Stay away from high-nitrogen fertilizers such as urea, ammonium sulfate or fresh manure, which will help produce dark green, tall tomato plants but fewer tomatoes. Phosphorus. Phosphorus (the second number in the N-P-K ratio) encourages flowering, and therefore fruiting. Potassium.
Keeping this in consideration, what type of fertilizer to use on tomatoes?
Choose a fertilizer that has a balanced ratio of the three major elements, such as 10-10-10, or where the middle number (phosphorus) is larger than the first number (nitrogen), such as 2-3-1. Tomatoes are heavy feeders and usually do need fertilizer unless your soil is very rich.