According to IPCC GPG-LU-LUCF, root biomass or below-ground biomass is equal to above-ground biomass multiplying root-to-shoot ratio (R). You can use the default values of R recommended by IPCC for different forest types, . Also, you can have your specific values from destructive samples of root biomass.  

Simply take out the roots from the culture media and weigh them on weighing balance. But before weighing the roots should be blotted against filter paper to remove the excessive water of washing. For further elaboration root length,  number of lateral roots formation and square area occupied by the roots are also the worthy data for biomass accumulation study. 

there some advance tools available for studying the root architecture, these may help you but might not of yours concern. Find the given links: 

http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3444351/

http://aob.oxfordjournals.org/content/105/5/783.full.pdf+html  

According to IPCC GPG-LU-LUCF, root biomass or below-ground biomass is equal to above-ground biomass multiplying root-to-shoot ratio (R). You can use the default values of R recommended by IPCC for different forest types, . Also, you can have your specific values from destructive samples of root biomass.  

you can contact with Dr yasser 

he is an expert in this field : [email protected]