"Plants require 16 elements for growth. Carbon, hydrogen, and 
oxygen are obtained from air and water. The remaining 13 
elements.nitrogen, phosphorus, potassium, calcium, magnesium, 
sulfur, boron, copper, chlorine, manganese, molybdenum, iron, 
and zinc.are supplied by the soil."


"Apart from carbon, hydrogen and oxygen, only 14 elements
are addressed in agriculture by consultants, namely N,
Fe, Mn, Zn, Cl, Ca, Mg, S, Mo, Cu, B, P, Co & Si. It has
been reported that the very first cell that sprang from
the Precambrian Ocean contained 77 minerals."
http://www.biodynamic.org.nz/guides/intro_ch1.pdf


"Notable plants useful for supplying a wider range of nutrients 
are comfrey (Ca), bracken fern (P), Equisetum (Si), and nettles"

"The C/N ratio of the oil cake is low, ranging from 3-15 which 
facilitates in its quicker decomposition."