My understanding of Earth Boxes is that a tight fitting plastic film cover is an important part of the system.
With the cover in place, evaporation at the surface is minimized and water retention maintained. Water level should never fall beneath the level of the wicking system, and overflow holes prevent overwatering.

TJon

But will the results be better than a good container with a good mix?

Impossible to answer. There is nothing stopping one from using a 'good mix' in an earthbox. How do you know where the PWT will be?

There won't be one. Well, practically speaking there won't be one as the mix will never dry out. There is no excess water to drain away as all water is introduced from the bottom and works up via capillary action. If you have a small container with soil in it for the wick, the water will only wick so high right? Will the top layer get wet enough From humidity in the box?

Assuming the potting mix can wick at all, it will wick to the top. The limiting factor is evaporation and if the top inch or two lose water to evaporation faster than the media can wick it up, then the top will be dry. This really is only an issue with young, shallowly rooted plants in a super coarse media comprised of materials that wick poorly. Once plant roots go deeper it's a non issue and with earthboxes it is a complete non issue as the top is covered which sharply limits evaporation. It sound to me that you would want to keep the reservoir kind of low. So the PWT is as low as it can get?

With an earthbox the water reservoir should be filled to capacity in order to extend watering intervals. The height of the water in the reservoir will have no noticeable impact on anything other than the watering interval. The concept of a perched water table is irrelevant in a self watering container where the idea is to keep the mix evenly moist at all times. I am sure Al would disagree and point out that a fast draining, well oxygenated mix is still the way to go. And I am sure that there is still a perched water table. It's just that it really doesn't matter in a self watering container. Oxygen is introduced in the bottom of the media via an aeration screen so the area that typically suffers from low oxygen doesn't in an earthbox.

I don't think earthboxes are the be all, end all of container growing, but for annual plants, particularly veggies, I think they are terrific and work well. Go ahead and get one or two and try it out.

Just follow the instructions that come with each box and you should have no trouble getting great results.

Thanks alot justa. Some of the things I read were very positive. Some said the vegies did not grow any higher than a container with the same mix. Some said they did better. I should try it just for yucks. But I will make my own. Filix