Watering volume per planting (rather than by 'inches')
Since I only grow a few plants (6 plants in my community garden, and a few more in my back yard where I rent) I was wondering if someone can help me estimate watering needs based on plant rather than "inches", since using a soaker/drip irrigation system isn't really worth the effort and cost for me. If I know about how much water I need per plant, I can simply hit each one with a watering pot each time I water them. Waiting around in the community garden for 1 - 2 hours for a soaker hose just doesn't make sense, even if I wanted to spend the cash on it. Currently I just lay a hose spray nozzle turn to low output at the base of the plant and let it soak the ground for 1-2 minutes, but this seems kind of wasteful and not very consistent.
Each plant is spaced about 20 inches apart in a hilled up row (1 ft wide) in a raised bed (I would say 2 1/2 feet of soil depth in total), and has its own small crater where water can accumulate. I have them mulched with burlap. I would say the soil is fairly loamy, maybe even a bit on the dusty side, and reasonably well drained but absorbent.
If a cubic foot of water is 7.5 gallons, then an "inch" of water would come to about .6 gallons per square foot of ground space. So I am guessing that about 1 gallon per plant space per watering, applied slowly enough to soaks in without running off, should be enough to get the soil moisture right without flooding the plant or watering too shallowly. Based on the soil parameters dimensions, does this seem like a good estimate?
Since advice always tells you to "water deeply" it seems to me it is best to base watering volume on spacing/soil characteristics, and then chose when to water based on how dry the soil feels according to the finger/stick test. Is there any flaw to my reasoning here?