It's 100% the nutrients + minerals. When you get right down to it, you're just trading one growing medium for another. That said, hydroponics allows for a leve

It's 100% the nutrients + minerals. When you get right down to it, you're just trading one growing medium for another. That said, hydroponics allows for a level of control in nutrients that soil does not, generally leading to weighty, tasteless veggies.