ABSTRACT
Methods of fractionating soil into aggregate size fractions usually involve some variation of the wet sieve method (Yoder, 1936). This method is cumbersome and laborious (Kemper and Rosenau, 1986), and unable to accurately simulate the physical energies imparted to aggregates in rainfall and runoff events (Bruce-Okine and Lai, 1975; De Vleeschauwer et al., 1978;Mbagwu, 1986). Hence, the wet sieving alone cannot supply a very accurate measure of the size pools of stable soil aggregates and associated soil organic carbon (SOC) and nutrients available for transport by water erosion. A raindrop impact method for testing aggregate stability (Bruce-Okine and Lai, 1975) represents a better simulation of erosion-induced aggregate breakdown. The purpose of this chapter is to report on testing of a realistic method to fractionate raindrop-stable soil aggregates into size pools using a rainfall simulator.
