Aggregate Disintegration and Wettability for Long‐Term Management Systems in the Northern Appalachians

Assessment of the structural properties of discrete soil aggregates is fundamental to understanding soil erosional processes. Management‐induced changes in soil organic carbon (SOC) concentration may significantly alter aggregate properties. The disintegration and wetting characteristics of individual aggregates and their relationships with SOC concentrations were determined for a Rayne silt loam (fine‐loamy, mixed, mesic Typic Hapludult) under long‐term (>22 yr) moldboard plow (MP), no‐till with (NTm) and without manure (NT), pasture, and forest systems in the northern Appalachian region. Aggregate disintegration was assessed based on the kinetic energy (KE) of simulated raindrops required to detach 1‐ to 8‐mm aggregates at −0.01, −0.1, −1, and −154 MPa soil water potentials. Management affected aggregate resistance to the erosive energy of raindrops (P < 0.01). Aggregates from forest soils required the highest KE (>5.0 μJ) for disintegration and those from MP soils the lowest (<1.9 μJ). At the −0.01 MPa potential, the KE needed to disintegrate aggregates in NTm was about three times higher than for NT, indicating that manure addition improved aggregate stability. Aggregates from cropland had very low water repellency, but those from forest management have some water repellency. Aggregate disintegration was correlated with measured soil erosion in which MP required the lowest raindrop KE to produce the highest runoff and soil loss. The SOC concentration explained 48% of the variability in aggregate disintegration and 86% in aggregate wetting. Long‐term management altered aggregate disintegration, but its effects on aggregate wetting within agricultural practices were small.