Comparison of Chemical Conversion of Humus Compounds in Some Soils of Aqra District

Abstract

A field study was carried out to determine the effect of vegetation cover on the decomposition of humus compounds in some soils in Aqra district, in the north of Iraq. The humus compounds were divided into three components; humic acid, fulvic acid, and humine. Four different vegetation areas were selected plums, walnuts, almonds and unused soil at different depths. The soil samples were air dried and screened on the sieve of 2 mm, to measure some physical and chemical properties. The results showed a variation in the organic content of soil horizons within the same horizon or compared with other horizons. The organic compounds ranged from 9.490 – 48.661 gkg-1 for the surface horizon of the walnut vegetation soil and the subsurface horizon of the unused soil respectively. The concentration of humic acid was higher in the surface horizon of plum vegetation as recorded at 36.190 gkg-1 compared to the lowest concentration of the subsurface horizon of unused soil 4.846 gkg-1. The concentration of fulvic acid was higher at the walnut vegetation 32.080 gkg-1compared to 1.130gkg-1as it was lowest recorded with the subsurface horizon of unused soil. While, the concentration of humic acid was higher with the plum vegetation soils as it was recorded of 1.190 gkg-1 at the surface horizon of plum vegetation soil compared to the lowest concentration of subsurface horizon with the walnut vegetation soil as it was down to 0.77 gkg-1.