Aggregate disintegration and crust formation at soil surfaces exposed to rain are caused by rapid wetting of the dry aggregates and by raindrop impact. The relative importance of these two mechanisms was evaluated by studying the effects of the wetting rate (WR) and raindrop impact on crust strength and crust micromorphology. Two soils, a loess (Typic Haplustalf) and a black soil (Pachic Udic Argiboroll), varying in their organic matter content (15.2 and 42.6 g kg-1, respectively) and aggregate stabilities, were packed in splash cups, prewetted at WRs of 2 or 50 mm h-1, and exposed to 5 to 60 mm of simulated rainfall. For the unstable loess soil, crust strength increased and crust microfabric deteriorated with increases in cumulative [...]