I use it only for seedlings and containers at planting. As for how often to use it in raised bed... hmm what your tomatoes look like... how is that lack of nitrogen shows...
here is best article I know about soils ...NPK levels are only small part of tomato growing
http://foliarsprays.com/en/mineralized-soil.html

Several things:

First raised beds that have to be watered daily? Something in wrong there. Even in the heat of the deep south a raised bed seldom requires daily watering. Frequent shallow watering only encourages shallow rooted and water dependent plants. So can you clarify why you feel they have to be watered daily?

Second, nitrogen always tests low even with a professional soil test - in fact most of the labs don't bother to test it - simply because it is so volatile. Home test kits are exceptionally unreliable.

So great care is usually cautioned against going over-board with making corrections based on home test kits results and even professional tests will make only minimal recommendation on adding nitrogen since too much N is worst than too little in many ways.

Third, while the Fox Farm product is fine the "with each watering" instructions is normally intended for plants grown in containers where the nutrients can leach out every time you water. Even then one often sees the recommendation for diluting it to half strength.

So a raised bed dosed with 6-4-4 every time you watered - even if it was only weekly - would be heavily over-fertilized. Big bush huge green plants with lots of blossom drop, blossom end rot, and very little fruit production results. Plus you get lots of run-off wasted fertilizer and ground water contamination issues.

The Neptune's product is also quite good and its 2-3-1 rating much more in keeping with the recommended ideal levels.

So one or the other but you sure don't need both.

If I were going to use the Fox Farm I would dilute it to 1/2 strength and give each plant (tomato plants I mean as that's what we are talking about here and other plant needs differ) a 1 gallon dose (depending on plant size) no more often than every 3 weeks. This of course depends on what amendments were added to your soil prior to planting.

With the Neptune's - 1/2 strength dose weekly or full strength dose every 2 weeks. I much prefer the Neptunes.

IMO the secret to proper use of fertilizers is just like watering - taking your clues from the plants themselves - not some fixed schedule. Learn the signs the plant will display of various nutrient deficiency and the symptoms it shows of nutrient excess and when in doubt - less is better.

Hope this helps.

Dave

Here is a link that might be useful: Symptoms of Nutrient Deficiency in Tomato Plants

I shouldn't haven't said raised beds I apologize. They are raised rows in garden and they dry out rather quickly. I dont water everyday but it seems I need to sometimes when it dries out. I would never use the grow big every watering which was why i asked how often I should when it says to use every other watering. Thanks for the info on the soil home kits very informative about the nitrogen makes sense. I will stick with the Neptunes fertilizer!

Just because the surface is dried out, have you dug down 6 to 8 inches to see whether it is dried out there? Part of my garden is also raised rows, and while I might water very small seedlings every couple of days, when I plant tomatoes starts in deep holes I do little more than provide a very good, very deep watering about once a week. I know that at least a part of the root mass from when I initially put them in the ground is at least 8" below the soil surface, and that part of my garden never dries out, particularly as I mulch the surface once the temperature is solidly high.

Yeah I agree that raised rows (aka wide-row gardening) dries out faster but not that much faster. As drmbear said if you are using the soil surface as the indicator for watering then you are over-watering.

I use a soaker hose under heavy mulch on my 3' wide raised rows and once every 7-10 days is plenty for them even in my much warmer and drier climate here.

Please give some thought to modifying your watering regimen.

Dave

Nitrogen level at any given time depends on organic mater one used for the soil, i.e. compost, manure etc and its processing. What I am looking in the plant is a color of green, i.e. green and green is different. Ability to branch out and grow well, push those sideshoots plenty and multiple- that is all telling me I have plenty of nitrogen supply. Generally if I apply good compost- manure either in the fall or early spring, there will be plenty of nitrogen in the soil for plants. Ability of plant to use it generally is not a problem, it is other components and minerals that often are not presented in the form plant can use, even if they are present in the soil. Famous Ca comes to mind.
As for liquid ferts, I recently switched to Urban Texas tomato fertilizer and All purpose TF. When you go on tomato- veggie forum and it has a lot of rave reviews from unedited posters, you know you got a winner.