Greenhouse offers a controlled environment for growing plants. So a grower can check temperature, humidity or air circulation at any time and adjust as necessary. There are 7 types of greenhouse sensors you can use to do so.
Although primarily you should be monitoring greenhouse temperature and humidity with thermometer and hygrometer, it is very important to measure the temperature of the soil especially before planting. So today we are going to talk how to test the temperature of the soil.
What is the average temperature of soil?
Soil temperature shows how warm the soil is. There is no average soil temperature as such because it is affected by the season, composition of the soil and its structure along with other factors, but you should keep the soil temperature at around 45° to 70°F (7°-21°C) for successful plant growth.
Why to measure soil temperature?
Soil temperature is an essential measurement for the optimal plant growth. Moreover, soil also absorbs heat during the day and releases it at night. The same principal applies to the seasons, so in spring and summer soil absorbs warmth and stores energy to then release it during the autumn and winter.
The importance of soil temperature is in its impact on seed germination, it also drives nitrification, directly affects the humidity of the soil as well as its aeration and makes nutrients available to be absorbed by plants.
What time of day should you measure soil temperature?
You should measure the temperature of the soil in the first part of the day. The ideal time would be early in the morning (9-11 AM) because later in the day sun will warm the soil and before that it is still going to be cold from the night frosts.
When growing plants in a greenhouse I would recommend taking measurements two times a day, once in the morning and then late in the evening to make sure that the temperature does not go below the minimum threshold.
Learn the best way to test soil temperature in just 4 easy steps:
- Figure out where you are going to plant your seedlings;
- Dig the soil 3 or 4 inches deep (that is the most common depth for planting seedlings);
- Take a soil thermometer and position it to a side across the perimeter of the hole (take at least two probes at different sides);
- Leave the thermometer in for a few minutes and take a note of the temperature reading on the dial.
That way you will measure the exact soil temperature in the root zone, that is where the roots are going to be. By measuring soil temperature you will have an idea if plant roots are going to be warm enough for successful plant growth. Don’t measure the temperature just at the top of the soil!
When to check soil temperature?
Check the temperature of the soil during the growing season to see how healthy the ground is. Ideally, in June, July and August. Soil temperatures indicates on the health benefits of the ground.
Where to check soil temperature?
Once you decided where you are going to plant your seeds or seedling, be consistent at take the probes at the same place. Measure the temperature of the same type of soil, when the weather and precipitation levels are the same.
Can you use a meat thermometer for soil?
Yes, you can use a meat thermometer to measure temperature of the soil, however, do make sure it can test the temperatures up to 40°F (4°C) and lower. Before using a meat thermometer for soil give probe a good rinse and dry it thoroughly. Also, a standard digital thermometer is as good to take temperature readings.
What affects soil temperature?
Multiple facts can alter soil temperature, the most common ones are:
- Seasonality and Climate
- Composition, Structure and Texture of the soil
- Humidity and Compactness of the soil
- Density of Vegetation
- Irrigation and Drainage of the soil
What is the ideal soil temperature for transplanting vegetables?
Although every plant is unique in its soil temperature requirements, you can group them according to the temperature preferences as well as ‘optimum’ and ‘realistic’ temperatures. What is the difference between both?
‘Optimum’ refers to the ideal temperature where 100% of seeds will germinate. On the other hand, ‘realistic’ also known as practical temperature at which seeds give 70 – 80 % germination rate and provide strong early plant growth. In other words, you should not expect every seed to germinate but you can start planting quicker. For example, the optimal temperature to germinate tomato seeds is 85 °F but the realistic temperature is 55 °F.
So, when it comes to transplanting vegetables you need to keep two things in mind: 1) seeds and seedlings need need minimum soil temperature to germinate and grow; 2) seeds and seedlings need optimal temperature to thrive. Keeping that in mind, the ideal temperature for transplanting vegetable seedlings is between 60° to 85°F (15°-29°C).
How warm does the soil need to be to plant tomatoes?
Most gardeners plant tomato seedlings when the soil temperature is 70°F (21.1°C). Also, the soil is warm enough if a night air temperature is at least 55 °F (12.7 °C) meaning that during the day soil is going to warm up and be suitable for seedling cultivation. Even at 55 °F (12.7 °C) it is warm enough to plant tomatoes in soil but the growth is going to be slow.
– Is soil temperature usually cooler or warmer than air temperature?
Sun warms the soil surface and soil heats the air near the surface of the ground, so in a day time soil temperature is warmer than temperature of the air. However, as the sun goes down, there is less heat to warm the ground. In the late afternoon or early evening both ground and above air temperatures start to cool.
If we are talking about seasons, soil takes longer to warm, so in spring air temperatures are warm enough but soil temperature is as low as 45 °F. Soil and air above loose heat while releasing infrared energy. Soil is better at retaining heat than air, so in winter soil can be warmer than air.
Soil Thermometer Specifications
The best soil thermometer should be accurate, easy to clean, handy to keep and corrosion resistant. I found a very cheap option which meets all the requirements – REOTEMP K82-3 Soil Thermometer.
Is it long enough? Yes, it is 7 inches long so you can measure soil temperature at a good depth.
Is display easy to read? Yes, 2″ Dial is easy to read while looking straight down.
Is it accurate? Yes, readings are accurate and you can re-calibrate, simply turn the calibration screw.
Is it protected? Yes, it comes with protective sheath and clip so you can clip it to your pocket.
Is it fast? Yes, you can get the reading in around 10 seconds because of the quality bimetal element which does not need batteries.
