Taking the Soil's Temperature!
record air and soil temperatures in their Journey North garden each
month through the winter and spring.
bulbs are settled seven inches underground, the temperature outside (on
most parts of the continent) is dropping, and we're in the darkest time
of year. What's going on underground? Before you have students ponder
that question, read this short teacher
background on soil temperatures.
students to ponder the conditions their bulbs might be experiencing.
cold does it feel outside today? What is the air temperature? Use
a school thermometer or newspaper to find out.
do you think the temperature is underground where our bulbs are?
(Or, Do you think the underground temperature is the same
as the outside temperature? Do you think it's higher or lower?) Ask
students to explain their thinking. How do you think we could
the class to set up an investigation in search of answers.
you live where the ground freezes solid in the winter,
you can drive a long nail into the ground with a hammer. Or, if your garden is soft enough,
make a pencil hole for your soil thermometer. But if you
start this activity before the soil freezes, you
can put a drinking straw into a hole in the soil to keep
it open. Cover the hole with a coffee can so it will not
be buried under the snow.
you mulched your bulb garden or had an early snow cover,
you may find that the soil is actually warm enough to work
with — even in mid-winter.
the soil thermometer; explain that it
can take the temperature underground.
Ask, What question do we
want to answer? For instance, you might choose, Is the
soil temperature the same as the air temperature? Discuss
how you might answer the question.
For Grades 4 and Up: Help older students plan
their own science study. See Temperature
Experiments: Starting with a Good question.
out copies of the "What's
Happening Underground?" Data Sheet or
create a chart for the entire class to use. Students will fill
them in as they conduct the next few steps.
the air temperature. Look
at an outdoor thermometer to find the air temperature. Do this
just before going out to measure the soil temperature. Ideally,
you'll have a thermometer you can bring right to the garden so
you can measure the air temperature just above where you'll measure
the soil temperature.
the soil temperature and then find it. Have students predict
the soil temperature in their garden on that day. If the ground
in your garden is hard, make a hole with a pencil before inserting
the thermometer. If the ground is frozen, hammer a long nail into the ground for the thermometer. Try to make the hole about the depth of your tulips; leave the thermometer in place for a few minutes. Record the temperature on the data sheets. (Note: Always
bring the soil thermometer inside when you're through.)
steps 3 and 4 each month from January through May or June.
Try to take the measurements on about the same day at about the
same time each month. Before students predict each month's soil
temperatures, they should review and reflect on earlier data. Each
time you return to class, ask students to share other observations
about the garden site (e.g., presence or depth of snow, amount
sunshine or rainfall) along with questions they have. Keep a dated
class list of observations and questions.
Connections: Discussion and Journal Questions
As a class
or individually, make a graph to represent the data. As students review
the data and their observations, ask,
patterns do you notice? (How do soil and air temperatures change
from winter to spring?)
does our data "tell" us about soil and air temperatures?
Which are warmer?
would you explain our findings? What questions do you still have?
do you think soil temperatures (or air temperatures) have to do
with tulips emerging and flowering? What other "signals" might
affect tulip growth? (Think about other things, besides temperature,
that change in the spring.)
students this photo
of thermometers in snow and share this: One winter, Journey
North staff dug through the snow and stuck in a soil thermometer.
When the air temperature was 2 degrees F. below zero, the soil two
inches down was 27 degrees F above zero! Do you think they made a
mistake? How would you explain what happened?
to Purchase a Soil Thermometer
You can purchase inexpensive soil thermometers from many nurseries and
stores with garden supplies, such as Home Depot. Kidsgardening.com has
a nice 7 1/2-inch soil thermometer. It has a disk at the top that gives
readings from 0 to 220 degrees F. for just $10.95. You can order
it here or by calling 800-538-7476.