How to Measure the Subsurface Soil Temperature

It is important for a farmer -- whether a professional or a backyard gardener -- to know the soil temperature of his field before planting seeds. Once you know the soil temperature at the planting depth, you can determine if it is safe to plant the seeds. Planting seeds at the right soil temperature will result in a much higher yield. Finding the subsurface soil temperature is a fairly easy process that will take only several minutes to accomplish.

Glass aquarium thermometer
Dowel
Tape measure
Marker

Instructions

- 1
  Find the planting depth on the seed packaging or from the seed vendor. Seed-planting charts are also on the Internet, showing soil temperatures, planting depths and seed-spacing details.
- 2
  Measure the seed-planting depths on the dowel, using a tape measure and a marker. Mark off the planting depth for each seed before going out into the field. Take the dowel and a glass aquarium thermometer out to the soil where you will be planting your seeds.
- 3
  Use your thermometer to find the air temperature by holding the thermometer at shoulder height for one minute. Record your reading. Check the ground-level temperature by placing the thermometer on the ground for one minute and record that reading.
- 4
  Push the dowel into the ground until the first mark is at ground level. Pull out the dowel and place the thermometer into the same hole to find the subsurface soil temperature. Check the thermometer after a minute and write down your temperature reading.
- 5
  Repeat the process until you have depth measurements and subsurface soil temperature readings for every seed that you will plant.

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