence hericides. HortScience 27: Rowell, R.M., nd H.P. Stout Jute nd Kenf. p In M. Lewin (ed.) Hndook of Fier Chemistry: 2 nd ed. Mrcel Dekker, Inc., New York. Shermn, B.C., T.P. Riordn, nd P.G. Johnson Bufflogrss. p In 99

116 L.E. Moser et l. (ed.) Wrm-seson (C 4 ) Grsses. Agron. Monogr. no. 45. ASA,CSSA,SSSA, Mdison, WI U. S. Eviromentl Protection Agency Storm wter technology fct sheet Office of Wter. EPA-832-F U.S. Gov. Print. Office, Wshington, DC. Wtschke, T.L., R.E. Schmidt, nd R.E. Blser Responses of some Kentucky luegrsses to high temperture nd nitrogen fertility. Crop Sci. 10:

117 Chpter 5 - Utilizing hyperspectrl rdiometry to predict green lef re index of Kentucky luegrss 101

118 Astrct Determining green lef re index (LAI) is n importnt method for inferring the photosynthetic cpcity of turfgrss cnopy. There re severl methods for determining LAI, ut typiclly destructive smpling nd scnning of leves is used. Destructive smpling requires lrge reserch plots in order to ccount for multiple smpling dtes over growing seson. Rpid, non-destructive estimtion of LAI would e useful for turfgrss reserchers nd reeders. The ojectives of this study were to I) evlute whether hyperspectrl rdiometry cn e utilized to ccurtely predict LAI of Kentucky luegrss (Po Prtensis L.); nd II) determine which regions of the spectrum provide the est LAI predictions. For empiricl clirtion using spectrl dt we used prtil lest squres regression (PLSR). In the 2010 growing seson, the PLSR method creted only one vile model on only one smpling dte(24 June 2010) (R 2 =0.57). In 2011, vile first itertion PLSR models were creted on four of the seven smpling dtes. When compring ll first itertion models for 2011, the strongest ws for the 17 My (R 2 =0.85) smple dte. Fctor weights were nlyzed for the first itertion regression models nd second itertion of models were creted. The new models included only regions centered round 600, 690, 761, 960, 1330, 1420 nm (±10 nm). In this study, two of the five first itertion models contining ll wvelengths (except wter sorption nds) hd higher r- squred vlue thn those second itertion models with selected spectrl regions. This suggests for the other three first itertion models the informtion contined in the remining (~2250) wvelengths ws either redundnt or hd miniml influence on the model for predicting LAI. Overll, the results of this study suggest tht spectrl rdiometry hs the potentil to ccurtely predict LAI. In our study, however, the roustness of the prediction models vried over the course of the growing seson. The dynmic cnopy of turfgrss ccumultes more iomss 102

119 during erly spring compred to middle nd lte summer. Therefore, finding one model roust enough to ccurtely predict LAI from spectr t ny point during the growing seson still seems unrelistic. 103

120 Introduction Green lef re index (LAI) is n importnt indictor of the photosynthetic cpcity of turfgrss cnopy. For turfgrss reserchers, this cn e n importnt indictor of turfgrss helth in studies where turfgrss is exposed to vrious forms of environmentl stress such s drought, het, etc. Mesuring LAI in turfgrsses is typiclly ccomplished y destructive smpling nd scnning of green leves. Unfortuntely, destructive smpling is time consuming nd requires lrge reserch plots in order to ccommodte multiple smpling dtes over growing seson. Therefore, development of rpid, non-destructive mens to estimte LAI would e significnt dvncement for turfgrss reserchers nd reeders. Recently, cnopy reflectnce s mesured with spectrl rdiometry hs een used s n lterntive to destructive smpling to estimte LAI in turfgrss cnopies (Trenholm et l., 1999; Fitz-Rodriguez nd Choi., 2002; Jing et l., 2004; Jing nd Crrow, 2007; Merewitz et l., 2010). In order to extrct iophysicl or iochemicl informtion from the reflectnce spectrum, vegettion indices (VI), defined s simple mthemticl reltionships etween reflectnce vlues t different wvelengths, re clculted (Field et l., 1994). Vegettion indices re typiclly designed to highlight prticulr property of vegettion such s green LAI or iomss, wter content, or nutrient sttus. Specific VIs such s the normlized difference vegettion index ((NDVI, computed s (R NIR R RED) /(R NIR + R RED )) nd the simple rtio (SR, computed s R NIR / R RED ), where R NIR is reflectnce in the ner-infrred region nd R RED is reflectnce in the red region of the spectrum, hve een used to predict photosyntheticlly ctive iomss (Rouse et l., 1973; Penuels et l., 1997). Higher LAI vlues correspond with increses in chlorophyll sorption nd ner infrred (NIR) scttering, which results in decresed red nd incresed NIR reflectnce (Roerts et l., 2012). 104

121 Severl studies conducted on grsslnd hve reported strong correltions etween the mount of green LAI or iomss nd VIs (e.g. NDVI) otined from spectrl reflectnce dt (Mutng nd Skidmore, 2004; Vescov et l., 2004; Lee, 2008; Ginelle et l., 2009; Mskov et l., 2008; Chen et l., 2009; Fn et l., 2009). Vegettion indices such s NDVI hve, however een shown to lck sensitivity when pplied to crops with high iomss ecuse the spectrl response sturtes (Bret nd Guyot, 1991). For exmple, NDVI ws sensitive to chnges in vegettion frction nd LAI only t the eginning of the growing seson, when LAI rnged from 0 to 1.2 (Gitelson, 2004). Lef pigments nd structures gretly influence spectrl reflectnce chrcteristics of turfgrss cnopy. For instnce, chlorophyll pigments influence the reflectnce of wvelengths in the visile portion of the spectrum ( nm) (Jensen, 2007). Specificlly, reflectnce in the rnge nm is highly correlted with chlorophyll concentrtions, with reflectnce decresing s chlorophyll content increses (Gitelson, 2012). Furthermore, lef structurl components, including stomt, nuclei, cell wll constituents, nd cytoplsm lso contriute to reflectnce in the NIR ( nm) (Gusmn, 1977; Jensen, 2007). Wter content in plnt leves crete strong sorption responses in the middle-infrred wvelengths. ( nm) (Jensen, 2007). The red edge is n rupt increse in reflectnce in the nm region of the reflectnce spectrum, cused y chlorophyll sorption in the lower (visile) end nd light scttering y intercellulr spces of the spongy mesophyll cells in the upper (NIR) end (Jensen, 2007). This region is used for mny vegettion indices due to its strong reltionship to chlorophyll content. In turfgrss studies, VIs hve een developed using multispectrl nd hyperspectrl reflectnce rdiometry (Trenholm et l., 1999; Jing et l., 2004; Jing nd Crrow, 2005, 2007; 105

122 Merewitz et l., 2010). Multispectrl rdiometry mesures the spectrl reflectnce of plnt cnopies in pproximtely eight nds. Those spectrl nds re not contiguous nd ech nd intervl is rod, normlly greter thn 25 nm (Ling, 2004). Becuse multispectrl rdiometry integrtes over wide rnges of wvelengths, it my msk sutle effects of LAI on reflectnce in the nrrower nds. Hyperspectrl rdiometry, however, llows for mesurements of spectrl reflectnce in pproximtely two thousnd nrrow wvelengths. The incresed spectrl resolution of the nrrower ndwidths ssocited with hyperspectrl mesurements my permit greter spectrl sensitivity to sutle vritions in the cnopy properties. Therefore, if chnges in LAI ffect cnopy reflectnce in specific regions of the spectrum, hyperspectrl rdiometry my detect these effects etter thn the roder nds ssocited with multispectrl rdiometry. For exmple, reflectnce in the green region ( nm) of the spectrum ws ffected s LAI incresed (Ustin et l., 1996). Brodnd spectrl rdiometers such s the Cropscn MSR- 16(CropScn, Inc. Rochester, MN) hve two nm integrted wvelengths locted t 509 nm nd 559 nm. Therefore, it is possile they my msk sutle effects of LAI on reflectnce in the nrrower nds in the green portion of the spectrum. Although direct reltionships etween LAI nd spectrl reflectnce hve een determined for numer of crops (Asrr et l., 1994, Dughtry et l., 1992, Vescovo et l., 2004), few studies hve evluted those reltionships in turfgrss. However, study conducted y Lee (2008) evluted the reltionship of reflectnce with green LAI, oveground iomss, nd chlorophyll content in five cool-seson nd two wrm-seson turfgrsses. Results of the study indicted correltions etween green LAI nd reflectnce t 507,559, 613, nd 706 nm( r 2 = 0.30 to 0.40) when dt from numer of turfgrss species nd mowing heights were pooled. 106

123 Furthermore, when the dt from the study were nlyzed seprtely y species, stronger correltions etween LAI or iomss nd reflectnce were found in some turfgrss species (r=0.80 to 0.99) (Lee, 2008). However, overll the use of multispectrl rdiometry hs provided mixed results when ttempting to ccurtely predict LAI. We hypothesize tht if spectrl reflectnce is ffected y LAI primrily in nrrow spectrl regions, then hyperspectrl rdiometry would detect these effects etter. The min ojective of this study ws to evlute whether hyperspectrl rdiometry cn e utilized to ccurtely predict LAI of Kentucky luegrss. Since the potentil reltionship etween LAI nd the reflectnce spectr of the cnopy is not fully understood, empiricl clirtion is needed in order to model LAI from rw spectrl dt. Therefore, second ojective of this study ws to identify nds with the highest influence on spectrl models for predicting LAI of Kentucky luegrss. Becuse turfgrss properties tht ffect spectrl reflectnce, such s iomss density, my vry temporlly, mesurements were tken on numer of dtes throughout the growing seson. Mterils nd Methods Study Site nd experimentl design Reflectnce dt were collected on 24 June, 30 July, 28 Sept., nd 4 Nov. in In 2011, dt were collected on 28 April, 17 My, 8 June, 30 June, 18 July, 24 Aug., nd 28 Sept. Nine plots of Kentucky luegrss were mintined t the Rocky Ford Turfgrss Reserch Center ner Mnhttn, Knss, USA (39 o N, 96 o W). The soil t the site ws Chse silt lom (fine, smectitic, mesic, Aquertic Argiudoll) with ph of 6.9. A soil test prior to the study 107

124 indicted P nd K levels were dequte. Plots (1.5 m x 1.8 m) were mowed nd mintined t three heights, 5, 8.9, nd 12.7 centimeters, were rrnged in completely rndomized lock design with three replictions (Figure 5.1). All tretments were fertilized with 49 kg N h -1 on 13 My, 15 Septemer, nd 16 Novemer For 2011, ll tretments were fertilized with 49 kg N h -1 on 3 My, 12 Septemer, nd 10 Novemer. Irrigtion ws pplied three times weekly for totl of 25 mm of wter per week. Plot Mintennce Imidcloprid (1-[(6-chloro-3-4 pyridinyl) methyl 3 (2-chloro-3,3,3-trifluoro-1-propenyl)- 2,2-dimethylcyclopropnecroxylte) ws pplied t 0.12 kg.i. h -1 to control illug grus nd white grus (Cyclocephl lurid Blnd) on 1 My 2010 nd 3 My The hericides crfentrzone-ethyl (Ethyl α,2-dichloro-5-[4(difluoromethyl)-4,5-dihydro-3-methyl-5-oxo-1h- 1,2,4-trizol-1-yl]-4-fluoroenzenepropnote) (0.03 kg.i. h -1 ) + 2,4-D [2-ethylhexyl ester (2,4 dichlorophenoxycetic cid] (1.29 kg.i. h -1 ) + Mecoprop-p cid [(+)-R-2-(2-methyl-4 chlorophenoxy)propionic cid] (0.27 kg.i. h -1 ) + dicm cid (3,6-dichloro-o-nisic cid)(0.08 kg.i. h -1 ) were pplied on 6 April 2010, 23 Oct. 2010, nd 9 April 2011 for rodlef weed control. Applictions of dithiopyr [S,S -dimethyl 2-(difluoro-methyl)-4-(2- methylpropyl)-6-(trifluoromethyl)-3,5-pyridin-edicrothiote] were mde t 0.58 kg.i. h -1 on 6 April 2010 nd 9 April 2011 to control nnul grssy weeds. Mesurements Hyperspectrl reflectnce ws mesured monthly with FieldSpec 3 Portle Spectordiometer (ASD Inc., Boulder, CO) (Figure 5.2). The ASD spectordiometer hs 2150 chnnels rnging from 350 nm to 2500 nm. Spectrl resolution for the instrument is 1.4-nm in the visile spectrum nd 10-nm in the middle infrred. For ech plot nd mesurement dte, 108

125 three rdiometer scns were otined nd then verged into single reding (Figure 5.3). The rdiometer mesurements were consistently cquired with ndir viewing ngle t 1.2 m ove the cnopy using n 18 degree field of view dpter tht yielded n instntneous field-of-view of, pproximtely m 2 t turfgrss surfce. Direct mesurements of green lef re index were otined immeditely fter collection of rdiometer mesurements y destructively hrvesting two rndom res of the turfgrss cnopy, ech 45.6 cm 2 (7.62-cm dim. PVC ring). Prior, to imge nlysis rown senesced leves nd deris were sorted from green lef tissue. Green lef re ws then mesured with n imge nlysis system (WinRHIZO Model 2002, Regent Instruments, Queec, Cnd).) (Figure 5.4). Therefter, the lef smples were dried t 75 o C for 48 hours nd then weighed to mesure totl oveground iomss. Initilly, spectrl dt were reviewed using (Viewspec Pro, ASD Inc., Boulder, CO) softwre to ensure tht ll redings were cceptle. Redings which were lnk or contined errnt spectrl responses were discrded. Next, the portions of the spectrum (<400nm, nm, nm, >2400nm) tht re highly influenced y tmospheric ttenution were removed prior to nlysis (Pimstein et l., 2011). For empiricl clirtion using spectrl dt, pproches such s the use of prtil lest squres regression (PLSR), re recommended (Beee nd Kowlski, 1987; Mrtens nd Nes, 1991). PLSR is prticulrly suited for use when there re more predictor vriles thn response vriles, which is quite often the cse when using chemometrics techniques. Stndrd regression is not suited for dt sets contining more predictor vriles (e.g wvelengths) thn response vriles (9 tretments). Sttisticl Anlysis 109

126 Dt were nlyzed using the PLSR method contined within GRAMS softwre (Thermo Fisher Scientific, Hnover Prk, IL). The first itertion of PLSR models included ll (~2400) spectrordiometer wvelengths mesured to uild the model. These first itertion models were evluted on dte-y-dte sis to determine which smpling periods yielded vile models. The GRAMS softwre predicts/recommends the numer of fctors tht should e used for the model. In the cse where the softwre did not recommend ny numer of fctors it ws considered not vile model. Fctor weights were nlyzed for ll the vile first itertion regression models. One of the most powerful pieces of informtion provided y the PLSR method is in the form of the model fctor weights. This informtion provides insight into the wvelengths tht re hving the gretest influence on your prediction model. Regions of the spectrum with the highest fctor weights were selected, nd second itertion of PLSR models ws creted using the selected wvelengths. In this study, the new models included only regions centered round 600, 690, 761, 960, 1330, 1420 nm (±10 nm). These res were selected due to their high fctor weights s determined y studying ll the first itertion models. Results nd Discussion The R-squred criticl vlue for sttisticl significnce for this dt set ws If correltion vlues re greter thn or less thn , it cn e concluded the odds re less thn 5 out of 100 tht this is chnce occurrence. All the vile prediction models for this study were found to e sttisticlly significnt t (P < 0.05). For the 2010 growing seson, only one model on one smpling dte (24 June) ws found to e sttisticlly significnt using the PLSR method (R 2 =0.57) (Figure 5.5). For 24 June, there were two fctors for the first itertion model. Fctor one hd the highest fctor weight (0.039) t wvelength 1119 nm(figure 1.6). Fctor two 110

127 hd the highest fctor weight (0.023) t wvelength 706 nm (Figure 5.6). Fctor weights from 24 June 2010, in ddition to the remining 2011 smpling periods tht yielded vile models, were studied to determine regions in the spectrum tht most highly influenced spectrl models for predicting LAI. A second model ws creted tht included only selected regions of the spectrum with the highest weights (centered round 600, 690, 761, 960, 1330, 1420 nm ±10 nm). For the 24 June model, the coefficient of determintion (R 2 =0.46) ws lower thn the originl (Figure 5.5) For 2011, sttisticlly significnt PLSR models were creted for four of the seven smpling dtes. On the remining three smpling dtes the reltionship etween reflectnce nd LAI ws so wek tht there were no fctors suggested nd no vile models produced. The first sttisticlly significnt model for 2011 ws creted on 17 My, (R 2 =0.85) (Figure 5.7). When compring ll first itertion models cross the two yer study, this dte yielded the strongest prediction model. The 17 My model gin ws defined y two mjor fctors. Fctor one hd the highest fctor weight (0.043) t wvelength 761 nm (Figure 5.8). For fctor two, the highest weight (0.003) ws recorded t wvelength 684 nm. Once gin, second model ws creted for this 17 My smpling dte using only selected spectrum regions round (600, 690, 761, 960, 1330, 1420 nm ±10 nm). For the second model, the (R 2 =0.83) ws slightly lower thn the originl. The next dte in 2011 tht resulted in sttisticlly significnt model ws 30 June (R 2 =0.73) (Figure 5.9). The 30 June 2011 model only consisted of single fctor. Fctor weights for the single fctor model were highest (0.04) t 761 nm (Figure 5.10). For the second model, which only included the selected spectrl regions (centered round 600, 690, 761, 960, 111

128 1330, 1420 nm ±10 nm), the coefficient of determintion (R 2 =0.86) ws higher thn the originl model (R 2 =0.73). The next sttisticlly significnt first itertion model ws creted on 18 July 2011 (R 2 =0.52) (Figure 5.11). Similr to the 30 June model, this 18 July model only consisted of single fctor. Fctor weights for the single fctor model were highest (0.04) t 761 nm (Figure 5.12). For the second itertion model, the coefficient of determintion improved (R 2 =0.71) when compred to the originl model contining ll portions of the spectrum. The finl sttisticlly significnt model for the study occurred on 24 August 2011 (R 2 =0.79) (Figure 5.13). This model only consisted of single fctor which hd the highest weight (0.04) t wvelength 870 nm (Figure 5.14). For the second itertion model, the coefficient of determintion once gin improved (R 2 =0.81) when compred to the first-itertion model, which contined ll (~2400) wvelengths mesured y the spectrlrdiometer. Fctor weights for 3 of the 5 first itertion models creted in this study were highest round 761 nm. Chlorophyll pigments strongly influence reflectnce t wvelengths in the visile portion of the spectrum ( nm) (Jensen, 2007). The pek sorption wvelengths of chlorophyll re 430 nm nd 664 nm; peks for chlorophyll re 460 nm nd 647 nm (Lrkum, 2003). However, Gitelson nd Merzlyk (1994 nd ) found tht reflectnce in spectrl nds locted quite fr from these min sorption nd pigments ner 550 nm nd 700 nm were closely relted to chlorophyll for wide rnge of plnt species. In the present study, the highest fctor weights occurred round 761 nm, which is locted in the middle of the red edge nd suggests tht chlorophyll sorption hd miniml impct on prediction of LAI from spectr. However, fctor weights from the models presented in this study suggest the red edge where the shift from sorption of visile spectrum y plnt pigments to reflectnce in the NIR is 112

129 indeed n importnt region of the spectrum when ttempting to ccurtely model nd predict LAI. For ll the second itertion models we included wvelengths centered round 960, 1330, 1420 nm (±10 nm), which re in the NIR. Lef structurl components, including stomt, nuclei, cell wll constituents, nd cytoplsm ffect reflectnce in the NIR ( nm) (Gusmn, 1977; Jensen, 2007). Furthermore, wter content in lef hs strong sorption of middleinfrred wvelengths ( nm) (Jensen, 2007). Both the 24 June 2010 nd 24 August 2011 models hd highest fctor weights locted t 1119 nm nd 870 nm respectively. Therefore, it is resonle to ssume tht on oth of these dtes, lef structurl components of the turfgrss cnopy tht, ffect reflectnce in the NIR, were hving the gretest influence on LAI prediction models. We originlly hypothesized tht if LAI is ffected y spectrl reflectnce primrily in nrrow spectrl regions, then hyperspectrl rdiometry would detect these effects etter. However, in this study two of five of the first itertion models tht contined ll (~2400) wvelengths hd greter coefficient of determintion thn those with selected spectrl regions (centered round 600, 690, 761, 960, 1330, 1420 nm, ±10 nm). This suggests for the other three models most of the informtion contined in the remining ~2250 wvelengths ws either redundnt or ws hving miniml influence on the model for predicting LAI. One of the mjor dvntges in using selected wvelengths over the ~2400 wvelengths of hyperspectrl rdiometer is relted to the cost ssocited with construction of such n instrument. If you cn find few wvelengths tht explin most of the vrition, then much less expensive instrument cn e constructed tht will permit more users to use this rdiometer s opposed to more expensive hyperspectrl rdiometer. 113

130 Overll, the results of this study suggest there is promise for using spectrl rdiometry to predict LAI. In our study however, the roustness of the prediction models vried over the course of the growing seson, with mesurements on some dtes yielding stronger models thn others. The dynmic cnopy of turfgrss ccumultes more iomss during erly spring compred to middle nd lte summer. Therefore, finding one model roust enough to ccurtely predict LAI from spectr t ny point during the growing seson still seems unrelistic. Perhps severl models ccounting for the chnge in cnopy dynmics which occurs throughout growing seson my e necessry. Since the potentil reltionship etween LAI nd the reflectnce spectr of the cnopy is not fully understood, further reserch is needed in order to model LAI from rw spectrl dt. Further reserch studying cnopy reflectnce over the course of n entire yer on severl species of cool-seson turfgrss my help to develop more roust models for predicting LAI from spectr. Conclusions Results of this study suggest tht spectrl rdiometry hs the potentil to predict LAI. Five first itertion models were creted for the eleven smpling periods during the two yer study. However, the ccurcy of this method vried over the course of the growing seson with some periods yielding much stronger models thn others. Perennil cool-seson turfgrsses such s Kentucky luegrss produce lrge mounts of iomss over the course of growing seson. In ddition, there my e dditionl, poorly understood fctors of the turfgrss cnopy tht chnge over the course of the growing seson (e.g. cnopy rchitecture, internl lef properties). Therefore, finding one model roust enough to ccurtely predict LAI from spectr t ny point during growing seson still seems unrelistic. 114

131 Previous studies y other hve reported tht the red edge ( nm) is strongly ffected y chlorophyll concentrtions in plnts. Fctor weights otined from this dt set suggest these regions in the red edge re indeed correlted with LAI. Three of the models in this study hd the highest loding occurring t 761 nm which is locted in the middle of the red edge. Acknowledgments I would like to extend my grtitude to Dr. Kevin Price for the use of his hyperspectrl rdiometer nd consulttion for this project. Furthermore, I would like to extend my grtitude to Nn An for his help with dt cquisition nd nlysis for this project. Without the help of either of these individuls this project would not hve een possile. 115

132 Figures nd Tles Figure 5.1- Tretments for the study included plots mowed t 5, 8.9, nd 12.7 centimeters. Figure 5.2- Reserchers set up nd clirte the spectrordiometers prior to mesurements eing cquired. 116

133 Figure 5.3- Reserchers otining rdiometer redings from the vrious mowing heights. Figure 5.4- Imge nlysis system (WinRHIZO) ws used to clculte totl lef re index. 117