Greenfig,

Nice experiment that you have going here. It will be interesting to see the temps on a sunny hot day! Tks for sharing your info.

Sure, Mark.
Now I am more curious than before to try with the real soil. I think the results will be different because the soil density and heat capacity are different.

Greenfig,
Thanks for posting the results.
I'll be watching for updates and future experiments.

You know something that might need to be compared is the soil temp inground compared to the containers.

green, now that you have the equipment, may i suggest another test? i think it would be very interesting to measure the temps in two identical pots, one on pavement, one on soil. i have been warned about placing pots on pavement.

Just read back thru and saw that. Your doing a great job!

Hi,

Here is the results of the Test 2. It is very similar to the Test 1, the only difference is the weather. It was very sunny all day, very hot with max temp at 36C or 97F :(
Today was a perfect day to bake my imaginary figs..

To remind the setup: 3 pots are on the concrete on the South side of my house filled with the dry sand.
The data collection is every 5 min from the sensors buried 10 cm in the center of the pots. The control sensor is in the ground at 10 cm depth.

Max temp for the fabric pot: 51C or 124F
Max temp for the terra-cotta pot: 46C or 115F
Max temp for the plastic pot: 50C or 122F
Max temp for the unground sensor: 30C or 86F

The best performing pot is terra-cotta, the worst: fabric.

Now I feed sorry for my real figs that are about 5 feet away. They are not growing fast enough and now I know why!
I am surprised they are not dead. It is the time to save them. 

Please see the figure attached.

Tomorrow I will add the 1/2 gal of water to the sand and that will be all for the sand. I need to buy a bag of soil to try the soil on the concrete and on the grass.

Wow, the forecast today is 37C or 98.6F and those high temps are going to be around all September.

Hi again,

Please see my final report on the temp testing in the silica sand.
I joined all 3 test (today's and the previous ones) on one plot.
The Test 3 was with the water saturated sand that I added last night, the pots were still on concrete.

The results are very interesting for me.

Some points:
The atmospheric temperature was higher than yesterday (see the green line for the soil temp) but the pot temps were much lower! My explanation is that the water evaporation cools the media down, by a lot!  And in different ways for different pots.

The largest impact was on the fabric pot. Its highest temp today was 35C vs. 52C yesterday! Wow! That is 13 degrees!

The terra-cotta dropped 6 degrees (40C today).

The plastic dropped only 4 degrees (46.5C today).

So, if you want to keep your figs happier in the hot climate, water them well! 

It seems there is a huge benefit in growing the figs in fabric. They provide enough oxygen and cooler when watered.

The black plastic pots need to be shielded from the sun, the plants will just cook there.

I will try on the grass and with the real soil next.

Enjoy!

P.S. Two figures attached are the same but one is larger if you want to see more details. It is better to do this in a separate window. Or as snagplus is saying:
TO ENLARGE THESE PICS, MOUSE OVER, RIGHT CLICK, OPEN IN NEW TAB OR WINDOW

Thanks for the sharing.This place takes a step further with your analysis
probably thats why the japanese di it like in the picture with fabric supported by plastic pots like the ones used for chicken live stock.

Thanks, Eli!
Interesting idea, and a cheap one, fabric in plastic crates.

Found it on ken love website http://www.hawaiifruit.net/

http://www.hawaiifruit.net/figstation/index.html 
I think we should do the same experiment and compare the state among different pots.

Good experiments require a good preparation :)
I discovered that it was a little challenging to find different 3 pots of similar shape and size in my area (without going far and order online paying extras).
But hay, it is all fun now since I know how to do it :)

Even more, yesterday I found a way how to get 5 min interval data from my local weather station about a kilometer away so now I can compare the soil temps with the ambient air temp.
Care for an extra line on the plots?

probably a direct relation?

Almost direct, you will see a delay at night since the air temp cools down quicker.

Great information. Keep up the good work!

Thanks! 
It is hot like hell today.
I didn't have time to get the soil and just put the pots with sand on the grass and watered them.
I will post the wet-sand-on-grass results tonight. Stay tuned!

Ok, here is the last sand measurement plot!
I joined all 4 days in one figure.
The today's numbers were collected on the loan grass and, as you have already probably known, you figs are the happiest there!

Looking at the green line of the soil temps you can tell that today was as hot as yesterday, which allows you to directly compare today's grass with yesterday's concrete temps.
The difference is huge and the temps for the terracotta and fabric pots are very close to the soil temp.
The plastic pot temp sucks big time. Although it is still lower than on the concrete, it is much worse than anything else.

My thoughts: People always go around blaming one pot or another but at the end it seems the cheapest one wins (i.e. a black nursery ).
I think the pot selection should depend on your climate. I don't think mine in LA would be suitable in the same way in Maine, for example. The temp, precipitation, and humidity are totally different. As you can see from the plots, the watering and the pot placement location make a huge difference too. As far as the soil selection goes, I will try to test it during the next few days after I buy some soil.

As before, as snagplus was saying:
TO ENLARGE THESE PICS, MOUSE OVER, RIGHT CLICK, OPEN IN NEW TAB OR WINDOW

Greenfig, Thanks for your hard work with this experiment! Your results were quite surprising and I learned a lot too! :D

GreenFig, Keep the data coming! Really good comparative information for one and all. Tks

Greenfig,
Thanks for the experiment and the updated data.
One benefit of the black pots on concrete that may not be evident...
The tree is automatically pruned by the heat, the root growth is decreased, decreasing the vegetative growth. This helps keeps the trees smaller for those who are growing in containers ; )

If your still doing more tests, I'd like to see the black nursery pot on grass but shielded with reflective material (aluminum, or white paint, etc).  Thanks for the great info!

Nice experiment! It was very educational.