Large and small macroaggregates were mixed in proportions similar to their distribution in the original soil and then separated further according to the method outlined by Six et al. (2000) to isolate microaggregates occluded in the macroaggregates. A 5-g subsample of the macroaggregates was overnight soaked in 50 ml deionized water in the cold room. The next morning the macroaggregates were immersed in water on top of a 250-mm mesh screen with 50 metal beads (4-mm diameter) and shaken on a reciprocal shaker at 250 rpm under a continuous flow of water.
This was done to ensure that microaggregates were immediately flushed onto a 53-mm sieve to avoid breakdown of the microaggregates into silt and clay fractions. When all the macroaggregates were broken up (achieved after approximately 5 min), the material collected on the 53-mmsievewas wet sieved following the procedure described above in order to ensure that the isolated microaggregates (53e250-mm) were water-stable. The coarse POM collected on the 250-mm mesh, microaggregates with in macroaggregates (53e250-mm) and the silt and clay within macroaggregates
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