This is the best educational material I have read about nitrogen. Now I understand why plants can over dose very easy with Ammonium Nitrate 33-0-0 and not over dose easy with Urea 45-0-0. Plants can only use Nitrate NO3 and Ammonia NH3. Ammonium Nitrate converts to Nitrate and Ammonia vary fast. Urea converts to Ammonia very slow. Your soil needs to contain Calcium Carbonate for Urea to convert to Ammonia.
Corn, Cotton, Tomatoes remove nitrogen from the soil.
BEANs take Nitrogen N2 from the air and put it into the soil in a form of nitrogen plants can use.
It is best to fertilize a little every week rather than 1 large dose of fertilizer. Several things can remove nitrogen from the soil.
Get your soil tested find out what it needs. If it is low in Calcium Carbonate Urea will be very slow to convert to Ammonia. You also need to know how much nitrogen is in your soil so you know how much fertilizer to add to the soil.
Ammonium Nitrate is no longer available. Another good choice is Ammonium Sulfate, Ammonium Phosphate, Urea.
Plant BEANS with your Corn & Tomatoes you will not need to buy factory fertilizer.