Abstract Soil organic matter, in its usual sense,is the totality of organic components of the solid phase consisting of both non-humic substances and humus,other than the undecayed plant and animal residues. A typical agricultural soil may contain between 1 and 5% organic matter in the top 15 cm. The greatest content of humus , in the territory Sânandrei there are in the Gleysols (3.72% ) Solonetz ( 3.63% ) and Phaeozems ( 3.41% ). A typical agricultural soil may contain between 1 and 5% organic matter in the top 15 cm. The dead plant material of lignocelluloses with an average composition of 15-60% cellulose,10-30% hemicelluloses,5-30% lignin and 12-50% protein. Almost 95% of total soil N is associated with soil organic matter. Humus is a mixture af dark-coloured amorphous and colloidal substances made up of strictly humic subtances, of products of the advanced decomposition of organic residues and of microbial biomass. The study is based on soil survey report effectuated by OPSA Timișoara or in doctorate thesis. The greates values for Humus and N content are in the Phaeozems, Vertisols and Chernozems. The C/N ratio determines the rates at which N and C are released and mineral N becomes available for plant uptake. In the case of Uivar territory the maximum value for humus content is at Vertisols (3.74% ) and Phaeozems ( 3.72% ) , and the minimum for Fluvisols ( 2.59% ). It can be noticed that in soil types from plain region, like as Chernozems, Vertisols and Solonetz, prevails humic acids and the ration of NA/FA is over 1. In the soil type from the hilly region – Dealurile Lipovei and mountain region – Muntele Mic, prevails fluvic acids and the NA/FA ratio is under 1.

Key words: soil, organic matter, carbon, humus acids

Presentation: oral