LV,
The amount of water compared to the number and size of the pots doesn't seem to be much different from I do (if I converted metric to US close to correctly!) but it depends on how often you do it.
Most of my technique is based on growing in dirt for decades. The first thing I learned, at maybe six years of age, was that it is better for plants to be thirsty rather than over-hydrated. It will force the roots to grow stronger. I've gotten to the point that unless seedlings are starting to wilt a tad, I don't worry much about watering them.
I also know that the moistness or dryness of the top of the ground is immaterial. Anything less than three inches deep doesn't count.
Nitrogen is great - early in a plant's life. After that, it does nothing that helps the plant produce more fruit. This is especially true if one adds organic matter to the soil, even more so when it is four-six inches deep. We always sowed winter wheat on the fields where we raised tobacco. We plowed it (roots and foliage alike) under in mid to late April and planted in late May. I have adapted the idea for containers - put a layer of dirt in the bottom, then green leaves and more dirt. Mix it up than keep adding dirt, potting mix or compost until I fill the container.
Thankfully, I don't raise many plants in containers (~40) so this doesn't take weeks to do!
Mike