chelation in the nitrogen cycle

Spencer can you tell me specifically which lecture and which slide?

You move quick Sandra! The diagram in question is in lecture 23 (slide 5) and also on Soilweb 200 (http://soilweb200.landfood.ubc.ca/soil-biology/nutrient-cycles/4-nitrogen-n/).

Metalo-organic complexes are indeed chelates
Since both organic compounds and clay particles are charged, they can interact with each other, forming complexes of organo-clay complexes. We did not cover this in our course, but this is something that does happen often in soils.