The first application should be applied one to two weeks prior to when the first tomato ripens. Two weeks after ripening, it's time for the second application. The third round of fertilizer should be applied one month after the second. Basically, there should be one month of time between each application.
Common sources of nitrogen-only fertilizers include nitrate of soda, urea and ammonium sulfate. Blood meal contains primarily nitrogen but is not exclusive. Apply one of the following fertilizers at the rate provided:
Nitrate of soda (16-0-0): 2/3 pound (1.5 cups) fertilizer per 30 feet of row
Blood meal (12-1.5-.6): 14 ounces (1.75 cups) fertilizer per 30 feet of row
Urea (46-0-0): 4 ounces (1/2 cup) fertilizer per 30 feet of row
Ammonium Sulfate (21-0-0): 0.5 pounds (1 cup) fertilizer per 30 feet of row
Alternatively, lawn fertilizer, free of weed killer/preventer, can be used at a rate of 1/3 pound (3/4 cup) fertilizer per 30 feet of row. Choose a fertilizer that is about 30% nitrogen (the first number in the set of three). (Cynthia Domenghini)