Boron is extracted by boiling under reflux 10 g of air dry soil with 20mL of 0.01M CaCl2 for 5 min. in a fiber digestion apparatus. After slight cooling, the sample is filtered and the filtrate is acidified and analyzed by Inductively Coupled Plasma Atomic Emission Spectroscopy (ICP-AES).
(See Method References No. 19, 20, & 21)