Just got this from my agronomist.  I have been working on a plan for foliar feeding for the last couple of years and will do a large strip trial this summer.

"

.  We have seen that materials are absorbed by the plant and move rather freely in the plant. The amounts may at first seem relatively small, but to offset this handicap, the efficiency is high. In fact, this is the most efficient method of applying fertilizer to plants that we have yet discovered. If we apply these materials to the leaves in soluble forms, as much as 95 percent of what is applied may be used by the plant. If we apply a similar amount to the soil, we find about 10 percent of it to be used. This chart helps to clarify this matter of efficiency. We apply the material here to the leaves and of course the fruit is quite near the leaves,

which may be a point. Now if we follow this curve to the total phosphorus in the fruit derived from foliar application, we find a substantial amount at 14, 15, 16 perhaps 30 to 40 hours after application. Contrast this with the soil application where the rate is much slower. This is very important in certain critical times of the year. For example, the soil may be cool and low in phosphorus at just the time it is needed by a transparent vegetable or strawberry plant. Or there are cases where the soil locks up certain materials that are applied, like potash and magnesium. Under such conditions we find leaf application very significant and very effective."

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