Granulometric fractionation of organic matter (OM) provides insights into its quality and effects on soil biological fertility. OM is divided into coarse (>50??m) and fine (<50??m) fractions, where carbon and nitrogen are distributed. The fine fraction, representing 70–90% of total carbon in temperate soils, corresponds to humidified OM and indicates long-term carbon storage. High carbon in this fraction suggests strong chemical stabilisation. It may also reflect OM mineralisation (CO? loss), but supports physical stabilisation and soil aggregation. High nitrogen in coarse fractions benefits crop nutrition. The fine fraction influences water retention and cation exchange capacity. Coarse fractions, or labile OM, consist of decomposing plant debris, a key energy source for soil organisms. Labile carbon, also called active or oxidised carbon, is the least stable and degrades quickly, but plays a vital role in soil biological activity.