Soil Heating temperature Advice required

murihikukid · June 21, 2016

Hi..Today I put soil in my Stainless drums and switched the panel heater on which is located (on stilts) in the bottom of a freezer shell .....Due to my having no fitting for a cable to my STC 1000 Thermostat I just powered it so I could get a Temperature reading and Switched the panel heater on....I watched the temperature rise to round 45F and unplugged the heater and watched the temperature fall and repeated this several times....
Tomorrow I should have the Thermostat up and controling the heater.....Now I am only guessing but it will take several days of continuous warming to get the soil to the required temperature...so as I can transplant my plants..

So heres what I need advice on...What is the correct soil temperature for tomatoes cause I have seen a wide variance in articles....and I would not heat up to 80 degrees F as I have seen .. I would sooner go for a lower number like 60 to 70 .....and am I right to think that the air heat will take several days to actually warm the soil...Again I have read 100degrees F air temperature equals 75F soil temperature ....
Regards Ron ..NZ

Cole_Robbie · June 21, 2016

Soil temperature, for outdoor plants in the soil, depends on the depth at which the measurement is taken.

Here is a chart I found with google images that demonstrates:

I'd probably put the cable toward the top of the soil, and try to mimic the way the sun warms the ground from the top down. In hydroponics, keeping the root zone cool enough is always a challenge. If plants like it to be 85, roots prefer closer to 65. Those are not exact numbers, but you get the idea.

June 21, 2016	#2
Cole_Robbie Tomatovillian™ Join Date: Jun 2012 Location: Illinois, zone 6 Posts: 8,407	Soil temperature, for outdoor plants in the soil, depends on the depth at which the measurement is taken. Here is a chart I found with google images that demonstrates: I'd probably put the cable toward the top of the soil, and try to mimic the way the sun warms the ground from the top down. In hydroponics, keeping the root zone cool enough is always a challenge. If plants like it to be 85, roots prefer closer to 65. Those are not exact numbers, but you get the idea.