Aggregate stabilities of some southeastern US soils

Soils from humid regions have traditionally been considered to have stable aggregates, Some humid southeastern U.S. soils have demonstrated poor structural stability, We hypothesized that a sensitive measure of aggregate stability of southeastern U.S. soil., would demonstrate that stability of macroaggregates may depend on some soil properties and may not correlate with soil erosivity. This study evaluated the stability of aggregates from southeastern U.S. soils employing a sensitive aggregate stability test, and compared it with previously published data for the same soils, Stability of 0.5- to 1.0-mm aggregates of 11 Georgia topsoils were determined using the high-energy-moisture-characteristic method, where the destructive force used to break the aggregates is a controlled wetting process. Aggregates were wetted either rapidly by a matric potential of 0.0 J kg(-1), or slowly where they were initially subjected to a matric potential of -2.0 J kg(-1), which was then gradually increased to 0.0 J kg(-1). Two water qualities were used for wetting: tap water (electrical conductivity [EC] 0.097 mS cm(-1)) and a saturated CaSO4 solution (EC 2.24 mS cm(-1)). Stability ratio (ratio of fast to slow structural indices) of the soils ranged between 0.40 and 0.95, Six soils had a stability ratio of less than or equal to 0.5 (low aggregate stability), Aggregate stability in unstable soils with pH >6.5 rose to greater than or equal to 0.62 when saline solution was used. The measured aggregate stability indices significantly correlated with published infiltration rate data (R = 0.622), but not with soil splash or soil loss.