Agronomy Journal Grow Your Career With ASA
HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS
QUICK SEARCH:   [advanced]


     

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 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 HighWire
Right arrow Citing Articles via Web of Science (3)
Right arrow Citing Articles via Google Scholar
Google Scholar
Right arrow Articles by Tompkins, D. K.
Right arrow Articles by Moroz, D. L.
Right arrow Search for Related Content
PubMed
Right arrow Articles by Tompkins, D. K.
Right arrow Articles by Moroz, D. L.
Agricola
Right arrow Articles by Tompkins, D. K.
Right arrow Articles by Moroz, D. L.
Related Collections
Right arrow Agroclimatology
Right arrow Turfgrass Management
Right arrow Crop Physiology & Metabolism
Right arrow Turfgrass
Agronomy Journal 92:5-9 (2000)
© 2000 American Society of Agronomy

TURFGRASS MANAGEMENT

Dehardening of Annual Bluegrass and Creeping Bentgrass during Late Winter and Early Spring

Darrell K. Tompkinsa, James B. Rossa and David L. Moroza

a Prairie Turfgrass Research Centre, Olds College, 4500 50th St., Olds, AB, Canada T4H 1R6

dtompkins{at}admin.oldscollege.ab.ca


   ABSTRACT
TOP
 ABSTRACT
INTRODUCTION
 Materials and methods
 Results and discussion
 REFERENCES
 
Changes in cold hardiness levels of annual bluegrass (Poa annua L.) and creeping bentgrass (Agrostis palustris Huds.) were monitored under field conditions during the dehardening period of late winter and early spring. During the course of two spring periods the cold hardiness levels of the two species were monitored in conjunction with the following hydration treatments: snow cover maintained to prolong dormancy, snow removal in March, and hydration of crown tissues in combination with snow removal. Cold hardiness levels, percent crown moisture, and soil temperatures were monitored throughout this period. Cold hardiness levels were significantly influenced by year, species, hydration treatment, and a number of interactions of these factors. Generally, plants dehardened 2 wk earlier in 1997 than in 1996. On 1 April, creeping bentgrass had cold hardiness levels averaging -20°C compared to -13°C for annual bluegrass. By 15 April, creeping bentgrass plants had lost their cold hardiness advantage. Increased soil temperature was the greatest contributor to the loss of hardiness in the spring. An increase in crown moisture of 4% for annual bluegrass and 6% for creeping bentgrass occurred during the period from 25 March to 22 April. Maintaining a snow cover on plots delayed the loss of cold hardiness by 6 to 9 d in 1996 but had no effect in 1997. Maintaining a snow cover also delayed the increase in crown hydration by a week. Plants were able to partially regain cold hardiness when soil temperatures dropped.

Abbreviations: LT50, the lowest temperature at which 50% of the plants survived freezing injury


   INTRODUCTION
TOP
 ABSTRACT
 INTRODUCTION
Materials and methods
 Results and discussion
 REFERENCES
 
FOR MANY GOLF COURSES with creeping bentgrass greens, annual bluegrass invasion is a major weed problem. Consequently, older turf is often entirely taken over by annual bluegrass. Then maintenance, rather than eradication, is the primary concern. Winter damage to annual bluegrass greens is a problem that affects golf courses in cold climate areas (Beard and Olien, 1963). In these areas, where creeping bentgrass or annual bluegrass greens are commonly maintained on golf courses, cold hardiness levels are greater for creeping bentgrass than for annual bluegrass (Beard, 1966).

Cold hardiness levels for plants fluctuate from year to year. Soil temperature during the cold hardening period plays a critical role in determining the hardiness level. In order to achieve the full level of cold hardiness, a period of freezing temperatures may be required (Gusta and Fowler, 1977a). Cold hardiness levels decline slowly with time when plants are maintained at temperatures just below freezing, but this loss of cold hardiness occurs more rapidly if plants are stored at colder temperatures (Gusta et al., 1997).

While cold hardiness levels can vary widely for different species (Gusta et al., 1980), conditions during the dehardening period in the spring may play an important role in determining the amount of winter damage that occurs (Gusta and Fowler, 1977b). Many golf course superintendents remove snow in late winter in order to reduce ice injury and to provide an earlier start for the turf in the spring. Unfortunately, this may increase the risk of winter injury to the greens. Therefore, it would be useful to determine the effect of dehardening temperatures on cold hardiness levels.

There is also a lot of concern about injury associated with crown hydration on annual bluegrass greens. Widespread injury to annual bluegrass is common and often associated with lower lying areas where water can collect. Therefore, it would be useful to determine the relative importance of crown hydration as a predisposing factor to cold temperature injury.

The specific goals of this study were to determine the relationship between dehardening temperature, crown hydration, and cold hardiness levels for annual bluegrass and creeping bentgrass during the transition from winter to spring.


   Materials and methods
TOP
 ABSTRACT
 INTRODUCTION
 Materials and methods
Results and discussion
 REFERENCES
 
A field trial was conducted in the spring of 1996 and 1997 on plots established at the Prairie Turfgrass Research Centre (PTRC), Olds, AB, Canada, to examine the effects of snow removal and crown hydration on annual bluegrass and creeping bentgrass plants. The plots were constructed with a 1% grade with drainage trenches between the plots so that water from one plot would not drain across another. Plots were established in a split-plot design with four replicates. Main plots included two species, annual bluegrass (biotype Mn42 from the Univ. of Minnesota) and creeping bentgrass (cv. Penncross). Subplots included four hydration treatments:

  1. maintenance of a snow cover for as long as possible (snow cover treatment);
  2. snow removed manually in early March (dry treatment);
  3. snow removed in early March and piled around plot edges so that the snow would melt across the plots (partial wet treatment); and
  4. snow removed in early March and piled around plot edges with additional water applied at the rate of 5 L m-2 prior to sampling (wet treatment).

Plants were sampled on a weekly basis during the springs of 1996 and 1997 to monitor changes in the LT50 value (lethal temperature for 50% of the plants) and percent crown moisture. Sampling dates for 1996 included 18 and 25 March and 1, 9, 15, and 22 April. Sampling dates for 1997 included 19 and 24 March, and 1, 7, 14, and 21 April. To simplify matters, the combined years' data are grouped and presented using the 1996 dates. In addition, plants were sampled in late November the previous year (November of 1995 and 1996) to determine baseline hardiness levels. In 1997, plants were also sampled in mid-January to assess the midwinter cold hardiness level. Soil temperature at the soil/thatch interface was monitored using a datalogger (Model Li-Cor Li 1000). In 1996, temperature was monitored on the snow-covered plots. In 1997, temperature was monitored for each of the four hydration treatments.

At each sampling period, a 6-by-6 cm plug was removed from each plot for a freeze test. The plugs were removed from the frozen turf using a hammer and chisel. Each plug was divided into six smaller plugs and placed in test tubes. The plants in these plugs were then subjected to a freeze test in a circulating bath (Model LT50, Neslab Instruments, Portsmouth, NH). This methodology was developed to prevent the plants from thawing prior to the freeze test. Premature thawing may influence hardiness levels. In the circulating bath, plants were allowed to equilibrate for 8 h at -2°C. The temperature was then decreased by 2°C h-1 in a stepwise fashion. When the temperature was in the selected temperature range, a test tube with plants from each treatment was removed and the temperature was further decreased by 2°C. For example, plants may have been removed at -6, -8, -10, -12, -14, and -16°C. After the freeze test, the plugs were allowed to thaw at 4°C and individual plants were separated and transplanted into trays. The plants were then transferred to the greenhouse for 4 wk and plant regrowth was rated for survival to establish an LT50 value, which represents the lowest temperature at which 50% of the plants survived.

At the time of field sampling, 100 crowns of plants from each treatment were removed to determine the percent crown moisture. Wet weights were taken prior to oven drying for 24 h and then dry weights were measured. The percent moisture was then determined on a wet weight basis.

When treatment effects were significant based on ANOVA; LSD was used for mean separation. A multiple-regression analysis was used to examine the relationship between LT50 values, percent crown moisture, and soil temperature.


   Results and discussion
TOP
 ABSTRACT
 INTRODUCTION
 Materials and methods
 Results and discussion
REFERENCES
 
Changes in LT50 Values during the Dehardening Period
Year, species, and the year x species interaction significantly influenced LT50 values at most sampling dates during the March-to-April period (Table 1) . The hydration treatment and the interactions involving year, species, and hydration treatment significantly influenced LT50 on the 9 April sampling date. This period in early April coincided with rapid changes in soil temperature.


View this table:
[in this window]
[in a new window]
  		Table 1 Analysis of variance for different sources of variation for LT50 values

 
Cold hardiness levels declined rapidly during the March-to-April period (Table 2) . In 1996, during the 2-wk period from 1 to 15 April, average LT50 levels changed from -22 to -10°C. In 1997, during the 2-wk period from 18 March to 1 April, LT50 levels changed from -21 to -11°C.


View this table:
[in this window]
[in a new window]
  		Table 2 Effect of year, species, year x species interaction, hydration treatment, year x hydration treatment interaction, and species x hydration treatment interaction on LT50 values (°C) during the dehardening period

 
Baseline LT50 levels for annual bluegrass plants sampled in the early part of the winter averaged -20°C (-21°C in fall 1995 and -18°C in fall 1996). Baseline LT50 levels for creeping bentgrass plants sampled in early winter averaged -40°C (-39°C in fall 1995 and -40°C in fall 1996).

During late March and early April, creeping bentgrass had superior cold hardiness but by late April, the differences between species had largely disappeared. In fact, the cold hardiness levels for annual bluegrass were marginally better than those of creeping bentgrass by then.

In 1996, rapid dehardening occurred between 1 and 9 April, particularly for creeping bentgrass. During this time, the cold hardiness level in creeping bentgrass declined from -31 to -18°C. This loss of cold hardiness corresponded with a period of elevated soil temperatures prior to 9 April (Fig. 1) .



View larger version (12K):
[in this window]
[in a new window]
  		Fig. 1 Soil temperature measured at 4 p.m. daily in the spring of 1996 on plots with a snow cover

 
In 1997, both species dehardened earlier than in 1996 (Table 2). For annual bluegrass, cold hardiness levels declined from -17°C on 13 January (data not shown) to -13°C on 18 March. For creeping bentgrass, cold hardiness levels declined from -40°C on 13 January (data not shown) to -26°C on 25 March and -12°C on 1 April. Therefore, the differences in cold hardiness between annual bluegrass and creeping bentgrass largely disappeared in the week between 25 March and 1 April. On 25 March the creeping bentgrass was more cold hardy by 16°C (-26 vs. -10°C). On 1 April the difference in hardiness level was 1°C (-12 vs. -11°C). This rapid loss of cold hardiness was associated with increased soil temperature in the last 2 wk of March on plots with no snow cover (Fig. 2) .



View larger version (12K):
[in this window]
[in a new window]
  		Fig. 2 Soil temperature measured at 4 p.m. daily in the spring of 1997 on snow cover plots and dry treatment plots (snow removed)

 
Differences in LT50 levels between hydration treatments were significant only on 9 April (Table 2). However, on 15 April, differences were significant at . On both of these dates, the greatest difference in the cold hardiness level was between the snow cover treatment and the wet treatment (i.e., snow removed and water added). The other hydration treatments had LT50 levels intermediate between these two extremes.

The year x hydration treatment interaction was significant at a number of dates. Generally, in 1996, plots with a snow cover had better levels of cold hardiness until 9 April. On that date LT50 levels were -21°C for plots with a snow cover compared to -15°C for the dry treatment and -11°C for the wet treatment. On the snow-cover plots, the snow did not melt until the first week of April. Prior to 7 April, the soil temperature on these plots remained at or below 0°C (Fig. 1). Consequently, on 9 April there was a relatively large difference in cold hardiness level between the snow-cover treatment and all others. On 8 April the soil temperature warmed to 4°C and on 9 April the soil temperature warmed to 8°C. For the next few days, soil temperatures warmed to above 10°C each day. This greatly influenced the LT50 levels between the 9 and 15 April sampling periods.

Between 1 and 9 April, 1997, plants from plots where the snow had been removed regained some cold hardiness (Table 2). For example, for the dry treatment, cold hardiness levels improved from -10°C on 1 April to -16°C on 9 April. During this period of time, the soil temperature had decreased. The soil temperature on 8 April at 1600 h was only 2°C. The following night the 0400 h soil temperature was -7°C (data not shown).

There was a significant interaction between species and hydration treatment on 9 and 15 April. On both these dates, the difference between the snow cover and the snow removed treatments was more pronounced for creeping bentgrass than for annual bluegrass. This was particularly true in 1996 producing a significant year x species x hydration treatment interaction (data not shown).

Changes in Percent Crown Moisture during the Dehardening Period
The percent crown moisture was significantly influenced by year and species at most sampling dates (Table 3) . The hydration treatment had a significant effect on the percent crown moisture on the 15 April sampling date.


View this table:
[in this window]
[in a new window]
  		Table 3 Analysis of variance for different sources of variation for percent crown moisture

 
The percent crown moisture levels were higher in 1997 than in 1996 (Table 4) . In both years, the percent crown moisture was higher by the end of April than in mid-March.


View this table:
[in this window]
[in a new window]
  		Table 4 Effect of year, species, and hydration treatment on percent crown moisture values (%) during the dehardening period

 
Similarly, the percent crown moisture was higher for annual bluegrass than for creeping bentgrass. It is possible there is a relationship between the lower percent crown moisture in the creeping bentgrass and improved cold hardiness in comparison to annual bluegrass. However, by 15 April the creeping bentgrass had no cold hardiness advantage over the annual bluegrass, but the percent crown moisture was still lower.

The hydration treatment significantly influenced the percent crown moisture on 15 April. On this date, plants from the snow cover treatment had a lower percent crown moisture than the other treatments. This difference was not due to the addition of water to the wet treatment, as there was no difference between the percent crown moisture for the dry and wet treatments. This indicates that maintaining a snow cover not only helped plants retain cold hardiness, but delayed hydration of the crowns in the spring.

Relationship between LT50 Level, Percent Crown Moisture, and Soil Temperature
Increased soil temperature was associated with a reduced cold hardiness (Fig. 3) and an increase in percent crown moisture (Fig. 4) . In addition, there was a highly significant positive correlation between reduced cold hardiness and increased percent crown moisture. The relationship between LT50 level, soil temperature (average daily maximum for 2 d preceding sampling date), and percent crown moisture can be described by the equation

where level, , and . *** Denotes significance at ). The relationship between these three factors was more pronounced for creeping bentgrass than for annual bluegrass, as the annual bluegrass plants lost much of their cold hardiness prior to the 18 March sampling date.



View larger version (8K):
[in this window]
[in a new window]
  		Fig. 3 Relationship between LT50 value and average maximum soil temperature for the 2-d period prior to the sampling date, based on pooled averages

 


View larger version (9K):
[in this window]
[in a new window]
  		Fig. 4 Relationship between percent crown moisture and average maximum soil temperature for the 2-d period prior to the sampling date, based on pooled averages

 
One way to delay the loss of cold hardiness in the spring is to maintain a snow cover. Snow covered plants are also less likely to be subjected to killing temperatures. Maintaining a snow cover delayed the loss of cold hardiness by 6 to 9 d in 1996, but had no effect in 1997. In either year, the dehardened plants did not experience winter damage, because the cold hardiness levels were adequate for the temperatures experienced. In a year when colder temperatures follow a warm period, these exposed plants would be more susceptible to freezing injury.

The initial loss of cold hardiness may be partially recovered if the plants are once again exposed to cold temperatures (Gusta and Fowler, 1977a). In the present study, this was noticeable in 1997 on the plots where the snow had been removed. For example, plants from the dry treatment had cold hardiness levels of -10°C on 1 April and -16°C on 9 April. However, with every dehardening cycle, plants have a reduced ability to regain hardiness. In a year where the temperature fluctuations were more dramatic, a snow cover that prevents the initial loss of dormancy would be an advantage.

During the early spring, plants dehardened considerably before there were any visual signs of growth. This dehardening was associated with an increase in the percent crown moisture. Maintaining a snow cover delayed the increase in percent crown moisture as well as helping to maintain cold hardiness.

Other studies have emphasized the relationship between cold hardiness level and soil temperature (Gay and Eagles, 1991), tissue water content (Brule-Babel and Fowler, 1989) and both soil temperature and percent crown moisture (Limin and Fowler, 1985).

From a management standpoint, it is preferable to maintain dormancy as long as possible. Snow cover helps maintain dormancy and prevent crown hydration.


   ACKNOWLEDGMENTS
 
The authors acknowledge the financial support of the Canadian Turfgrass Research Foundation and the Alberta Parks, Recreation and Wildlife Foundation. Alberta Agriculture supplied an additional low-temperature circulating bath. Seed for the annual bluegrass biotype Mn42 was supplied by Dr. Don White of the Univ. of Minnesota. Dr. Larry Gusta of the Univ. of Saskatchewan provided assistance in developing the methodology.

Received for publication April 20, 1998.
   REFERENCES
TOP
 ABSTRACT
 INTRODUCTION
 Materials and methods
 Results and discussion
 REFERENCES
 




This article has been cited by other articles:


Home page
 Crop Sci.Home page
P. Rochette, J. Dionne, Y. Castonguay, and Y. Desjardins
Atmospheric Composition under Impermeable Winter Golf Green Protections
Crop Sci., June 20, 2006; 46(4): 1644 - 1655.
[Abstract] [Full Text] [PDF]

Home page
 Crop Sci.Home page
D. K. Tompkins, J. B. Ross, and D. L. Moroz
Effects of Ice Cover on Annual Bluegrass and Creeping Bentgrass Putting Greens
Crop Sci., November 1, 2004; 44(6): 2175 - 2179.
[Abstract] [Full Text] [PDF]

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 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 HighWire
Right arrow Citing Articles via Web of Science (3)
Right arrow Citing Articles via Google Scholar
Google Scholar
Right arrow Articles by Tompkins, D. K.
Right arrow Articles by Moroz, D. L.
Right arrow Search for Related Content
PubMed
Right arrow Articles by Tompkins, D. K.
Right arrow Articles by Moroz, D. L.
Agricola
Right arrow Articles by Tompkins, D. K.
Right arrow Articles by Moroz, D. L.
Related Collections
Right arrow Agroclimatology
Right arrow Turfgrass Management
Right arrow Crop Physiology & Metabolism
Right arrow Turfgrass

HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS
The SCI Journals Crop Science 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