I don't know that there really is a definitive answer. The amount of fertilizer to use isn't determined by the size of the container, but by the needs of the plant, how quickly those nutrient become available to the plant etc.

This whole business of mixing granular ferts into the potting mix in SWC is sort of a trial and error thing.

I think using 1 cup is probably as good a starting point as any. Just have on hand a water soluble fertilizer such as Miracle Grow 24-8-16. This way if you get to the mid point of the season and the plants start looking like they are having nutrient deficiencies you can use that to rapidly get them the nutrients they need to remain healthy and growing strong.

I would suggest either mixing the fert into the mix completely. The idea of placing it in a concentrated area is fine when you have room (surface area) to keep it away from the roots, but I doubt that will be the case in a 5gal bucket system.

There are a bunch of folks who come around these parts who have done the bucket system so hopefully they will be along shortly to share their experiences.

Just wanted to confirm what JaG said.

I did the 5 gal. bucket system and had very good results with my smaller crops by mixing the food into the soil less mix directly. However, be aware that tomato plants require a good deal more food and you will need to supplement just prior to the mid-point. My own sad tomato plants last year proved that they need more than what I could add to the mix at planting time.

This year, I plan on taking JaG's advice and supplementing with a WATER SOLUBLE liquid fertilizer directly into the reservoir at 1/2 strength once per week while keeping the reservoir filled with water as needed.

Donna H.

I have some experience with the 2 four gallon swc, but only with broccoli and cherry toms right now. I'll be testing beefsteak varieties this coming spring - so I should have more data then.
Although I would certainly say that broccoli and tomatoes are completely different veggie plants, their needs should be pretty similar. For the recently grown broccoli, I mixed 1/2 cup of Osmocote into the top 2" of soil at the time of transplant, then another 1/4 cup once florets began to form. They performed beautifully, and the roots were amazing.....

EG

EG: Do you cover your SWC's?

I covered mine last season but am thinking that it would be easier to 'work the soil' for fertilizer application if it was uncovered -OR- covered with an organic type of 'mulch' where I could just push it aside.

My tomatoes grew really tall last year, but the foliage was sparse and they were struck with some kind of fungus. I thought it was early blight, but perhaps not. Anyway, had the plants been fed sufficiently, I'll bet the plants would have fared pretty well in health and subsequent yields.

When I pulled the plants, the root development was very good...and they weren't pot-bound so changing up the soil mix (to avoid compacting) and adding a boost of food should help tremendously.

I sure hope we get a decent growing season this year. I don't think I can take another one like last season...ughh!!!

Donna H.

I have hard water so I am forced to acidify my water. What I do is every watering is done by half strength water soluble fertilizer. I add about 2 teaspoons of it per 5 gallon instead of 5 teaspoons then I add white vinegar to adjust the PH of the water down even more into the low 6.0s.

I would get a PH meter durable to find out the PH of your water and the runoff from the containers. Having an optimal PH will help your plant greatly, and make the plant able to absorb the needed nutrients.