This is interesting: https://carbonlogicus.com/wp-content/uploads/2017/08/CL_datasheet.pdf
A company called Carbon Logic "utilizes a unique process to create crop specic formulations to maximize growth and yield of cannabis crops". They show data from in-house studies with increases in marijuana yield when you add their biochar to a good (Sunshine Mix) growing media. With several states essentially legalizing marijuana, you will be seeing more such studies, and we have had inquires here at UCR.
The University of California is applying for a special Federal exemption to allow us to grow marijuana in controlled experiments.