Soil microaggregate size composition and organic matter distribution as affected by clay content

Aggregation assembles different size mixtures of soil particles into a larger architecture. Such mixtures impede resolving which particles build aggregates and how these control the accumulation of soil organic matter (OM). Here we present an approach to differentiate the size distributions of soil fractions in the size range of microaggregates ( 250 μm were sonicated to isolate occluded size fractions 250 μm) and larger microaggregates in the 50–180 μm size range. The low-clay soils, on the other hand, contained more non-aggregated sand-sized particles >100 μm which probably hampered the buildup of larger aggregates. The size distribution of particles