Perhaps he used minute quantities of sea salt in sprays.
Many kinds of plants benefit from minute quantities of Sodium, such as found in many conventional fertilizer blends: Sodium Borate and Sodium Molybdate. Since Sea Salt is way more than half Sodium Chloride, one could easily over-do the dosage, of both Sodium and Chloride.
I use Kelp. It provides some Sodium and Chloride, as well as a little of all the other essential elements and all the beneficial elements, as well as many elements of no known nutritional use to plants (but some, such as Iodine, are useful to animals who eat the plants), and contaminants.