The source of a hydroponics solution will come from an overlooked source. The primary cause leading to the destruction of most vegetative life on Earth, volcanic ash, which will cloud the atmosphere preventing sunlight, will have another purpose. Have you ever noticed that the sides of volcanoes support lush vegetation? The ash is composed of Carbon, Nitrogen, Phosphorus, Hydrogen, Sulfur, Sodium, Iron and other trace elements found in hydroponics solutions on the market today. Rainwater will contain most chemicals needed to provide a nutrient solution, as it washes the air from the volcanic ash. The concentration of the nutrient solution does not have to be high since it can be discarded after one use, though that can be adjusted up by evaporation. The fact that rain will be constantly falling, provide an unlimited source during the first few years. Minerals containing those same elements in compound form can replace elements that may be missing in the rainwater every so often. These minerals can be sized to pea gravel size form and placed as part of the growing medium. Leaching of these chemicals naturally as rainwater pass over should be sufficient to replace shortages.
Offered by Robert.
Atmospheric nitrogen can't be used by plants as a source of nitrogen (except for legumes which have a bacteria which can convert atmospheric nitrogen for the plant's use). Plants need most of their nitrogen in the nitrate form, although they can use some ammonia (too much is toxic). It is good to see someone recognizes volcanic ash as the wonderful fertilizer it is.
Offered by Jennifer.