For tomatoes it's recommended that you add lime or dolomite to your potting mix.

I'm also struggling with the tomato-in-container fertilizer issue because I'm using the Earth Box which deviates from normal fertilizing practice.

I don't think potting mix necessarily has fertilizer. You should add fertilizer even the first time around, I believe.

Anyway, for tomatoes, the K of NPK - potassium, must be as important as the nitrogen since you want to grow large tomatoes and not just leaves. At your gardening center you'll find fertilizers recommended for tomatoes with instructions.

Thanks. My question was kind of a crazy one to start with. Trying to decide if I should dose it good at the start with XXX and then add a TBS of XXX every week, 2 weeks, or monthly. Or even more often. Guess the plants will let me know if too much or too little. FWIW, I grew two 6 foot tall tomatoes with MG potting mix with NO added fertilizer. That is contrary with standard opinion around here.

In conventional containers, low doses at more frequent intervals are MUCH to be preferred to extra high doses at any time. The amount of fertilizer (actually, the total amount of solubles in the soil solution) has a DIRECT effect on how easy/difficult it is for the plants to take up water and the nutrients they need that are dissolved in the water. Too much fertilizer and your plants will die of thirst in a sea of plenty.

I looked at your original question, but decided it was kind of like asking, "How much gas will my car use in its lifetime." ... tough to answer.

Al

Thanks Al. I want to bring this discussion to and end. I would however say that most farmers any more, do exactly that. They know how much crop they shoot for, how much fertilizer is needed and even use a GPS to distribute it so not to waste what is not needed.

That's true, but they are working with a soil that for the most part retains nutrients. They also have the benefit of field/crop studies showing how much of a nutrient is removed from the fields by a crop, yield curves at various nutrient rates etc.

In a container I don't know how to calculate the same thing. Most of the nutrients added are lost with watering. To the extent the nutrients are water soluble they run out the drain hole with the drain water.

If one is using SWC, it's a little different in that there doesn't have to be any run off loss.