GROTEK ORGANICS - CORE - 10LCORE ESSENTIAL ELEMENTS At the heart of our line is the essential NPK that provides the foundation for our multi product formula. Core is based on plant matter, which provide key minerals but also high levels of humates and other plant and mineral derived metabolites. This formula can also be used to feed and stimulate soil biology, increasing production of substances known to accelerate plant growth. Just like the rest of the Grotek liquid organic