more about soil temps

Hi All,

Recently there have been more questions about soil temperatures here.  In
the past I have ask the group about soil temperature and growth but there
seems to be little info.  Below are 2 excerpts about soil temps that I
found somewhere.
(I would be happy to hear from anyone who has any more pumpkin specific
soil temp info.)

Bart
Wallingford, CT
===============================================================


Check Soil Temperature

Soil temperature is a factor few gardeners check before planting, yet it is
probably the most important factor affecting seed germination and plant
growth.

Soil temperatures at which vegetable seed will grow include the minimum
temperature required for seed growth, an optimum temperature and a
"realistic" soil temperature. The realistic soil temperature is somewhere
between optimum and minimum; it is the temperature at which you should
plant to insure maximum success.

For instance, the optimum soil temperature for seed germination of
vegetable crops, such as cucumber, cantaloupe, okra, pumpkin, squash and
watermelon, is 95°F. However, if planted late enough during the year for
soil to reach this temperature, summer heat will decrease plant vigor and
yield. The minimum soil temperature for these crops is 60°F; yet, at this
temperature the seed will not grow vigorously. Thus, there must be an
intermediate soil temperature that is more realistic. Realistic soil
temperatures for the best plant production are cucumber (64°F), cantaloupe
(68°F), okra (73°F), pumpkin (75°F), squash (70°F) and watermelon (72°F).

Crops such as beans, beets, cabbage, chard, eggplant, pepper, radish,
tomato, turnip and corn have an optimum soil temperature for seed
germination of 85°F. The minimum soil temperature required for some of
these cold-tolerant crops, such as beets, cabbage, chard, radish and
turnip, is as low as 40°F. The realistic soil temperatures recommended for
these crops are beans (72°F), beets (45°F), tomato (55°F), turnip (50°F)
and corn (55°F).

As might be expected, vegetables which are really cold-tolerant, such as
carrots, parsley, lettuce and spinach, have lower optimum soil temperatures
for seed germination. For instance, the optimum soil temperature for seed
germination of carrots is 80°F, for parsley and lettuce 75°F, and for
spinach 70°F. The minimum temperature required for these crops is 35°F. The
realistic soil temperature at which all of these crops should be planted is
45°F.

===================================
                             Soil Temperature

Soil temperature determine the rate of plant growth, and whether a plant
will even survive. Temperature will change in each soil layer (see soil
profile).

To measure soil temperature, find an area that is not in direct sunlight.
Using a centigrade thermometer, measure the air temperature at shoulder
height. Hold the thermometer still for about one minute (make sure your
fingers are not on the thermometer bulb), read and record the temperature.
Next, measure the temperature at the surface of the ground. Let the
thermometer lie on the ground and record the temperature after one minute.
Below ground temperature readings should be made at several levels, one
inch, 2 inches and 6 inches. Pound a dowel into the ground the desired
distance, insert the thermometer for one minute. Read the thermometer
quickly when it is removed from the soil. The temperature reading will
change in air.

Take temperature readings at different times throughout the day at the same
location.

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  Soil Temperature             Conditions during growing season
   Less than 40 F     no growth, bacteria and fungi are not very active
    40 F to 65 F                          some growth
    65 F to 70 F                        fastest growth
    70 F to 85 F                          some growth
      above 85 F                           no growth

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