Soil Thermometer

Quick Answer: The Soil Thermometer is a thermometer designed to be pushed or set into the ground so its sensing end reads the temperature at seed or root depth while the scale stays above the surface. A soil thermometer tells farmers, gardeners and students whether the ground is warm enough for sowing and how soil warms and cools through the day.

Why Ground Temperature Matters

Seeds respond to soil temperature, not air temperature. Each crop has a minimum below which germination is slow or fails and seeds may rot, and root growth and soil microbial activity depend on it too. Air warms and cools quickly; soil lags behind and changes less with depth, so a few centimetres down can be noticeably cooler at midday and warmer at dawn than the surface.

To measure, make a pilot hole with a rod of similar diameter so the thermometer is not forced past stones, insert it to the depth of interest and let it settle for several minutes. Read at the same times each day, since early-morning and mid-afternoon readings bracket the daily range. Meteorological stations record soil temperature at several fixed depths, and a school weather station can follow the same idea with thermometers set at two or three depths.

The title does not state whether this model is glass in a protective case or a dial type, nor its length and range; those decide the depths it can reach. The brass cone soil thermometer is a related model with a metal tip for better thermal contact, and the soil pH and moisture meter records two other factors that affect germination.

Applications

• Deciding when beds are warm enough to sow seasonal crops
• Recording soil temperature beside air temperature at a school weather station
• Comparing mulched and bare soil, or shaded and sunny beds, in a biology investigation
• Following the warmth of compost heaps and seed-raising trays

Specifications

Care & Handling

• Never hammer it into hard ground; make a pilot hole first.
• Pull it out straight, without levering, and wipe off the soil before storing it.
• If it stays in place, protect it from mowers and foot traffic with a marker stake.
• Compare it occasionally with a laboratory thermometer in a water bath.

Why Choose LabEquip

Agricultural colleges, nurseries and schools with growing plots buy these thermometers to time sowing and to teach how ground temperature behaves. LabEquip lists this one in General Lab Products; tell us the depths you need through the contact page.

Frequently Asked Questions

At what depth should soil temperature be read?

For sowing decisions, read at the depth the seed will be planted. For studies of how soil warms, measure at two or three depths and compare. Keep the depth the same from day to day.

What time of day is right for readings?

Morning readings show the coolest soil conditions and mid-afternoon readings the warmest. For planting decisions, many growers use early-morning readings over several days.

Why is soil temperature different from air temperature?

Soil stores heat and passes it slowly downward, so it changes more slowly than air and lags behind it. Deeper soil changes least over the day.

Can it be left in the ground all season?

It can if it is protected from damage and the scale remains readable, which avoids disturbing the soil. Mark the spot, and remove it before the bed is cultivated.

How long should I wait before reading?

Leave it for several minutes after insertion so the sensing end reaches the temperature of the surrounding soil. Read once the value has stopped changing.

How is this different from a lab thermometer?

A soil thermometer is built to be pushed into the ground and read at the surface, often with a pointed tip and a protective case. A bare lab thermometer would break in soil and is designed for liquids.

Last Updated: September 2026