The best way to apply a folar feed is to use a liquid and spray on the foliage, as the term implies.

Nonetheless, corn is a heavy N feeder and it is far better, in the future, to prepare the soil properly.

Dan

There are a number of reasons why the foliage of any plant might turn yellow and a soil that is too cold could be one since a too cold soil will prevent the plants growing in that soil from getting the nutrients they need. In this instance foliar feeding will not help.
If the leaf yellowing is caused by a soil nutrient deficiency foliar feeding is a short term aid, but that soil problem needs to be corrected for the future.

I assume you are concerned with saving your crop, and you will deal with soil issues later. Yellowing leaves on corn stalks is almost always a sign of a nitrogen deficiency, of which corn is a very heavy feeded. Foliar sprays, like fish emulsion do not contain enough nitrogen to correct a deficiency, let alone quickly, as the situtition seems to indicate. They are a great "pick-me-up" during the growing season.
I would quickly side dress with blood meal or feather meal, work it into the top inch or so of soil, and water well. You should see a difference in a week or two.

Ron
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Yellowing of leaves on any plant may be a sign of Nitrogen deficiency but a number of other nutrients can also cause chlorosis, yellowing, of plant leaves. The chlorosis could also be from a Potassium, Magnesium, Zonc, Iron, Sulfur, Boron, Manganese, or Molybdenum deficiency, or maybe the results of a too high or too low soil pH that keeps one of these nutrients from being uptaken by the plant.
That every plant problem is related to the soil is a basic tenet of organic gardening, so when there is a plant problem the soil is the first place to look for the reason.