Contribution of Particulate and Mineral-Associated Organic Matter to Potential Denitrification of Agricultural Soils

Water-extractable organic carbon (WEOC) is considered as the most important (C) source for denitrifying organisms, but contribution of individual matter (OM) fractions (i.e., particulate (POM) and mineral-associated (MOM)) to its release and, thus, denitrification remains unresolved. Here we tested short-time effects POM MOM on potential estimated POM- MOM-derived WEOC CO 2 production three agricultural topsoils. Suspensions bulk soils with without addition soil-derived or were incubated 24 h under anoxic conditions. Acetylene inhibition was used determine respective product ratio at constant nitrate supply. Normalized added OC, production, total denitrification, ratios much stronger than those MOM. While OM generally increased (N O + N )-N/CO -C ratio, O/(N ) changed differently depending soil. Gas emissions shares initial then estimate , O, production. OC derived from accounted 53–85% released 15–47%. Total gas partly over- underestimated, mainly due nonproportional responses fractions. Our findings show that plays a role in providing substrates during less dominant POM. We conclude not predictable based C distribution over alone. Instead, strength plus WEOC’s quality turned out decisive determinants denitrification.