Good post, Rick!
A note about "too much": it's almost impossible to get there with compost, well-rotted manure, or other slow-decomposing organic matter. Where people get in trouble is by adding nutrient sources that are too harsh (often described as "hot") such as fresh manure or high-NPK chemical fertilizer.
In my garden, I like to get most of my nutrients from compost and plant matter, but when things need an extra boost, I'll add a bit of pelleted chicken manure. The NPK (Nitrogen-Phosphorus-Potassium) varies a bit by brand, but is in the 4-2-2 to 5-3-2.5 range. Compare that to Miracle-Gro at 24-8-16, and you can see why one is so much easier to overdose than the other!
