Freezing Effects on Aggregate Stability Affected by Texture, Mineralogy, and Organic Matter

Aggregate stability, an important property influencing a soil's response to erosive forces, is affected by freezing. The objectives of this laboratory study were to determine how constrainment, number of freeze‐thaw cycles, and water content at freezing affect the aggregate stability of six continental USA soils differing in texture, mineralogy, and organic‐matter content. Moist aggregates, after being frozen and thawed either zero, one, three, or five times, were vapor wetted to 0.30 kg kg −1 and analyzed by wet sieving. Soils with clay contents of 17% or more and organic‐matter contents >3% were the most stable after freezing. Aggregate stability for fine‐ and medium‐textured soils generally decreased linearly with increasing water content at freezing. This linear decrease in stability was more rapid for constrained samples than for unconstrained samples. The stability of field‐moist aggregates generally increased from zero to one or three freeze‐thaw cycles. For at least one low‐organic‐matter soil, stability increased from one to three freeze‐thaw cycles, but then decreased at five cycles. After thawing, aggregates at water contents of 0.15 kg kg −1 or more that were constrained when frozen were always significantly less stable than aggregates that were unconstrained when frozen.