Abstract
Humus compounds contribute improving the soil chemical and physical characteristics which give buffering capacity feature to the soil, these compounds expose to several processes that decompose them to another form by internal environmental of soil system and external conditions. This study concerning the chemical transformation through the depth of soil pedon in some calcareous soils of semi-arid regions of Northern Iraq. Results showed that humic acid concentration was more than fulvic acid, as well as the percentage between the acids was higher than one (1), indicating to a high organic decomposition which related to climate conditions. Also results stated that there was a decreasing in humic and fulvic acid values with soil depth, in such condition results gave an indicating presence of fulvic transformation to humic acid which causing an increasing in its concentration due to condensing process considered as a characteristics happen in the agriculture soils which have high temperature and dry season during the year.
