Redbeard,
Studies have shown that nutrients are more readily absorbed through foliar feeding than through root zone intake. Therefore, while the plant is in active growth it is more efficient. If it isn't, you may possibly be wasting your time unless your spraying large amounts of product. When spraying, we are concerned with foliar feeding and dealing with parts per million due to intake from foliage directly, at other times to alter soil chemistry, we then are dealing with pounds per acre. If someone were to use a spray and hope to alter the conditions by one application only, it would be in vane. As you know, tobacco is a fast growing plant that runs it's cycle in one season's time... Give it what it needs at the right time and it will make in just a few weeks.
Spraying the ground and hoping for a fix to a soil chemistry problem is like your truck being 2 quarts low of oil and then only adding a tablespoon. Have you helped the problem? Yes.... Has it really made a difference? No.
It also depends on what it needs and what you feed it. I think many gardeners make this mistake. Let's make a comparison here:
Nitrogen and phosphorous are good for plants,Right? And, milk does a body good!
Well, if a man is sick with a stomach virus and doesn't look so good then, let's force feed him some milk... He throws it up and we then give him some more. He get's sick again. What's wrong, milk does a body good ,right? So then comes the task of finding out exactly what the ginseng is lacking.
Long story short..The easiest fix to this is using areas containing the same companion plants that live alongside wild ginseng. If you can't, get the chemistry as close to right as possible. You can then use foliar feeding as a boost to plant growth. When we are talking about a seven to ten year crop, you have to prepare for the long haul. If it's a happy plant, in it's happy home,free from disease, foliar feeding will help a lot but it will not fix an existing problem.
Hillopper