Intercation Between Some Micro-Elements And Humic Substances in Some Forest Soils Northern Iraq

Abstract

Four pedons were selected for different soils in the forest cover, two in each of Mankeesh and Atrush areas in Dohuk governorate, under pine and oak trees, in order to study the distribution of the main groups of humic compounds (humic and fulvic acids) and their association with iron and manganese ions. The results showed that the variation in the nature of the forest cover and the speed of decomposition of its remains led to a difference in the distribution of the content of organic matter, the ratios of Humic acid / fulvic acid (FA / HA) and the amount of humic substances produced in each soil, regarding the optical density of the extracted humic compounds, which is expressed as E4/E6, this ratio depends on the chemical composition of these Humic compounds. It is noted from the results that this ratio between E4: E6 ranged between (0.43 - 1.79), low values reflect the presence of aromatic Humic compounds with relatively low molecular weights, while high values indicate the presence of aliphatic humic compounds, the study also showed a difference in the values of iron and manganese associated with humic and fulvic acid as organic complexes, which is consistent with the difference in the degree of decomposition of forest tree residues and plant residues, and in turn is reflected on the quantity and type of humic compounds resulting from the decomposition. The Atrush soil under pine forests excelled in its composition of chelated iron with fulvic acid, Humic acid and manganese chelated with fulvic acid, while the Atrush soil under oak forests excelled in the composition of chelated manganese with humic acid on the rest of the studied soils.