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Old Apr 6, 2017, 4:44 pm   #11
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Name: craig
Southern, Michigan USA
Join Date: Apr 16, 2010
Posts: 199

Re: Soil Temps

I've honestly never cared or even looked at soil temps. I base it purely on the weather. It doesn't take much at all for blacks to start.
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Old Jun 27, 2018, 1:16 am   #12
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Name: Tony
Southern, Indiana USA
Join Date: Jun 26, 2018
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Re: Soil Temps

Originally Posted by Frank View Post
When we lived up north I tried to track the relation between ground temp and morels showing up. I used to take temp 4" deep and I would check it ever couple of days.

Never found a sweet spot of preferred temps for morels.
I've seen the morels start when ground was still in low 40's, and some years not until 50's.
Unfortunately it's not that easy...
In a Missouri experiment, which took 15 years, they had very good results by counting 410 Degree Days in 20 days before the morels fruited. That's DDs soil temp. (not air)
That's easy, isn't it? Actually doing so is far less easy...

To know the DDs over 20 days you obviously need to measure temps for 20 days. The problem is that you never know when those 20 days start. If you knew you wouldn't need to measure and just mark 20 days later on your calendar

So you may need to start taking temps 10+20=30 days before you think the season starts. Maybe the season starts 10 days later than expected and you end up measuring 40 days.

At the very minimum you need the high and low of the day to calculate the DD for that day.
That's 40x2=80 measurements.
But when are the highs and lows? You don't really know, so you need far more than two. Likely every hour. That's just impossible. So a simple but good $10 thermometer won't work. You need a fancy logging thermometer that tells you the high and low.
And that thermometer needs to be in the soil permanently for say 2 months.

High and low is ok if the temps are stable. But not so good if they bounce all over the place. As an extreme example: 35F all day long, except for a 1 hour temp peak at 55F. Is that really an of average of 45F? Or is ((23x35)+(1x55))/24=36F a more realistic average?
So your thermometer needs to log temps every hour.

Assuming a fancy thermometer you still need to make 40 trips to get your daily readings.
Unless your thermometer calculates DDs, or can log many days of temps.
If such a thermometer exists, it likely quite expensive. But worth it because it saves you 40 trips. That's a lot of time and gas.
But even such a thermometer doesn't save you all the trips. You still have check if you (nearly) reached the 410 DDs.

If your hunting grounds are 20 sq miles of burned forest on level ground you just stick your thermometer in the middle of it. That will be enough, because soil temps will be the same all over the area.
But most likely your hunting grounds are 20 spots; and look like this:
- Spots on a south and north facing slope.
- Shady and sunny spots.
- Spots without leafs and spots that are packed with leafs.
- A spot with stable moisture near a creek, and a not so stable spot on a hill. ->Different soil (moisture) means different response to heat.
- A windy spot and a spot without wind (dries out soil)
- Etc
- Etc

That means you need a thermometer at each of your 20 spots ($$$). That's a lot of data to collect. Until a turkey hunter shoots it to kingdom come, or a deer steps on it.
Not to mention 20x40=800 trips at minimum if you don't have a fancy thermometers.

The method described above proved to be over 84% accurate. The years it failed had very mild winters. There is a solution for that...
Count all days in January and February that have temps above 40F.
If more than 20 use the method described above and add a certain number of days to the predicted/calculated date.
That means another 2 months of measuring soil temps.

So.... if you had 100%, total, ultimate trust in that method, would you take all the trouble and do it?
If you do it as a hobby likely not (costs, time). If you do it for a living and find truckloads maybe you do; but only when using fancy thermometers. The reason is obvious. If you have to check your thermometers daily, you can just as well look for Morels...

In another thread I requested historical soil temps so I can compare methods in a spreadsheet. If all those methods point to about the same day I start to trust them. Then I would pick the method requiring least work.
The online data (used by farmers) may be state of the art, it never accounts for your leaf covered spot in the sunny, moist, hidden valley, with its own soil temp. The soil-temperature zones on those maps often are the size of half a state or much bigger, and don't account for a shady spot below some evergreen shrubs.
So I would try to figure out a way to take a few temp reading on the spot and adjust the online readings. So, for example take a few readings at the most strategic spots during the weekends and use the difference to correct online values.

And after a lot of temp readings I hope that I may draw conclusions about the online data and my own measurements. For example: The temp at spot-X is always 4F below the online temp. Or the temp at location-Y is always the average of the temps listed for two nearby towns..
In that ideal situation I could do most things from my PC; and only take soil temps if I'm in the forest anyway.

Last edited by Morelist; Jun 29, 2018 at 10:25 am.
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Old Jun 27, 2018, 8:46 am   #13
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Name: Sharon
Southern, Michigan usa
Join Date: Apr 23, 2006
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Re: Soil Temps

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