Growing corn, organically, is less about what "fertilizer" to use and how often and more about getting the soil into a good healthy condition that will grow that crop. What was done last fall to begin to prepare this soil for this crop?

What is the soil pH?

What major nutrients are there?

How much organic matter is in that soil?

Con grows best in soils with a pH of 5.5 to 7.0 that are well endowed with organic matter and is evenly moist but well drained.

kimmq is kimmsr

Corn is a very heavy feeder. Kimmq is right, the best option is to get the soil tested and amend accordingly. However, since not everyone is going to do that here is a generic suggestion. A couple of weeks before planting, prepare the bed. Add a complete organic fertilizer that has been formulated for tomatoes / vegetables or is labeled "all purpose". The package will tell you how much to use. Mix it in to the top couple of inches of soil. I like the Down to Earth line, but there is also Dr. Earth, Fox Farm, and Espoma to name a few brands.

Plant your corn 2 weeks after last frost date. Around July 4 scratch in another feeding into the top inches of the soil. You can use the same vegetable formula, or if you want to be more targeted use one designed for promoting flowers and blooms. (It will have a higher phosphorous number than the general purpose fertilizer. P doesn't stay in the soil for long, so it needs to be replenished.)

Be sure to mulch to prevent weeds and retain water.