CHAPTER 4. Surface Root-zone Water Content and Bentgrass Water Stress. During Drydown for Selected Putting Green Construction.

Transcription

1 CHAPTER 4 Surfce Root-zone Wter Content nd Bentgrss Wter Stress During Drydown for Selected Putting Green Construction Systems ABSTRACT Creeping entgrss, cool-seson grss used extensively in golf courses nd in recretionl turf, often declines during hot summer periods. The reltionships etween the shoot wter potentil of entgrss nd the root zone wter content of snd-sed medi with mendments during drought periods re not well understood. The ojective of this study ws to determine the wter reltions of Penncross creeping entgrss (Agrostis plustris Huds.) greens nd the root zone wter content during drought periods s ffected y root zone construction systems with selected mendments. Four tretments were developed: Cliforni (100% snd), USGA (90% snd nd 10% pet, v/v), Cliforni-P (82% snd nd 15% Profile, v/v with 3% humte), nd Cliforni-Z (85% snd nd 15% zeolite, v/v). Once mture, the plots were llowed to drydown over 30 dys from 24 June to 24 July 47

2 2000 nd The four tretments were rrnged in rndomized complete lock with four replictes. The Cliforni tretment mintined higher root zone volumetric wter content during the 2000 nd 2001 drought periods compred with the other tretments. This tretment hd root zone wter content tht ws equl to or higher thn the Cliforni-P nd Cliforni-Z tretments during The USGA tretment hd the lowest root zone wter content during In 2001, the Cliforni-Z tretment hd higher entgrss shoot wter potentil (lest stress). The USGA tretment hd the lowest entgrss shoot wter potentil (most stress) during the drydown period in The Cliforni-P nd Cliforni-Z tretments hd higher entgrss qulity nd color rtings when compred with the USGA tretment nd equl to or etter thn the Cliforni tretment fter the drought stress period in The Cliforni construction system seems to e etter thn the USGA construction system during drought since the Cliforni uses ntive silt lom soil elow the constructed root zone nd therefore hs higher plnt ville wter cpcity. Thus, the Cliforni construction system my improve creeping entgrss growth during drought periods y 48

3 llowing etter root zone wter uptke nd less drought stress. SIGNIFICANCE TO THE NURSERY INDUSTRY Snd-sed putting green root zones constructed with Cliforni system (without grvel su-lyer in the root zone) improved Penncross creeping entgrss (Agrostis plustris Huds.) performnce compred to USGA construction system during drought periods in 2000 nd Snd-sed root zones with Profile or zeolite nd the Cliforni construction system is not well understood regrding its impct on putting green root zone plnt wter reltions nd grss qulity. The effects of root zone construction systems on entgrss wter stress nd qulity were evluted in this study. The ddition of Profile nd zeolite to the snd for the Cliforni construction system ws shown to offer some enefits during the drought period. These tretments were found to hve higher root zone volumetric wter content, entgrss shoot wter potentil (less stress), nd nutrient content. The Cliforni construction system with Profile or zeolite mendment ws found to e superior replcement to the USGA construction system with pet mendment. 49

4 INTRODUCTION Summer decline of cool-seson grsses is mjor prolem in turfgrss mngement in the trnsitionl nd wrm climtic region. Creeping entgrss grows vigorously when cnopy nd soil tempertures, nd soil moisture re within its preferred rnge. During hot summer periods, when tempertures increse to 90 o F or higher, root zone soil moisture my decline due to incresed evpotrnspirtion rtes nd the turf cnopy my thin nd turn rown. Although snd is n idel medium for entgrss greens s fr s physicl chrcteristics re concerned (e.g., prticle size, compction resistnce, infiltrtion rte, nd ertion porosity), it is lcking in wter holding cpcity nd nutrient retention (Berd, 1982; Miller, 2000). Addition of n orgnic mendment such s pet increses wter nd nutrient retention; however, pet decomposes over time (Heck nd Christins, 2000; McCoy, 1992). The use of inorgnic mendments for putting green root zone mixtures such s Profile TM (clcined clys) nd ZeoPro TM (clinoptilolite zeolite) offers numer of enefits for improving snd-sed root zones. They re less prone to compction thn orgnic mterils, hve higher ction exchnge cpcities, dequte wter holding 50

5 cpcities without reducing ertion porosity, nd they re essentilly permnent dditions to the root zone persisting over longer period (Bigelow et l., 2000; Heck nd Christins, 2000; Hung nd Petrovic, 1996; McCoy, 1992). Creeping entgrss often requires dily irrigtion nd syringing (dry spot irrigtion y hnd) to persist in turf res with wrmer environments nd high evpotrnspirtion rtes. Recently, Miller (2000) found tht ermudgrss grown in inorgnic mteril s n mendment for sndsed root zone hd the est qulity during drought stress when compre to the 100% snd tretment. Thus, snd-sed root zones mended with inorgnic mterils hve the potentil to influence root zone soil wter content, nd lso ffect the evpotrnspirtion response during drought periods. Bigelow (2001) reported tht the presence (USGA green system) or sence (Cliforni green system) of pe grvel su-lyer ffected the root zone wter retention. The presence of pe grvel su-lyer significntly reduced root zone wter retention. A study ws plnned to investigte the effects of two inorgnic soil mendments: Profile nd zeolite, incorported into snd-sed root zone with the Cliforni construction system on entgrss qulity, root 51

6 zone volumetric wter content, nd shoot wter potentil during periods without irrigtion. These tretments were compred with 100% snd Cliforni construction system nd trditionl USGA construction system tht contined pet mendment. The hypothesis of this study ws tht the Cliforni construction system with inorgnic mterils my hve higher root zone volumetric wter content due to the sence of pe grvel su-lyer which would result in higher entgrss shoot wter potentil during periods of drought. 52

7 MATERIALS AND METHODS Four tretments were compred: Cliforni profile, USGA profile, nd two modified Cliforni profiles. The Cliforni profile (referred to s the Cliforni tretment) consisted of 0.3 m of 100% snd over 0.13 m lyer of silt lom soil with drin system (PVC pipe), which ws plced elow the root zone mixture lyer. The USGA profile (referred to s the USGA tretment) consisted of 90% snd nd 10% Dkot reed sedge pet y volume, with 0.3 m root zone mixture over 0.13 m pe grvel lyer (2-7 mm dimeter) with drin t the ottom of the this grvel lyer. The snd/pet mixture ws lended t the supplier, Cpitol Snd, Jefferson City, MO. There were lso two modified Cliforni profile green tretments, ech consisting of 0.25 m root zone mixture over 0.18 m lyer of silt lom with drin which ws plced elow the root zone mixture lyer. The first modified profile referred to s the Cliforni-P tretment consisted of 82% snd, 15% Profile, nd 3% humte in root zone mixture; the second modified profile referred to s the Cliforni-Z tretment consisted of 85% snd nd 15% zeolite y volume. These two mixtures were lended t the Turf Reserch Center with smll cement mixer. Two wshed river snds were 53

8 used for the different root zone mixtures in this study: corse to medium snd (C-M-S) ws lended with Dkot reed sedge pet for the USGA tretment nd medium to fine snd (M-F-S) ws used in the three Cliforni-style tretments. The prticle size nlyses of two snds, the mendments, nd snd-sed root zone mixtures re presented in Tle 3.1. Tretments were estlished in 1.2 m y 1.2 m wooden oxes. The four tretments were rrnged in rndomized complete lock with four replictes. The mended nd unmended root zones were instlled in August nd Penncross creeping entgrss ws seeded on Septemer 27, 1998 t 49 kg h -1. From seeding through My 1999, ech plot ws supplied with kg N h -1, 97.6 kg P h -1, nd kg K h -1, either from grnulr fertilizer or, in the cse of the ZeoPro mended plots, s nutrients estimted to e ville from the nutrient-chrged ZeoPro ( ). From June 1999 through July 2001 ll plots received kg N h -1, 76.1 kg P h -1, nd kg K h -1. The green ws initilly mowed to height of 13 mm (Octoer 98), reduced to 9 mm (Novemer 98), nd then lowered to 6 mm (Mrch 99). It ws mowed to consistent height of 4 mm eginning My Mowing occurred four times weekly nd 54

9 clippings were collected. Irrigtion ws pplied every two dys sed on tmometer-estimted evpotrnspirtion (n evportion mesurement djusted for evpotrnspirtion from grss; Ervin nd Koski, 1997), except during the drought stress periods for the experimentl study during oth 2000 nd All experimentl dt were collected using the following procedures. Irrigtion ws not pplied from June 24 to July 24, 2000 to compre chnges in the root zone volumetric wter content. Tempertures of the root zone t 0.15 m were mesured iweekly (three times per dy; 8:00 m, 12:00 pm, nd 4:00 pm) during the drought period in the field with n AquTerr Instruments Meter (TEMP 200) (Spectrum Technologies, 1990) which is portle. This is simple multi-function meter to use for mesuring soil wter content nd soil temperture. The meter proe requires good contct with soil to function ccurtely. The proe is pushed into the ground until the temperture sensor is covered (0 to 199 o F; -18 to 92 o C). Root zone volumetric wter content ws mesured immeditely fter mesurement of the root zone temperture. Mesurements were tken iweekly three times per dy in the 0 to 0.1 m depth (8:00 m, 12:00 pm, nd 4:00 pm) during the drought period in the 55

10 field with ThetMeter (soil wter content sensor) (Delt- T Devices Ltd, 1997). The ThetMeter is portle nd hs self-contined power supply with redout unit which, when used with ThetProe Type ML1, provides compct nd fully portle volumetric moisture mesurement system. The ThetMeter converts the output signl from the ThetProe into volumetric wter frction reding with units of m 3 m -3. The working rnge is 0 to 0.54 m 3 m -3. The ThetMeter proe ws field clirted with grvimetric wter content mesurements djusted with mesured ulk density. The regression etween the ThetMeter nd grvimetric wter content mesurements is shown in Figure 4.1. Visul rtings for creeping entgrss shoot color nd qulity were mde two times for ech plot t the eginning of the drought period (June 25) nd the end of the drydown period (July 25). Creeping entgrss color rtings were mesured on scle in which 1 = rown nd 9 = drk green grss. Qulity rtings were lso mesured on scle in which 1 = no live grss nd 9 = dense, uniform stnd of turf (Skogley nd Swyer, 1992). After the 2000 drydown period, irrigtion wter ws pplied normlly to rechrge the root zones. Bentgrss in ech plot recovered to cceptle qulity levels fter the 2000 drydown period. 56

11 Volumetric wter content mesurement (%) y = x R 2 = ThetMeter wter content mesurement (%) Figure 4.1. Clirtion etween volumetric wter content(%) nd ThetMeter predicted wter content(%). 57

12 Irrigtion ws lso not pplied from June 24 to July 24, 2001 to mesure the effects on root zone volumetric wter content nd shoot wter potentil. The volumetric wter content (%) ws mesured with the ThetMeter nd shoot wter potentil (MP) of the creeping entgrss tillers were mesured with pressure chmer (Lssoie nd Hinckley, 1991) t the eginning of the drought period (June 24) nd t the end (July 24). The pressure chmer cn e one of the most relile instruments ville for plnt wter reltions reserch. Simple construction nd durility hs mde it the preferred method for mesuring ψ W (plnt wter potentil) in the field. The pressure chmer ws used following the procedures descried y Turner (Lssoie nd Hinckley, 1991). Ech entgrss shoot per plot ws excised nd enclosed in plstic gs with moistened cheesecloth immeditely fter excision t noon. Shoot wter potentil ws mesured under rpid processing of smples to minimize wter loss of excised smples. Root zone volumetric wter content ws determined efore mesuring shoot wter potentil using the ThetMeter. The first mesurements were mde under irrigtion sed on the every other dy evpotrnspirtion rte (ET) during the growing seson (June 24). The second mesurements were 58

13 mde fter no irrigtion for 30 dys on July 24 (end of dry down). Visul rtings for shoot color nd qulity were mde two times for ech plot (June 25 nd July 25). Rinfll ws mesured using tipping ucket rin guge. Potentil evpotrnspirtion (PET) ws estimted using the modified Penmn eqution (Rosenerg, 1974). Mesurements were mde of temperture, wind speed, reltive humidity nd solr rdition nd used in the modified Penmn ET eqution. The estimted potentil evpotrnspirtion ws djusted y fctor of 0.8 to pproximte the potentil evpotrnspirtion of grss (Crrow, 1995). Sttisticl nlysis of the dt ws computed using nlysis of vrince in the Michign Stte Sttisticl softwre progrm (MSTAT, 1988) nd the GLM model in the SAS softwre progrm (SAS, 1990). Mens were seprted with Fisher s protected lest significnt difference (LSD) test t 95% proility level. 59

14 RESULTS AND DISCUSSION Rinfll nd estimted potentil evpotrnspirtion djusted for grss surfce (PETgrss) were estimted for ech dy from June 24 to July 24, 2000 nd 2001 (Figures 4.2 nd 4.3). Figures 4.4 to 4.6 show the root zone tempertures from 8:00 m, 12:00 pm, nd 4:00 pm for the 2000 drought period. Figures 4.7 nd 4.8 show the cumultive rinfll, estimted potentil ET of grss, nd the difference (rinfll PETgrss) for time periods fter no irrigtion ws pplied for oth 2000 nd 2001 drought periods. During these periods, irrigtion ws not pplied from June 24 to July 24 in ech yer. Plots pprently underwent stress in 2000 pproximtely 11 dys fter irrigtion cesed (Figure 4.7). Figure 4.8 indictes tht the experimentl plots underwent stress ner the eginning of the drydown in The potentil evpotrnpirtion rte of the grss (PETgrss) ws slightly higher in 2001 during this month period compred to The cumultive difference etween rinfll nd potentil ET for the grss ws out the sme (-49 mm) for oth yers during this month drydown period. 60

15 30 25 Rinfll PET grss 20 mm/dy Time fter no irrigtion, d Figure 4.2. Rinfll nd estimted PET djusted for grss surfce during the 30 dys of no irrigtion from June 24 to July 24,

16 Rinfll PETgrss mm/dy Time fter no irrigtion, d Figure 4.3. Rinfll nd estimted PET djusted for grss surfce during the 30 dys of no irrigtion from June 24 to July 24,

17 Temperture (F) Cliforni USGA Cliforni-P Cliforni-Z Tretments 6/26/2000 6/29/2000 7/3/2000 7/6/2000 7/11/2000 7/13/2000 7/18/2000 7/22/2000 7/24/2000 Figure 4.4. Tempertures in the snd-sed root zone of 15 cm depth for the four tretments with AquTerr t 8:00 m during drought periods (from June 24 to July 24, 2000). 63

18 Temperture (F) Cliforni USGA Cliforni-P Cliforni-Z Tretments 6/26/2000 6/29/2000 7/3/2000 7/6/2000 7/11/2000 7/13/2000 7/18/2000 7/22/2000 7/24/2000 Figure 4.5. Tempertures in the snd-sed root zone of 15 cm depth for the four tretments with AquTerr t 12:00 pm during drought periods (from June 24 to July 24,2000). 64

19 Temperture (F) Cliforni USGA Cliforni-P Cliforni-Z Tretments 6/26/2000 6/29/2000 7/3/2000 7/6/2000 7/11/2000 7/13/2000 7/18/2000 7/22/2000 7/24/2000 Figure 4.6. Tempertures in the snd-sed root zone of 15 cm depth for the four tretments with AquTerr t 4:00 pm during drought periods from June 24 to July 24, 2000). 65

20 Depth of wter, mm Rinfll PETgrss Difference Time fter no irrigtion, d Figure 4.7. Cumultive rinfll, estimted potentil ET of grss, nd difference (rinfll PET grss) for time periods fter no irrigtion: June 24 to July 24,

21 Depth of wter, mm Rinfll PETgrss Difference Time fter no irrigtion, d Figure 4.8. Cumultive rinfll, estimted potentil ET of grss, nd difference (rinfll PET grss) for time periods fter no irrigtion: June 24 to July 24,

22 Figure 4.9 shows the verge of root zone volumetric wter content during the 2000 drydown period. The verge includes mesurements mde t 8:00 m, 12:00 pm nd 4:00 pm. Trends in root zone wter content dt for the tretments were similr: vlues remined higher during the first 10 dys (7/4 mesurement) nd then dropped drmticlly fter 15 dys (7/9 mesurement). Root zone volumetric wter content verged out 22% t the eginning of the drydown period. Results indicte tht the root zone volumetric wter content for the Cliforni tretment were lwys higher for ech mesurement dte when compred to the other tretments. This difference ws not significnt t the first dte of mesurement ut ws for ll susequent dtes. Bigelow (2000) reported tht snd size hd significnt effect on porosity nd wter retention. Fine snd (0.1 to 0.25 mm) hd significntly higher ville wter holding cpcity thn either medium (0.25 to 0.5 mm) or corse snd (0.5 to 1.0 mm). In this study, higher content of fine nd medium snd ws used for the Cliforni tretments. The USGA tretment used snd with higher percentge of medium to corse snd. Results show tht the highest wter content tht occurred in the Cliforni tretment ws prtilly ttriuted to higher fine snd content 68

23 Volumetric wter content (%) Cliforni USGA Cliforni-P Cliforni-Z 0.0 6/25 6/27 7/1 7/4 7/9 7/11 7/16 7/20 7/24 c c Dte of mesurements Figure 4.9. Averge root zone volumetric wter content (%) for the 0 to 10cm depth for the selected tretments. Averge ws determined for the 8:00 m, 12:00 pm, nd 4:00 pm mesurement times during the drought period (from June 24 to July 24, 2000). Mens seprtion were determined y LSD 0.05 nd indicted y letters t ech mesurement dte. 69

24 (Tle 3.1 nd Figure 4.9). It is not understood why the Cliforni-Z tretment hd lower wter content from 10 to 30 dys fter the eginning of the drydown period. Figure 4.10 shows the difference in root zone volumetric wter content from 8:00 m to 4:00 pm (vlue t 8:00 m minus vlue t 4 pm) during the drydown period. Lrger differences etween the morning nd fternoon mesurements were found during the eginning of the drydown period (except for the USGA tretment on the first dte). The lrgest wter content differences etween the 8:00 m nd 4:00 pm mesurements were found three (6/27) to seven (7/1 mesurement) dys fter no irrigtion for ll tretments. This implies tht there were lrger dily losses of wter in the 0 to 0.1 m root zone depth when lrger mounts of wter were ville in the root zones. There were only couple of mesurement dtes tht showed differences mong the tretments. For ll tretments in 2001, root zone volumetric wter content t the eginning of the drydown period verged 28% nd t the end verged 7% (Figure 4.11). Root zone volumetric wter content t the eginning of the drydown period ws not significntly different mong tretments. 70

25 Difference in volumetric wter content (%) Cliforni USGA Cliforni-P Cliforni-Z 6/25 6/27 7/1 7/4 7/9 7/11 7/16 7/20 7/24 Dte of mesurements Figure Difference in root zone volumetric wter content (%) etween 8:00 m nd 4:00 pm (vlue t 8:00m vlue t 4:00pm) during the drought period (from June 24 to July 24, 2000). Men seprtion were determined y LSD 0.05 nd indicted y letters t ech mesurement dte. 71

26 Root zone volumetric wter content (%) Cliforni USGA Cliforni-P Cliforni-Z Tretments 7.5 LSD:3.9 (6/24/2001) LSD:3.1 (7/24/2001) 6/24/2001 7/24/2001 Figure Root zone volumetric wter content (%) mong tretments t the eginning (6/24/01) nd end (7/24/01) of the drought period. Mens seprtion were determined y LSD 0.05 nd indicted y letters t ech mesurement nd verticl rs represent LSD

27 At the end of the drought period, wter content ws not significntly different mong the Cliforni tretments (Cliforni, Cliforni-P, nd Cliforni-Z) while the USGA tretment hd the lowest vlue of 4.3%. The higher root zone wter content for the Cliforni tretments compred to the USGA tretment my hve een prtly due to these root zone mixtures hving higher fine nd medium snd content compred with medium to corse snd content for the USGA tretment. Even though the USGA tretment contined pet s root zone mendment, it did not retin more moisture during the drought stress period. In this study, differences in root zone wter content mong the tretments were proly lso ffected y the presence or sence of the pe grvel su-lyer. Bigelow (2001) reported tht the presence or sence of grvel su-lyer ffected the root zone wter retention. The presence of grvel su-lyer significntly reduced root zone wter retention. The grvel su-lyer tretment reduced root zone wter roughly 50%. In our study, the Cliforni tretments (without grvel su-lyer) hd higher root zone wter content t the end of the drydown period in 2001 nd only the Cliforni tretment hd higher (0 10 cm) wter content in 2000 when compred to the USGA tretment (with grvel su-lyer). 73

28 Results of the shoot wter potentil mesurements t the eginning nd end of the drydown period in 2001 re shown in Figure The highest shoot wter potentil (lest stress) occurred in the Cliforni-Z tretment t oth the eginning nd end of the drydown period. Only slight reductions (-0.08 MP) in shoot wter potentil occurred in the Cliforni tretments during the drydown period. The shoot wter potentil for the USGA tretment ws not significntly different from the Cliforni tretments t the eginning of the drydown period ut hd lrge reduction (77%; -0.6 MP) over the dry down period. The differences in the creeping entgrss shoot wter potentils (vlue t 6/24 minus 7/24, 2001) re shown in Figure The USGA tretment hd the lrgest shoot wter potentil difference etween eginning nd end of the drydown. Lehmn (1993) reported tht lef wter potentil ws ssocited with mintennce of growth under declining soil wter content levels. Our results demonstrte tht the gretest negtive shoot wter potentil (-1.38 MP) for the USGA tretment ws ssocited with the lowest root zone volumetric wter content fter the drought stress period (Figures 4.11 nd 4.12). 74

29 Shoot Wter Potentil (-MP) c Cliforni USGA Cliforni-P Cliforni-Z Tretments LSD:0.27 (6/24/2001) LSD:0.18 (7/24/2001) 6/24/2001 7/24/2001 Figure Shoot wter potentil (-MP) mong tretments t the eginning (6/24/01) nd end (7/24/01) of the drought period. Mens seprtion were determined y LSD 0.05 nd indicted y letters t ech mesurement nd verticl rs represent LSD

30 Chnge in Shoot Wter Potentil (MP) Cliforni USGA Cliforni-P Cliforni-Z Tretments Figure Chnge in the creeping entgrss shoot wter potentil (vlue t 7/24 minus 6/24, 2001). Mens seprtion were determined y LSD 0.05 nd indicted y letters t ech mesurement nd verticl rs represent LSD

31 Bentgrss leves on the USGA tretment were oserved to hve completely wilted t the end of the drought stress period nd most of the grss in the plots hd turned rown. This resulted from the fct tht the USGA tretment experienced the highest entgrss shoot wter stress during the drydown period. The results of the qulity nd color rtings for the four tretments t the eginning nd end of the drydown periods for 2000 nd 2001 re shown in Tles 4.1 nd 4.2. The qulity nd color rtings of entgrss for the Cliforni tretment were equl to or lower thn the Tle 4.1. Qulity nd color rtings of entgrss under irrigted conditions (6/25) nd dry conditions (7/25) in Tretments Qulity rting+ Color rting+ 6/25 7/25* 6/25 7/25* Cliforni c 4.0 USGA c 3.1 Cliforni-P Cliforni-Z LSD Rting scle of 1 to 9, 1=completely ded or dormnt, 6-7=cceptle, 9=idel. *End of drydown (mesured fter no irrigtion from June 24 to July 24, 2000). Letters following vlues within column indicte men comprison. 77

32 Tle 4.2. Qulity nd color rtings of entgrss under irrigted conditions (6/25) nd dry conditions (7/25) in Tretments Qulity rting+ Color rting+ 6/25 7/25* 6/25 7/25* Cliforni USGA Cliforni-P Cliforni-Z LSD Rting scle of 1 to 9, 1=completely ded or dormnt, 6-7=cceptle, 9=idel. *End of drydown (mesured fter no irrigtion from June 24 to July 24, 2001). Letters following vlues within column indicte men comprison. Cliforni-P nd Cliforni-Z tretments nd equl to the USGA tretment t the initition of the drought period for oth 2000 nd However, the Cliforni tretment hd equl to or etter qulity nd color rtings compred with the Cliforni-P nd Cliforni-Z tretments in 2000 t the end of the drydown period nd hd vlues in 2001 tht were not significntly different thn the Cliforni-P nd Cliforni-Z tretments (which hd the higher qulity rtings tht yer). The USGA tretment hd the lowest qulity nd color rtings t the end of the drydown period in

33 Greter nutrient content in the inorgnic mended tretments (Tles 4.3 nd 4.4) my hve contriuted to the higher entgrss qulity nd color rtings t the eginning of the drydown periods in 2000 nd The Cliforni-P tretment hd the highest ction exchnge cpcity, nd C nd Mg levels in oth 2000 nd The Cliforni-Z tretment hd the highest P nd K levels for the four tretments. The qulity nd color rtings of the entgrss for the Cliforni-Z tretment hd the higher rtings under well irrigted conditions which were oserved t the eginning of the drydown periods in 2000 (Tle 4.1). Tle 4.3. Chemicl properties in the root zone during the entgrss mture green phse (June 2000). Tretments ph CEC OM P C Mg K cmol kg -1 % mg kg -1 cmol kg -1 cmol kg -1 cmol kg -1 Cliforni c c 0.16 USGA c c 0.16 Cliforni-P Cliforni-Z LSD 0.05 NS NS : Nonsignificnt. 79

34 Tle 4.4. Chemicl properties in the root zone during the entgrss mture green phse (My 2001). Tretments ph CEC OM P C Mg K cmol kg -1 % mg kg -1 cmol kg -1 cmol kg -1 cmol kg -1 Cliforni c c 2.12c 0.41c 0.18 USGA c Cliforni-P Cliforni-Z c 0.81 LSD 0.05 NS NS : Nonsignificnt. However, the rtings for this tretment hd the gretest decline during the drydown period in 2000 mong the four tretments. This result my hve een due to the Cliforni-Z tretment hving the lowest root zone volumetric wter content mong the four tretments from 17 to 30 dys fter no irrigtion (Figure 4.9). Figures 4.14 nd 4.15 show the root zone wter loss from the eginning to end of the drydown. The Cliforni-Z tretment hd the highest root zone wter loss in 2000 while root zone wter loss mong the tretments were not significntly different in The Cliforni-Z tretment did not decline in qulity nd color s much in 2001 compred with Also, the Cliforni-Z tretment hd the highest shoot wter 80

35 Chnge in root zone volumetric wter content (%) Cliforni USGA Cliforni-P Cliforni-Z Tretments Figure Chnge in the root zone wter content (%) (vlue t 6/24 minus vlue t 7/24, 2000). Mens seprtion were determined y LSD 0.05 nd indicted y letters t ech mesurement nd verticl rs represent LSD

36 Chnge in root zone volumetric wter content (%) Cliforni USGA Cliforni-P Cliforni-Z Tretments Figure Chnge in the root zone wter content (%) (vlue t 6/24 minus vlue t 7/24, 2001). Mens seprtion were determined y LSD 0.05 nd indicted y letters t ech mesurement nd verticl rs represent LSD

37 potentil with highest creeping entgrss qulity when compred with other tretments fter the drought stress period in Miller (2000) reported tht turf grown in Profile nd ZeoPro mended snd hd the highest qulity when compred with ntive soil, pet, nd ditomceous erth mended snd. These mendments hd the potentil to influence root zone wter content, ultimtely influencing trnspirtion response to drought stress. Although the pet mended USGA tretment hd etter nutrient levels (C nd Mg) reltive to the Cliforni tretment (Tles 4.3 nd 4.4), color nd qulity t the eginning of the drydown period ws similr to tht of the Cliforni tretment. However, the USGA tretment showed significntly lower color nd qulity t the end of the drydown period for oth yers, proly due to higher plnt wter stress (Figure 4.12). Hung nd Petrovic (1996) reported tht clinoptilotlite zeolite (ZeoPro) hs positive effect on turfgrss growth nd qulity. Zeopro exhiits selective retention of NH 4 + nd K +, which my provide dded enefits for turf growth. The Cliforni-Z tretment hd the highest creeping entgrss qulity t the eginning of the drydown period which ws proly due to greter nutrient 83

38 content for this tretment (Tles 4.3 nd 4.4). Lower root zone volumetric wter content for the Cliforni-Z tretment t the end of the drydown period in 2000 my hve een result of higher wter loss (Figure 4.9) due to greter trnspirtion. Since the plnts in this plot hd the highest qulity rting (potentilly more lef re) t the eginning of the drydown, when compred to the other tretments, they my hve hd higher wter trnspirtion which my reduce the qulity for the Cliforni-Z treted plots. However in 2001, the Cliforni-Z tretment lost out the sme mount of wter during the drydown period s the other tretments. It lso hd the highest shoot wter potentil t the end of the drydown period. This study showed tht creeping entgrss my perform differently when grown in four different root zone mixtures. The dt suggest tht the Cliforni putting green root zone system ws the etter tretment for mintining entgrss qulity nd color during drydown periods compred to the USGA construction system. The Cliforni construction system lso resulted in the highest entgrss shoot wter potentils (lest stress) during the drydown period. These results re ttriuted to the lck of pe grvel su-lyer in the Cliforni system which results in 84

39 higher plnt ville wter in the root zone. The ddition of Profile nd zeolite to the snd for the Cliforni construction system ws shown to offer some enefits during the drought period. These tretments were found to hve higher entgrss shoot wter potentil (less stress) nd nutrient content mong the tretments. In this study, the Cliforni construction systems were found to provide etter performnce fter drydown period in 2001 thn the USGA construction system. 85

40 REFERENCES Berd, J. B Turf mngement for Golf Courses. Burgess Pulishing, Minnepolis MN. Bigelow, C. A., D. Bowmn, nd K. Cssel Snd- sed root zone modifiction with inorgnic soil mendments nd sphgnum pet moss. USGA Green Section Record. 38(4):7-13. Bigelow, C. A., D. Bowmn, nd K. Cssel wter retention of snd-sed putting green mixtures s ffected y the presence of grvel su-lyers. Interntionl Turfgrss Society Reserch Journl. 9: Crrow, R. N Drought resistnce spects of turfgrss in Southest: evpotrnspirtion nd crop coefficients. Crop Sci. 35: Delt-T Devices Ltd Instruments for environmentl industril mesurement. ThetMeter, Type ML1. User mnul. Ervin, E. H., nd A. J. Koski A comprison of modified tmometer estimtes of turfgrss evpotrnspirtion with Kimerly-penmn lflf reference evpotrnspirtion. Interntionl Turfgrss Society Reserch Journl. 8:

41 Heck, J. nd N. Christins Time lters greens key chrcteristics. Golf Course Mngement. 68(5): Hung, Z. T. nd A. M. Petrovic Clinoptilolite zeolite effect on evpotrnspirtion rte nd shoot growth rte of creeping entgrss on snd sed greens. Journl of Turfgrss Mngement. 1(4):1-9. Lssoie, J. P. nd Hinckley, T. M Techniques nd pproches in forest tree Ecophysiology. Boc Rton. Ann Aror. Boston. P Lehmn, V. G., M. C. Engelke., nd R. H. White Lef wter potentil nd reltive wter content vrition in creeping entgrss clones. Crop Sci. 33: McCoy, E. L Quntittive physicl ssessment of orgnic mterils used in sports turf root zone mixes. Agron. J. 84: Miller, G. L Physiologicl response of ermudgrss grown in soil mendments during drought stress. HortScience. 35(2): MSTAT MSTAT-C:A microcomputer progrm for the design, mngement nd nlysis of gronomic reserch experiments. MSTAT/Crop nd Soil Sciences. Michign Stte University, Est Lnsing, MI. 87

42 Rosenerg, N. J Microclimte: the iologicl environment. Wiley, NY. SAS Institute Inc SAS/STAT user s guide. Sttistics 6 th. SAS Inst., Cry, NC. Skogley, C. R., nd C. D. Swyer Field reserch. p In A. Wddington (ed.) Turfgrss. Agron. Monogr. 32. ASA nd SSSA, Mdison, WI. Spectrum Technologies, Inc AquTerr Instruments, Temp-200. Users mnul. 88