Restoration of Prime Farmland Disturbed by Mineral Sand Mining in the Upper Coastal Plain of Virginia

Abstract

Economic deposits of heavy mineral sand were identified in the late 1980's under prime farmland along the Upper Coastal Plain of Virginia. Mining in Virginia will commence in 1997 on the Old Hickory Deposit in Dinwiddie/Sussex Counties. Experiments were established on two mine pits representing two likely pit closure scenarios; regrading the surface with unprocessed subsoil (Pit 1) or filling to the surface with processed material (Pit 3). To evaluate topsoil replacement vs. organic amendment, each pit was split into two experiments, and an adjacent undisturbed control was established. One half of each pit was covered with approximately 30 cm of topsoil, and the other half of each pit received 112 Mg ha of yard waste compost. The -1 experiment was double-cropped with wheat ( Triticum vulgare) and soybeans (Glycine max) in 1995/1996. The control and Topsoil treatment on Pit 1 produced the highest wheat yield, but soybean yield was highest on the Control and the Topsoil and Compost treatments on Pit 3.

Wheat yield was positively related to root length, while soybean yield varied with soil bulk density. Soybean rooting was found throughout all horizons in the undisturbed soils, but was limited to the surface 20 to 40 cm in all mine soil treatments. Very wet weather masked treatment effects in both crops, but the physical and chemical properties of the mine soils indicate that the key to reclaiming these areas lies in effective remixing of mined materials, and developing and maintaining soil humus levels.