Crop Science Journal of Natural Resources and Life Sciences Education
HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS
QUICK SEARCH:   [advanced]


     

Published online 2 December 2005
Published in Crop Sci 46:81-89 (2006)
© 2005 Crop Science Society of America
677 S. Segoe Rd., Madison, WI 53711 USA
This Article
Right arrow Abstract Freely available
Right arrow Figures Only
Right arrow Full Text (PDF) Free
Right arrow Alert me when this article is cited
Right arrow Alert me if a correction is posted
Services
Right arrow Similar articles in this journal
Right arrow Similar articles in ISI Web of Science
Right arrow Alert me to new issues of the journal
Right arrow Download to citation manager
Right arrow reprints & permissions
Citing Articles
Right arrow Citing Articles via ISI Web of Science (6)
Right arrow Citing Articles via Google Scholar
Google Scholar
Right arrow Articles by DaCosta, M.
Right arrow Articles by Huang, B.
Right arrow Search for Related Content
PubMed
Right arrow Articles by DaCosta, M.
Right arrow Articles by Huang, B.
Agricola
Right arrow Articles by DaCosta, M.
Right arrow Articles by Huang, B.
Related Collections
Right arrow Water Stress
Right arrow Water Use
Right arrow Turfgrass Management
Right arrow Turfgrass

TURFGRASS SCIENCE

Minimum Water Requirements for Creeping, Colonial, and Velvet Bentgrasses under Fairway Conditions

Michelle DaCosta and Bingru Huang*

Department of Plant Biology and Pathology, Rutgers University, New Brunswick, NJ 08901

* Corresponding author (huang{at}aesop.rutgers.edu)


   ABSTRACT
TOP
 ABSTRACT
INTRODUCTION
 MATERIALS AND METHODS
 RESULTS
 DISCUSSION
 REFERENCES
 
Knowledge of water use requirements of various grass species is important for identifying grasses that persist with reduced water inputs and also for developing efficient irrigation management practices. This study was designed to examine minimum water requirements for maintaining acceptable quality fairways established to creeping (Agrostis stolonifera L.), colonial (A. capillaris L.) and velvet (A. canina L.) bentgrasses. Field experiments were conducted from July to November in 2002 and 2003. Plots were irrigated at four levels of irrigation on the basis of the percentage of actual evapotranspiration determined with minilysimeters (ETa): 100, 80, 60, and 40% ETa replacement. Turf performance was evaluated by measuring visual turf quality (TQ), canopy spectral parameters, canopy photosynthetic rates (Pn), and soil moisture status. Results generally demonstrated that irrigating at 100% ETa was not necessary to maintain acceptable TQ and physiological processes and that the minimum water requirements depended on species and time of year. Colonial bentgrass required irrigating at 80 to 100% ETa, while creeping and velvet bentgrasses required 60 to 80% ETa to maintain acceptable turf performance in the summer of 2002. During the summer treatment period in 2003, however, irrigating at 60% ETa was sufficient for all three species. Irrigating at 40% ETa in the fall treatment period in both 2002 and 2003 was sufficient to maintain acceptable TQ, canopy Pn, and comparable canopy growth parameters to plots receiving 100% ETa. The results from this study demonstrate the potential for significant water and monetary savings by utilizing deficit irrigation practices on bentgrass species used for golf course fairways.


   INTRODUCTION
TOP
 ABSTRACT
 INTRODUCTION
MATERIALS AND METHODS
 RESULTS
 DISCUSSION
 REFERENCES
 
WATER AVAILABILITY for irrigation of turfgrasses is becoming increasingly limited, making water conservation a prime concern of turfgrass growers and managers across many areas of the country. Knowledge of water use requirements of various grass species is important for identifying grasses that persist with reduced water inputs and also for developing efficient irrigation management practices. Water requirements for turfgrass growth have been based on water use rates and quantified through measurement of evapotranspiration rate (ET). Water requirements vary with turfgrass species (Youngner et al., 1981; Aronson et al., 1987; Kim and Beard, 1988; Fry and Butler, 1989; Fu et al., 2004) and within cultivars of the same species (Shearman, 1986; Kopec et al., 1988; Shearman, 1989; Bowman and Macaulay, 1991; Salaiz et al., 1991; Ebdon and Petrovic, 1998). Water use rate is also affected by environmental factors, such as the availability of soil moisture. Generally, higher water use rate has been related to increases in water availability (Beard, 1973; Biran et al., 1981; Gibeault et al., 1985; Kneebone et al., 1992). Under restricted irrigation or limiting soil moisture conditions, turfgrasses may use significantly less water compared with well-irrigated plants (Kneebone and Pepper, 1984; Qian and Engelke, 1999).

Deficit irrigation is the practice of deliberate under-irrigation of a plant to below its maximum potential water demand, resulting in overall water savings and increases in water use efficiency (Feldhake et al., 1984; English and Raja, 1996; Kirda, 2002). This irrigation strategy has been successfully applied in many agronomic and horticultural crop species, such as wheat (Triticum aestivum L.), sorghum (Sorghum bicolor L. Moench), maize (Zea mays L.), and fruit tree species (Chalmers et al., 1985; Mpelasoka et al., 2000; Goodwin and Boland, 2002; Panda et al., 2003). Investigations utilizing deficit irrigation have also been conducted on some warm- and cool-season turfgrass species to determine the lower limits of irrigation that maintain minimum acceptable turf quality (Feldhake et al., 1984; Fry and Butler, 1989; Brown et al., 2004; Fu et al., 2004). Overall, studies on deficit irrigation of turfgrasses have shown that the extent of allowable deficit irrigation may vary between species and within cultivars of the same species, with warm-season grasses typically being better able to withstand greater levels of deficit irrigation compared with cool-season grasses (Meyer and Gibeault, 1986; Qian and Engelke, 1999). Under low maintenance conditions, Qian and Engelke (1999) reported the minimum irrigation quantity to prevent drought stress and maintain acceptable quality for tall fescue (Festuca arundinacea Shreb.) was 50 to 70% of evaporation from a class A pan (Epan), while 10 to 50% of Epan was required for several warm-season grasses. Under intensive management conditions, Carrow (1995) found that irrigation at 80% Epan was necessary for tall fescue, and 60 to 80% Epan was needed for the warm-season grasses.

In addition to the benefit of decreased total water use, turfgrasses can tolerate certain levels of deficit irrigation with little or no loss in turf quality. Applying irrigation to 80% of field capacity reduced water use of Kentucky bluegrass (Poa pratensis L.) by 20% and only reduced quality by 10% (Danielson et al., 1981). In Kansas, tall fescue and bermudagrass [Cynodon dactylon (L.) Pers.] maintained similar quality levels at 60 and 40% of ETa, respectively, compared with the same species under well-watered conditions (Fu et al., 2004). The proper use of a deficit irrigation strategy, either through decreased irrigation quantity or irrigation frequency, has also been found to promote plant tolerance to subsequent severe drought stress associated with increased root growth and enhanced osmotic adjustment (Beard, 1973; Qian, 1996; Jiang and Huang, 2001).

The ability to maintain quality turfgrasses with minimum irrigation could result in significant monetary and water savings, particularly in irrigating areas such as fairways that may occupy significant acreage on golf courses. In cool climatic regions bentgrasses have become popular for use on fairways, in part related to factors such as increased disease epidemics on perennial ryegrass (Lolium perenne L.) fairways and improved characteristics of bentgrasses for fairway use, such as higher shoot density. While there have been investigations conducted on deficit irrigation for other turfgrass species, information is generally lacking on the effects of deficit irrigation and general irrigation requirements of different bentgrasses under fairway conditions. The minimum water requirements for bentgrass species have not been evaluated, particularly in regards to variability in requirements among different bentgrass species used for high maintenance, close-cut turf. Each bentgrass species retains particular qualities relating to color, density, playing quality, and stress resistance characteristics that may result in more widespread use of one bentgrass species over another. However, general information on minimum water requirements would be valuable for providing better irrigation management recommendations for conserving water in bentgrasses, as well as providing insight on selecting bentgrasses better adapted to limited irrigation conditions.

Therefore, the objective of this study was to determine and compare minimum water requirements for maintaining acceptable quality fairways established to creeping (A. stolonifera), colonial (A. capillaris), and velvet (A. canina) bentgrasses. Turf performance under varying levels of deficit irrigation was evaluated by measuring turf quality, canopy spectral characteristics, and canopy photosynthetic rates.


   MATERIALS AND METHODS
TOP
 ABSTRACT
 INTRODUCTION
 MATERIALS AND METHODS
RESULTS
 DISCUSSION
 REFERENCES
 
Creeping bentgrass ‘L-93’, colonial bentgrass ‘Tiger 2’, and velvet bentgrass ‘Greenwich’ were examined because the three cultivars have been observed to perform well in field trials and had great potential use for golf course fairways in the Northeast (W.A. Meyer and S.A. Bonos, personal communication). On 19 Sept. 2001, the three species were seeded at a rate of 4 g m–2 per plot (1.5 x 2.4 m) on a sandy loam soil (fine-loamy, mixed, mesic, Typic Hapludult; pH of 6.55, 260 kg P ha–1, and 300 kg K ha–1 by Mehlich-3 extraction) at the Rutgers Turfgrass research farm in North Brunswick, NJ. Grasses were covered with a single layer woven polyethylene tarp (Hinspergers Poly Industries, ON, Canada) during winter months to enhance seedling establishment. Turf was mowed at 0.95 cm three times per week, with clippings collected and removed from the experimental site. Applications of a 16–4–8 (N-P-K) fertilizer were applied once per month in April, May, September, and November in 2002 and 2003 for a total of 122 kg/ha of nitrogen for the growing season. Fungicides were applied monthly from May through September in 2002 and bi-monthly from June to September in 2003. The fungicides chlorothalonil [2,4,5,6-tetrachloroisophthalonitrile], azoxystrobin [methyl (E)-2-{2-[6-(2-cyanophenoxy)pyrimidin-4-yloxy]phenyl}-3-methoxyacrylate], propiconazole [1[[2-(2,4-dichlorophenyl)-4-propyl-1,3-dioxolan-2-yl]methyl]-1H-1,2,4-triazole], triadimefon [1-(4-chlorophenoxy)-3,3-dimethyl-1-(1H-1,2,4-triazol-1-yl) butanone], and iprodione [3-(3,5-dichlorophenyl)-N-(1-methylethyl)-2,4,-dioxo-1-imidazolidinecarboxamide] were applied alone or in combination to primarily control dollar spot (caused by Sclerotinia homoeocarpa, F.T. Bennet) and brown patch (caused by Rhizoctonia solani, Kühn). Chlorpyrifos [O,O-diethyl O-3,5,6-trichloro-2-pyridyl phosphorothioate] and bendiocarb [2,2-dimethyl-1,3-benzodioxol-4-yl methylcarbamate] were applied in July of 2002 and 2003, respectively, to control black cutworm [Agrotis ipsilon (Hufnagel)].

The experiment was conducted in 2002 and 2003 under a fully automated, mobile rainout shelter (10.7 x 20.1 m) (modified commercially available greenhouse, Stuppy Greenhouse Manufacturing, North Kansas City, MO; designed and constructed by Agricultural Engineering staff, New Jersey Agricultural Experiment Station, Rutgers University). A Campbell Scientific data acquisition system (Model CR-23X, Campbell Scientific, Logan, UT) monitored weather variables and controlled the operation of the rainout shelter. A heated grid sensor located approximately 3 m off the ground detected rainfall, which then initiated the process of moving the shelter over experimental plot area during rain events. Powered by an electric motor and set on rails, the shelter automatically returned back to its original position after approximately thirty minutes of a rain event. The shelter excluded unwanted rainfall from test plot areas and allowed quantitative control of soil moisture and irrigation while retaining the advantages of practical field conditions.

An additional on-site weather station located approximately 130 m from the rainout shelter monitored temperature, relative humidity, wind speed, and solar radiation parameters in both 2002 and 2003 (Model CR-10X datalogger, Campbell Scientific, Logan, UT). Sensors for the different climatic variables were located 2 m off the ground.

Plots were arranged in a randomized split-plot design, with irrigation levels as the main plots (4.5 x 9.6 m) and species as the sub-plots (1.5 x 2.4 m). Plots were irrigated three times per week, generally between 0800 and 1100 h, at four levels of irrigation quantity on the basis of different percentages of the maximum daily water loss through evapotranspiration (ETa). Plots were irrigated to replace (i) 100% ETa (control); (ii) 80% ETa; (iii) 60% ETa; and (iv) 40% ETa. Each species and irrigation treatment was replicated four times for a total of 48 plots. Each subplot was individually irrigated with a hand-held hose with a fan-spray nozzle and water quantity was monitored with a digital flow meter attachment (Cat.# 4352K63, McMaster-Carr Supply Co., New Brunswick, NJ). The flow rate to dispense a given amount of water was determined for one irrigation pass to maintain even distribution and uniformity of irrigation application within and among plots. To prevent subsurface lateral water movement between different irrigation treatments, plots were separated with 41-cm deep plastic edging. To limit lateral surface water movement between plots, total irrigation amount was applied in separate quantities to be less than infiltration rate.

Irrigation treatments were applied from July to November in 2002 and 2003, with two deficit irrigation treatment cycles (summer and fall) in each year. Treatments during the summer deficit irrigation period ceased when plots under the lowest irrigation regimes demonstrated significant drought injury (plant tissue brown and desiccated). Fall treatments ceased when temperatures dropped to below optimum for active turfgrass growth. In 2002, treatments ran from 1 July through 18 August (48 d), and then again from 13 September through 1 November (50 d). In 2003, treatments ran from 27 June through 8 September (73 d), and then again from 1 October to 1 November (31 d). In between the summer and fall irrigation treatments was a re-watering period to allow the turf in deficit irrigation plots to completely recover to prestress levels (dense, green turf canopy) before the initiation of the fall irrigation cycle. During the recovery period, all plots were watered three times per week to replace 100% ETa and maintain soil moisture at field capacity (approximately 30% volumetric soil moisture).

ET rates of individual plots were measured by the gravimetric mass balance method with minilysimeters to represent actual ET (ETa). Minilysimeters allow for direct calculation of mass changes due to plant water uptake and soil evaporation (Young et al., 1997) and have been utilized in several investigations on turfgrass ET (Feldhake et al., 1983; Aronson et al., 1987; Qian et al., 1996; Fu et al., 2004). Measurement of ETa based on weighing lysimeters is distinguished from ETp, where ET is estimated instead by means of an empirical model and on the basis of climatic data (Kneebone et al., 1992). Approximately 1 mo before the initiation of irrigation treatments, cores including intact plants and soils (10-cm diam and 20 cm deep to include a majority of the root system) were removed from established field plots with a cup cutter and placed into polyvinyl chloride (PVC) tubes of the same size as the cores to form minilysimeters. Nylon mesh screen was taped to the bottom of each PVC tube to maintain the plant and soil column intact while allowing for water infiltration out of the minilysimeters. In 2002, minilysimeters were installed only in plots of the 100% ETa treatment (one minilysimeter in all replications of each species). In 2003, minilysimeters were installed in plots of all four irrigation treatments (three lysimeters per species per irrigation treatment) to determine the differences in water use among the different irrigation treatments. Minilysimeters received the same environmental and management conditions as the rest of the surrounding plot area. Soil moisture content was measured within minilysimeters and surrounding plot area at different times throughout the experimental period and found to be comparable (data not shown); however, vertical water movement and moisture of the soil layer immediately next to the PVC was not determined. Minilysimeters were pulled out of the plots daily and weighed at 24-h intervals with a balance providing accuracy to the nearest gram. Daily ET was calculated on the basis of the difference in the weight of minilysimeters at 24-h intervals. Average daily loss in mass from the minilysimeters was converted on an area basis into the amount of irrigation water to replace onto individual plots.

General turf performance was evaluated weekly by rating turf quality (TQ) on a 1-to-9 scale (1 = worst, completely brown and desiccated and 9 = best, green, dense turgid canopy). A rating of 6 was considered to be the minimum acceptable turf quality. Canopy reflectance characteristics of turf plots were measured with a hand-held multispectral radiometer (MSR) (Cropscan, Rochester, MN) on clear and sunny days, approximately between 1100 and 1400 h. Spectral assessment of canopy characteristics gave an additional measure to visual qualitative estimates of turfgrass performance. Normalized difference vegetation index (NDVI), as a measure of canopy green leaf biomass, and ratio of near infrared (IR) (935 nm) to red (R) (661 nm), which has been correlated with leaf area index (LAI) (Hatfield et al., 1983; Asrar et al., 1984; Daughtry et al., 1992), were calculated on the basis of canopy reflectance values:


MSR data were taken in 2002 but not collected in 2003 because of instrument malfunction. Consequently, canopy chlorophyll index was utilized as an additional method to objectively analyze turfgrass vigor. The extent of canopy color has been correlated with visual assessment of turfgrass color and also associated with improved turfgrass performance (Beard, 1973; Karcher and Richardson, 2003; Jiang et al., 2004). In 2003, canopy color was assessed with a Field Scout CM-1000 chlorophyll meter (Spectrum Technologies, Plainfield, IL) and expressed as chlorophyll index.

Volumetric soil moisture content was measured one to two times weekly using time-domain reflectometry (TDR) (Trase System I, Model 6050X1; Soil Moisture Equipment, Santa Barbara, CA). Soil moisture measurements were collected approximately 24 h after an irrigation event. A pair of stainless steel 15-cm long probes were inserted vertically into the soil profile at two locations per plot. The two measurements were then averaged to determine soil moisture for each plot.

Canopy net photosynthetic rate (Pn) was measured using an infrared gas exchange analyzer with a modified canopy chamber provided with 400 µL L–1 CO2 (LI-COR 6400, LI-COR, Inc., Lincoln, NE). The canopy chamber consisted of an acrylic cylinder (10 cm diameter and 8 cm height), which was pressed into the ground approximately 3 cm to provide an adequate seal for canopy gas exchange measurements (similar canopy chamber available from LI-COR, Inc.). Photosynthesis measurements were performed on days with minimal to no cloud cover, and at times of maximal solar radiation (approximately between 1100 and 1400 h).

Treatment effects were determined by analysis of variance for a split-plot design according to the general linear model procedure of the Statistical Analysis System V.8.2 (SAS Institute Inc.). To remove the effect of year and sampling date, data were analyzed separately for each year and date for statistical analysis. Variation was partitioned into irrigation regime, grass species, and corresponding interactions. Analysis showed a significant interaction between deficit irrigation regime and grass species for TQ, chlorophyll index, and canopy Pn. Therefore, deficit irrigation levels within each grass species were analyzed, and differences between irrigation treatment means within a species were separated by Fisher’s protected least significance difference (LSD) test at the 0.05 probability level. There were no irrigation x species interactions for volumetric soil moisture, NDVI, and IR/R parameters; therefore irrigation and species main effects are presented along with means separation by Fisher’s protected LSD test at the 0.05 probability level.


   RESULTS
TOP
 ABSTRACT
 INTRODUCTION
 MATERIALS AND METHODS
 RESULTS
DISCUSSION
 REFERENCES
 
Volumetric Soil Moisture Content
Soil moisture content over the 2-yr period was significantly affected by irrigation regime and species main effects; however, there were no significant irrigation x species interactions in either 2002 or 2003. Plots of all three species receiving 60 and 40% ETa showed significant decline in soil moisture compared with that irrigated at 100% ETa by 3 wk of treatment (23 July) in 2002 (Fig. 1). Velvet bentgrass plots retained higher soil moisture content than both creeping and colonial bentgrasses under all deficit irrigation regimes. In the fall, soil moisture of plots of all three species at 60 and 80% ETa irrigation was not significantly different from that at 100% ETa irrigation. Soil moisture of plots at 40% ETa irrigation during the fall months was lower than plots receiving 100% ETa for all three species; however, no visual water deficit symptoms were observed in the turf (Fig. 2).



View larger version (30K):
[in this window]
[in a new window]
  		Fig. 1. Changes in volumetric soil moisture content under deficit irrigation in 2002 and 2003. In 2002, irrigation treatments were applied from 1 July through 18 August and then again from 13 September through 1 November. In 2003, treatments were applied from 27 June through 8 September and then again from 1 October to 1 November. Graphs (A) and (B) demonstrate general species changes in soil moisture as a result of the deficit irrigation. Graphs (C) and (D) demonstrate the general changes in soil moisture in response to varying levels of deficit irrigation for all three bentgrass species. Symbols indicate the irrigation treatment as a percentage of ET measurements using weighing minilysimeters. Vertical bars are LSD values (P = 0.05) indicating statistically significant differences for species and irrigation treatment comparisons at a given day of treatment.

 


View larger version (44K):
[in this window]
[in a new window]
  		Fig. 2. Changes in turfgrass quality (TQ) for creeping (CRP), colonial (CO), and velvet (V) bentgrasses under deficit irrigation in 2002 and 2003, where 9 represents the best quality (green, dense canopy) and 1 represents the lowest quality (brown, desiccated). In 2002, irrigation treatments were applied from 1 July through 18 August and then again from 13 September through 1 November. In 2003, treatments were applied from 27 June through 8 September and then again from 1 October to 1 November. Symbols indicate the irrigation treatment as a percentage of ET measurements with weighing minilysimeters. Vertical bars are LSD values (P= 0.05) within a species indicating statistically significant differences for treatment comparisons at a given day of treatment.

 
Soil moisture depletion patterns in 2003 showed similar trends to that in 2002 for all three species among the different irrigation treatments. Plots receiving 100% ETa replacement retained the highest soil moisture, and those with 40% replacement showed the most decline in moisture over time in summer months (Fig. 1). Soil moisture in 2003 did not decline as rapidly as what had been observed in 2002, particularly during the months of July and August. After 5 wk (12 August) of irrigating at 60% ETa in 2002, soil moisture declined to approximately 14%. Following the same treatment duration (6 August) in 2003, however, soil moisture of plots at 60% ETa were as high as 27%. During the fall deficit irrigation cycle soil moisture of all plots, regardless of irrigation treatment, were statistically not different for all species (approximately 25–30% v/v).

Visual Turf Quality and Canopy Characteristics
Both irrigation regime and species significantly affected TQ on most rating dates, and an irrigation x species interaction also occurred in both 2002 and 2003 on 50% of dates. This suggested that the species differed in their response to varying levels of deficit irrigation. In 2002, all three species maintained acceptable TQ (greater than 6.0) at 100% ETa throughout the summer and fall irrigation periods (Fig. 2). In the summer, both creeping and velvet bentgrasses irrigated at 80% ETa maintained quality levels equivalent to those at 100% ETa. TQ for colonial bentgrass irrigated at 80% ETa declined to 6.0 by the end of the summer deficit irrigation period, which was below the quality observed at 100% ETa (8.0). TQ of colonial and creeping bentgrass declined below the minimal acceptable quality (6.0) under 60% ETa irrigation, which was 1 wk earlier in colonial bentgrass than in creeping bentgrass. Velvet bentgrass maintained acceptable TQ when irrigated at 60% ETa for most of the summer irrigation period but started to decline during the final week of the summer treatment period. Irrigation at 40% ETa had adverse impact for all three species in the summer, with quality declining to approximately 2.0 to 3.0, but TQ for velvet was maintained at a higher level for a longer period of time than that for colonial and creeping bentgrasses. Irrigation at 40% ETa was sufficient to maintain acceptable TQ throughout September and October (Fig. 2).

In 2003, TQ changed more slowly under deficit irrigation compared with that observed in 2002 (Fig. 2). In 2003, average maximum air temperatures, wind speed, and solar radiation were lower, and relative humidity was higher compared with those in 2002 (Table 1). Plots irrigated at 100% ETa showed decline in turf quality below the minimum acceptable level in both summer and fall for all three species. Irrigating at 80 or 60% ETa maintained acceptable TQ levels throughout most of the summer irrigation period for all three species. After approximately 8 wk (27 August) of 60% ETa irrigation, TQ of colonial bentgrass declined to approximately 5.0, while creeping bentgrass plots declined to a level of 4.0 after 9 wk (8 September) of 60% ETa irrigation. Velvet bentgrasses maintained acceptable TQ levels at 60% ETa. Similar to summer 2002, 40% ETa replacement was detrimental for all three bentgrass species in summer 2003, with quality at this irrigation level declining fastest in colonial (3 wk, 18 July), followed by creeping (5 wk, 6 August ), and slowest in velvet (7 wk, 20 August). In the fall, acceptable TQ for all three species was maintained at 40, 60, and 80% ETa replacement.


View this table:
[in this window]
[in a new window]
  		Table 1. Meteorological parameters from an on-site weather station located approximately 130 m from the rainout shelter in North Brunswick, NJ, in 2002 and 2003. Data presented include monthly means for maximum air temperature, relative humidity, daily solar radiation, and wind speed during the study period. Sensors for the different climatic variables were located approximately 2 m off the ground.

 
No significant interactions occurred, but irrigation and species significantly affected canopy spectral characteristics on all three (irrigation) and two of three (species) measurement dates in 2002. At the end of 6 wk (12 August) of deficit irrigation in the summer, IR/R of the three species was significantly lower in plots at 60 and 40% ETa than that at 100% ETa irrigation (Table 2). Under 40% ETa, IR/R declined to approximately 40% of plots receiving 100% ETa irrigation; however, there were no significant differences in IR/R between plots at 80 and 100% ETa irrigation. Velvet bentgrass generally had higher IR/R throughout the experimental period regardless of irrigation regime compared with colonial and creeping bentgrasses. NDVI declined significantly for all species at 40 and 60% ETa by the end of the summer deficit irrigation period. Similar to results for IR/R, velvet bentgrass generally maintained higher NDVI during prestress, summer, and fall treatment periods. In 2002, all three species exhibited similar or greater IR/R and NDVI in the fall deficit irrigation period compared with summer and initial, prestress levels.


View this table:
[in this window]
[in a new window]
  		Table 2. Changes in turf canopy characteristics for normalized difference vegetation index (NDVI), as a measure of canopy green leaf biomass, and ratio of near infrared to red (IR/R), as a measure of leaf area index (LAI). Data presented are for spectral assessment on 1 July (initial, prestress levels), 12 August (end of summer deficit irrigation period), and 20 September (fall irrigation period) in 2002.

 
Differences in color of turf plots were also observed with the chlorophyll meter in 2003. Irrigation regime and species significantly affected chlorophyll index values on most rating dates, and an irrigation x species interaction also occurred on 60% of dates. In general, plots under 80 and 60% ETa replacement in the summer irrigation period had highest chlorophyll index readings compared with plots receiving 100 or 40% ETa (Fig. 3). This was similar to trends observed for TQ (Fig. 2). There was approximately a 50% reduction in chlorophyll index values at 40% compared with 60 and 80% ETa irrigation by the end of the summer deficit irrigation period. Among the three species, velvet bentgrass maintained the highest chlorophyll readings under the same irrigation regimes. In the summer of 2003, plots irrigated at 100% ETa exhibited 20, 35, and 35% lower chlorophyll index than plots receiving 60 and 80% ETa irrigation for creeping, colonial, and velvet bentgrasses, respectively. For velvet bentgrass, even plots irrigated at 40% ETa had higher chlorophyll index values than those irrigated at 100% ETa throughout most of August. In the fall of 2003, chlorophyll index values of plots irrigated at 100% ETa remained 20 to 30% lower compared with plots receiving 60 and 80% ETa.



View larger version (33K):
[in this window]
[in a new window]
  		Fig. 3. Changes in chlorophyll index for creeping (CRP), colonial (CO), and velvet (V) bentgrasses under deficit irrigation in 2003. In 2003, irrigation treatments were applied from 27 June through 8 September and then again from 1 October to 1 November. Symbols indicate the irrigation treatment as a percentage of ET measurements with weighing minilysimeters. Vertical bars are LSD values (P= 0.05) within a species indicating statistically significant differences for treatment comparisons at a given day of treatment.

 
Canopy Photosynthesis
Irrigation and species main effects occurred for canopy Pn on 85 and 33% of dates, respectively, in 2002 and on 85 and 60% of dates, respectively, in 2003. While no significant irrigation x species interactions occurred in 2002, interaction occurred on 60% of dates in 2003. Therefore, data are presented for irrigation regime effects within each grass species for comparison of both years. In 2002, plots at 80% ETa maintained the same level of canopy Pn as those at 100% ETa for all three species (Fig. 4). Canopy Pn of colonial and velvet plots irrigated at 60 and 40% ETa were significantly lower compared with that at 100% ETa after approximately 4 wk (2 August) of treatment in the summer months. Velvet and creeping bentgrasses generally had higher canopy Pn rates compared with colonial bentgrass when irrigated at 60% ETa. In the fall deficit irrigation period, canopy Pn rates did not differ among irrigation treatments.



View larger version (33K):
[in this window]
[in a new window]
  		Fig. 4. Changes in canopy net photosynthetic rate (Pn) for creeping (CRP), colonial (CO), and velvet (V) bentgrasses under deficit irrigation in 2002 and 2003. In 2002, irrigation treatments were applied from 1 July through 18 August and then again from 13 September through 1 November. In 2003, treatments were applied from 27 June through 8 September and then again from 1 October to 1 November. Symbols indicate the irrigation treatment as a percentage of ET measurements using weighing minilysimeters. Vertical bars are LSD values (P= 0.05) within a species indicating statistically significant differences for treatment comparisons at a given day of treatment.

 
In 2003, canopy Pn of plots at 60 and 80% ETa were the same as that of plots at 100% ETa for all species. It was significantly lower at 40% ETa than at 100% ETa during August and September. After approximately 6 wk (17 August) at 40% ETa irrigation, canopy Pn approached close to zero. In the fall, however, plots under 40% deficit irrigation recovered and canopy Pn increased and eventually reached to the levels of the other irrigation treatments.


   DISCUSSION
TOP
 ABSTRACT
 INTRODUCTION
 MATERIALS AND METHODS
 RESULTS
 DISCUSSION
REFERENCES
 
Results from the present study demonstrated that minimum water requirements for maintaining acceptable turf performance based on turf quality, canopy spectral characteristics, and canopy Pn varied with bentgrass species, time of the year, and between years. In 2002, colonial bentgrass required 80 to 100% ETa irrigation during the summer, while creeping and velvet bentgrasses maintained acceptable turf performance at 60 to 80% ETa. These results suggest that irrigation to replace 100% ET water loss was not necessary even in the typically high evaporative conditions of summer. Reducing irrigation quantity by 20 to 40% (80–60% ETa replacement) was still able to maintain high quality and physiological activities for creeping, colonial, and velvet bentgrasses. Previous studies reported that replacing 50 to 80% of either ETa or Epan was adequate to maintain acceptable quality in other cool-season turfgrasses such as tall fescue (Carrow, 1995; Qian and Engelke, 1999; Fu et al., 2004) and Kentucky bluegrass (Feldhake et al., 1984). However, 40% ETa irrigation was inadequate to meet water demand and maintain physiological activities for bentgrasses during summer months in both years. Fry and Butler (1989) and Minner (1984) also found that irrigating hard fescue (Festuca longifolia Thuill.) and Kentucky bluegrass below 50% ETa was detrimental and resulted in poor overall quality characteristics. Our results suggest that bentgrasses could be effectively managed for water conservation under fairway conditions by practicing deficit irrigation to certain levels, as long as no detrimental effects on turf growth occurs.

Moderate deficit irrigation has been associated with better quality and other positive growth responses in many turf and forage grasses (Fry and Huang, 2004), such as increased rooting (Qian, 1996; Jordan et al., 2003), increased persistence to subsequent stresses (Qian, 1996), and decreased clipping production (Biran et al., 1981). In a growth chamber study with Kentucky bluegrass, withholding irrigation from the upper 20 cm of soil resulted in a 40 to 50% reduction in shoot extension while maintaining turf quality, leaf water content, and cell membrane stability similar to levels in well-watered plants (DaCosta et al., 2004). Bastug and Buyuktas (2003) also reported that a reduction in irrigation to 75% of evaporation from Class A Pan maintained better color, ground cover percentage, and increased root weights for a turf mixture of Kentucky bluegrass, red fescue (Festuca rubra L.), and perennial ryegrass compared with the same grasses maintained at 100% Epan.

The minimum irrigation requirement for all three species was less in September and October compared with that in July and August in both years. Acceptable turf performance in the fall for all three species could be maintained by irrigating at 40% ETa. This is most likely due to changes in ET rates resulting from lower evaporative conditions in the fall months associated with lower air temperatures (fall average temperature of 19.5°C versus summer average temperature of 28.1°C). Changes in water use over seasons have been reported previously (Beard, 1973; Feldhake et al., 1983, Salaiz et al., 1991).

The comparison of irrigation requirement between the 2 yr revealed that minimum irrigation requirement to maintain acceptable turf performance was generally lower in 2003 than in 2002. In 2003, plants were able to maintain acceptable performance with 60% ETa irrigation throughout the majority of July and August for all species. The lower irrigation requirements in 2003 could be attributed to the combination of higher relative humidity (average of 82.7 vs. 71.4% in 2002), lower air temperatures (summer average of 27.5 vs. 28.8°C in 2002), decreased wind speed (average of 1.4 vs. 2.0 m s–1 in 2002) and lower solar radiation (average of 977 vs. 1186 µmol m–2s–1 in 2002) during July and August that could result in lower evaporative demand (Table 1). In fact, plots receiving 100% ETa irrigation showed a significant decrease in overall turf performance throughout the summer 2003, as exhibited by the decrease in overall color and density of plots (Fig. 2 and 3). Irrigating at 100% ETa under conditions of decreased water demand may be excessive. Excessive irrigation has been reported to be a problem for vigor and persistence of turfgrasses, leading to reduced soil aeration, reduced shoot and root growth, decreased chlorophyll concentration, and increased susceptibility to temperature, desiccation, and traffic stresses (Beard, 1973). Additionally, colonial, creeping, and velvet bentgrasses all exhibited increased incidence of dollar spot and algae formation under 100% ETa, while colonial bentgrass also exhibited severe incidents of brown patch in 2003 (data not shown). Frequent or excessive irrigation has also been associated with enhanced dollar spot in bermudagrass (Qian and Engelke, 1999) and perennial ryegrass (Jiang et al., 1998), and enhanced brown patch in St. Augustinegrass [Stenotaphrum secundatum (Walter) Kuntze] (Qian and Engelke, 1999).

Compared among the three species, velvet bentgrass plots retained greener color, higher canopy Pn, and lower soil moisture depletion than creeping and colonial bentgrass under deficit irrigation regimes. These results indicated that velvet bentgrass had lower water requirements than the other bentgrass species. Morphological and physiological factors associated with lower irritation requirement in velvet bentgrass are under further investigation.

In the present study, ET from turf plots was measured with weighing lysimeters to represent actual ET (ETa). In practice, however, ET-based irrigation is generally performed by mathematical models based on weather data, such as a modified Penman equation (ETp) (Penman, 1948; Kneebone et al., 1992). In a previous investigation comparing ETa to ETp, Qian et al. (1996) found that the Penman–Monteith model generally overestimated ET when evaporative conditions were low, and underestimated ET when water demand was high, such as under conditions of high air temperature, high solar radiation, and high wind. However, a significant relationship has been observed between climatic variables, Penman-based models, and turfgrass ET in studies conducted in both arid (Kopec et al., 1986) and humid climates (Aronson et al., 1987). Therefore, on the basis of our results, replacement of 100% ET, whether measured via lysimeters or model, may not be necessary to sustain plant growth and physiological processes for creeping, colonial, and velvet bentgrasses in cool climatic regions.

In summary, colonial bentgrass had the highest irrigation requirements, while velvet bentgrass exhibited lowest irrigation requirements. In 2002, the minimum irrigation requirements to maintain acceptable summer-long quality and other evaluated parameters were as follows: colonial required 80 to 100% ETa, and creeping and velvet required 60 to 80% ETa. In 2003, under conditions of lower temperatures, higher humidity, and higher cloud cover, the minimum irrigation requirements for colonial, creeping, and velvet bentgrasses was 60% ETa to maintain minimum acceptable quality in the summer months. During the cooler months of fall, irrigation requirements for all three species decreased compared with summer. In both 2002 and 2003, irrigating at 40% ETa was adequate to maintain acceptable quality for all three species during the fall months. In many cases, there may actually be unnecessary over-irrigation of turf if irrigation regimes are based on replacing 100% ET. This study demonstrated potential savings of 20 to 40% irrigation in the summer and 60% savings in fall months for maintaining bentgrasses with minimal effects on turfgrass quality and other physiological parameters. Consequently, the use of deficit irrigation practices could be an essential component in the development of irrigation management programs that result in both water and monetary savings in managing bentgrass fairways.

This study was conducted under constant mowing height, mowing frequency, and fertility levels, and without traffic stress. Changes in these practices or presence of additional stresses have been shown to modify water requirements in other turfgrass species (Dernoeden and Butler, 1978; Biran et al., 1981; Feldhake et al., 1984). Further evaluation is required to determine the effects of different cultural practices and stress parameters on irrigation requirements in bentgrasses. In addition, it should be noted that the minimum irrigation quantity was determined for three bentgrass species when irrigated three times weekly, and irrigation quantity is expected to change with changes in irrigation frequency.


   ACKNOWLEDGMENTS
 
This research was supported by the O.J. Noer Research Foundation, the Rutgers Center for Turfgrass Science, and the Cook College Agricultural Experiment Station at Rutgers University. We also wish to thank Tracy Newton, John Pote, T.J. Lawson, William Dickson, and Joseph Clarke for technical assistance in the field.

Received for publication February 4, 2005.


   REFERENCES
TOP
 ABSTRACT
 INTRODUCTION
 MATERIALS AND METHODS
 RESULTS
 DISCUSSION
 REFERENCES
 





This Article
Right arrow Abstract Freely available
Right arrow Figures Only
Right arrow Full Text (PDF) Free
Right arrow Alert me when this article is cited
Right arrow Alert me if a correction is posted
Services
Right arrow Similar articles in this journal
Right arrow Similar articles in ISI Web of Science
Right arrow Alert me to new issues of the journal
Right arrow Download to citation manager
Right arrow reprints & permissions
Citing Articles
Right arrow Citing Articles via ISI Web of Science (6)
Right arrow Citing Articles via Google Scholar
Google Scholar
Right arrow Articles by DaCosta, M.
Right arrow Articles by Huang, B.
Right arrow Search for Related Content
PubMed
Right arrow Articles by DaCosta, M.
Right arrow Articles by Huang, B.
Agricola
Right arrow Articles by DaCosta, M.
Right arrow Articles by Huang, B.
Related Collections
Right arrow Water Stress
Right arrow Water Use
Right arrow Turfgrass Management
Right arrow Turfgrass

HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS
The SCI Journals Agronomy Journal Vadose Zone Journal
Journal of Natural Resources
and Life Sciences Education		 Soil Science Society of America Journal
Journal of Plant Registrations Journal of
Environmental Quality		 The Plant Genome