They're all root bound, thanks for the help.

The answer for me personally is.....don't grow corn in a 5gal. bucket.

Can you lift them and put them in a tub of water?
If you can, let them soak for an hour or two every few days.
Another approach would be to use a drip system which would lessen the soil compaction.
Is the only problem the compacting of the soil?

I'm not sure why you say it's obviously wrong and the soil is compacted...if the plants are growing well I wouldn't worry too much.

The best way to make sure they are periodically thoroughly watered is to set each bucket in a larger container which holds enough water to come 1/2+ way up the bucket with corn in it. Water the corn, allowing the corn to sit, partially submerged in the reservoir for a good 30 minutes.

But I'm not sure you need to...

They're all root bound, thanks for the help.

My other half has been growing plants in pots, up to 1/2 whiskey barrels for decades and no matter what mix, usually combination of top line bagged potting soil and garden soil, with a few variations, and it -- always -- compacts without exception.

If you have a 1 inch gap at the top just fill the pail to the top and the water will drain into the soil; I have done this for as long as she has had large pots.

They're all root bound, thanks for the help.

They're all root bound, thanks for the help.

They're all root bound, thanks for the help.

The shade of green on your leaves show a lack of Nitrogen but they are showing more effect of poor irrigation.

Improper Irrigation
Sweet corn needs ample water to produce ears, but inadequate watering may also affect the leaves. Corn that does not receive enough water can dry out, and the leaves will turn brown and crack. Sweet corn requires at least 1 inch of water per week, and ample water is essential during the hot months of July, August and September and when silks appear.
--
High-temperature stress is usually associated with drought. Heat stress and drought intensify damage to corn and soybeans but either may cause major crop injury alone. The recent high temperatures, i.e., record numbers of days above 90° F, and in some locales 100° F, have generated questions about the impact of high temperatures on corn and soybeans.

How much heat stress can these crops withstand without incurring major yield losses even when adequate soil moisture is available?

Corn originated as a tropical grass and can tolerate exposures to adverse temperatures as high as 112° F for brief periods. Optimal daytime temperatures for corn typically range between 77° F and 91° F. Growth decreases when temperatures exceed 95° F.

Give them a NITROGEN heavy fertilizer and a lot more water.
Those pails will heat the soil, shed water, evaporate from soil, at a rate exceedingly above soil planted.

They're all root bound, thanks for the help.

They're all root bound, thanks for the help.

Corn does not like to be crowed and you probably also have too many stalks in each pail.

Corn planted close, in ground can send roots side ways as fars as it chooses, in a pails/pots roots fight each other with negative results.ed
Having grown corn for decades your shows signs of lack of water and nitrogen.
Besides nitrogen, chelated liquid iron would help your stalks.

Give them a heavy dose of liquid fertilizer (when I worked at the Minn. Zoo, we gave all potted plants doses of fertilize way, way above label doses every week).

They're all root bound, thanks for the help.

At this point leave the three and see what happens.

Water flushes fertilizer out of pots quickly,

Fertilize at your level every other day, IF, you are using liquid fertilizer.
If water drains out of the drain hole, water every other day.

What system are you using for watering and fertilizing?
When I fertilize, I fill and spray can or pail with water, dump in liquid fertilizer till I say , that looks good and apply liquid to plants.

They're all root bound, thanks for the help.

Put the entire 1.5 gallons in each pot instead of watering with the hose once a week.

Would one plant per pot work better?

I wiggled a corn plant out of a bucket dirt intact and found it was root bound in 13" of dirt. So all of my 5gal. bucket corn is root bound.

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Then do as I said, water and fertilize often, the roots will still absort it but they only have that to live on.