Total and young organic matter distributions in aggregates of silty cultivated soils

摘要

SummaryThe distribution of organic matter in soil aggregates was investigated by fractionating aggregates and measuring carbon contents. The distribution of recently incorporated organic carbon was analyzed using13C natural abundance. The soils of the experiment, which previously only had C3vegetation, were cropped to maize, aC4plant, for 6 or 23 years.Aggregate size distributions were determined for silty soils with different organic matter contents. Slaking‐resistant macroaggregates were enriched in C as compared to dry‐sieved macroaggregates or to microaggregates, and the C content increased with the size of aggregates. The δ13C value was used to calculate the amount of C3‐derived and C4‐derived organic carbon in the fractions. The larger carbon contents in stable macroaggregates were due to young C4‐derived organic carbon (<6 or 23 years), and we concluded that young organic matter was responsible for macroaggregate