I guess you could use the guide lines on the fertilizer container you buy .What size buckets ?

Fertilizer spikes are a very inefficient way of delivering nutrients so they would not be my first choice. You could try something like Osmocote 14-14-14, which is an all-purpose controlled release product that is appropriate for any container planting. The problem is CRF's are activated by soil temperatures as well as moisture so they should be incoporated into the soil mix before planting - their effect will not be nearly as efficient or effective if applied to the top of the container after the fact.

This product lasts 3-4 months depending on temps, so reapplication may not be necessary, depending on your crop and growing season. Follow instructions on the label for rate of application.

Because you have no control on how the nutrients are dispersed from this type of product, you may not be supplying what your plants need when they need it or at the appropriate levels. Many container gardeners who do use CRF's in their soil mix initially also supplement with a liquid fert (like MG or Dyna Gro) that supplies all necessary trace elements as well as NPK.

alamoo- I'm using Lilly Miller 18-6-12 time release fert in all of my swc's and some of my buckets. I like the results so far. I'm using at half the recommended strength which is 1 tbs per 2 gallons of mix. Here is a couple pics, one of a swc and one of my buckets, both with the LM 18-6-12 at half strength.

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Damon

I'd much rather see you use a slow release product such as mentioned above than spikes. Not only are they ineffecient, as gardengal says, but can actually cause root damage and even fertilizer burn.

But not why look into one of the zillions of granulated fertilizers on the market? You can probably find a perfectly good product right in your own garden center. And there is no 'best' tomato fertilizer. Granulated products can be top dressed or lightly stirred into the container after planting.