wolfcry
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Soil vs Air Temperature?

Hey all,

I wasn't sure where to put this so I put it here. For the life of me I cannot remember how the two (soil vs air temp) differ.

Meaning, if your soil is 80 degrees, is your air the same temperature, lower or higher and how does one average it out?

I've searched and searched and searched. Even dug up some old science books but I just can't seem to pin point this and it's driving me insane lol.
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tomf
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The soil and air temp may not be the same. The sun and air heat the soil so soil in the shade will be cooler than in the sun. As air looses heat easy and soil being more massive holds it the soil will be warmer than the air at night. Often the air is hotter in the day than the soil.

DoubleDogFarm
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Temperature at what depth?
Bare soil or mulched?
Water content?
Soil in different colored containers.

I would think all of these make some difference.

Eric

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rainbowgardener
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As tom said, air temperature is much more variable. Soil holds heat and gives it back at night or later in the year when things are cooler. The farther down in the soil you go, the less temperature variation. The caves around where I am stay at 55 degrees year round, which is our mean temperature for the year.
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tedln
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Soil is a heat sink at the surface and it has a constant temperature at a specific depth. The sun and ambient air temperature warm the upper few inches of the soil in the summer depending on if the soil is shaded or covered with mulch. The cold air and ice of winter cool or even freeze those upper few inches. Below the upper few inches the soil temperature doesn't change as rapidly as the upper few inches with weather changes, but it will change eventually. It depends on how long the ambient temperature is either hot or cold. Going farther into the soil, the temperature doesn't change year round. Since heat rises, the lower soil will eventually warm the soil above even in cooler weather.

It seems to work best if you can cause your plants to develop deep roots to take advantage of the more available minerals, moisture, and moderated temperatures. With deep roots, many plants will appear to wilt in the hot summer sun. They can not move enough moisture through the plant tissues to replenish the moisture lost through the leaves due to the extreme heat. Overnight, with cooler air and lower transpiration through the leaves, the moisture content recovers and the leaves usually look normal in the morning.

I always attempt to plant transplants deep to take advantage of the more constant soil temps and more constantly available subsurface moisture. By limiting the amount of moisture and mineral nutrients I apply from the surface of the soil, the roots tend to develop deeper in search of moisture and nutrients. They also remain cooler in the hot summer sun.

Ted
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wolfcry
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Thanks for all the help and replies guys. It's helping quite a bit.

The reason I'm even hitting this subject is because I was recently reading an article pertaining to gardening and temperature control, but the values differed to such a degree it didn't make sense.

For example, in one part of the article, it was talking about cucumbers and it said that cukes grow best when the soil temp. is 80° - 85° F with an air temperature of 70° - 72°F temperature in the daytime.

How can this be? Wouldn't that air temperature mean the cukes were growing in the shade if the soil was that much higher than the air around it? I'm not even sure the soil could get that high in the shade unless it was an extremely hot day. Also, Cukes require full sun to grow, so this I'm not understanding.

Unless I'm missing something here, those numbers seem way off base. That's why I was trying to figure out the differences of soil temp and air temps to try to get an understanding of where they were coming from.

Again, thanks for the help!
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DoubleDogFarm
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Is this a online article? What is the title? Maybe we could look it up and read. May help.


Eric

tedln
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I have spring planted and late summer/fall cucumbers growing right now. I plant my spring seed while the soil is a little to cool for the seed to germinate. It sometimes takes two weeks. The plants grow slowly until the air temp is warm enough on average.

The fall plants are planted in summer heat warmed soil and germinate in about four days. The plans grow vigorously and start producing quickly until first frost. I've never checked the soil temps when I do it. I just allow nature to determine when it is ready for the plants to germinate and grow.

Ted
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