The question becomes how do we measure success and the cost to achieve it, and that depends on our objectives. For a farmer, it is largely profit and loss. How much crop can he extract from the land and sell for the highest price vs. his cost to grow it. When the short-term boost from of foliar fertilizer keeps a crop alive long enough for soil amendments to provide nutrients, it can make the difference between a smaller profit and a big loss of a failed crop.
Food plotters have different objectives. One is QDM which is benefitting the health of the local deer herd. On the other end of the spectrum you have attracting deer improving the huntability of the property. Of course, many folks have some combination of these two. The first requires significant scale, the latter does not.
So how do we measure success? Deer eat mostly native foods and these each have their own nutritional value which differs as they go through the natural life cycle. Those native foods, along with the deer herd that consumes them, is limited by the fertility of the soil in the general area as an upper limit. In most places, the herd is further limited by the climate. With the natural cycle, thee are times of bounty and quite lean times. These lean times when quality native foods are scarce is where we can raise that lower limit of herd health closer to the upper limit by filling these gaps with food plots with quality food. This is where food plots apply to the the QDM objective. To have a measurable impact on herd health, you need to turn 1% - 3% of a deer's home range from poor to high quality food during these gaps. So the key for QDM is the timing of quality food production to match the dips in nature in your region year round.
For those that don't have such scale, making their land more huntable by influencing deer movement is where food plots come in. For this objective, rather than looking at year-round, you are looking for attraction during a specific time period, hunting season. It could be even a smaller period that you focus on like archery season, but in general it is hunting season. Here, the location of the food plots relative to the rest of the habitat and hunting pressure is probably the driving factor. At this point, depending on location, you may be competing with quality native foods. No matter what I plant and how attractive it is, when we get a heavy acorn crop, deer become very pressure sensitive. They still use our food plot, but the do it after dark. During shooting hours, they can just lay down in acorn flats or ridges. When hungry, they stand up and walk 20 yards sucking up acorns and then lay back down. They are getting quality food with very little risk. In mast crop failure years, they will tolerate a lot of pressure of guys hunting the food plots themselves, not just the travel corridors and staging areas.
In both cases, QDM and huntability, non-food plot habitat improvement can be even more important than food plots in achieving your objectives.
Commercialization of the food plot industry has really distracted many of us from defining success in terms of meeting our objectives. We look at a nice green farm like weed free monoculture and think "WOW! What a wonderfully successful food plot" We watch deer feeding in it before hunting pressure begins and are even more convinced of success.
I love the OPs rational for using a foliar fertilizer. "I have it and I want to experiment with it" (paraphrase) . Experimenting and learning is fun and informative. But, judging success is more than looking at what a food plot looks like.
Thanks,
Jack