Learning from past mistakes - Watering crops

Somewhere along the way I learned that when you make a mistake, it's best to admit it, try to learn from it, and do better in the future.  I've made a lot of mistakes (and there'll be more, I'm sure) since I started monkeying around with organic vegetable gardening.  Remember that scene from Zoolander where Hansel and Derek finally realize, "It's in the computer........!"  That's reasonably close to how things have gone for me with trying to work toward sustainable, self-sufficient organic gardening.

Rather than have a number of incredibly long post threads, I'll do a series of, hopefully, shorter ones on a variety of topics where I've screwed up and what, I think, are ways around them.  Or, at least, my attempt to improve in the future.
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Plants need water.  No doubt about that.  The question -- and it's an important one -- is how much do they need?

As I mentioned before, my parents have a 20'x20' garden.  My father waters faithfully when they have something they're trying to grow.  Grass, veggies, household plants, it doesn't matter -- that stuff is getting W A T E R E D.  For the garden, it seems like it's 7 days a week for 1/2 hour via a pulsating sprinkler head.

With my garden plot (and also when I was doing square-foot gardening in the backyard), I tried doing the same.  I found that there are right and wrong ways to water.

Lesson 1: Be careful when you water
Last year when I was screening the soil and sinking my garden boxes, I didn't want to work in mud.  As a result, I held off on watering in the summer (I didn't have spring crops) until I was about done at the plot.  1/2 hour before I planned on leaving (generally at dusk), I pulled out the hose and started watering.

Many plants (notably tomatoes) developed some fungus problems.  After doing some research, I learned that watering late in the day gave insufficient time for above-ground water to evaporate.  Water still on plants themselves can create fungi.

Lesson 2: Don't overwater.
As I said, my dad faithfully waters his plants.  He and I have joked about it: if in doubt, water it.  I learned that that doesn't work in my back yard or plot, though.

This past year, it took me a long time to identify my problems at the plot.  Complicating matters is that I had a lot of issues compounding one another.  One baffling problem, though, was why my tomatoes and cucumbers did very little and looked very sickly.  The cucumbers grew to approx 1' tall then stopped.  The tomato plants always looked yellowish.  A number of people at the plot would walk by and "helpfully" boast that I was doing it wrong and that I had _________ problem.  The most common diagnosis was a nutrient deficiency.  Well, I tried a number of different organic means of fertilizing in addition to the already well-aged plant compost I'd mixed into the soil when I first populated the boxes.  No improvement.

The proverbial light bulb lit up, however.  In reading up about my plants, I found that many of my problems could possibly be attributed to overwatering.  I was watering each area in the box with a wand (water the roots, not the leaves) for approx 30 sec a nervous minimum of three times a week.  If your hose puts out even 10 gallons of water per minute, that's a lot more water than the plants really need.

I cut back on watering to twice a week and the plants improved markedly.