Using Soil Temperature Reports for
Turf Management
NOTE: portions taken from a TCNC
article written by Greg Johnson, Meteorologist and Art Bruneau, Turfgrass
Specialist
Soil temperature reports from around the
state are available at: http://www.nc-climate.ncsu.edu/jet/. These reports can
be accessed by following the instructions below:
- Select
ECONet
- Select
the town/county or area nearest to you.
- Select
the retreive data button
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- Scroll
down to Soil Parameters.
- Select
soil temperature information.
- Click
on the Retrieve Data button.
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- Summary
page of your Soil Temperatures is produced
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Using Soil Temperature Reports
In general,
turf-covered areas will warm more slowly in the spring and cool down more
slowly in the fall on any given day as opposed to bare ground. In addition,
there is less chance of reaching extreme high and low temperatures on any given
day or season because of the buffering effect provided by the vegetation. The
differences should be less pronounced on cloudy, windy days, with turf-covered
areas staying somewhat warmer than bare ground after the passage of a strong
cold front. Areas with sparse vegetation (new seedlings or thin turf) would
expect to have temperatures approaching those reported for bare ground more so
than areas with a dense turf cover.
Soil
temperatures under turf-covered areas can be 1 to 4 days behind the
temperatures reported by the Extension Service. This can be an advantage for
turf managers because time can be allotted for planning. For example,
goosegrass and spurge usually germinate when soil temperatures approach 60°F in
the spring. A turf manager monitoring the soil temperatures reported for bare
ground will know that (s)he may have several days grace to apply preemergent
herbicides even though the reported soil temperature is 60°F. Soils that are
sandy will reduce this grace period.
The
following is a partial list of soil temperatures (°F) at the 4-inch depth that
should be of the association with certain biological events.
Turfgrass Growth and Development, Art Bruneau
Cool Season Grasses
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90°F
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Shoot
growth ceases.
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77°F
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Root
growth ceases.
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70°F
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Maximum
temperature for root growth of any consequence.
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70°F
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Time
to plant grasses in late summer.
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60-75°F
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Optimum
temperature for shoot growth.
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50-65°F
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Optimum
temperature for root growth.
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40°F
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Shoot
growth ceases.
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33°F
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Root
growth ceases.
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20°F
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Low
temperature kill possible if temperature subsequently drops rapidly below
20°F
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Warm Season Grasses
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120°F
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Shoot
growth ceases.
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110°F
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Root
growth ceases.
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80-90°F
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Optimum
shoot growth.
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75-85°F
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Optimum
root growth.
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74°F
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Optimum
time to overseed bermudagrass with ryegrass in the fall. Time to plant
grasses in the spring.
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64°F
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Expected
spring root decline is triggered and roots turn brown and die within 1 or 2
days.
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50°F
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Root
growth begins to slow below this temperature.
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50°F
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Chilling
injury resulting in discoloration is possible.
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50°F
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Initiation
of dormancy occurs resulting in discoloration.
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25°F
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Low
temperature kill possible.
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60-65°F
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Germination
of spurge and goosegrass is expected, therefore, apply preemergent material
when soil temperatures approach this level.
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53-58°F
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Germination
of crabgrass is expected, therefore, apply preemegent material when soil
temperatures approach this level.
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55°F
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Minimum
temperature for white grub and male cricket activity.
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Soil
temperature is a very important parameter for turf diseases, especially the
root and crown diseases. Here are some examples of target soil temperature ranges
for control if important root and crown diseases:
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65°F
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 Summer
Patch (Magnaporthe poae) - infects roots during spring and summer when soil
temperatures are above 65°F
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40-60°F
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Take-all
Patch (Gauemannomyces graminis) - infects roots during fall and spring when
soil temperatures are between 40°F and 60°F. Fall applications most important
for preventative control.
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60-80°F
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 Spring
Dead Spot (Ophiosphaerella korrae) - infects bermudagrass roots in
the fall when soil temperatures are between 60°F and 80°F. Preventative
fungicide applications should be applied in this target zone.
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70°F
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 Large Patch
(Rhizoctonia solani) - begins to infect in fall when soil temperatures dip to
70F. Preventative applications should be targeted to this soil temperature.
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