English

Abstract

Significant areas of prime farmland in the upper Coastal Plain of Virginia have been disturbed by heavy mineral sands (Ti/Zr-bearing ilmenite, rutile, zircon) mining over the past 7 years. Previous work has shown that separation of sandy particles (tailings) from finer particles (slimes) in dewatering pits leads to significant lateral variability in the soils. The objectives of this study were 1) to characterize the chemical, morphological and physical properties of these mine soils and 2) to classify these soils. Thirteen soil profiles, ranging in age from 2 to 6 years, were described and sampled to 2 m. Samples were analyzed for particle size distribution, pH, exchangeable bases, exchangeable acidity, extractable Al, and organic matter (OM). The plow layers, which in most cases included topsoil, fertilizer, lime, and biosolids additions during reclamation, ranged from 10 to 24 cm in depth. These horizons were typically loamy sands and sandy loams with OM ranging from 0.2 to 1.5% and pH ranging from 5.6 to 8.0. Subsurface horizons were typically sands, loamy sands, sandy loams, sandy clay loams, and clays with lower pH, (< 5.5) low OM (< 0.5%), and low plant- available nutrients. Some profiles were relatively consistent in the subsurface, or changed only gradually with depth. Others contained adjacent dissimilar layers with abrupt horizons in between, such as alternating sands and clays. Several profiles contained dissimilar materials within a horizon, expressed as banded materials or as clayey fragments within a sandy matrix. Many profiles exhibited overturned stratification that we refer to as convoluted banding and may prove to be a diagnostic feature of some mineral sand mine soils. Heavy compaction was indicated in most profiles by the presence of densic layers in both loamy and clayey materials. The thirteen profiles were classified according to Soil Taxonomy into 4 subgroups, including one Fluventic Dystrudept, two Typic Udifluvents, three Typic Quartzipsamments, and seven Typic Udorthents.