Humic acid buffers soil pH to 5.5 to 7.5 levels which is ideal for plant development and nutrients absorption. Thus acting as a natural chelator, they help plant roots to absorb nutrients more efficiently to create long term positive effect on soil quality and productivity.The best source of humic acids are the sedimentation layers of soft brown coal, which are referred to as Leonardite. (pic. 1.2, pic. 1.3) Humic acids are found in high concentration here.