Im no expert only a amature trust me!
But this is partly what i understand .
Ottawan,
here is what he says about plastic cover,
The plastic covering stays on all year. The only time I take it off is to fertilize the plant, then I put it back on. The cover is 3 mil plastic but thicker would be better. The plastic cover has two purposes: first, to seal the pot so no water escapes (see wicking system in the presentation) and it helps to warm the pot (figs like warm soil).
He has 2 holes toward the bottom of pot not 3, one hole has hose fitting for filling with water the other hole opposite of hose fitting is an overflow which tells him when to stop filling bottom of pot with water.
With so many trees to water for HIM its much easier this way to get them all watered as opposed to watering them from the top like i do my container grown trees.
His way the tree sucks water from the bottom upwards not from top to bottom as most do .
The pvc holds water when filled and would also support weight of soil resting on top , he uses a screen with burlap on top to help stop root growth from clogging the system as he explains. He fills with soil and as noted there are 3 voids of space around those pvc tubes where the soil actually goes to bottom of pot as he states this and can be seen in his pictures
There are three places where the dirt goes into the water (for wicking purposes).
Ottawan im not sure if plastic would be good or bad for your pots.
Steve, yes i actually had a small container that i grew flowers in and it sat on patio few years back that performed a similar function as his method, it simply had a place for the hose to fill at bottom with water and a drain hold also to let you know when its filled up. The water would be gone after several days as pot sat on hot patio due to evaporation from heat thru bottom sitting on hot cement patio in summer conditions. There was a plastic type screen that sat above the water line several inches above bottom. The pot eventually dried out and cracked as most due every so many years.
I noticed he mentioned his pots have life span of 20 years so his are very well made.
Your very right fig plants do not like wet feet, i dont think his have wet feet as the water is drawn upwards as it seems the heat source is actually from the top with the sun beating down on the plastic cover and also the sides. What i think helps in not keeping the feet wet in his pots is those 3 spots where the dirt goes to bottom of pot to draw water upwards.
I could be wrong but this is what i gather from his explanation of his way as i do the opposite from top downwards and get my heat source from cement patio which helps draw water from the top downward when i water mine. In summer every other day my pots are drying out and i use a 5 gallon bucket for each one to water, when temps get into high 80s or 90s i have to use a tree root feeder to give them a good soaking.
They do love the heat in a pot and the full sun beating on them long as i can keep up with the watering. Also with mine i keep the tree's smaller than his (more pruned) simply to allow space for storage and not to get poked in face when moving them .
Truly if i had as many big potted plants as he does i would use his way of watering them because i would never be able to keep up with them come summer and im sure his keeps him busy!
I only wish i could afford the greenhouse he has to extend growing season but its just not feasable for me .
In the end i think his way works excellent for him in his situation and will help some here that grow a lot of trees in pots if they choose that route.
He surely must be a strong person when it comes time to root prune as i have shown in some pictures i posted its a lot of work and i only did 4 trees.
Best Health