I have heard that in Japan one very famous tomato grower adds nigari to his water mix.
Nigari is derived from seawater.
Nigari is a natural coagulant to turn soy milk into tofu.
From Wikipedia:
Culinary use
Magnesium chloride is an important coagulant used in the preparation of tofu from soy milk. In Japan it is sold as nigari (にがり, derived from the Japanese word for "bitter"), a white powder produced from seawater after the sodium chloride has been removed, and the water evaporated. In China it is called "lushui" (卤水 in Chinese). Nigari or Lushui consists mostly of magnesium chloride, with some magnesium sulfate and other trace elements. It is also an ingredient in baby formula milk.
Jeff