They knew it worked but were told it shouldn't work because so little fertilizer was being applied per acre. It has only been recently that research has been done that shows how a small amount of potash or phosphate applied by foliar spraying can increase the yield of crops so significantly, actually providing a better return per dollar invested than soil applied fertilizer. Foliar fertilization doesn't totally replace soil applied fertilizer but it does increase the uptake and hence the efficiency of the soil applied material. The increased efficiency can reduce the need for soil applied fertilizer and reduce leaching and run off of fertilizer nutrients, reducing the impact on the environment of fertilizer salts. It was learned in the 1950's that foliar fertilization was effective.
Water diffuses into cells independently of minerals.
Often the concentration of a given mineral is greater inside a cell than in the solution which bathes it. According to the law of diffusion, the mineral in question should diffuse out of the cell. Actually, in many instances the cell continues to take up the mineral. A milliequivalent of an ion is one-thousandth its gram ionic weight divided by its valence. Timing and alleviation of nutrient stress periods in the physiology of the crop plant is crucial.