I think you're forgetting one important thing, and that is the concentration of nitrogen that is in your foliar spray. Applying 1 pound of Nitrogen dissolved in one gallon over 1000 square feet would yield a different result than applying 2 pounds in one gallon over 1000 square feet. This is a really interesting question actually, and it made me go look up a few articles. I'm certainly no expert, but here's what I found:
-The maximum amount of foliar nitrogen that was going to be taken up by bentgrass greens in studies was taken up within the first four hours. After that, you could basically wash the leaves off with irrigation, thereby washing the rest of the N off of the leaves
-The foliar nitrogen seemed to have a higher absorption rate in more relatively humid climates. They postulated that when the droplets dried, they were no longer available for absorption.
-There is a maximum amount of N that can be absorbed, and a maximum amount that can be applied before turf injury occurs. The recommended amount appears to be in the range of 0.1 lb of N/1000sq ft.
-Urea seems to be the most preferred choice of N source to mix in a foliar spray
-The amount of N actually measured to be absorbed by the turf was between 30-70%
-There are no current head to head studies comparing root absorption by Nitrogen salts vs. foliar sprays
Here are some articles for your viewing pleasure:
Thanks for bringing this up. I think it would be awesome to have a better understanding of how to possibly incorporate this better in a home lawn setting. It appears that the more frequent applications of lower rates of fertilizer (spoon feeding) act almost like a slow release fertilizer, feeding the turf steadily over time. It's just that you're controlling when the release happens.